[Federal Register Volume 60, Number 188 (Thursday, September 28, 1995)]
[Notices]
[Pages 50338-50377]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-24112]



      

[[Page 50337]]

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Part IV





Environmental Protection Agency





_______________________________________________________________________



Dichlorvos; Notice of Preliminary Determination to Cancel Certain 
Registrations and Draft Notice of Intent to Cancel; Notice

  Federal Register / Vol. 60, No. 188 / Thursday, September 28, 1995 / 
Notices   

[[Page 50338]]


ENVIRONMENTAL PROTECTION AGENCY

[OPP-30000/56; FRL-4954-7]


Dichlorvos; Notice of Preliminary Determination to Cancel Certain 
Registrations and Draft Notice of Intent to Cancel

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of preliminary determination.

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SUMMARY: This Notice sets forth EPA's preliminary determination 
regarding the continued registration of pesticide products containing 
dichlorvos and sets forth the Agency's assessment of the risks and 
benefits associated with dichlorvos products. This Notice announces the 
Agency's preliminary determination to propose cancellation of certain 
registrations of dichlorvos products and to propose modification to 
other registrations which would not be canceled. In addition, this 
Notice serves as a Draft Notice of Intent to Cancel.

DATES: Written comments must be received on or before December 27, 
1995.

ADDRESSES: Submit three copies of written comments bearing the docket 
control number ``OPP-30000-56'' by mail to: Public Response and Program 
Resources Branch, Field Operations Division (7506C), Office of 
Pesticide Programs, Environmental Protection Agency, 401 M St., SW., 
Washington, DC 20460. In person, deliver comments to: Rm. 1128, Crystal 
Mall #2, 1921 Jefferson Davis Highway, Arlington, VA 22202.
    Comments and data may also be submitted electronically by sending 
electronic mail (e-mail) to: [email protected]. Electronic 
comments must be submitted as an ASCII file avoiding the use of special 
characters and any form of encryption. Comments and data will also be 
accepted on disks in WordPerfect in 5.1 file format or ASCII file 
format. All comments and data in electronic form must be identified by 
the docket number ``OPP-30000/56.'' No Confidential Business 
Information (CBI) should be submitted through e-mail. Electronic 
comments on this document may be filed online at many Federal 
Depository Libraries. Additional information on electronic submissions 
can be found in Unit VII. of this document.
    Information submitted as a comment concerning this document may be 
claimed confidential by marking any part or all of that information as 
confidential business information (CBI). Information so marked will not 
be disclosed except in accordance with procedures set forth in 40 CFR 
part 2. A copy of the comment that does not contain CBI must be 
submitted for inclusion in the public record. Information not marked 
confidential may be disclosed publicly by EPA without prior notice. All 
written comments will be available for public inspection in Rm. 1132 at 
the address given above, from 8 a.m. to 4:30 p.m., Monday through 
Friday, except legal holidays.
FOR FURTHER INFORMATION CONTACT: By mail: Dennis Utterback, Special 
Review and Reregistration Division (7508W), Office of Pesticide 
Programs, Environmental Protection Agency, 401 M St., SW., Washington, 
DC 20460. Office location and telephone number: Special Review Branch, 
3rd floor, Crystal Station #1, 2800 Crystal Drive, Arlington, VA, 
Telephone: 703-308-8026: e-mail: [email protected].

SUPPLEMENTARY INFORMATION: This Notice is organized into the following 
units: Unit I. is the introduction which includes background 
information related to dichlorvos, a description of the Agency's 
Special Review process, and the regulatory history of dichlorvos (2,2-
dichlorovinyl dimethyl phosphate), also known as DDVP, including the 
initiation of Special Review. Unit II. summarizes the risk assessment. 
Unit III. summarizes the benefits of dichlorvos uses. Unit IV. explains 
the Agency's risk/benefit analysis and proposed regulatory decisions. 
Unit V. describes the Agency's existing stocks policy. Unit VI. 
describes the procedures related to the referral of this document to 
the U.S. Department of Agriculture and FIFRA Scientific Advisory Panel. 
Unit VII. describes the opportunity for public comment, and Unit VIII. 
describes the availability of information in the Public Docket. 
Finally, Unit IX. lists references to this document.

I. Introduction

A. Summary

    EPA has concluded that the risks outweigh the benefits for most 
uses of dichlorvos, and therefore, recommends a variety of measures to 
reduce those risks. Dichlorvos poses carcinogenic risks of concern to 
the general population from dietary exposure and risks of 
cholinesterase inhibition (including cholinergic signs) to individuals 
mixing, loading, and applying this pesticide, as well as to those 
reentering treated areas. The Agency believes that the economic 
benefits associated with the continued use of dichlorvos are not 
significant for most uses. After careful consideration of the risks and 
benefits, EPA is proposing the following actions: Cancellation of all 
uses in or on residences, tobacco warehouses, ornamental lawns, turf 
and plants, commercial, institutional and industrial areas, airplanes, 
trucks, shipholds, and rail cars, warehouses, and use on bulk, packaged 
or bagged nonperishable processed and raw food (except for impregnated 
resin strips in silos). In addition, EPA is proposing to cancel other 
registrations unless certain modifications are made to the label, 
including: prohibit hand-held application in mushroom houses, 
greenhouses, on food and nonfood animals (other than poultry), and in 
passenger buses; allow other application methods in mushroom houses, 
greenhouses or passenger buses, as long as the applicator and others 
are prohibited from remaining in these facilties during treatment; 
restrict all remaining registered products to use by certified 
applicators only, except for impregnated resin strips used in museums 
(closed spaces) and in insect traps, and require personal protective 
equipment (PPE) during handling; and require reentry intervals for 
mushroom houses, greenhouses and passenger buses. EPA is proposing to 
retain the following uses: mushroom houses and greenhouses (only 
automatic foggers or fogging through a port, and restricted reentry), 
kennels, feedlots, insect traps, garbage dumps, direct application to 
poultry, automated application to livestock, animal premises, manure, 
and buses (fogger use).
    In addition to the Special Review, there are three activities which 
may affect dichlorvos registrations. First, EPA published the Final 
Revocation Notice for the food additive regulation (FAR) of dichlorvos 
residues on packaged or bagged nonperishable processed food in the 
Federal Register of November 10, 1993 (58 FR 59667). The effective date 
of this Notice was stayed indefinitely. Second, if that revocation 
becomes effective, under current policy, EPA would issue a notice of 
its intent to cancel the related uses under the Federal Insecticide, 
Fungicide, and Rodenticide Act (FIFRA). Third, EPA received a request 
from Amvac Chemical Corporation, the sole technical registrant of 
dichlorvos, to voluntarily delete several uses from its technical 
label. EPA intends to accept Amvac's request unless the Company 
withdraws or modifies its request.

[[Page 50339]]


B. The Statute

    A pesticide may be sold or distributed in the United States only if 
it is registered or exempt from registration under FIFRA as amended (7 
U.S.C. 136 et. seq.). Before a product can be registered 
unconditionally, it must be shown that it can be used without 
``unreasonable adverse effects on the environment'' (FIFRA section 
3(c)(5)), that is, without causing ``any unreasonable risk to man or 
the environment, taking into account the economic, social, and 
environmental costs and benefits of the use of the pesticide'' (FIFRA 
section 2(bb)). The burden of proving that a pesticide meets this 
standard for registration is, at all times, on the proponent of initial 
or continued registration. If, at any time, the Agency determines that 
a pesticide no longer meets this standard for registration, then the 
Administrator may cancel the registration under section 6 of FIFRA.

C. Regulatory Background

    Dichlorvos is an organophosphate insecticide registered for use in 
controlling flies, mosquitos, gnats, cockroaches, fleas, and other 
insect pests. Amvac Chemical Corporation is the sole producer of 
technical grade dichlorvos in the U.S. There are currently 182 product 
registrations for formulations containing dichlorvos. In addition, 
there are three section 24(c) Special Local Need Registrations. 
Formulations include: Pressurized liquids, granulars, dusts, wettable 
powders, emulsifiable concentrates, total release aerosols, and 
impregnated materials. Applications are made with aerosols and fogging 
equipment, with ground spray equipment, and through slow release from 
impregnated materials, such as resin strips and pet collars.
    Dichlorvos has been registered in the U.S. since 1948. The Shell 
Chemical Company marketed the product under the trademark Vapona, and, 
in 1963, Shell began marketing the No-Pest Strip. In 1985, 
approximately 2 million pounds of dichlorvos active ingredient were 
used annually in the U.S. on a variety of sites. At that time, 
agricultural applications constituted 60 percent of the total 
dichlorvos usage, including use on beef and dairy cattle, poultry, 
sheep, livestock living quarters and other farm buildings, greenhouses, 
mushroom houses, stored agricultural products, stored food facilities, 
and tobacco warehouses. In addition, approximately 25 percent was used 
on commercial, institutional, and industrial sites, including food 
processing areas, food handling establishments, sewage and dump sites, 
lawns, and turf. The remaining 15 percent was applied in and around 
homes and on pets. These estimates are based on 1985 data and it is 
believed that dichlorvos usage has declined significantly in recent 
years (currently 250,000 to 500,000), but not necessarily 
proportionally across all sites.
    Amvac has also notified EPA that it is not supporting uses on the 
following sites and requests their voluntary cancellation: Rangeland 
grasses, greenhouse food crops (cucumber, tomato, lettuce, radish), 
greenhouse non-food crops, tobacco, tobacco warehouses, tomato (post 
harvest), domestic dwellings (except for impregnated resin strips, 
total release foggers, and crack and crevice treatment; impregnated 
resin strips will not be permitted in kitchens); aircraft and buses; 
food service establishments, including eating establishments (except 
for non-food service areas); food manufacturing establishments, 
including bottling plants and frozen food plants (except for non-food 
manufacturing areas); food processing establishments, including meat, 
poultry and seafood slaughtering and/or packing plants, and dairy 
product plants (except for non-food processing areas); and all aerial 
applications. EPA has published a notice of receipt of voluntary 
cancellation request for these uses in the Federal Register pursuant to 
section 6(f) of FIFRA on April 19, 1995 (60 FR 19580).
    In 1980, the Agency referred dichlorvos to the Rebuttable 
Presumption Against Registration or RPAR process under FIFRA, now 
called the Special Review process. The RPAR referral was based on 
scientific studies which indicated that dichlorvos was mutagenic and 
might cause cancer, nerve damage, and birth defects in laboratory 
animals.
    In 1982, the Agency issued a document reporting the results of its 
evaluation of dichlorvos (47 FR 45075). Initial concern had been based 
on the results of animal studies that were later found to be equivocal 
or to show no positive evidence of the suspected effects of exposure to 
dichlorvos. The Agency concluded that the existing information did not 
support the initiation of the RPAR process at that time. However, a 
determination was made to review results of carcinogenicity studies 
being conducted for the National Cancer Institute/National Toxicology 
Program when completed, and to issue a Data Call-In (DCI) for four 
mutagenicity studies in March 1983.
    The Natural Resources Defense Council (NRDC), et al., brought suit 
against the Agency in 1983, in part, to require a reassessment of 
several RPAR decisions. A settlement agreement was reached in September 
1984, in which the Agency agreed to reassess the pre-RPAR decision on 
dichlorvos. The parties also agreed that reassessment of dichlorvos 
would begin once the mutagenicity and carcinogenicity studies were 
received and evaluated.
    The dichlorvos Registration Standard, issued in September 1987, 
stated that the Agency was considering further regulatory action for 
all registered uses of dichlorvos. The Registration Standard classified 
all dichlorvos products as restricted use, except for resin pest 
strips, pet uses, and all remaining products allowing household use 
only. The Agency also determined that all products must contain a 
hazard warning for cancer, liver effects, and cholinesterase 
inhibition. An interim 48-hour reentry interval was imposed for the 
agricultural and commercial uses of dichlorvos. The Registration 
Standard also identified and required additional data necessary to 
evaluate fully the human and environmental risks associated with the 
use of dichlorvos as an insecticide.
    Amvac Chemical Corporation formally requested that EPA reconsider 
the requirements for a cancer warning statement and 48-hour reentry 
interval in February 1988. In September 1988, EPA formally deferred 
imposition of all Registration Standard label modifications and data 
requirements pending evaluation of comments and additional data 
regarding the label requirements, due to uncertainty concerning the 
cancer classification of dichlorvos. (These data requirements were 
later reinstated in August 1991 and January 1994.) Registrants were 
also informed that the Agency would amend the dichlorvos Registration 
Standard after completion of the reassessment.
    On February 24, 1988, EPA initiated a Special Review for pesticide 
products containing dichlorvos. EPA determined that exposure to 
dichlorvos from the registered uses may pose an unreasonable 
carcinogenic risk and inadequate margins of exposure for cholinesterase 
inhibition and liver effects to exposed individuals. The risks of 
concern detailed in the Notice were for the general population from 
consumption of foods containing residues of dichlorvos, for those 
involved in the application of dichlorvos, for workers reentering 
treated areas, for residents/occupants of treated areas, for people 
exposed to pets 

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treated with dichlorvos, and for pets treated with dichlorvos.
    On May 25, 1989, the State of California, NRDC, Public Citizen, the 
AFL-CIO, and several individuals filed a petition which asked the 
Agency to revoke FARs for seven potentially carcinogenic substances, 
including FARs for residues of dichlorvos in or on dried figs, and on 
packaged or bagged nonperishable processed food. The petitioners argued 
that these FARs should be revoked because the seven pesticides to which 
the regulations applied were animal carcinogens and thus the 
regulations violated the Delaney clause of section 409 of the Federal 
Food, Drug and Cosmetic Act (FFDCA). The Delaney clause provides that a 
FAR may not be approved for a food additive if it ``is found to induce 
cancer when ingested by man or animal. . . .'' 21 U.S.C. 348(c). In 
responding to the petition, EPA reiterated its 1988 interpretation that 
the Delaney clause is subject to an exception for pesticide uses which 
posed no greater than a de minimis cancer risk (56 FR 7750, February 
25, 1991). Although EPA concluded that several of the challenged 
regulations met this de minimis standard, EPA found that the dichlorvos 
FAR for packaged or bagged nonperishable processed food did not meet 
this standard.
    Therefore, in the Federal Register of October 3, 1991 (56 FR 
50190), EPA proposed to revoke the FAR for residues of the pesticide 
dichlorvos on packaged or bagged nonperishable processed food, under 
section 409 of the FFDCA. Subsequent to that Notice, on July 8, 1992, 
in, Les v. Reilly, 968 F.2d 985 (9th Cir.), the Ninth Circuit Court 
ruled that the Delaney clause was not subject to an exception rule for 
those pesticides that pose a de minimis cancer risk. Following the 
Ninth Circuit Court decision, EPA revoked the section 409 FAR of 
dichlorvos on packaged or bagged nonperishable processed food (58 FR 
59663, November 10, 1993) on the basis that it was in violation of the 
Delaney clause. EPA later stayed the 120-day effective date 
indefinitely, pending Agency consideration of a request for a hearing 
from Amvac. Legal pesticide residues on food are permitted by FFDCA; 
however, the use of a pesticide is permitted separately under FIFRA. 
Because the revocation was stayed, residues in food are currently 
allowed. When the stay is lifted, pesticide residues will be illegal; 
however, the use of dichlorvos will still be permitted under FIFRA. 
Therefore, under current policy, EPA intends to cancel the related uses 
as soon as possible after the FAR revocation becomes final. That 
cancellation will prevent the potential situation in which foods 
legally treated with dichlorvos under FIFRA would be considered 
adulterated and subject to seizure under FFDCA.
    In August 1991, EPA reimposed indoor use data requirements that 
were required in the 1987 Registration Standard, and were deferred in 
1988. These data have since been submitted by Amvac and reviewed by the 
Agency, and are used in the risk assessment presented here. In 
addition, the 1987 residential outdoor and terrestrial non-food use 
data requirements were reimposed on January 3, 1994. Another DCI was 
issued on February 22, 1994, for additional studies to support 
terrestrial non-food and residential outdoor uses. EPA has received 
some studies as a result of this DCI and the last study is due in March 
1996. A further DCI was issued on November 10, 1994, for residue data 
relating to crack and crevice treatment around packaged and bagged 
food.
    Based on information received in public comments and on additional 
analyses performed since the Special Review process began, EPA is now 
issuing this Notice of Preliminary Determination. Issuance of this 
Notice means that the Agency has assessed the potential adverse effects 
and the benefits associated with the use of pesticide products 
containing dichlorvos and that the Agency has preliminarily determined 
that, unless the terms and conditions of registration are modified as 
proposed in this Notice, the risks from the use of dichlorvos outweigh 
the benefits of their continued use.
    EPA's position and a summary of the rationale underlying that 
position are set forth in this Notice. The basis for EPA's action is 
explained more fully in documents contained in the dichlorvos docket. 
The docket also contains references and background information 
pertinent to the registration of pesticide products containing 
dichlorvos.
    This Notice serves both as a preliminary determination of the 
Special Review process and as a draft Notice of Intent to Cancel 
dichlorvos registrations. FIFRA requires that a draft Notice of Intent 
to Cancel be prepared and forwarded to the Scientific Advisory Panel 
(SAP) and the Secretary of the United States Department of Agriculture 
(USDA) to permit their review of the Agency's proposed action. The 
draft Notice of Intent to Cancel is not now legally effective but is 
intended only to provide a basis for comment by the SAP, USDA, 
registrants, and the public. EPA's compliance with this review 
requirement is discussed in Unit VII. of this Notice. Comments on this 
preliminary determination and Draft Notice of Intent to Cancel must be 
filed within 90 days of the issuance of this Notice.

II. Risk Assessment

A. Summary of Risk Assessment

    Risk assessment is the process used to estimate the likelihood and 
magnitude of health effects that result from environmental exposures. 
This process consists of the following four components: Hazard 
identification, dose-response assessment, exposure assessment, and risk 
characterization. The first component, hazard identification, is a 
determination whether a particular chemical is or is not causally 
linked to particular adverse health effects. Dose-response assessment 
estimates the amount of a chemical that could potentially cause an 
adverse health effect. The amount of a chemical that did not result in 
an observable or measurable effect in an animal study is the no-
observed-effect level (NOEL). All substances can cause a toxic effect 
at some level. The extent to which a chemical is toxic depends on the 
amount of the chemical needed to produce the adverse effect. Low 
toxicity chemicals require a large amount of the chemical to produce 
the adverse health effect, while highly toxic chemicals require only a 
small dose to produce the toxic effect. Exposure assessment describes 
the level or magnitude of exposure to the chemical, the route of 
exposure (inhalation, dermal, or oral), and the frequency of the 
exposure. Finally, risk characterization involves describing the nature 
and magnitude of human risk. The dose-response and exposure assessments 
are combined to estimate some measure of human risk. The potential for 
possible non-cancer health effects in humans is generally expressed as 
the margin of exposure (MOE) which is the ratio of the NOEL (dosage 
producing no effects) to the estimated exposure. For cancer, the risk 
is expressed as a probability of developing cancer over a lifetime, 
which is based on exposure and the chemical's cancer potency. The risk 
characterization component also summarizes the major strengths and 
weaknesses of the risk assessment.
    In the case of dichlorvos, the Agency has determined that the 
adverse effects of primary concern for dichlorvos are those related to 
cancer and inhibition of cholinesterase activity including cholinergic 
signs (clinical signs indicative of cholinesterase inhibition in test 
animals). Based on data from 

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several carcinogenicity studies, the Agency has concluded that 
dichlorvos meets the criteria for a Group C (possible human) 
carcinogen. Dichlorvos has been shown to induce forestomach tumors in 
mice and leukemia in rats. Results from acute/short-term, subchronic 
and chronic toxicity studies have shown dichlorvos to be a potent 
inhibitor of plasma, red blood cell and brain cholinesterase in several 
mammalian species, and to produce cholinergic signs.
    In the Notice initiating the Special Review, EPA estimated cancer 
risks for those individuals potentially exposed to dichlorvos through 
dietary and non-dietary (i.e. inhalation and dermal contact) routes. 
Since that time, EPA has determined that it is not appropriate to 
extrapolate from oral carcinogenicity data for estimation of excess 
individual cancer risks for exposure by the dermal and inhalation 
routes. Therefore, cancer risk estimates for workers and residents 
exposed to dichlorvos by the dermal and inhalation routes are not 
included in this revised risk assessment. EPA only estimated excess 
individual lifetime cancer risks for dietary exposure to the general 
population.
    Dietary exposure to dichlorvos residues may occur as a result of 
use on a variety of sites, including greenhouse food crops, mushroom 
houses, bulk-stored and packaged or bagged nonperishable processed and 
raw food, commercial food processing plants, groceries, eating 
establishments, and direct animal treatment. Some of these exposures 
and resulting risks may be eliminated due to voluntary cancellations or 
cancellation of uses related to the revocation of the FAR for packaged 
or bagged nonperishable processed food; however, since these actions 
are not final yet, for purposes of this document, EPA will assume that 
these uses will continue. EPA estimates dietary cancer risks from 
registered uses of dichlorvos to be 4.4 x 10-6. The major source 
of this estimated risk is from consumption of bulk, packaged or bagged 
nonperishable raw and processed food treated with dichlorvos (3.4 x 
10-6).
    In addition to registered uses of dichlorvos, naled provides an 
additional source of dietary risk from dichlorvos. Naled, an 
insecticide, is metabolized to dichlorvos by plants. As a result, the 
Agency felt it appropriate to characterize the total risk from 
dichlorvos even though naled itself is not under Special Review. The 
combined dietary cancer risk from dichlorvos is 5.1 x 10-6 which 
includes risk directly from dichlorvos (4.4 x 10-6) and from 
naled-derived dichlorvos (7.2 x 10-7).
    EPA completed a series of exposure assessments in 1987 for the 
Registration Standard and PD 1 that estimated the exposure to 
individuals mixing, loading and applying dichlorvos, as well as to 
those reentering areas treated with dichlorvos. These estimates were 
based on the best available data, which in most cases were exposure 
data derived from other pesticides applied in a similar manner as 
dichlorvos. Additional exposure data have been submitted since that 
time and the Agency has determined that revisions to the original 
assessments are appropriate based on these new data. EPA has revised 
its original exposure estimates for several uses of dichlorvos, 
including: Crack and crevice application, greenhouses, mushroom houses, 
dairy barns and milk rooms, household aerosol and total release fogger 
products.
    Red blood cell, plasma and brain cholinesterase inhibition and/or 
cholinergic signs are the basis for the short-term, intermediate, and 
long-term MOE estimates. For pesticides, EPA classifies occupational/
residential exposure patterns as short-term (1 to 7 days), intermediate 
(1 week to several months per year), or long-term (a substantial 
portion of the lifetime). These scenarios could vary by region or from 
year-to-year depending on the severity of the pest problem. Separate 
NOELs were selected from acute (0.5 mg/kg/day), subchronic (0.1 mg/kg/
day), and chronic (0.05 mg/kg/day) toxicity studies to estimate MOEs 
for varying durations of exposure. Margins of exposure are outlined in 
Table 1 in Unit II. of this document for individuals reentering treated 
facilities and for individuals exposed during the application of 
dichlorvos. Most of the MOEs are below the level which the Agency 
believes is protective of public health (100).

B. Effects of Concern

    1. Carcinogenicity. EPA has determined that the risk criteria for 
carcinogenicity as set forth in 40 CFR 154.7 (a)(2) has been exceeded 
for dietary exposure. Based on the studies described below, EPA has 
classified dichlorvos as a Group C (possible human) carcinogen (Ref. 1) 
.
    i. Hazard identification. In July 1987, the Office of Pesticide 
Program's Carcinogenicity Peer Review Committee (CPRC) classified 
dichlorvos as a Group B2 (probable human) carcinogen, based primarily 
on the results of National Toxicology Program (NTP) studies in mice and 
rats. Since that time, EPA has reevaluated the carcinogenic potential 
of dichlorvos and concluded that dichlorvos is a Group C (possible 
human) carcinogen. The basis for that determination is summarized 
below.
    (a) Mouse study. Dichlorvos was administered by gavage to B6C3F1 
mice (60/sex/group) for 103 weeks (5 days/week) using corn oil as the 
vehicle (Ref. 2). Doses were 0, 10, or 20 mg/kg/day for male mice and 
0, 20, or 40 mg/kg/day for females. Administration of dichlorvos to 
female mice was associated with a statistically significant dose-
related trend and statistically significant increase in squamous cell 
forestomach papillomas and combined squamous cell forestomach 
papillomas and carcinomas at the high-dose. The forestomach tumors were 
outside the historical control range. In male mice, an increase in 
squamous cell forestomach papillomas was associated with a significant 
dose-related trend, but was not statistically significant by pairwise 
comparison at either dose level. No other tumor types were identified 
in this study. No malignant squamous cell tumors were found in the 
historical controls.
    (b) Rat study. Dichlorvos was administered, with corn oil as the 
vehicle, by gavage to F344 rats (60/sex/group) for 103 weeks (five 
days/week) (Ref. 3). The dosages were 0, 4, or 8 mg/kg/day. The study 
resulted in a statistically-significant increase in mononuclear cell 
leukemia in males by pairwise comparison at both dosage levels. The 
increase in leukemia also exhibited a statistically significant 
positive dose-related trend. There was an increased incidence of lung 
adenomas in high-dose male rats which was significant only for a dose-
related trend. In addition, dichlorvos administration was associated 
with a statistically significant increased incidence of mammary gland 
adenomas and all mammary gland tumors at the low-dose only (by pairwise 
comparison) in rats. However, the incidence of lung adenomas and 
mammary gland tumors were within the historical control range.
    (c) Reexamination of cancer classification. The FIFRA Scientific 
Advisory Panel (SAP) reviewed the CPRC's Group B2 cancer classification 
and concluded that dichlorvos should be classified as a Group C 
(possible human) carcinogen since: (1) only benign tumors were induced 
by dichlorvos; (2) they were not dose-related; and (3) dichlorvos was 
not mutagenic in in vivo assays (although it was mutagenic in several 
in vitro test systems with and without metabolic activation) (Ref. 4).

[[Page 50342]]

    The CPRC met for a second time on September 29, 1987, to examine 
the issues raised by the SAP with respect to the classification of the 
carcinogenicity of dichlorvos (Ref. 5). Upon reconsideration, the 
Committee concluded that the results of the NTP studies indicate that 
dichlorvos demonstrates sufficient evidence of carcinogenicity in the 
male rat and female mouse to confirm the initial classification of 
dichlorvos as a Group B2 carcinogen.
    The committee concluded that ``the results of the NTP bioassays 
indicate that DDVP demonstrates sufficient evidence of carcinogenicity 
in the male rat and in the female mouse since: (1) A dose-response 
relationship of statistical significance was seen for pancreatic 
adenomas (which have the potential to progress towards malignancy) and 
mononuclear cell leukemia in male rats, (2) a dose-response 
relationship of statistical significance was seen in the female mouse 
for forestomach squamous cell papillomas which have the potential to 
progress to carcinomas, (3) the presence of some forestomach carcinomas 
(which are rare) was seen in the female mouse, (4) a significant 
positive trend was seen for forestomach papillomas in male mice at a 
dose that did not achieve an MTD, (5) supporting evidence provided by a 
statistically significant increase in mammary tumors at the low dose in 
the female rat which was associated with a significant trend, and (6) 
mutagenicity data was available indicating that DDVP is positive for 
mutagenicity in vitro in bacterial and mammalian cells both with and 
without metabolic activation. The Committee, thereby, confirmed their 
initial classification of DDVP as a B2 oncogen.''
    The CPRC had a third meeting on June 2, 1988, to review the 
conclusions of an April 1988 meeting of NTP Panel of Experts on the 
carcinogenic classification of dichlorvos (Ref. 6). Scientists at NTP 
had resectioned the pancreas of all test groups in the rat bioassay. 
The additional sectioning of pancreata resulted in an increased number 
of tumors in the control animals, thus diminishing the statistical 
significance of this lesion. Based on this finding, the NTP scientists 
concluded that the evidence for carcinogenicity in male rats should be 
downgraded from clear evidence to some evidence. The CPRC considered 
the NTP's information and concluded that dichlorvos should remain 
classified as a Group B2 carcinogen, because: (1) The incidence of 
mononuclear cell leukemia in dichlorvos treated F344 rats was 
treatment-related; (2) although the results of longitudinal sectioning 
of the pancreas diminished the significance of the pancreatic acinar 
adenomas in male rats, the incidence of animals with multiple adenomas 
was still increased with dichlorvos treatment; and (3) dichlorvos is a 
direct acting mutagen. The Committee considered this as an interim 
classification until the following additional data had been reviewed: 
(1) the results of a Japanese study in which dichlorvos was 
administered in drinking water to Fischer 344 rats and B6C3F1 mice; (2) 
additional data on a chronic rat inhalation study; (3) additional in 
vivo mutagenicity data, and (4) additional historical control 
information on pancreatic acinar adenomas.
    The CPRC met for a fourth time on July 19, 1989, the conclusions of 
which serve as the basis for the cancer hazard assessment in this 
proposed determination (Ref. 7). The purpose of this meeting was to 
reconsider the NTP rat study in light of the recent NTP Panel of 
Experts report, evaluate new oncogenicity studies with DDVP 
administered by inhalation or in drinking water and consider other 
ancillary information.
    As mentioned earlier, the NTP reexamined the pancreata of male and 
female rats using longitudinal sections which diminished the 
statistical significance of this lesion. The NTP analysis of the 
combined data indicated a statistically significant difference between 
the treated and control groups with a positive dose-related trend using 
the logistic regression analysis. However, EPA scientists concluded 
that the increase in pancreatic acinar tumors was neither significant 
in the Fischer Exact test for pairwise comparison, nor positive in the 
Cochran-Armitage test for dose-related trend, which are typically used 
for testing dose groups having no survival disparities. The incidence 
of animals with multiple pancreatic adenomas was still increased with 
dichlorvos treatment and outside of the historical control range.
    The Committee also reevaluated an inhalation oncogenicity study in 
which 50 CFE rats/sex/dose were exposed to concentrations of 0.05, 0.5 
or 5.0 mg/m3 of technical dichlorvos 23 hours per day for 2 years. 
This study was reviewed for the dichlorvos Registration Standard and 
the Agency considered the study inadequate for evaluating the 
carcinogenicity of the chemical. The study was upgraded after the 
individual animal data were submitted to the Agency. Agency scientists 
have concluded that administration of dichlorvos did not alter the 
tumor incidence in this study.
    In addition to the Japanese drinking water study in Fischer 344 
rats, Amvac Chemical Corporation submitted a study to the Agency in 
March 1989, using B6C3F1 mice which was also conducted in Japan. In 
both studies, dichlorvos was administered in drinking water for 2 
years. The CPRC considered both studies to be deficient in conduct and 
reporting, including incomplete histopathologic evaluation, absence of 
water consumption data, and failure to include individual animal data 
in the final report. As a result of these deficiencies, the studies are 
not amenable to statistical analyses. However, the studies are useful 
in identifying a qualitative trend in that dichlorvos treatment induced 
some tumors similar to those induced in the oral gavage studies. In the 
rat study, there appeared to be an increased incidence of mononuclear 
cell and lymphocytic leukemia in treated males, as well as mammary 
gland fibroadenomas in females. In the mouse study, there appeared to 
be an increased incidence of fibrous histiocytomas and thymomas in 
males.
    The Committee agreed, based upon the available information to 
reclassify dichlorvos as a Group C carcinogen, in accordance with the 
Agency's Guidelines for Carcinogenic Risk Assessment. This downgrading 
from the previous classification as Group B2 was due to: (1) Erosion of 
the evidence on the pancreatic acinar adenomas in male rats; (2) 
upgrading and consideration of the negative inhalation study in CFE 
rats; and (3) questions regarding the biological significance of the 
primary tumors in the NTP studies, i.e., leukemia in rats (variable 
tumors in historical controls) and forestomach tumors in mice and its 
relevance to man.
    ii. Weight-of-the-evidence for carcinogenicity. In its most recent 
evaluation, the fourth cancer peer review, the CPRC considered the 
weight-of-the-evidence and concluded that dichlorvos should be 
classified as a Group C (possible human) carcinogen based on inadequate 
human data and limited data from animal bioassays. The Group C 
classification is supported by the following points:
    (a) In B6C3F1 mice, dichlorvos induced a statistically significant 
increase in forestomach squamous cell papillomas and combined 
forestomach squamous cell carcinomas and papillomas in high-dose 
females. This tumor-type (squamous cell papillomas) was also increased 
in high-dose males but was significant only for a positive dose-related 
trend.

[[Page 50343]]

    (b) In Fischer 344 rats, dichlorvos was associated with a 
statistically significant increase, with a positive dose-related trend, 
in leukemia (of all sites and types) in males at both dosage levels. 
This evidence is supported by the results of the transplantable rat 
mononuclear cell leukemia model. The treatment was also associated with 
a numerical (not statistically significant) increase in pancreatic 
acinar adenomas in males. The incidence of animals with multiple 
pancreatic acinar adenomas was also increased.
    (c) The Group C classification is further supported by studies 
indicating that dichlorvos is a direct acting gene mutagen in bacteria, 
fungi and mammalian cells in vitro, and suggesting in vivo mutagenic 
activity. (Refs. 8-17). Dichloroacetaldehye, a product of hydrolytic or 
oxidative cleavage of dichlorvos, has also been reported to be 
mutagenic in the scientific literature (Ref. 18). Additionally, 
dichlorvos is structurally similar to known chemical mutagens/
carcinogens (i.e., tetrachlorvinphos and phosphamidon).
    iii. Dose-response assessment. The CPRC concluded that a 
quantitative estimate of the carcinogenic potency should be performed 
for dichlorvos. Cancer potency (or Q1*) is a quantitative estimate 
of the relationship between exposure to increasing doses of a chemical 
and the chemical's ability to induce tumors (i.e., increased number of 
tumors per unit dose). Because most animal studies do not include a 
sample size large enough to detect carcinogenic responses at low doses 
comparable to environmental exposures, the Agency normally estimates 
the cancer potency of a chemical by extrapolating from responses in 
high-dose animal experiments.
    Several mathematical models have been developed to estimate the 
cancer potency. In the absence of information demonstrating a more 
appropriate model, the Agency generally uses the linearized multi-stage 
model to extrapolate from effects seen at high-doses in laboratory 
studies to predict tumor response at low-doses. This model is based on 
the biological theory that a single exposure to a carcinogen can 
initiate an irreversible series of transformations in a single cell 
that will eventually lead to a tumor. In addition, the linearized 
multi-stage model assumes that the probability of each transformation 
is linearly related to the degree of exposure (i.e., a threshold does 
not exist for carcinogenicity).
    Using this model, the Agency estimated the cancer potency 
(Q1*) for dichlorvos based on the tumor incidence data in female 
mice and male rats in the NTP studies. The cancer potency in human 
equivalents is 1.22 x 10-1 (mg/kg/day)-1, which is the 
geometric mean of the Q1* for female mouse forestomach tumors and 
the Q1* for leukemia in male rats (Ref. 19). The Q1* 
represents the 95 percent upper confidence limit of tumor induction 
likely to occur from a unit-dose.
    The CPRC (fourth cancer peer review) also recommended not to 
quantify the cancer risk by a low-dose extrapolation model for the 
inhalation route of exposure. The primary basis for this recommendation 
was the upgrading of a 2-year inhalation study in rats which did not 
result in an increased tumor incidence. The recommendation was based on 
the following considerations: The quality of the oral cancer data, the 
route specificity of the target organs, the reliability and accuracy in 
estimating the target-dose and the unlikelihood that exposure via the 
inhalation route would lead to the formation of a reactive metabolite.
    In addition, the OPP Reference Dose Committee concluded that 
extrapolating the results from the oral gavage studies to the dermal 
route of exposure is not appropriate for dichlorvos (Ref. 20). This 
decision was based on the following considerations: (1) There was no 
dose-response relationship in the leukemia observed in male Fisher 344 
rats; (2) the tumors observed in female B6C3F1 mice were contact site 
tumors, the relevance of which to humans is unknown, and the incidence 
of which, at all dose levels, including the concurrent controls, was 
outside the National Toxicology Program's control range; (3) the 
dynamics of absorption, distribution, metabolism and excretion do not 
favor retention of the chemical in animal tissues and makes it 
difficult to determine accurately the concentration at the target site; 
and (4) it is not expected that topically applied doses would reach the 
target organ(s) in sufficient quantity to produce a carcinogenic 
response or would be sufficient to alkylate macromolecules in the 
target tissues to produce contact site tumors. Therefore, extrapolation 
from oral data to dermal or inhalation routes is not appropriate, for 
estimation of excess individual cancer risk, for exposure to 
dichlorvos.
    2. Cholinesterase inhibition. Cholinesterase (ChE) refers to a 
family of enzymes that are essential to the normal functioning of the 
nervous system. These enzymes are necessary for the transmission of 
nerve impulses. Inhibition of ChE activity can result in a number of 
cholinergic signs and symptoms in humans, depending on the rate and 
magnitude of exposure, including: Headaches, dizziness, nausea, 
vomiting, diarrhea and increased urination, blurred vision, pinpoint 
pupils, increased salivation, labored breathing, muscle paralysis, slow 
heart rate, respiratory depression, convulsions, coma and even death. 
These enzymes have been identified in nearly every tissue of the body; 
however, ChE activity is usually measured in blood plasma and red blood 
cells in humans, while ChE levels in laboratory animals are measured in 
plasma, red blood cells as well as brain tissue.
    Organophosphate pesticides, such as dichlorvos, are known to 
inhibit ChE activity and some cause delayed neurotoxic effects. EPA has 
evaluated the available information and concluded that dichlorvos is a 
potent ChE inhibitor. This determination is based on toxicological data 
using laboratory animals, human poisoning incidents, and limited human 
toxicity information, which are discussed below.
    i. Laboratory data. Acute, subchronic and chronic laboratory 
studies using experimental animals have shown dichlorvos to be a potent 
ChE inhibitor, significantly reducing blood plasma, red blood cell and 
brain ChE. ChE inhibition has been demonstrated in several mammalian 
species following oral, inhalation, and dermal administration of 
dichlorvos. Only the primary studies selected for use in assessing risk 
from short-term, intermediate, and long-term exposures are discussed 
below.
    (a) Acute toxicity data. Acute neurotoxicity data are limited in 
comparison to available subchronic and chronic data, but are more 
relevant for assessing risk from single and short-term repeated 
exposure scenarios. Acute neurotoxicity studies have been conducted in 
both hens and rats. An acute neurotoxicity study in rats evaluated the 
neurobehavioral signs and the neuropathological effects following 
single exposures, but did not measure ChE inhibition (Ref. 21). Groups 
of 12 male and female Sprague-Dawley rats were administered single oral 
doses of 0, 0.5, 35 or 70 mg/kg/day by gavage. At the mid- and high-
doses, administration of dichlorvos resulted in a variety of 
neurological and physiological changes (e.g., alterations in posture, 
mobility and gait, reduced or absent forelimb/hindlimb grasp, tremors). 
Most of these changes were observed about 15 minutes after compound 
administration, while no toxicity was apparent for the survivors (there 
were several deaths at the high-dose) 7 days following administration 
of dichlorvos at all dose 

[[Page 50344]]
levels. Based on the study results, the NOEL for signs associated with 
ChE inhibition was established at 0.5 mg/kg/day.
    An acute delayed neurotoxicity study in hens resulted in 
cholinergic signs of ChE inhibition and neuropathic effects (Ref. 22). 
Ten birds were administered a single dose of 16.5 mg/kg/day by oral 
intubation. The test birds were given another oral dose at 21 days and 
observed for an additional 21 days. Dichlorvos-treated birds 
demonstrated signs of ChE inhibition shortly after dosing, including: 
lethargy and depression, incoordination, limb weakness, wing drop, and 
reduced reaction to external stimulation. The birds were asymptomatic 
by day 3 after dosing. Administration of dichlorvos did not produce 
overt signs of acute delayed neurotoxicity, but neuropathic effects 
(peripheral nerve lesions which are associated with paralysis) did 
occur in one hen. A NOEL was not shown for this effect in this one dose 
study.
    Additional information about short-term exposure is provided by a 
range-finding study in which dogs (one male and one female for each 
dose) were administered dichlorvos by capsule for 2 weeks at the 
following doses: 0, 0.1, 1.0, 5.0, 10, 15, 30, or 60 mg/kg/day (Ref. 
23). Plasma and red blood cell ChE levels were decreased in the 1.0 mg/
kg/day group and above as early as 6 days after dosing. The degree of 
ChE inhibition increased with dose. During the first week following 
dosing, severe cholinergic signs were observed in animals at 30 and 60 
mg/kg/day and death occurred at these doses during the second week of 
dosing. However, this study is not appropriate for short-term risk 
assessment because only a limited number of animals were treated at 
each dose and dichlorvos was administered repeatedly. This study 
indicates that short-term exposure to dichlorvos at low levels produces 
ChE inhibition in plasma, red blood cells and brain tissue, and 
contributes to the overall weight-of-the-evidence.
    (b) Subchronic toxicity data. A study was performed in rats 
providing ChE inhibition data following subchronic exposure to 
dichlorvos (Ref. 24). Groups of 10 male and 10 female rats were 
administered doses of 0, 0.1, 1.5 or 15 mg/kg/day by oral gavage for 13 
weeks (5 days/week). Observations recorded approximately 30 to 60 
minutes post-dose included salivation in 7 males and 4 females treated 
with 15 mg/kg/day. Urine stains were also seen in 7 males and 5 females 
at this dose. These observations were seen on certain days during weeks 
6 through 12 for males and 8 through 12 for females. At week 7, plasma 
ChE activity was significantly reduced in mid- and high-dose male and 
high-dose female rats when compared to the controls. Mid- and high-dose 
male and female rats also demonstrated significantly reduced red blood 
cell (RBC) ChE activity when compared to the controls at 7 weeks. At 
the 14-week interval, plasma ChE activity was significantly reduced in 
high-dose males and females, while RBC activity was significantly lower 
than controls in mid- and high-dose animals. Red blood cell ChE 
activity was also reduced in low-dose (0.1 mg/kg/day) females at 14 
weeks; however, the RBC ChE inhibition was not considered biologically 
significant since it was less than 10 percent below ChE activity in 
control animals. Brain ChE activity in high-dose female rats was 49 
percent lower than in control females and was statistically 
significant, while brain ChE activity in high-dose males was reduced 28 
percent below control males but inhibition was not statistically 
significant. The data presented support a NOEL of 0.1 mg/kg/day based 
on plasma and red blood cell ChE inhibition at doses of 1.5 mg/kg/day 
and above.
    An additional subchronic study in rats evaluated neurobehavioral 
signs, neuropathological effects, and also measured ChE activity (Ref. 
25). Dichlorvos was administered by oral gavage to male and female rats 
at doses of 0, 0.1, 7.5, or 15 mg/kg/day (15 animals/sex/dose) for 90 
days. There were no significant differences between the control and 
treated animals with respect to the functional observational battery or 
locomotor activity evaluations, nor were any neuropathological lesions 
attributable to dichlorvos. However, administration of dichlorvos was 
accompanied by cholinergic signs (tremors, salivation, exophthalmos, 
lacrimation) approximately 15 minutes after dosing in the high-dose 
animals and, to a lesser extent, in the mid-dose animals. In general, 
cholinergic signs occurred during the first dosing week in high-dose 
animals and during the third dosing week in mid-dose animals and 
persisted to study termination in both groups. Plasma ChE inhibition 
was statistically significant at all time periods measured; however, 
RBC ChE inhibition was only statistically significant for high-dose 
males at week 3. ChE levels in RBC were reduced 23, 12, and 18 percent 
in the mid-dose males and 35, 8, and 11 percent in the high-dose males 
compared to controls during weeks 3, 7, and 13, respectively. In 
females, RBC ChE inhibition of 13, 38, and 33 percent at the mid-dose, 
and of 4, 42, and 35 percent at the high-dose were noted during weeks 
3, 7, and 13, respectively. Brain stem and brain cortex ChE activity 
were also reduced from 11 to 12 percent in low-dose animals and from 10 
to 16 percent in high-dose rats as compared to controls. Inhibition of 
brain stem ChE activity was statistically significant in high-dose 
males only, while in the cerebral cortex ChE was significantly reduced 
for animals in the mid- and high-dose groups. The NOEL from this study 
was 0.1 mg/kg/day based on ChE inhibition (plasma, RBC, brain) and 
cholinergic signs occurring at 7.5 mg/kg/day.
    A developmental toxicity study in New Zealand white rabbits 
produced signs of ChE inhibition at similar dose levels as the 
subchronic rat studies (Ref. 26). Groups of 16 pregnant females were 
administered doses of 0, 0.1, 2.5, or 7.0 mg/kg/day by oral gavage on 
gestation days 7 through 19, inclusive. The doses were selected based 
on the results of a range-finding study conducted in the same strain of 
pregnant rabbits at dose levels of 0, 0.1, 1.0, 2.5, 5.0 or 10 mg/kg/
day (8 per group, except for 7 in the 2.5 mg/kg/day group) in which 
there were statistically significant reductions in maternal plasma and 
RBC ChE activity in a dose-related manner at all doses except 0.1 mg/
kg/day. Profound treatment-related maternal mortality (5/8 died) and 
cholinergic signs occurred at 10 mg/kg/day. In the definitive 
developmental toxicity study, mortality was observed at 2.5 mg/kg/day 
(13 percent) and 7.0 mg/kg/day (25 percent). ChE inhibition was not 
measured; however, apparent anticholinesterase-related signs and 
symptoms were observed at the high-dose, including ataxia, prone 
positioning, tremors, excitation, salivation, diarrhea and difficulty 
in breathing. Based on the range-finding and definitive study results, 
the maternal toxicity NOEL and Lowest Effect Level (LEL) were 
demonstrated at 0.1 and 2.5 mg/kg/day, respectively.
    An inhalation developmental toxicity study in rabbits produced 
findings similar to those of the oral developmental toxicity study 
(Ref. 27). Groups of 20 female Dutch rabbits were exposed to 0, 0.25, 
1.25, or 6.25 g/L of dichlorvos for 23 hours per day, from day 
1 of mating to gestation day 28. No cholinergic signs were noted at 0, 
0.25, or 1.25 g/L, but severe toxicity and mortality occurred 
after the 6th day of exposure to 6.25 g/L. Cholinergic signs 
observed included anorexia, lethargy, muscular tremors, mucous nasal 
discharge and diarrhea. Sixteen of the 20 does at the high-dose died or 
were killed because of intoxication. There 

[[Page 50345]]
were statistically significant reductions in plasma, RBC and brain ChE 
activity at 1.25 and 6.25 g/L, while at 0.25 g/L ChE 
activity was depressed less than 15 percent. The NOEL for this study is 
0.25 g/L based on ChE inhibition in plasma, RBC and brain 
tissue. The NOEL of 0.25 g/L corresponds to approximately 0.14 
mg/kg/day. In converting from g/L to mg/kg/day, EPA assumed 
that 100 percent of the dichlorvos vapor is absorbed by inhalation and 
also that the rabbit breathing rate is constant over time.
    Additional information on neuropathological effects can be drawn 
from a 28-day delayed neurotoxicity study in hens, from which 
preliminary results were submitted to the Agency (Ref. 28). This study 
was required based on the results of the acute study in hens discussed 
above. Groups of 21 hens were administered dichlorvos orally at doses 
of 0, 0.3, 1.0, or 3.0 mg/kg/day for 28 days. These data suggest that 
significant axonal degeneration in the spinal cord occurred following 
oral administration of 1 and 3 mg/kg/day, while at 0.3 mg/kg/day only 
minor effects were noted. While such findings must be regarded as 
preliminary, they should be regarded as potentially serious, since such 
lesions represent an irreversible and relatively serious effect. In 
addition, this report notes that significant (34 to 63 percent) brain 
ChE inhibition was seen at 1 and 3 mg/kg/day. The final report was 
submitted to the Agency and is currently under review.
    (c) Chronic toxicity data. Both oral and inhalation toxicity data 
demonstrate that long-term exposure to dichlorvos results in plasma, 
RBC, and brain ChE inhibition. In a chronic rat inhalation study, 
groups of 50 male and 50 female CFE rats per dose level were exposed to 
0, 0.05, 0.48, or 4.7 mg/m3 of dichlorvos for 2 years (Ref. 29). 
There was a statistically significant decrease in ChE activity in 
plasma, red blood cells, and brain in the mid- and high-dose groups 
(76, 72, 90 percent and 83, 68, 90 percent of control activity in mid-
dose males and females; and 38, 4, 21 and 22, 5, 16 percent of control 
activity in high-dose males and females, respectively). Red blood cell 
ChE was reduced to 88 percent of control activity in females dosed at 
0.05 mg/m3, but this decrease was not statistically significant. 
The NOEL was established at 0.05 mg/m3 based on ChE inhibition in 
plasma, red blood cells and brain tissue. The concentration of 0.05 mg/
m3 corresponds to approximately 0.055 mg/kg/day, assuming a 
constant breathing rate in rats and 100 percent absorption of 
dichlorvos vapor.
    Groups of 4 male and 4 female dogs were administered dichlorvos by 
capsule 7 days per week at doses of 0, 0.05 (0.1 for the first 3 weeks 
of study), 1.0 or 3.0 mg/kg/day for 1 year (Ref. 30). Plasma ChE was 
inhibited (21.1 to 66.6 percent) in males and females in the 0.1, 1.0, 
and 3.0 mg/kg/day groups during week 2. The low-dose was consequently 
reduced to 0.05 mg/kg/day on day 22 due to the plasma ChE inhibition 
(26 percent in females) noted after 12 days of dichlorvos 
administration. Red blood cell ChE was only slightly decreased (less 
than 2 percent) in the 0.1 mg/kg/day group at week 2, while animals in 
the 1.0 and 3.0 mg/kg/day groups exhibited RBC ChE inhibition of 33 to 
75 percent. Statistical analyses were not conducted prior to week 13. 
Statistically significant depression in plasma and RBC ChE occurred at 
week 13 in males and females in the 1.0 and 3.0 mg/kg/day groups. In 
addition, brain ChE was significantly reduced in males and females in 
the high-dose group and in the males of the mid-dose group at 
termination. Brain ChE activity was inhibited approximately 22 percent 
in males in the 1.0 mg/kg/day group and 47 percent and 29 percent, 
respectively, in males and females in the 3.0 mg/kg/day group compared 
to controls. Study results correspond to a NOEL of 0.05 mg/kg/day, 
based on plasma, RBC, and brain ChE inhibition.
    A two-generation reproductive study was conducted in which Sprague-
Dawley rats were exposed via the drinking water to dichlorvos at 
concentrations of 0, 5, 20, or 80 ppm (males - 0.5, 1.9 or 7.2 mg/kg/
day; females - 0.6, 2.3, or 8.3 mg/kg/day) (Ref. 31). ChE assays 
(plasma, RBC and brain) were performed on males and females of both the 
F0 and F1 generations at terminal sacrifice. The data 
indicate that RBC ChE was inhibited in both males and females at all 
doses and in a dose-related manner. At the low-dose, RBC ChE activity 
was decreased 7 to 14 percent in males and 17 to 23 percent in females. 
RBC ChE inhibition was statistically significant for both males and 
females at all dose levels, except for the F0 males at 0.5 mg/kg/
day (7 percent inhibition). Plasma ChE inhibition was statistically 
significant for both males and females at the mid- and high-dose 
levels. The plasma ChE inhibition for F1 males at the low-dose 
(0.5 mg/kg/day) was also statistically significant (15 percent). In 
addition, brain ChE activity was inhibited in males and females of both 
generations at all dose levels. Statistically significant reductions 
occurred only at the mid- and high-doses. The study results establish a 
NOEL of less than 5 ppm for RBC and plasma ChE inhibition (males - 0.5 
mg/kg/day; females - 0.6 mg/kg/day).
    ii. Human data--(a) Toxicity data. EPA reviewed several studies in 
the scientific literature that measured ChE inhibition in humans 
following exposure to dichlorvos (Ref. 32). The studies only covered a 
few exposure scenarios, including occupant exposure to resin pest 
strips and workers reentering treated warehouses. There were few, if 
any, adverse effects following most resin pest strip exposures. Only 
one headache was reported which may have been associated with 
dichlorvos exposure. Usually only plasma ChE inhibition was 
statistically significant with statistically significant RBC ChE 
inhibition occurring only rarely. However, interpretation of the study 
results is difficult because of methodological problems and utilization 
of outdated methods for measuring ChE activity. In addition, the 
studies only examined small numbers (less than 20) in any one test 
group.
    (b) Poisoning incidents. Exposure to dichlorvos has resulted in 
poisoning incidents. Although the number of incidents is not large, it 
is sufficient to be of concern and can be viewed as confirmatory of the 
inadequate MOEs. Several sources are available indicating that exposure 
to dichlorvos has resulted in poisoning incidents. As part of the 
assessment for the dichlorvos Registration Standard, the Agency 
reviewed the Pesticide Incident Monitoring System (PIMS) data base 
covering a period from 1964 to 1980 (Ref. 33). Only 182 of the 598 
dichlorvos incidents could be identified as involving products that 
contained dichlorvos as the sole active ingredient. A majority (147) of 
these 182 reports involve humans and domestic animals in the home 
environment, with 114 incidents resulting from ingestion and 
application of dichlorvos. One death was reported. Ingestion incidents 
usually involved children chewing flea collars and resin pest strips. 
Most of the application incidents involved situations where the 
existing label precautions were not followed. Of the remaining 416 
incidents in which dichlorvos was cited in combination with other 
chemicals, there were 9 human fatalities reported. EPA's Incident Data 
System, in operation since June 1992, does not contain any human 
poisoning incidents attributed to dichlorvos exposure.
    Case reports from the California Pesticide Illness Surveillance 
Program are available for dichlorvos from 1982 to 

[[Page 50346]]
1990 (Ref. 34). A total of 78 poisoning incidents were attributed to 
dichlorvos exposure. Sixty were classified as systemic poisonings, 12 
caused eye problems and the remaining 6 resulted in skin irritation. 
The majority of these incidents involved active ingredients in addition 
to dichlorvos. In addition, poisonings were attributed to both 
occupational and residential exposures.
    Finally, the American Association of Poison Control Centers (AAPCC) 
reported that for the years 1985 - 1992 there were 21,006 exposures of 
all kinds for dichlorvos alone and 21,844 exposures for dichlorvos 
alone and in combination with other active ingredients (Refs. 35 and 
36). Of the 21,006 exposures, 2,671 individuals were treated and 
released and 350 were hospitalized. There were 259 occupational cases 
involving dichlorvos alone and an additional 57 occupational cases 
involving dichlorvos in a mixture with another pesticide. Of the 259 
cases, 99 workers were treated and released and 13 were hospitalized. 
Only one of the occupational cases was considered life-threatening, 
while 10 of the non-occupational cases were so categorized.
    iii. Animal health and safety data. EPA reviewed 3 animal heath and 
safety data studies which examined the effect on dogs and cats of 
wearing registered cat and dog flea collar products. These studies 
provide strong evidence that dichlorvos, used in combination with other 
active ingredients, has a significant effect on reducing ChE activity 
in dogs. Although the ChE inhibition could result in part from another 
pesticide active ingredient, the Agency has no data to disprove that 
ChE depression is a result of dichlorvos exposure (Refs. 37-39).
    In the first study, groups of 3 male and 3 female dogs per group 
served either as controls, or wore 1, 3, or 5 collars containing 9.3 
percent dichlorvos and 4.2 percent chlorpyrifos. In the 1-collar group, 
5 out of 6 dogs averaged RBC ChE inhibition (statistically significant) 
of 20 to 30 percent during the period day 3 through week 2. Plasma ChE 
inhibition was even greater, averaging 65.6 percent as compared to pre-
test values during the perod day 3 through week 4 in 5 animals.
    Another study was conducted in which 3 male and 3 female dogs were 
each assigned to a control group, a group wearing a collar containing 
7.8 percent dichlorvos and 4.34 percent chlorpyrifos, a group wearing a 
collar containing 8.87 percent dichlorvos and 4.44 percent 
chlorpyrifos, and a group wearing an 8 percent chlorpyrifos collar. The 
mean percentage plasma ChE activity was significantly different from 
that of the control group among dogs wearing collars containing 
dichlorvos from day 7 through week 6. Differences in RBC ChE activity 
were not statistically significant. More specifically, in animals 
wearing the product containing 7.8 percent dichlorvos, plasma and RBC 
ChE activity were inhibited 49 percent and 19 percent as compared to 
pre-test values. This study demonstrates that plasma and RBC ChE 
inhibition also can occur from use of these products.
    In the last study, ChE activity was measured in dogs over a 98-day 
period, during which time the dogs wore a placebo collar or 1, 3, or 5 
collars containing a mixture of 7 percent dichlorvos and 9 percent 
propoxur. There was a considerable drop in plasma ChE activity in the 
first 7 days of exposure (in 1-collar dogs by 30 percent, in 3-collar 
dogs by 57 percent, and in 5-collar dogs by about 63 percent). In the 
1-collar exposure group there was essentially complete plasma ChE 
recovery by day 56; however, in the 3 and 5-collar females there was 
still significant plasma ChE inhibition (35 and 43 percent, 
respectively) on day 98. There was no evidence of any RBC ChE 
inhibition in any group at any time during this study.
    iv. Dose-response assessment. Results from acute, subchronic, and 
chronic toxicity studies have shown dichlorvos to be a potent inhibitor 
of plasma, RBC, and brain ChE. In most instances, inhibition of brain 
ChE occurred at similar doses as plasma and RBC ChE inhibition. 
Moreover, cholinergic signs were usually associated with actual 
measurements of ChE inhibition. Neurotoxicity data indicate a 
correlation between ChE inhibition and neuropathological effects. 
Overall, the various indicators of ChE inhibition (i.e., altered ChE 
activity in plasma, RBC, brain, neuropathological effects or 
cholinergic signs) are observed within a relatively narrow dose range. 
In addition, the effects indicative of ChE inhibition observed in 
laboratory studies are further validated by actual human poisonings 
accompanied by cholinergic signs.
    Dose-response data for ChE inhibition and/or cholinergic signs are 
available for acute, subchronic, and chronic toxicity studies using 
rats, rabbits, dogs and hens as the test species. EPA selected the 
lowest NOELs from acute, subchronic, and chronic toxicity studies to 
calculate MOEs of exposure for individuals exposed to dichlorvos for 
varying durations of time. The NOELs are based on either brain ChE 
inhibition and/or cholinergic signs following administration of 
dichlorvos by the oral and inhalation routes of exposure. Neurotoxicity 
data following dermal administration of dichlorvos are not available.
    (a) Acute/short-term exposure. EPA scientists believe that a NOEL 
of 0.5 mg/kg/day is most suitable for calculating MOEs of exposure for 
acute dietary and short-term occupational or residential (1 to 7 days) 
exposure scenarios. This NOEL is based on the acute neurotoxicity study 
in rats resulting in neurological and physiological changes observed 
shortly after dosing, including alterations in posture, mobility, and 
gait, reduced or absent forelimb/hindlimb grasp, increased time to 
first step, pupillary constriction, tremors, clonic convulsions, 
increased response time, catalepsy, and reduction in body temperature 
at 35 mg/kg/day. ChE activity was not measured in this study. There is 
some uncertainty with this acute NOEL because of the wide gap between 
dose levels (0, 0.5, 35, or 70 mg/kg/day). Since there are no 
intermediate doses between the no effect level of 0.5 mg/kg/day and the 
next level, 35 mg/kg/day, at which a variety of behavior changes were 
seen, it is possible that additional data might result in a slightly 
higher NOEL. However, Agency scientists do not believe that such a new 
acute NOEL would differ greatly from 0.5 mg/kg/day because short-term 
exposure data from other studies yielded similar results.
    (b) Intermediate exposure. EPA selected a NOEL of 0.1 mg/kg/day for 
assessing intermediate occupational and residential exposure (1 week to 
several months) to dichlorvos. This NOEL was derived from examining 
several oral and inhalation toxicity studies. In the subchronic rat 
neurotoxicity study, administration of dichlorvos at 7.5 mg/kg/day 
inhibited plasma, RBC, and brain ChE activity, as well as producing 
cholinergic signs during the third week of dosing. Based on these 
findings, a NOEL was established at 0.1 mg/kg/day. The inhalation 
developmental toxicity study in rabbits demonstrated a NOEL of 0.14 mg/
kg/day (converted from 0.25 g/L) based on statistically 
significant plasma, RBC and brain ChE inhibition occurring at 0.71 mg/
kg/day. A maternal toxicity NOEL of 0.1 mg/kg/day was demonstrated in 
the oral developmental toxicity study in rabbits, based on the results 
of the range-finding and definitive studies. In the range-finding 
study, statistically significant plasma and RBC ChE inhibition occurred 
at all doses except 0.1 mg/kg/day, while cholinergic signs occurred at 
2.5 mg/kg/day and above. ChE inhibition was not measured in the 
definitive study, but 2 

[[Page 50347]]
deaths (13 percent) occurred at 2.5 mg/kg/day. The developmental 
toxicity study results are supported by the 1 year dog study in which 
significant plasma and RBC ChE inhibition occurred as early as 2 weeks 
following administration of 1.0 and 3.0 mg/kg/day. In addition, plasma 
ChE inhibition ranged from 21 to 26 percent in the 0.1 mg/kg/day group 
at 2 weeks. These studies indicate that effects associated with ChE 
inhibition occur at levels slightly higher than 0.1 mg/kg/day. 
Therefore, EPA has determined that the study results support a NOEL of 
0.1 mg/kg/day for calculating margins of exposure for intermediate 
exposure.
    (c) Chronic/long-term exposure. The oral and inhalation toxicity 
studies that EPA has evaluated resulted in comparable NOELs for 
assessing chronic dietary and long-term occupational and/or residential 
exposure (substantial portion of a lifetime). The inhalation study in 
rats demonstrated a NOEL of 0.055 mg/kg/day (converted from 0.05 mg/
m3) based on statistically significant ChE inhibition in plasma, 
RBC, and brain at 0.48 mg/m3. The oral study in dogs resulted in a 
NOEL of 0.05 mg/kg/day, based on statistically significant plasma, RBC, 
and brain ChE inhibition at 1.0 mg/kg/day. EPA rounded the inhalation 
NOEL to 0.05 mg/kg/day for ease in calculating MOEs. In addition, there 
is uncertainty associated with converting from mg/m3 to mg/kg/day 
in the chronic inhalation study.
    3. Adverse liver effects. The PD 1 also cited a concern for adverse 
liver effects resulting from exposure to dichlorvos. A 2-year dog 
feeding study indicated increased liver weight and enlargement of liver 
cells with a NOEL of 0.08 mg/kg/day. EPA recently reevaluated this 
study and downgraded its acceptability from minimum to invalid. The 
study was reclassified because the actual dose ingested by the animals 
cannot be confirmed, due to impurities and decomposition products in 
the test material.
    In addition, the 1 year oral dog study cited above was reviewed for 
the purpose of evaluating the validity of the liver effect concern. No 
liver effects were reported after 1 year of treatment at higher doses 
than the doses in the invalidated 2-year study. Therefore, this 
endpoint is no longer of regulatory concern.

C. Exposure Analysis

    1. Dietary exposure--i. Background. Dietary exposure to a pesticide 
depends on two components: the amount of pesticide residue on a 
commodity and how much of that commodity is consumed. In estimating 
dichlorvos residues on food, EPA relied on a variety of data for 
dichlorvos, including tolerance levels (the legal maximum residue) and 
field trial data (measured residues resulting from actual application 
of dichlorvos). In addition, these estimated residues can be further 
refined by taking into account the effects of processing and cooking on 
treated foods, and by estimating the percent of the crop that is 
treated.
    The Agency currently uses food consumption values derived from a 
USDA survey to estimate dietary exposure to pesticides. The USDA 
conducted a nationwide survey (1977-1978) of the food consumption 
patterns of 30,770 individuals for 3 days. Based on this survey, EPA 
can estimate the dietary exposure and risk for the U.S. population and 
22 subgroups of the total population using a computer-based tool called 
the Dietary Risk Evaluation System (DRES). DRES multiplies the average 
daily consumption values by residue information for each commodity to 
obtain the total dietary exposure. In the absence of data for residues 
of dichlorvos on crops and an estimate of the percent of the crop 
treated with a pesticide, EPA estimates exposure based on the 
Theoretical Maximum Residue Contribution (TMRC). The TMRC assumes 
residues on crops are present at tolerance levels (the maximum residue 
limit allowed by law) and 100 percent of the crop is treated. When EPA 
has additional data to refine the TMRC, based on residue data and 
estimates of percent of crop treated, the Agency uses this new 
information to calculate the Anticipated Residue Contribution (ARC). 
When available, the ARC is used instead of the TMRC in estimating 
residues.
    Dietary exposure to dichlorvos residues may occur as a result of 
use on a variety of sites. These sites include greenhouse food crops, 
food or feed containers, bulk-stored, bagged or packaged nonperishable 
raw agricultural commodities (RACs) food, and bulk stored, bagged or 
packaged nonperishable processed commodities, commercial food 
processing plants, groceries, eating establishments, livestock (direct 
animal treatment), swine feed (as a dewormer), and food in homes where 
resin pest strips are located.
    Tolerances and FARs exist for residues of dichlorvos in or on raw 
agricultural and processed products and on meat, milk, poultry and 
eggs. As noted in the Registration Standard, even though dichlorvos is 
registered for use in food handling establishments (including food 
processing, food manufacturing and eating establishments), there are no 
FARs for the related uses.
    In estimating dietary exposure for the initiation of Special Review 
in 1988, the Agency did not have sufficient data on actual residue 
levels. Therefore, EPA's dietary exposure estimate at that time was 
based on the assumption that residues were present at tolerance levels 
(40 CFR 180.235). Residues were adjusted based on cooking data on small 
grains and on an estimate of percent of crop treated. At the time of 
the initiation of Special Review, EPA estimated that the average 
consumer in the U.S. population was exposed to 4.2 x 10-2 mg/kg/
day of dichlorvos. This may have been an overestimate of chronic 
exposure because tolerance level residues were assumed. However, 
limited data available at that time suggested that some residues were 
at or above tolerance levels (nonperishable stored foods). In addition, 
exposure could have been underestimated because, in the absence of a 
FAR for food handling uses, the exposure estimate did not consider 
residues from food handling uses, or any degradation resulting from two 
related pesticides, naled and trichlorfon.
    Amvac recently notified the Agency (Ref. 40) that it is not 
supporting the reregistration of greenhouse food and nonfood uses and 
that it requests voluntary deletion of those uses. Therefore, some 
exposure may be eliminated as a result of these voluntary deletions, or 
due to cancellation of uses related to the revocation of the FAR for 
packaged or bagged nonperishable processed food. However, since these 
actions have not occurred, EPA will continue to consider these residues 
for this proposed determination.
    ii. Naled and trichlorfon. Naled and trichlorfon degrade to 
dichlorvos through plant metabolism. Three factors will significantly 
affect dietary exposure to dichlorvos from registered uses of naled and 
trichlorfon; these include, the preharvest interval (PHI), the 
condition and length of storage, and cooking and processing. Naled is 
metabolized to dichlorvos by plants. Plant metabolism studies show that 
dichlorvos residues are formed 1 to 3 days after treatment with naled 
and trichlorfon; however, dichlorvos residues are less than the limit 
of detection (0.01 to 0.05 ppm) 7 days after treatment. In general, 
registered uses of naled have PHIs of less than 7 days, while 
trichlorfon registrations have PHIs greater than 7 days. Because of the 
short PHIs for naled products, measurable residues of dichlorvos may be 
present in the U.S. diet from naled treated food. EPA does not expect 
measurable residues from 

[[Page 50348]]
trichlorfon because of the longer PHIs. As a result, the dietary 
exposure assessment for dichlorvos includes residues of dichlorvos 
resulting from the application of naled but not from trichlorfon. 
Neither naled or trichlorfon, themselves, have carcinogenic potential 
in humans as concluded by EPA (Refs. 41 and 42)
    iii. Data available for determining the ARC. Possible sources of 
data to estimate the levels of residues to which the public is exposed, 
when consuming treated commodities include: Tolerance levels, 
controlled field trials, Food and Drug Administration (FDA) 
surveillance and compliance monitoring data, FDA Total Diet Study data 
(market basket survey based on a random sampling of residues on food in 
grocery stores), USDA pesticide data program, and USDA/FSIS (Food 
Safety Inspection Service) livestock monitoring data. The estimated 
levels of residues can then be adjusted for the effects of processing 
using processing studies, including commercial processing studies, 
washing studies, cooking studies, and residue degradation studies. Of 
these sources, the Agency relied on tolerance levels and field trial 
data (adjusted for the effects of processing and cooking) to estimate 
dietary exposure to dichlorvos. For a variety of reasons, the other 
sources did not provide useful data (Ref. 43).
    (a) Tolerance levels. Tolerance levels are used for an initial 
dietary exposure analysis. Use of tolerance levels typically 
overestimate chronic exposure because tolerance levels are set at a 
level that is not likely to be exceeded when the pesticide is used 
according to the label. Tolerance levels are also used in dietary 
exposure assessments when no other appropriate data are available. In 
the case of dichlorvos, no other data are available which reflect 
currently registered uses on cucumber, lettuce, tomato, and radish, 
and, therefore, tolerance levels are used here to estimate residues on 
these crops.
    (b) Field trials. Data from controlled field trials which reflect 
currently registered uses are not available for most agricultural uses 
of dichlorvos, since these uses are not being supported for 
reregistration. Field trial data are available for mushrooms and figs, 
and data from direct dermal treatments to cattle and poultry are 
discussed in the dichlorvos Registration Standard. Field trial data are 
also available for use on packaged or bagged food, use in food 
manufacturing and processing facilities, and for secondary residues in 
livestock commodities. EPA is including residue estimates for figs (raw 
and dried), even though these tolerances were revoked, because figs may 
be located in warehouses or areas where similar packaged, bagged, or 
bulk commodities are treated.
    (c) Processing and cooking studies. Residues for raw commodities 
can be modified by processing factors to account for changes during 
commercial or other processing and cooking. Processing, cooking and 
decline (half-life) studies were available for cocoa beans, dry pinto 
beans, tomato juice, ground roasted coffee beans, raw hamburger meat, 
raw eggs, and raw whole milk. The resulting cooking factors were used 
to reduce the Agency's estimate of residues for these commodities and 
were translated to other commodities based on similarity of cooking 
time and temperature. Additional cooking studies were available and 
discussed in the Residue Chemistry Chapter of the Registration 
Standard. Half-lives of dichlorvos in various commodities ranged from 0 
to over 1,000 hours. The reduction of dichlorvos in cooking appeared to 
be related to the length of time and temperature used in cooking. 
Residues were adjusted based on these cooking factors to obtain the 
ARC.
    (d) Anticipated residues for dichlorvos--(1) Raw commodities. The 
following registered uses are not being supported for reregistration 
and the Agency does not have residue data reflecting current uses: 
tomatoes, cucumbers, lettuce, and radishes. Therefore, current 
tolerance levels are assumed in the exposure assessment. Amvac has 
requested voluntary deletion of these uses from their labels; however, 
because the deletion of these uses is not final, EPA is including these 
commodities in the exposure assessment. Anticipated residues for raw 
commodities as bulk, packaged, or bagged food are discussed below.
    (2) Meat, milk, poultry and eggs. Residues in livestock tissues, 
including milk and eggs, may result from consumption of dichlorvos 
treated livestock feeds, direct dermal treatments, or from use as a 
drug in swine. Livestock metabolism studies done at exaggerated rates 
in ruminants and poultry have demonstrated that oral ingestion of 
dichlorvos by cattle and poultry will not result in detectable 
residues. This conclusion can be extended to the drug use of dichlorvos 
in swine. Secondary residues in livestock from consumption of treated 
feed are expected to be so low that EPA is estimating these residues as 
zero. Data reflecting direct livestock treatments are discussed in the 
Residue Chemistry Chapter of the Dichlorvos Registration Standard. Data 
from direct dermal studies indicate that detectable residues are not 
expected, except in skin. Residues are non-detectable (<0.01 ppm) in 
cattle tissue and milk, and non-detectable (<0.05 ppm) in poultry 
tissues and eggs. The exposure assessment uses one-half the limit of 
detection in both cases. In the absence of direct dermal studies for 
swine, the Agency estimated the residue on swine to be 0.08 ppm. This 
estimate was based on a study in poultry that approximated the rate for 
direct dermal swine treatment.
    (3) Bulk stored, packaged or bagged commodities, food and feed 
handling uses. The ARCs used in the exposure assessment for packaged, 
bagged or bulk stored food are based on studies submitted by Amvac 
(Ref. 44). Residue data were submitted for many commodities. For those 
commodities where data were not submitted, EPA translated residue data 
from similar commodities. For example, data on dry beans are translated 
to other legumes; data on wheat flour are translated to all flours and 
meals, etc. In addition, residue data were provided for corn and oats 
at various points during processing, and for flour, sugar, dried milk, 
dried eggs, shortening, and baking mix from a treated manufacturing 
facility. Bulk stored commodities are assumed to be uncovered when 
treated. Although pesticide labels state that bulk or unpackaged foods 
should be covered or removed before spraying, it is not possible to 
assess the effect of covering food since the type of material used in 
the cover is not specified and the manner in which food is covered 
would vary considerable. Therefore, food is assumed to be uncovered. 
Since the proportion of commodities stored in bulk vs. packaged/bagged 
is unknown, the ARCs are based on an average of the residues found in 
bulk and packaged/bagged food for any particular commodity.
    The FAR in 40 CFR 185.1900 for packaged or bagged nonperishable 
processed foods and the tolerance in 40 CFR 180.235 for nonperishable 
packaged, bagged or bulk raw food do not refer to specific commodities. 
Therefore, EPA has developed a list of commodities likely to be treated 
with dichlorvos that are covered by tolerances and/or FARs. Because 
these tolerances and FARs were established to cover residues resulting 
from use at different sites (for example, wheat could be treated in its 
raw form in a silo, later as flour, during processing into cake mixes, 
and finally as a stored packaged commodity), cancellation of any one of 
the site-specific uses does not necessarily eliminate the risk of a 

[[Page 50349]]
commodity from dichlorvos treatment. EPA did not combine the residues 
from different sites in creating the ARCs, although the cumulative 
residues from treating a commodity at different sites are considered in 
the estimation of percent of crop treated (see paragraph (e) below).
    Dichlorvos is registered for use in a variety of food handling 
establishments, including: food service establishments (such as 
restaurants and other locations where food is served and grocery 
stores); manufacturing establishments (such as candy plants, spaghetti 
and macaroni plants, bottling plants, and pizza plants); and processing 
establishments (such as meat, poultry and seafood packing plants, 
dairies and dairy product plants, frozen fresh food plants and grain 
mills). EPA has data for estimating residues in manufacturing 
establishments and processing establishments; however, there are no 
data for estimating residues in eating and serving areas of food 
service establishments. EPA did not include residues from this use in 
its exposure assessment. Therefore, to the extent that dichlorvos is 
used in food service establishments, the Agency's exposure assessment 
is an underestimate of potential dichlorvos dietary exposure.
    (4) Use of naled. All naled tolerances in 40 CFR 180.215 were 
evaluated as a potential source of dichlorvos residues. Anticipated 
residues are based on either tolerance levels or field trials. Naled 
and dichlorvos residue estimates were reduced when data were available 
for the effects of washing, cooking, and processing. In addition, wide 
area application of naled in mosquito and fly control use could result 
in residues potentially on all crops in the Agency's Dietary Risk 
Evaluation System. Therefore, EPA included all these crops in its 
estimate of anticipated dichlorvos residues. Although it is possible 
that dichlorvos residues could occur on any raw agricultural commodity 
from this use of naled, it is unlikely that residues would be found on 
all commodities. As a result, this inclusion of residues from all raw 
crops presents a possible source of overestimation of dietary exposure. 
As discussed earlier, EPA does not expect measurable residues from the 
use of trichlorfon because of the longer PHI for trichlorfon than for 
naled.
    (5). Percent of crop treated information. In conducting a chronic 
risk assessment, EPA refines its estimate of dietary exposure based on 
percent of crop treated when such information is available. In the 
absence of this information, EPA assumes that 100 percent of the crop 
is treated. Where a range of percent crop treated values are supplied 
for this analysis, the upper end of that range is assumed (Refs. 45-
47).
    (i) Dichlorvos. Although no quantitative estimates of percent of 
crop treated were given for the agricultural sites of dichlorvos 
(radishes, mushrooms, cucumbers, lettuce, and tomatoes), the Agency 
assumed that less than one percent of these crops has dichlorvos 
residues, because EPA's proprietary data indicates little or no use. 
EPA earlier assumed, in the proposed revocation of the FAR for residues 
of dichlorvos on packaged or bagged nonperishable processed food, that 
the percent of crop treated estimate of 7.5 percent for food processing 
plants should be applied to all sites, and therefore, to all raw and 
processed non-perishable packaged or packaged food. The present 
analysis assumes that the percent of sites treated at various points in 
the processing and distribution channels should be added rather than 
averaged, because, as discussed earlier, cancellation of any one of the 
site-specific uses does not necessarily eliminate the risk of a 
commodity from dichlorvos treatment. EPA now estimates that 20 percent 
of the crop is treated based on the sum of percent of crop treated 
estimates for bulk storage, processing plants, and warehouses.
    (ii) Naled. Naled is used for mosquito and fly abatement in 
municipalities, residential areas, swamps, tidal marshes, and 
woodlands. Naled is also registered for controlling pests on several 
specific agricultural sites. Application of wide area mosquito control 
by air can result in drift or direct treatment to small crop areas or 
margins of large fields. Because the mosquito and fly abatement use is 
applied in agricultural settings without regard to a specific crop, EPA 
has no way of eliminating any crops from its anticipated residue 
estimate. Therefore, EPA is assuming that one percent of all 
agricultural crops may potentially have dichlorvos residues resulting 
from mosquito and fly abatement use. For certain crops which are grown 
in water-filled areas (such as sugarcane) this may be an underestimate. 
However, this one percent is considered an overestimate of percent of 
crop treated across all commodities. For registered uses of naled on 
specific crops, EPA used that specific percent of crop treated data 
instead.
    2. Occupational and residential exposure. Dichlorvos is used in a 
wide variety of situations, involving different application methods and 
equipment; at home, at work and in public areas. Individuals are 
exposed to dichlorvos as professional applicators, and as reentry 
workers. Residents are exposed from applying dichlorvos themselves at 
home and from post application exposure. Individuals can also receive 
post-application exposure at work or in public places. Pet flea collars 
may pose a risk for both the pet and people who come in contact with 
the dog or cat. Depending on the method of application or use, exposure 
to dichlorvos can occur by either the dermal or inhalation route or 
both. Because of the wide variety of uses for dichlorvos it is 
difficult to estimate exposure for every possible situation. Therefore, 
the purpose of this assessment is to estimate exposure in those 
situations thought to have the greatest exposure and potential for the 
greatest risks. The Agency would particularly like comments regarding 
any uses with a significant exposure scenario not described in this 
Notice.
    EPA completed a series of exposure assessments in August 1987 for 
the Registration Standard and PD 1. Many of the exposure assessments 
were based on limited data. Since that time, additional exposure data 
have been submitted to the Agency. These data have been evaluated and 
EPA has determined that revisions to the original assessments are 
appropriate. Based on this analysis, the Agency has revised exposure 
estimates for the following uses: Crack and crevice application; 
application to greenhouses, mushroom houses, dairy barns and milk 
rooms. In addition, new data are available which allow the Agency to 
estimate exposure from use of household aerosol and total release 
fogger products. New exposure estimates have been developed for 
warehouse treatment, and use on dairy cattle, buses, and commercial 
vehicles. EPA used a variety of data for estimating occupational and 
residential exposures. These data included studies which measured 
dichlorvos following the use of a registered pesticide, surrogate 
studies involving other chemicals which used the same or similar 
application methods that would be used for dichlorvos uses, and in the 
absence of these two data sources, the Agency used its best 
professional judgment in estimating exposure. EPA's exposure estimates, 
including assumptions, are presented in Table 1 in Unit II.C.2. of this 
document (Refs. 48- 51).
    The revised exposure estimate for crack and crevice treatment by 
pest control operators (PCOs) considered data that were not available 
at the time of the original assessment. Under most conditions, the 
Agency assumed that professional applicators would wear a long sleeve 
shirt, long pants, and gloves.
    Data are also available to revise exposure estimates for 
application to greenhouses, mushroom houses, and 

[[Page 50350]]
dairy barns (milk rooms). Because a variety of application equipment 
could be used to treat these sites, depending on product formulation, 
the specific pest problem and personal preference of the applicator, 
EPA evaluated several studies, each using a variety of application 
equipment. Since these studies varied in design, it was not possible to 
pool the data into one large data set. Therefore, EPA calculated 
exposures separately for each study design, using correction factors 
for protective clothing where necessary. Normal work clothing (i.e., 
long sleeve shirt and long pants) was assumed to offer 50 percent 
protection, while gloves, coveralls and shoes were assumed to decrease 
exposure 90 percent. This approach resulted in a range of estimated 
exposures for each of the three sites. Table 1 in Unit II.C.2. of this 
document summarizes these data.
    The potential exposure of applicators using household aerosol 
products was not directly addressed in earlier Agency assessments. 
Since that time, EPA has received a study monitoring the exposure of 
individuals during application of a one percent propoxur aerosol 
product. This study can be used as a surrogate study for aerosol 
products containing dichlorvos. EPA believes that application of one 
entire can of pressurized aerosol represents a reasonable exposure 
estimate for acute exposure scenarios. This may be a conservative 
estimate in that not every resident will use an entire can at one time; 
however, it is reasonable to assume that some individuals may choose to 
apply an entire can. Exposure estimates were calculated for four 
different clothing scenarios: (1) Long sleeve shirt, long pants, and 
shoes; (2) short sleeve shirt, long pants, and shoes; (3) short sleeve 
shirt, shorts, and shoes; and (4) and minimal clothing consisting of 
shorts and shoes only. EPA is using a conservative clothing assumption 
of only shorts and shoes because insects may present the greatest 
nuisance in the summer when residents are likely to wear the least 
amount of clothing.
    EPA has also estimated exposures for individuals occupying or 
reentering residences following treatment of rooms with a total release 
fogger. These exposure estimates are also applicable to individuals 
reentering homes following crack and crevice treatment and aerosol 
spray application. The exposure estimates are based on a study that 
measured potential exposure by monitoring urinary amounts of dimethyl 
phosphate (DMP), a metabolite of dichlorvos, and by using whole body 
dosimeters consisting of cotton shirts, tights, gloves, socks and 
underpants. Because it appears that dichlorvos passed through the 
dosimeters, use of the dosimeter data alone would underestimate 
exposure. Therefore, EPA calculated total exposure by adding the 
biomonitoring component and the amount trapped by the whole body 
dosimeters. This is a conservative approach because it assumes that the 
entire amount of dichlorvos trapped in the clothing could serve as a 
pool for subsequent absorption. It is likely that some loss of 
dichlorvos from the clothing would occur and, therefore, would not be 
available for absorption. When biological monitoring alone is 
performed, it is not possible to separate the dermal and respiratory 
components of exposure. For this reason and because the study addresses 
a homeowner/resident scenario where protective clothing and respiratory 
protection do not apply, EPA has not separated these components but 
rather addressed the total exposure of the volunteers without regard to 
route. In addition, EPA is unable to estimate daily exposure values 
because biomonitoring data were collected over a 2-day period in this 
study. Rather, EPA estimated total exposure to individuals performing 
activities at various intervals following treatment on 2 consecutive 
days.

                                Table 1.--Summary of Dichlorvos Non-Dietary Risks                               
----------------------------------------------------------------------------------------------------------------
                                              Exposure (mg/kg/day)                                 Margin of    
                                     --------------------------------------                         Exposure    
       Uses              Notes                                              Exposure Pattern1   (Cholinesterase 
                                            Dermal           Inhalation                           Inhibition)   
----------------------------------------------------------------------------------------------------------------
Domestic                   2                                                                                    
 Dwellings                                                                                                      
 (application)                                                                                                  
  Pressurized              3          0.097              3.3 x 10-7         Short-term         47               
   aerosol                                                                                                      
----------------------------------------------------------------------------------------------------------------
  Crack and                4          0.018              2.3 x 10-4         Long-term          23               
   crevice                                                                                                      
   treatment                                                                                                    
----------------------------------------------------------------------------------------------------------------
Domestic                              No data                                                                   
 Dwellings (post-                                                                                               
 application)                                                                                                   
  Total release            5                             0.03               Short-term         17               
   fogger                                                                                                       
  Pressurized              6                             0.03               Short-term         17               
   aerosol                                                                                                      
  Crack and                7                             0.03               Long-term          2                
   crevice                                                                                                      
   treatment                                                                                                    
  Resin pest               8                             2.5 x 10-3         Long-term          20               
   strips                                                                                                       
  Pet flea                 9                             2.1 x 10-4         Long-term          240              
   collars                                                                                                      
----------------------------------------------------------------------------------------------------------------
Occupational               10                                                                                   
 Exposure                                                                                                       
----------------------------------------------------------------------------------------------------------------
  Crack & crevice          11         0.078              negligible         Long-term          6                
   treatment in                                                                                                 
   homes                                                                                                        
----------------------------------------------------------------------------------------------------------------
  Mushroom House           12                                                                                   

[[Page 50351]]
                                                                                                                
  Applicator                          4.0 x 10-5 to      1.8 x 10-5 to 6.7  Intermediate       Majority of      
                                       0.74               x 10-4                                scenarios have  
                                                                                                MOEs less than  
                                                                                                50, and some are
                                                                                                less than 10    
  Reentry                             ND                 1.5 x 10-2         Short-term         21               
----------------------------------------------------------------------------------------------------------------
Greenhouse                 13                                                                                   
  Applicator                          2.6 x 10-5 to      4.4 x 10-4 to ND   Short-term         Majority of      
                                       0.48                                                     scenarios have  
                                                                                                MOEs less than  
                                                                                                100, and 30% of 
                                                                                                scenarios have  
                                                                                                MOEs less than  
                                                                                                50              
  Reentry                             2.7 x 10-4         0.18               Short-term         2.8              
----------------------------------------------------------------------------------------------------------------
Domestic food/             14         0.15               No data            Intermediate       6.1              
 nonfood animals                                                                                                
 (non-poultry)                                                                                                  
----------------------------------------------------------------------------------------------------------------
Domestic food/             15         < non-poultry      No data            Intermediate       > 100            
 nonfood animals                                                                                                
 (poultry)                                                                                                      
----------------------------------------------------------------------------------------------------------------
Domestic animal            16                                                                                   
 premises (food                                                                                                 
 and non-food)                                                                                                  
 (Dairy barns)                                                                                                  
  Applicator                          1.2 x 10-5 to      ND - 2.0 x 10-4    Short-term         > 100            
                                       0.03                                                                     
  Reentry                             No data            No data            Short-term         > 100            
----------------------------------------------------------------------------------------------------------------
Feedlots                   17         < greenhouse       < greenhouse       Short-term         > 100            
----------------------------------------------------------------------------------------------------------------
Manure                     18         < greenhouse       < greenhouse       Short-term         > 100            
----------------------------------------------------------------------------------------------------------------
Tobacco warehouse          19                                                                                   
  Applicator -                        0.2                ND                 Long-term          2                
   sprinkling                                                                                                   
   with water can                                                                                               
  Mixer-loader                        1.4 x 10-5         ND                 Long-term          32,500           
  Warehouse                           No data            0.20               Long-term          0.3              
   worker                                                                                                       
   (reentry)                                                                                                    
----------------------------------------------------------------------------------------------------------------
Ornamental lawns,          20                                                                                   
 turf and plants                                                                                                
  Applicator                          2.6 x 10-5 to      4.4 x 10-4 -- ND   Short-term         32               
                                       0.48                                                                     
                                                                                               Similar to power 
                                                                                                sprayer in green
                                                                                                house           
----------------------------------------------------------------------------------------------------------------
Warehouse                  21                                                                                   
 treatment                                                                                                      
 (affects                                                                                                       
 nonperishable                                                                                                  
 bulk, packaged                                                                                                 
 and bagged raw                                                                                                 
 and processed                                                                                                  
 commodities)                                                                                                   
  Application                         0.1                0.002              Short-term         38               

[[Page 50352]]
                                                                                                                
  Reentry                             2.7 x 10-4         0.18               Short-term         2.8              
----------------------------------------------------------------------------------------------------------------
Kennels                    22                                                                                   
  Applicator                          similar to dairy   similar to dairy   Short-term         > 100            
                                       barn               barn                                                  
----------------------------------------------------------------------------------------------------------------
Insect traps               23         negligible         negligible         Short-term         negligible risk  
----------------------------------------------------------------------------------------------------------------
Garbage dumps              24         < greenhouse       < greenhouse       Short-term         > 81             
----------------------------------------------------------------------------------------------------------------
Commercial,                25                                                                                   
 institutional                                                                                                  
 and industrial                                                                                                 
 areas                                                                                                          
  Application                         0.1                0.002              Short-term         38               
  Reentry                             2.7 x 10-4         0.18               Short-term         2.8              
----------------------------------------------------------------------------------------------------------------
Commercial                                                                                                      
 transportation                                                                                                 
 vehicles                                                                                                       
Airplanes                  26                                                                                   
 (disinsection of                                                                                               
 aircraft)                                                                                                      
  Passenger -                         No data            3.7 x 10-3         Short-term         135              
   post-                                                                                                        
   application                                                                                                  
  Applicator                          No data            3.7 x 10-3         Long-term          14               
----------------------------------------------------------------------------------------------------------------
Buses - passenger          27                            9.2 x 10-3         Short-term         55               
Truck, shipholds,          28                                                                                   
 rail cars                                                                                                      
  Applicator                          < warehouse        < warehouse        Short-term         > warehouse      
  Reentry                             negligible         2.45 x 10-2        Short-term         20               
----------------------------------------------------------------------------------------------------------------



    ND--Not Detectable
    Notes: The following notes define the assumptions used in 
calculating the margins of exposure.
    1. Short-term MOEs based on NOEL of 0.5 mg/kg/day; Intermediate 
MOEs based on NOEL of 0.1 mg/kg/day; Long-term MOEs based on NOEL of 
0.05 mg/kg/day.
    2. An average resident weighs 70 kg and has a respiratory volume 
of 1.7 m3 per hour. No protective clothing is assumed.
    3. Resident use of pressurized aerosol product is based on 
application of an entire one percent 16 ounce can of pressurized 
aerosol. EPA estimated the risk to residents for different clothing 
scenarios. The MOE of 47 assumes the resident is wearing only shorts 
and shoes. Pressurized aerosol products containing dichlorvos do not 
have any clothing requirements, therefore EPA is assuming that 
dichlorvos is applied during hot weather when an individual will be 
wearing the least amount of clothing.
    4. Dichlorvos is applied once per week for 44 weeks while 
wearing no protective clothing.
    5. Assumes less than 24 days of exposure per year and less than 
2 days/month. The value 0.03 reported in the table includes both 
dermal and inhalation, since it is based on biomonitoring data 
(blood samples) and represents the dose to the individual rather 
than exposure. All other dermal exposure values in the table must be 
adjusted by the dermal absorption factor of 0.11 to arive at the 
dose.
    6. Same as for fogger.
    7. Same as for fogger.
    8. Assumes 365 days of exposure per year, 24 hours per day.
    9. Assumes 365 days of exposure per year, 24 hours per day.
    10. An average worker weighs 70 kg and has a respiratory volume 
of 1.7 m3 per hour. For mushroom houses, dairy barns, and 
greenhouses it is difficult to provide a single exposure estimate 
because of the variety of possible application equipment and 
differences in how studies were conducted. Therefore, a variety of 
scenarios are presented for these three uses. At a minimum, the 
following protective clothing was used in the exposure scenarios: 
gloves, long-sleeve shirt, long pants.
    11. A 0.5% solution of dichlorvos is applied using a hand held 
low pressure sprayer. It is assumed that dichlorvos is applied by 
PCO 10 times per day 1 day a week for 44 weeks. An average 
commercial applicator wears coveralls, chemical resistant gloves, 
and shoes. A respirator is not worn.
    12. An average mushroom house has a volume of 30,000 ft3. 
Dichlorvos is applied at a rate of 3.0 grams of active ingredient 
per 1000 ft3 or 30 grams per treatment; 16 days per year, 10 
houses per day; 4 minutes per house or 40 minutes per day. 
Protective clothing was slightly different for each application 
method. For reentry exposure, EPA assumed that a worker reenters a 
ventilated mushroom house 24 hours after treatment and is exposed 
for 8 hours. Dermal exposure is assumed to be negligible compared to 
respiratory exposure.
    13. A typical greenhouse operation consists of seven 
greenhouses, each with a volume of 85,000 ft3. All seven 
greenhouses are treated in one day. There are a maximum of three 
applications per crop and three crops are produced per year. 
Dichlorvos is applied at the rate of 1.4 grams of active ingredient 
per 1000 ft3. The total time spent applying the insecticide is 
26.25 minutes per day or 3.94 hours per year. The exposure value 
assumes that, at a minimum, a worker wears a long sleeve shirt, 
impervious gloves. In the absence of reentry data for a greenhouse, 
EPA is assuming that reentry exposure is similar to that of a 
warehouse.
    14. Worker exposure from direct application to animals is based 
on dairy cattle treatment. EPA does not believe that direct 
application with a handheld sprayer is used primary method of 
application. However, since several registered products provide 
guidance on use with a handheld sprayer, the exposure and risk are 
estimated here for that application method. A one percent solution 
of dichlorvos is applied with a handheld sprayer. An average herd of 
dairy cattle consists of 65 head, each requiring 24 seconds to 
spray, two times per day during treatment. Fly control is required 
from May to October with application 

[[Page 50353]]
occurring weekly during this time (26 times per year). Personal 
protective equipment consisting of impervious gloves (90 percent 
protection), long sleeve shirt and long pants (50 percent) 
protection are worn.
    15. Data for cattle cannot be extrapolated to poultry, because 
of the different application method and less frequent applications 
for poultry. As a result, exposure from applying dichlorvos to 
poultry is expected to be much lower than for cattle.
    16. An average dairy barn has the dimensions 30 ft x 100 ft x 9 
ft (total area covered is 4340 ft2 ). Dichlorvos is applied at 
two week intervals for 22 weeks, one barn per day. A 1.0 percent 
solution of dichlorvos is applied using a low pressure hand sprayer 
at a rate of 3.4 gallons per hour. Daily exposure time is 0.20 
hours. A worker wears a long sleeve shirt, long trousers, shoes and 
impervious gloves at a minimum. Gloves offer 90 percent protection 
to the hands and the other garments 50 percent protection. Coveralls 
are assumed to offer 90 percent protection.
    17. Feedlots include stockyards, corrals, holding pens and other 
areas where groups of animals are contained. This application method 
would probably be used for controlling insects on cattle. EPA 
assumes that some type of power sprayer capable of treating a large 
number of animals in a short time is probably used. A short 
application time period in an outdoor or partially enclosed area 
would minimize exposure to less than that of a greenhouse.
    18. MOE is expected to be greater than 100 for manure use. 
Application equipment may be similar to those used in a greenhouse; 
however, the application time would probably be less and the treated 
area would be well ventilated - either outdoors or in a partially 
enclosed area.
    19. Tobacco warehouse mixer/loader/applicator exposure is 
expected occur twice a week for 27 weeks, totaling 54 days of 
exposure. Warehouse reentry workers are expected to be exposed six 
days a week for 27 weeks per year.
    20. Use on ornamental lawns, turf and plants are expected to 
have an exposure pattern similar to a greenhouse sprayer.
    21. Dichlorvos can be applied to warehouses manually using 
foggers or with wall-mounted automatic foggers. Exposure to mixer/
loaders through automatic application is expected to be negligible; 
however, there would still be reentry exposure. In estimating 
reentry exposure, EPA assumed six hours elapsed before reentry is 
allowed, as required on labels; and that workers spend eight hours 
per day in the treated area for the next three days. In estimating 
exposure from manual application, EPA assumed that an average 
warehouse has a volume of two million ft3; dichlorvos is 
applied at the rate of 2.0 grams active ingredient per 1000 ft3 
over a period of 125 minutes per application. On average, dichlorvos 
is applied 12 times per year. Protective clothing consisted of 
impervious gloves, an apron, coveralls, boots, hood, goggles and a 
respirator during application.
    22. Exposure in a kennel is believed to be similar to a dairy 
barn.
    23. Exposure is believed to be negligible since the pesticide is 
in the form of an impregnated strip and the traps are placed in 
outdoor areas (such as forests) where there is no human exposure.
    24. Exposure at a garbage dump is believed to be less than 
greenhouse exposure.
    25. Exposure is believed to be similar to warehouse exposure.
    26. Aircraft personnel are exposed to dichlorvos 30 minutes once 
per week, 52 times per year. No protective clothing is worn, 
representing a chronic exposure scenario. Passenger exposure is an 
acute scenario.
    27. Passengers are exposed to airborne dichlorvos for four hours 
in buses following two hours aeration. Passenger respiratory volume 
is assumed to be 0.44 m3/hour which is less than for workers 
because passengers are at rest.
    28. EPA is assuming that exposure from application should be 
less than that for warehouses because of the smaller area to treat - 
therefore less exposure time. However, because a short term exposure 
scenario is involved, EPA is concerned about the potential risks 
from any type of hand application, assuming no respiratory 
protection. For reentry, the MOE of 20 is based on 8 hours of 
exposure after a 12-hour reentry period. Even a 24 hour reentry 
peroiod results in an MOE of 60.

D. Risk Characterization

    1. Chronic dietary. This section summarizes chronic risk estimates 
from dietary exposure to dichlorvos, including risks due to direct 
application of dichlorvos and dichlorvos which occurs as a metabolite 
from the use of naled. In initiating the Special Review in 1988, EPA 
estimated the upper bound dietary cancer risk from dichlorvos 
application alone to be 8.4 x 10-5 or in the range of 10-4, 
for the general U.S. population. EPA believed this to be an 
overestimate because it was based on a number of conservative 
assumptions. The Agency is now able to provide a more realistic dietary 
risk estimate based on field trial data, processing and cooking data, 
and refinements in percent of crop treated data (Refs. 52 and 53).
    i. Noncancer. The Agency estimates chronic dietary risks for 
noncancer endpoints by comparing dietary exposure to the Reference Dose 
(RfD). The RfD is an estimate of the daily oral exposure to humans over 
a lifetime that is not expected to result in adverse health effects. 
The RfD is based on the determination of a critical effect from a 
review of all toxicity data and a judgment of uncertainty. In the case 
of dichlorvos, the RfD is 0.0005 mg/kg body weight/day, based on a NOEL 
of 0.05 mg/kg body weight/day and an uncertainty factor of 100 to 
account for extrapolation from animal data to humans and variability in 
the human population. The NOEL, was taken from a 1 year feeding study 
in dogs in which plasma and red blood cell ChE inhibition (ChE) were 
the effects observed in males and females; in addition, brain ChE 
inhibition was observed in males (Ref. 54).
    Using anticipated residues and percent of crop treated data, EPA 
estimated the exposure from registered uses of dichlorvos to be 
0.000054 mg/kg body weight/day, which represents 11 percent of the RfD 
for the general U.S. population. EPA estimates that the ARC to the most 
highly exposed population subgroup, non-nursing infants under 1 year, 
is 0.000143 mg/kg body weight/day, or 29 percent of the RfD. The ARC 
for the U.S. population from dichlorvos derived from registered uses of 
naled is 0.000016 mg/kg body weight/day or 3 percent of the RfD. EPA 
estimates that the ARC to the most highly exposed population subgroup, 
``non-nursing infants under 1 year,'' is 0.000057 mg/kg body weight/
day, or 11 percent of the RfD. EPA concludes that the risk from ChE 
inhibition due to chronic dietary exposure is minimal and not of 
concern.
    The Agency does not have a concern for cholinesterase inhibition 
from DDVP use on foods at this time. This conclusion is based on the 
dietary risk assessment for DDVP alone. If exposure from other 
cholinesterase inhibitors, either on the same or different foods in 
addition to DDVP were considered, a cumulative exposure may trigger a 
risk concern. The Agency currently has no methodology for assessing 
cumulative exposure from cholinesterase inhibitors via ingestion of 
treated foods. However, the Agency plans to pursue options towards this 
end in the coming years and at that time will solicit public input on 
possible methodologies.
    ii. Cancer. In estimating the upper bound cancer risk, chronic 
dietary exposure is multiplied by the cancer potency of the chemical. 
This analysis uses the upper bound cancer potency factor (or Q1*) 
for dichlorvos of 1.22 x 10-1 (mg/kg/day)-1 and assumes that 
an individual is exposed over a 70-year lifetime. Based on these 
assumptions, the estimated upper-bound excess individual lifetime 
cancer risk from direct application of dichlorvos is 4.4 x 10-6 
and from naled-derived dichlorvos it is 7.2 x 10-7 for a total of 
5.1 x 10-6 (see Table 2 of this paragraph). At a future date, EPA 
will issue a Reregistration Eligibility Document for naled which 
provides further analysis of naled-derived dichlorvos. The major source 
of estimated risk is dichlorvos residues from use on packaged, bagged 
or bulk nonperishable processed or raw food (3.4 x 10-6). The 
estimated risk from the three individual tolerances and FAR (bulk raw, 
packaged or bagged raw, 

[[Page 50354]]
and packaged or bagged processed) cannot be separated because, as 
discussed earlier, a single commodity may be treated more than once at 
different stages of production. EPA has published a final revocation 
notice for the FAR for residues of dichlorvos on packaged or bagged 
nonperishable processed food. If this revocation becomes effective and 
the related uses are canceled under FIFRA, this source of dietary risk 
will be eliminated.

   Table 2.--Upper Bound Cancer Risk Estimates from use of Dichlorvos   
------------------------------------------------------------------------
        Tolerance Expression               Upper Bound Cancer Risk      
------------------------------------------------------------------------
Use of Dichlorvos                                                       
------------------------------------------------------------------------
                                                                        
Packaged or bagged, non-perishable   3.4 x 10-6                         
 processed food and RACs (including                                     
 bulk stored, regardless of fat                                         
 content)                                                               
------------------------------------------------------------------------
Milk                                 6.2 x 10-7                         
------------------------------------------------------------------------
                                                                        
Eggs                                 7.1 x 10-8                         
------------------------------------------------------------------------
                                                                        
Red Meat                             1.1 x 10-7                         
------------------------------------------------------------------------
                                                                        
  Poultry                            3.7 x 10-8                         
------------------------------------------------------------------------
                                                                        
  Agricultural uses                  2.1 x 10-7                         
    Lettuce                          1.6 x 10-7                         
    Cucumbers                        2.6 x 10-8                         
    Tomatoes                         1.4 x 10-8                         
    Mushrooms                        2.6 x 10-9                         
    Radishes                         9.8 x 10-10                        
------------------------------------------------------------------------
                                                                        
Naled derived dichlorvos             7.2 x 10-7                         
------------------------------------------------------------------------
Total                                5.1 x 10-6                         
------------------------------------------------------------------------

    2. Occupational and residential risks--i. Carcinogenicity. The PD 1 
in 1988 estimated risks from cancer to pesticide workers and residents 
based on dermal and inhalation exposure. Since that time, as discussed 
earlier in this unit, EPA has decided that it is no longer appropriate 
to quantify cancer risk for the inhalation and dermal routes, as 
discussed above in Unit II. Therefore, cancer risks for workers and 
residents by the inhalation and dermal routes are no longer a concern 
for this preliminary determination.
    ii. ChE inhibition. The duration and frequency of exposure vary 
considerably for the numerous uses of dichlorvos. MOEs are based upon 
comparison of exposure estimates against NOELs of 0.5 mg/kg/day for 
short-term, 0.1 mg/kg/day for intermediate, and 0.05 mg/kg/day for 
long-term exposure scenarios. The NOELs are based on brain ChE and/or 
cholinergic signs, and were derived from toxicological studies by the 
oral route; however, dermal exposure is an important route of 
occupational/residential exposure. Therefore, the Agency's oral 
exposure estimates are adjusted for the dermal absorption of dichlorvos 
(factor of 0.11), to account for the route-to-route extrapolation.
    For most uses in Table 1 of Unit II.C.2. of this document, a single 
exposure estimate and corresponding MOE are given. However, this was 
not possible for mushroom houses, greenhouses, and dairy barns because 
of the number of potential application methods and the inability to 
combine the various studies into one data set. The Agency does not 
believe there are any naled-derived dichlorvos risks resulting from 
occupational/residential exposure because a tank mix study showed that 
naled did not readily degrade to dichlorvos under actual use 
conditions. This is consistent with the finding that dichlorvos results 
from plants metabolizing naled, as discussed above.
    MOEs are used by EPA as an indication of the level of risk from ChE 
inhibition. EPA is generally concerned about exposures to humans where 
the MOEs are less than 100, since they may not provide an adequate MOE 
after accounting for uncertainty (i.e, extrapolation from animals to 
humans and variability in the human population). MOEs are less than the 
uncertainty factor of 100 for the majority of sites examined in this 
assessment, and some are less than 10. MOEs fall below 100 for both the 
applicator of dichlorvos and for individuals living or working in 
treated areas (Ref. 55).
    The occupational and residential risk assessment contains the 
following uncertainties that could result in an underestimate or 
overestimate of the true risk: (1) In the absence of actual dermal 
toxicity studies, toxicity by the dermal and oral routes were assumed 
to be comparable after adjusting for differences in absorption, (2) 
subchronic and chronic inhalation data are available, and EPA assumed 
that toxicity by the oral and inhalation routes are comparable, (3) the 
NOEL used to calculate short-term MOEs is based on cholinergic signs, 
(4) the exposure parameters are dated and may have changed for some 
scenarios, (5) in many cases surrogate exposure data were used for 
estimating occupational and residential exposure, and in the absence of 
such data, the Agency made assumptions that a particular exposure 
should not exceed that of a scenario where surrogate or actual data 
existed, and (6) MOE estimates may vary significantly depending on the 
method of application and protective clothing assumptions.
    There are additional uncertainties regarding potential risks to 
children exposed to dichlorvos from residential uses, including 
variability in activity patterns, the extent of non-dietary oral 
ingestion, due to hand object-to-mouth activity, respiratory rate and 
tidal volume, surface area to volume ratio, dermal absorption, and 
toxicological susceptibility. Consideration of children's risk could 
possibly have resulted in lower MOEs. However, the Agency believes that 
the proposed actions will nonetheless serve to adequately protect 
children from residential exposure. The Agency is currently conducting 
research to provide refinements to assess children's exposure, and is 
working to update our guidelines for household and work related 
exposures.
    3. Analysis of comments on the PD 1. The Agency received comments 
relating to risks discussed in the PD 1. Rebuttal comments and complete 
Agency responses are on file in the dichlorvos Public Docket. The 
following is a summary of the major comments, and the Agency's 
responses.
    Comment. Amvac Chemical Corporation argued that the ``weight-of-the 
evidence'' from animal studies is limited or inadequate to assess human 
cancer risk, and that the Group B2 classification is not appropriate.
    Agency Response. This comment is moot since dichlorvos was 
reclassified from a B2 to a C carcinogen, as explained above.
    Comment. With regard to the pancreatic tumors seen in F344 rats, 
``Since there are no pharmacokinetic or physiological reasons to expect 
females to be unique in their responsiveness to dichlorvos, the absence 
of an effect in females weakens the significance of the effect increase 
in males.''
    Agency Response. The pancreatic acinar adenomas were eliminated 
from consideration in the fourth cancer peer review.
    Comment. With regard to the dichlorvos swine feeding study, the 
registrant states that the ``histopathological results are of value for 
the assessment of the carcinogenicity of dichlorvos in a third 
species.''
    Agency Response. The Agency does not believe that this study would 
be 

[[Page 50355]]
adequate as an oncogenicity study in a third species because of the 
limited duration of the study and the limited histopathology apparently 
conducted.
    Comment. With regard to the dichlorvos dog feeding study (2-year), 
the registrant stated that ``[t]he study showed no suggestion of 
carcinogenic effects of DDVP in dogs.''
    Agency Response. The Agency does not believe that a 2-year feeding 
study in the dog is of long enough duration to conclude that there are 
no carcinogenic effects of dichlorvos.
    Comment. With regard to the mutagenicity of dichlorvos, the 
registrant states that ``dichlorvos has not been shown to present a 
significant risk of mutagenic effects to animals or humans.''
    Agency Response. The comment did not include a discussion of 
results of mutagenicity studies conducted by the NTP in conjunction 
with conducting the bioassays on dichlorvos. Dichlorvos was found to be 
positive in two mammalian systems, for point mutations in the mouse 
L5178 lymphoma cell assay without metabolic activation (assay with 
activation was not done) and for sister chromatid exchanges in Chinese 
hamster ovary cells both with and without metabolic activation.
    Comment. Amvac has supplied the Agency with additional information 
on the chronic rat inhalation study indicating that the test animals 
may have been exposed to substantially more dichlorvos than was 
measured in the inhalation chambers. The registrant estimated that the 
high-dose animals may have been exposed to 10 mg/rat/day, equivalent to 
25 mg/kg/day in males and 34 mg/kg/day in females.
    Agency Response. The Agency believes that the additional 
information provided by Amvac does not provide sufficient evidence to 
support adjusting the doses administered to the test animals.
    Comment. Amvac stated that the dog study, which formed EPA's 
initial concern about liver toxicity, did not satisfy Subdivision F 
guidelines.
    Agency Response. EPA has invalidated this study and liver effects 
are no longer of concern.
    Comment. Pest Control Services, Inc. commented that the Agency 
overestimated the exposure for the No-Pest strip for use in museums.
    Agency Response. First, EPA's exposure estimate was based on 
residential use where individuals are constantly exposed to dichlorvos. 
Because there are so many uses of dichlorvos, it is difficult to 
anticipate every possible exposure scenario. To protect the public 
health, the Agency focused on the high exposure scenario in the home. 
Use in museums (i.e., enclosed spaces such as display cabinets, display 
drawers, etc.) would be similar to that of grain silos, in that 
individuals would not be constantly exposed to the No-Pest Strip. 
Therefore, this preliminary determination does not propose any risk 
mitigation for use of No-Pest Strips in enclosed spaces in museums. In 
addition, an error in the Agency's 1987 exposure estimate has been 
corrected, reducing the residential exposure estimate from 9.6 mg/kg/yr 
to 0.93 mg/kg/yr. Even with this reduction in estimated exposure, the 
short-term and long-term MOEs for residential use are still far below 
100.

III. Benefits Assessment

A. Summary of Benefits Assessment

    EPA conducted a benefits assessment which concludes that the 
overall annual economic impact of a dichlorvos cancellation to users 
and consumers is not expected to be significant for most sites (Ref. 
56). EPA knows of no major benefits from retaining most uses of 
dichlorvos with the probable exception of packaged or bagged 
nonperishable raw and processed food; poultry and livestock premises; 
feedlots; and possibly mushroom houses. Furthermore, for most of the 
individual dichlorvos use sites, a number of alternatives are 
registered and available. Any economic impacts are expected to diminish 
over time as users adjust to the alternative control measures. The 
major benefits of dichlorvos relate to its chemical properties: 
knockdown action and vapor activity. Its quick knockdown ability makes 
dichlorvos desirable for fly control, although it has little residual 
activity. In addition, dichlorvos is said to have vapor action which 
gives it penetration characteristics similar to a fumigant. Because of 
this characteristic, some users claim that there are no equivalent 
alternatives for certain uses.

B. Background

    Dichlorvos, an organophosphate insecticide, kills insects on 
contact. Products containing dichlorvos are registered for use in 
controlling various invertebrate pests (insects, mites, spiders, 
scorpions, and sowbugs) in diverse situations. Dichlorvos is formulated 
alone and in combination with other active ingredients as emulsifiable 
concentrates, soluble concentrate liquids, granulars, pressurized 
liquids and dusts, smoke generators, impregnated materials, pellets/
tablets, liquids (ready to use), total release aerosols, and wettable 
powders. Although dichlorvos has little residual activity, the 
knockdown action and vapor activity of the chemical are said to make it 
a versatile and effective chemical for pest control. Applications are 
made with aerosol and fogging equipment, smoke generators, hand-held 
sprayers, other ground spray equipment, and through slow release from 
impregnated materials, such as resin strips and pet collars. Amvac 
Chemical Corporation is the sole producer of technical grade dichlorvos 
in the United States. Dichlorvos is registered for use on a number of 
diverse indoor and outdoor sites.

C. Usage Information

    Total annual usage of dichlorvos is estimated to range from about 
250,000 to 500,000 pounds of active ingredient. The Agency believes 
that most of the dichlorvos is used for animal, livestock and premise 
treatments, and on bulk, packaged or bagged raw or processed food. EPA 
estimates that these sites account for between 45 and 83 percent of the 
dichlorvos used in the United States annually. Most of the remaining 
dichlorvos is used in greenhouses, homes, and mushroom houses.

D. Method

    The approach of the benefits analysis was to evaluate, on the basis 
of available information, the potential economic impacts associated 
with the switch to alternative pest control technologies caused by the 
possible cancellation of certain dichlorvos uses. Future Agency action 
could change the availability and use of the alternatives. However, 
this analysis does not anticipate or speculate on the possible effects 
due to specific regulatory actions on the other chemical alternatives 
identified.
    The following analysis is qualitative in scope. The information 
presented in the specific site assessments identifies the major pests 
controlled by dichlorvos for these sites, identifies the major 
registered alternatives and their availability, estimates the change in 
pest control costs associated with the use of the alternatives, and, 
where possible, evaluates impacts to users.
    Usage estimates for the major dichlorvos use sites were based on 
various proprietary and non-proprietary usage data. Prices for 
dichlorvos and alternative products were based on pesticide product 
catalogues, quotes from pesticide distributors, and market surveys of 
consumer products. Determination of primary pests and major 
alternatives was based upon previous site-specific assessments prepared 
by a USDA/National Agricultural Pesticide Impact Assessment Program 
(NAPIAP) 

[[Page 50356]]
Assessment Team, a DPRA Inc. Benefits Assessment (a private source of 
benefits information), and Preliminary Benefits Assessments (PBAs) by 
EPA. If specific site assessments were not available, then state 
recommendations, specimen label guides, the 1992 Insect Control Guide, 
and the EPA Index to Pesticide Chemicals provided information about the 
primary pests and alternative chemical controls for each site.
    USDA completed a benefits assessment for dichlorvos in early 1990, 
based on survey data and expert opinion, that estimates the average 
annual benefit to be at least $120 million. This estimate was based on 
data from the mid-80's when usage was much higher than it is now. EPA 
estimates that dichlorvos usage has declined from approximately 2 
million pounds annually at the time of the PD 1 (1985 data) to about 
250,000 to 500,000 pounds per year at present. In addition, Amvac has 
requested voluntary deletion of several uses, which account for some of 
the current usage. Therefore, the use deletions will reduce usage even 
further.
    In conducting the benefits assessment, each site was analyzed to 
determine the impacts that would result if dichlorvos were canceled for 
that site, (See Table 3 in this Unit). Comparative performance data 
were not available; therefore, the analyses were based on comparative 
cost assessments under the assumption that sufficient products were 
available which would provide adequate control of the pests.
    The alternatives to dichlorvos include carbamates, 
organophosphates, natural pyrethrins and synthetic pyrethroid 
compounds. EPA has identified the following insecticides as likely 
alternatives to dichlorvos: bendiocarb, carbaryl, chlorpyrifos, 
diazinon, malathion, naled, phosmet, propoxur, permethrin, pyrethrins, 
resmethrin, and tetrachlorvinphos. In addition, non-chemical 
alternatives were also identified where information was available. In 
most cases these non-chemical alternatives help control insect 
populations which may result in a decrease in the frequency of chemical 
treatments. It is unlikely that these non-chemical alternatives would 
replace dichlorvos to the extent that a chemical alternative would.

E. Individual Sites

    Table 3 in Unit III.F. of this document lists detailed information 
on the benefits for each site.
    1. In and around domestic buildings. Dichlorvos is used in and 
around domestic buildings primarily as an aerosol treatment to control 
a variety of insects. It is also used in foggers and impregnated resin 
pest strips. A variety of chemical alternatives are available. In the 
absence of efficacy data, EPA is assuming that the alternatives would 
provide similar levels of control. Non-chemical alternatives are also 
available. EPA estimates that less than 1 percent of total dichlorvos 
is used in the home; however, it is unknown how much of this is applied 
by commercial applicators.
    2. Pets. Dichlorvos is used to control fleas and ticks on dogs and 
cats through the use of impregnated plastic flea and tick pet collars. 
There are a variety of alternative chemicals available to dichlorvos, 
some of which have had reports of tick and flea resistance. Due to the 
lack of comparative efficacy and resistance data, EPA assumes that 
collars with and without dichlorvos have equal efficacy. There are also 
non-chemical alternatives available which can reduce the frequency of 
pesticide treatment, including: sanitation, vacuuming pet living and 
sleeping quarters, and washing or replacing bedding. EPA estimates that 
pet collars represent 3 percent of total dichlorvos usage. EPA does not 
expect the economic impact from cancellation of dichlorvos to be 
significant, because dichlorvos is not one of the major insecticides 
used in cat and dog collars.
    3. Mushroom houses. Dichlorvos is used only as a space spray to 
control the adult mushroom fly complex after surface sprays and 
larvacides no longer provide adequate control; therefore, only 
permethrin is considered an actual alternative (Ref. 57). Non-chemical 
controls include black light traps to monitor fly emergence and 
quantify fly influx. There may be some pest resistance to both 
dichlorvos and permethrin; however, due to the lack of comparative 
efficacy or resistance data, EPA assumes that acceptable levels of 
control would be provided by both chemicals. EPA estimates that 2 
percent of total dichlorvos is used on mushrooms. The Agency has 
information that suggests dichlorvos is primarily used as an emergency 
treatment if larval treatments fail. Economic impacts to the mushroom 
industry cannot be accurately assessed due to the limited usage data 
available regarding the use of the alternative chemicals. Based on 
limited information, some impacts are possible; however, economic 
impacts are not expected to be significant if dichlorvos is not 
available.
    4. Greenhouses. Dichlorvos is used primarily as a space spray for 
control of a variety of insects on both food and nonfood greenhouse 
plants. The major direct alternatives, used as space sprays, aerosols, 
bombs, or pressure fumigators (smoke generators) include nicotine, 
pyrethrins, and resmethrin. There are also a variety of other 
alternatives used as greenhouse surface treatments and direct 
application to plants. There are reports that some whitefly species may 
be resistant to resmethrin; however, in the absence of comparative 
efficacy or resistance data EPA assumes that similar levels of control 
would be provided by the alternatives. Non-chemical mitigation measures 
to reduce pesticide applications include: sticky board traps, good 
sanitation practices and the use of insect free transplants. Total 
usage in greenhouses is less than 2 percent of total dichlorvos usage; 
however, available usage data do not separate food and non-food use of 
dichlorvos in greenhouses. If the number of applications is assumed to 
be equal for dichlorvos and the alternatives, then economic impacts 
resulting from the loss of dichlorvos are not expected to be 
significant.
    5. Direct application to animals and animal premises. Dichlorvos is 
applied directly to domestic food and non-food animals primarily to 
control flies. Other insects are also controlled with dichlorvos (See 
Table 3 in Unit III.F. of this document). There are various 
alternatives available, which vary somewhat for each type of livestock 
and poultry. There are reports that flies are resistant to permethrin; 
however, in the absence of comparative efficacy or resistance data, EPA 
assumes that all products would perform similarly. Non-chemical control 
measures include the use of parasitic and predatory wasps that have not 
gained much commercial acceptance; upgraded/improved sanitary 
conditions involving manure management, trapping insects, and the 
introduction of bacteria and viruses that are pathogenic to the pests. 
Most uses on animals make use of some type of automatic method rather 
than hand-held application, therefore the loss of hand-held application 
should not result in a significant impact on users.
    Dichlorvos is used as a space spray, animal spray, residual 
treatment, or bait in controlling flies in animal premises. There are a 
variety of chemical alternatives available. There are reports that 
flies are resistant to permethrin; however, in the absence of 
comparative efficacy or resistance data, EPA assumes that all products 
would perform similarly. Non-chemical controls include improved manure 
management, use of parasites, traps, sanitation, and electrocutors. EPA 
estimates the total usage for direct animal treatment and premise 
treatment for all domestic 

[[Page 50357]]
animals is 100,000 to 200,000 pounds of active ingredient or between 27 
percent and 54 percent of all dichlorvos usage. The actual cost of 
alternatives depends on the number of treatments needed to replace 
dichlorvos. Based on limited information, it is probable that some 
localized impacts would occur if dichlorvos were not available; 
however, EPA does not expect economic impacts to be significant overall 
(Refs. 58 and 59).
    6. Feedlots. Dichlorvos is used in feedlots (including areas around 
feedlots, stockyards, corrals, holding pens, fences etc.) primarily as 
a space spray (fog) and as an indoor residual premise treatment to 
control flies. There are chemcial alternatives for space sprays and 
indoor residual premise sprays. Non-chemical alternatives include 
parasites, predators, and sanitation practices (removal of manure and 
organic matter). Based on information from USDA NAPIAP (Ref. 60) there 
are probable benefits from use of dichlorvos in feedlots. Depending on 
the alternative, loss of dichlorvos could result in cost increases or 
decreases. Overall, the economic impact due to loss of dichlorvos is 
not expected to be significant.
    7. Manure. Dichlorvos is applied directly to manure (including 
dairy and beef cattle, and poultry) on farms to control flies. There 
are chemical alternatives for use as a direct manure treatment and as 
bait treatments. Non-chemical alternatives include the use of 
predators, parasites, insect traps, electrocutors, repellors, and 
removal of manure and organic matter. The cost per application is 
expected to be less for the alternatives. Therefore, the economic 
impact due to loss of dichlorvos is not expected to be significant.
    8. Garbage dumps. Dichlorvos is used as a surface spray or bait 
treatment in garbage dumps to control flies. Chemical alternatives 
exist for each application method, all of which are believed to provide 
similar levels of fly control. The nonchemical alternative is 
sanitation - i.e. frequent removal or burial of garbage. Use of 
alternatives is expected to result in cost increases; however, actual 
costs would vary according to application rate and frequency. Because 
of the existance of chemical and non-chemical control measures, the 
economic impact due to loss of dichlorvos is not expected to be 
significant for this site.
    9. Ornamental lawns and turf. Dichlorvos is used to control a 
variety of insects and related pests on these sites through the use of 
multi-active ingredient products. The major alternatives are considered 
to be equal to or superior to the efficacy of dichlorvos. Depending on 
the turf site and pest species, a wide variety of non-chemical control 
measures are available, including nematodes, flushing with water, 
improved management of turf, and use of resistant varieties of grass. 
EPA has no information suggesting that there is any significant usage 
of products containing dichlorvos on turf. The Agency believes that any 
such usage is likely to be by commercial applicators with multi-active 
ingredients containing both dichlorvos and chlorpyrifos. Because usage 
of products containing dichlorvos on turf appears to be negligible and 
the cost and efficacy of many of the alternatives are comparable to 
dichlorvos products, the impact of canceling dichlorvos on turf is 
expected to be negligible.
    10. Ornamental plants. Dichlorvos is used on a variety of 
ornamental plants, including shade trees, hardwoods, flowering trees, 
conifers, evergreens, woody shrubs, vines, flowering plants and grasses 
(excluding turf). A variety of alternatives are used which depend on 
the pest and host plant. No comparative efficacy data are available; 
therefore, the Agency assumes that similar levels of control would be 
provided by all the chemicals listed in Table 3 in Unit III.F. of this 
document. Depending on the host plant and pest species, a wide variety 
of non-chemical control measures are available, including hand picking, 
sanitation, mulching, and improved cultural management. Dichlorvos 
usage information is not available. However, economic impacts are not 
expected to be significant due to the availability of several 
alternatives.
    11. Bulk, packaged or bagged nonperishable processed and raw food. 
Dichlorvos is registered for use on bulk, packaged or bagged 
nonperishable processed and raw food to control a number of stored 
product insect pests. EPA believes that dichlorvos is used primarily as 
a space treatment with aerosols, foggers or as a fine stream applied to 
the cracks, crevices, and general storage areas of warehouses and 
similar facilities.
    EPA believes that the major alternative to dichlorvos when used as 
a space treatment would be the pyrethrins. No comparative efficacy data 
for dichlorvos and pyrethrins are available to EPA at this time; 
therefore, EPA assumes that all the registered pesticides would provide 
adequate control of the pests. However, dichlorvos, unlike pyrethrins, 
is said to possess fumigant-like properties (high vapor pressure) and 
to rapidly penetrate throughout areas containing stacked commodities. 
Due to the different properties of dichlorvos and pyrethrins, EPA 
believes dichlorvos has the potential to be a more effective 
insecticide than pyrethrins by requiring fewer treatments to provide 
the same level of control in these situations. The Agency does not have 
data available to be able to estimate the number of applications needed 
for dichlorvos compared to pyrethrins. Without these data, the Agency 
can only estimate the cost difference on a per application basis.
    The cost of treating 1,000 cubic feet would be $0.18 for pyrethrins 
and $0.04 for dichlorvos. Thus pyrethrins would cost $0.14 more than 
dichlorvos. EPA estimated that 50,000 to 75,000 lbs of the active 
ingredient of dichlorvos are applied to approximately 2 to 3 billion 
cubic feet of warehouse space for packaged or bagged nonperishable 
processed and raw food.
    The characteristics of pyrethrins suggest that fumigations with 
methyl bromide or aluminum phosphide may be needed to supplement 
pyrethrins. Without the use of additional fumigants to supplement the 
pyrethrins, there could be some loss in overall control; however, EPA 
has no basis to confirm or estimate the resulting loss. EPA estimates 
the additional cost of using pyrethrins instead of dichlorvos to be $12 
million per year. The additional cost of supplemental fumigations would 
be about $33 million with methyl bromide and $44 million per year with 
aluminum phosphide.
    12. Kennels. Dichlorvos is used primarily as a residual surface 
spray for treating outside runways, window sills and ledges in kennels, 
to control fleas, ticks, flies, and mosquitoes. There are a variety of 
chemical alternatives available. There are reports of flea resistance 
to chlorpyrifos, propoxur, and carbaryl; however, due to the lack of 
comparative efficacy or resistance data, the Agency assumes similar 
levels of control would be provided by the various alternatives. Non-
chemical alternatives include sanitation practices such as cleaning of 
kennels, laundering of bedding, and frequent changing of litter when 
used in combination with chemical treatment. There are no data on usage 
in kennels. No adverse economic impacts are expected to result from the 
cancellation of dichlorvos, since several alternatives are available 
and may cost less than dichlorvos per application.
    13. Insect traps. Dichlorvos is used in pheromone traps to monitor 
heavy populations of gypsy moths and other insects in remote forested 
areas. In other situations adhesive coatings are used. Non-chemical 
adhesive coatings can be 

[[Page 50358]]
as effective or more effective except when large numbers of insects 
entirely coat the strips. Economic impacts from cancellation would be 
negligible, since monitoring would only be less effective for heavy 
populations of insects.
    14. Commercial, institutional, and industrial areas. Dichlorvos is 
used primarily as a residual surface spray or space treatment in 
restaurants, food processing and storage areas, transportation 
facilities, lodging, schools, and hospitals, to control a variety of 
insects. There are a variety of alternative chemicals; however, due to 
the lack of comparative efficacy data or resistance data, EPA assumes 
these alternatives will provide equal efficacy. Economic impacts are 
not expected to be significant if dichlorvos is canceled, although 
there could be a slight increase in costs from use of alternatives.
    15. Commercial transportation vehicles--i. Airplanes and buses. 
Dichlorvos is used primarily as a space treatment in airplanes and 
buses for the control of a variety of pests including ants, 
cockroaches, fleas, flies, and quarantine pests. The major alternatives 
are phenothrin, pyrethrins, and resmethrin all of which are assumed to 
offer comparable efficacy to dichlorvos. No economic impacts are 
expected since current dichlorvos use is believed to be minimal.
    ii. Trucks, shipholds, and railroad cars. Dichlorvos is used 
primarily as a space treatment in these vehicles primarily to control a 
variety of stored product pests. Major alternatives are pyrethrins and 
resmethrin, and equal efficacy to dichlorvos is assumed. A variety of 
non-chemical alternatives are available, including sanitation, modified 
atmospheres, irradiation, and controlled temperatures (hot and cold). 
Economic impacts are not expected to be significant, based on the 
availability of alternatives and the similarity in costs.

F. Strengths and Uncertainties of Benefits Assessment

    The strengths of the benefits assessment include the identification 
of pests on which dichlorvos is used, alternative pesticides, methods 
of application, and application rates. There are also weaknesses in 
this benefits assessment: specific use and usage information is dated; 
many dichlorvos labels include a wide range of generalized use sites, 
making it difficult to describe specific uses (e.g. warehouses); 
comparative efficacy and product performance data do not exist for 
dichlorvos and its alternatives; there are no data regarding the number 
of treatments needed with an alternative to replace dichlorvos 
treatments; and there are no data regarding pest resistance to 
alternatives. Because of limited use and usage information, the 
benefits may be understated for fly control in feedlots, on livestock 
and livestock premises, and pest control in storage areas.
    Little usage information for dichlorvos is available. Products 
containing dichlorvos come in several formulations, may be applied by 
several different methods, and can be used in many situations (for 
example, different types of warehouses); therefore, determining the 
usage for a particular site is difficult. The lack of comparative 
efficacy and product performance data also presented problems when 
trying to compare dichlorvos to the alternatives. This lack of data led 
the Agency to assume that all products listed would provide adequate 
control of the pests identified for each site unless otherwise noted. 
EPA is aware that some of the pests may be resistant to some of the 
chemicals listed; however, without supporting data the Agency cannot be 
more specific or come to a more definitive conclusion regarding the 
effectiveness of the chemicals. Other areas of difficulty involved 
determining the amount of product applied per application, the number 
of treatments needed, and the effect these factors had on the cost per 
application. For example, dichlorvos products are applied on the basis 
of cubic feet of space (as a space treatment), per square feet (as a 
surface treatment), some for a certain length of time, others as crack 
and crevice or spot treatments, some as baits, and still others 
directly to animals. This diversity of area treated and the number of 
applications needed or recommended (for example, based on the season, 
geographical area, and pests) created difficulties for making 
comparisons between products. Until more information is made available, 
the Agency assumes, for most sites, that single treatments are 
equivalent.
    The Agency has no information regarding the use of dichlorvos on 
the following outdoor sites: Outdoor areas under the general category 
of farm buildings, outside surfaces of buildings, enclosed outdoor 
utility equipment, or urban and rural outdoor areas. Due to the 
complete lack of information, these sites have not been addressed in 
this assessment document. Table 3 below summarizes the benefits 
assessment for dichlorvos uses. In aggregate, the overall annual 
economic impact of a dichlorvos cancellation to users and consumers is 
expected to be negligible. Furthermore, for most of the individual 
dichlorvos use sites a number of alternatives are registered and 
available. Any economic impacts would be expected to diminish over time 
as uses adjusted to the use of these alternative control materials. 
EPA's benefits assessment is based on information currently available 
to the Agency. EPA would consider new information from interested 
parties that might modify this benefits assessment.

                                                                        

[[Page 50359]]
                                Table 3.--Summary of Dichlorvos Benefits by Site                                
----------------------------------------------------------------------------------------------------------------
                              Extent of Usage                                                                   
                  --------------------------------------                                                        
                       Lbs Active                                                 Major         Economic Impact 
       Site         Ingredient/Year    Percent of Site         Pests           Alternatives        Extent and   
                   (Percent of Total       Treated                                                Significance  
                   Dichlorvos Use)**                                                                            
----------------------------------------------------------------------------------------------------------------
In and around      3,000-4,000 (1%)   unknown            ants               Aerosols (for      Not expected to  
 domestic                                                bees                homeowner use):    be significant  
 dwellings                                               bedbugs            bendiocarb                          
                                                         cockroaches        chlorpyrifos                        
                                                         firebrats          diazinon                            
                                                         flies              malathion                           
                                                         hornets            permethrin                          
                                                         mosquitoes         propoxur                            
                                                         silverfish         pyrethrins                          
                                                         spiders            resmethrin                          
                                                         wasps                                                  
                                                         yellow jackets                                         
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Domestic animals   9,000-10,000 (3%)  unknown            American dog tick  Impregnated        Not expected to  
 (cats and dogs)                                         brown dog tick      collars:           be significant  
                                                         cat flea           carbaryl                            
                                                                            chlorpyrifos                        
                                                                            naled                               
                                                                            phosmet                             
                                                                            propoxur                            
                                                                            pyrethrins                          
                                                                            tetrachlorvinphos                   
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Mushroom House     6,000 - 7,000      12.5% of site      phorid flies       Space spray:       Possible impacts 
                    (2%)               treated           scairid files       Permethrin                         
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Greenhouse uses:   Total Greenhouse   unknown            aphids             malathion          Not expected to  
 Ornamentals and    usage for both                       leafminers         nicotine            be significant  
 Food crops         ornamentals and                      leafrollers        pyrethrins                          
 (primarily         food crops:                          mealybugs          resmethrin                          
 cucumbers,         6,000-6,500 (2%)                     mites                                                  
 lettuce,                                                thrips                                                 
 tomatoes)                                               whiteflies                                             
                                                         scale insects                                          
                                                         spider mites                                           
                                                                                                                
----------------------------------------------------------------------------------------------------------------
Direct             Total animal                                                                                 
 application to     usage for direct                                                                            
 domestic food/     application and                                                                             
 non-food           their premises:                                                                             
 animals:           100,000-200,000                                                                             
                    (27-54%)                                                                                    
------------------                   ---------------------------------------------------------------------------
Livestock (beef                       unknown            face fly           coumaphos          Probable regional
 and dairy                                               stable fly         fenvalerate         impacts         
 cattle)                                                 house fly          lindane                             
                                                         horn fly           malathion                           
                                                                            methoxychlor                        
                                                                            permethrin                          
                                                                            phosmet                             
                                                                            pyrethrins                          
                                                                            tetrachlorvinphos                   
------------------                   ---------------------------------------------------------------------------
                                                                                                                
Poultry                               unknown            northern fowl      carbaryl           Possible regional
                                                          mite              permethrin          impacts         
------------------                   ---------------------------------------------------------------------------
                                                                                                                

[[Page 50360]]
                                                                                                                
Horses (including                     unknown            house fly          permethrin         Possible regional
 ponies)                                                 stable fly         pyrethrins          impacts         
                                                         face fly           tetrachlorvinphos                   
                                                         horn fly                                               
                                                         mosquitoes                                             
------------------                   ---------------------------------------------------------------------------
                                                                                                                
Swine/hogs                            unknown            house fly          malathion          Possible regional
                                                         stable fly         permethrin          impacts         
                                                         horse fly          tetrachlorvinphos                   
                                                         little house fly                                       
                                                         dump flies                                             
                                                         mosquitoes                                             
                                                         biting gnats                                           
                                                         psychodid flies                                        
                                                         screwworms                                             
------------------                   ---------------------------------------------------------------------------
                                                                                                                
Sheep/goats                           unknown            horn fly           coumaphos          Possible regional
                                                         house fly          diazinon            impacts         
                                                         stable fly         fenvalerate                         
                                                         lice               lindane                             
                                                         ticks              malathion                           
                                                         sheep ked          methoxychlor                        
                                                         wool maggots       permethrin                          
----------------------------------------------------------------------------------------------------------------
                                                                                                                
In and around      Total animal                                                                                 
 premises housing   usage for direct                                                                            
 food and non-      application and                                                                             
 food animals:      their premises:                                                                             
                    100,000-200,000                                                                             
                    (27-54%)                                                                                    
------------------                   ---------------------------------------------------------------------------
  Dairy rooms and                     unknown            house fly          Space sprays:                       
   milk houses                                                              permethrin                          
                                                                                               Possible regional
------------------                   ---------------------------------------------------------------------------
Furbearing animal                     unknown            flies              methomyl (bait)    Possible regional
 units                                                                      permethrin          impacts         
                                                                            pyrethrins                          
                                                                            tetrachlorvinphos                   
  Such as mink                                                                                                  
   farms                                                                                                        
------------------                   ---------------------------------------------------------------------------

[[Page 50361]]
                                                                                                                
Poultry houses                        unknown            house fly (adult)                                      
                                                                            Space sprays:                       
                                                                                                                
                                                                                               Possible regional
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Feedlots,          unknown            unknown            house fly          Outdoor Space                       
 including around                                        stable fly         Sprays/Fog:                         
 feedlots,                                               horn fly           malathion                           
 stockyards,                                             face fly           naled                               
 corrals, holding                                                                                               
 pens, fences,                                                                                                  
 etc.                                                                                                           
                                                                                               Probable regional
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Manure (poultry    unknown            unknown            house fly          dimethoate         Negligible       
 and livestock                                           horn fly           malathion                           
 manure)                                                 face fly           tetrachlorvinphos                   
 treatments on                                                                                                  
 farm premises                                                                                                  
----------------------------------------------------------------------------------------------------------------
Ornamental lawns   Little or no use   Little or no use   ants               For commercial     Negligible       
 and turf           expected           expected          armyworm complex    applicator use                     
                                                         billbugs            only:                              
                                                         chiggers           acephate                            
                                                         chinch bugs        bendiocarb                          
                                                         clover mite        carbaryl                            
                                                         crickets           chlorpyrifos                        
                                                         cutworms           diazinon                            
                                                         earwigs            isofenphos                          
                                                         fleas              isazofos                            
                                                         grasshoppers       malathion                           
                                                         hyperodes weevils                                      
                                                         sod webworms                                           
                                                         ticks                                                  
                                                         white grubs                                            
----------------------------------------------------------------------------------------------------------------
Ornamental plants  unknown            unknown            aphids             acephate           Not expected to  
 (excluding lawns                                        bagworms           carbaryl            be significant  
 and turf)                                               borers             chlorpyrifos                        
                                                         cutworms           diazinon                            
                                                         eastern tent       malathion                           
                                                          caterpillar                                           
                                                         gypsy moth                                             
                                                         leafhoppers                                            
                                                         mealybugs                                              
                                                         webworms                                               
                                                         mites                                                  
                                                         spittlebugs                                            
                                                         whiteflies                                             
----------------------------------------------------------------------------------------------------------------
                                                                                                                

[[Page 50362]]
                                                                                                                
Nonperishable      20,000-35,000 (5-  5%                 almond             Space sprays:      Not expected to  
 bulk-stored        9%)                                  moth               pyrethrins          be significant  
 agricultural                                            angoumois grain                                        
 commodities (raw                                         moth                                                  
 and processed)                                          cigarette beetle                                       
                                                         confused flour                                         
                                                          beetle                                                
                                                         flat grain beetle                                      
                                                         granary weevil                                         
                                                         Indianmeal moth                                        
                                                         lesser grain                                           
                                                          borer                                                 
                                                         red flour beetle                                       
                                                         rice weevil                                            
                                                         sawtoothed grain                                       
                                                          beetle                                                
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Packaged or        50,000-75,000 (13- 5-10% for both     almond moth        Space sprays:      $12 million for  
 bagged non-        20%) for both      raw and           angoumois grain    pyrethrins          both raw and    
 perishable         raw and            processed non-     moth                                  processed non-  
 processed and      processed non-     perishable        cadelle                                perishable      
 raw food           perishable         packaged or       cigarette beetle                       packaged or     
                    packaged or        bagged            cockroaches                            bagged          
                    bagged             agricultural      confused flour                         agricultural    
                    agricultural       commodities        beetle                                commodities plus
                    commodities                          dermestid beetles                      the cost of     
                                                         drugstore beetle                       additional      
                                                         flat grain weevil                      fumigations if  
                                                         granary weevil                         needed.         
                                                         Indianmeal moth                                        
                                                         lesser grain                                           
                                                          borer                                                 
                                                         Mediterranean                                          
                                                          flour moth                                            
                                                         merchant grain                                         
                                                          beetle                                                
                                                         red flour weevil                                       
                                                         rice weevil                                            
                                                         sawtoothed grain                                       
                                                          beetle                                                
                                                         tobacco moth                                           
----------------------------------------------------------------------------------------------------------------
Kennels            unknown            unknown            fleas              carbaryl           Not expected to  
                                                         ticks              chlorpyrifos        be significant  
                                                         house fly          diazinon                            
                                                         mosquitoes                                             
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Insect traps       50-100 (0.01-      unknown            Adults of:         None               Not expected to  
 (Monitoring        0.03%)                               gypsy moth                             be significant  
 purposes only)                                          spruce budworm                                         
                                                         forest tent                                            
                                                          caterpillar                                           
                                                         fruit flies                                            
                                                         codling moth                                           
                                                         corn borers                                            
                                                         weevils                                                
----------------------------------------------------------------------------------------------------------------
                                                                                                                

[[Page 50363]]
                                                                                                                
Garbage dumps      unknown            unknown            Flies (adults and  Surface sprays:                     
                                                          maggots)          chlorpyrifos                        
                                                                            diazinon                            
                                                                            propoxur                            
                                                                                               Not expected to  
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Commercial,        unknown            unknown            ants               Surface sprays:                     
 Institutional,                                          cockroaches        chlorpyrifos                        
 and Industrial                                          fleas              cypermethrin                        
 areas                                                   flies              diazinon                            
                                                         moths              propetamphos                        
                                                         silverfish         propoxur                            
                                                         sowbugs                                                
                                                         spiders                                                
                                                         stored product                                         
                                                          pests                                                 
                                                         wasps                                                  
                                                                                               Not expected to  
----------------------------------------------------------------------------------------------------------------
                                                                                                                
Commercial         unknown            unknown                                                                   
 transportation                                                                                                 
 vehicles:                                                                                                      
                                                                                                                
  Airplanes,                                             ants               phenothrin         Not expected to  
   buses                                                 cockroaches        pyrethrins          be significant  
                                                         fleas              resmethrin                          
                                                         flies                                                  
                                                         moths                                                  
                                                         scorpions                                              
                                                         silverfish                                             
                                                         spiders                                                
                                                         ticks                                                  
                                                         wasps                                                  
                                                         quarantine pests                                       
------------------                                      --------------------------------------------------------

[[Page 50364]]
                                                                                                                
  Other                                                  angoumois grain    pyrethrins         Not expected to  
   transportation                                         moth                                  be significant  
   vehicles                                              ants                                                   
   including                                             cadelle                                                
   trucks,                                               cheese mite                                            
   shipholds, and                                        cigarette beetle                                       
   railroad cars                                         confused flour                                         
                                                          beetle                                                
                                                         dermestids                                             
                                                         drugstore beetle                                       
                                                         flat grain beetle                                      
                                                         granary weevil                                         
                                                         Indian meal moth                                       
                                                         lesser grain                                           
                                                          borer                                                 
                                                         mealworms                                              
                                                         Mediterranean                                          
                                                          flour moth                                            
                                                         red flour beetle                                       
                                                         rice weevil                                            
                                                         sawtoothed grain                                       
                                                         beetle                                                 
                                                                                                                
----------------------------------------------------------------------------------------------------------------
Total usage        250,000-500,000                                                                              
 accounted for      (52-90%)                                                                                    
 above                                                                                                          
----------------------------------------------------------------------------------------------------------------



    **Note: The total used in calculating percentage of dichlorvos 
use for a given site is based on the mid point (375,000) of the 
total range 250,000 - 500,000.

G. Analysis of Comments

    Comment. The Southeastern Peanut Association (SPA) commented that 
the substitutes to dichlorvos are substantially less effective on 
peanuts and not fully available for commercial use.
    Agency response. The Agency cannot fully respond to this comment as 
the substitutes for dichlorvos were not identified in the letter from 
the SPA. The Agency has identified the pyrethrins as a possible 
alternative to dichlorvos. Because the pyrethrins are registered for 
use in much the same way as dichlorvos and due to the lack of 
comparative efficacy or resistance data, EPA assumes that they would 
provide acceptable levels of insect control. Regarding the availability 
of the pyrethrins, because the growing conditions that affect 
chrysanthemums (the source from which pyrethrins are derived) can vary 
from year-to-year, the Agency recognizes that the availability and 
price of pyrethrins will fluctuate as well.
    Comment. The California Department of Food and Agriculture (CDFA) 
commented that dried fruit and tree nuts can be kept insect free if 
fumigated before entering storage and once in storage, receive regular 
treatments of dichlorvos. CDFA states that alternate methods of insect 
control, irradiation and controlled atmospheres are not feasible.
    Agency response. The Agency believes that the pyrethrins would 
serve to control insects in the above situation if used in the same 
manner as dichlorvos. EPA does not have data that indicate the number 
of treatments needed for the pyrethrins to replace dichlorvos and still 
provide the same level of control. The Agency also believes that as the 
fumigant methyl bromide is phased out under the Clean Air Act, 
alternative measures such as irradiation, heat, cold, and controlled 
atmospheres will become more important.
    Comment. The American Corn Millers Federation (ACMF) commented that 
the use of pyrethrins or resmethrin as alternatives to dichlorvos are 
not as efficacious in storage areas, warehouses, or processing areas of 
plants.
    Agency response. The Agency has identified the pyrethrins and 
resmethrin (aerosol treatments) as potential alternatives to fogging 
with dichlorvos in commercial, industrial, and institutional areas. The 
ACMF did not submit data to support their contentions of inadequate 
efficacy of the alternatives. In the absence of comparative efficacy 
and/or resistance data, EPA assumes that these registered alternatives 
would provide adequate levels of insect control.
    Comment. Two representatives from the popcorn industry commented 
that there are no replacements for the use of dichlorvos pest strips in 
popcorn storage facilities.
    Agency response. The Agency has no specific information regarding 
insect control in stored popcorn; however, EPA does have information 
regarding 

[[Page 50365]]
the treatment of other stored grain products. EPA believes the 
pyrethrins could be used as a head space treatment; however, EPA does 
not know how many treatments of pyrethrins it would take to provide the 
same level of control as obtained with the dichlorvos pest strips, 
which can last for several months.
    Comment. The Department of Defense (DOD), Armed Forces Pest 
Management Board, commented on the use of dichlorvos as a fogging 
material in warehouses containing food products and textiles. The DOD 
lists pyrethroids, pyrethrins, aluminum phosphide, and the use of 
residual sprays as either not as effective or not as available as 
dichlorvos.
    Agency response. In the most current benefits assessment, the 
Agency identified the pyrethrins and resmethrin as the most likely 
substitutes for dichlorvos when used as an aerosol or fog application. 
The Agency also listed products containing chlorpyrifos, cypermethrin, 
diazinon, propetamphos, or propoxur as surface residual treatments that 
could replace dichlorvos. In the absence of comparative efficacy or 
resistance data (DOD included no data with their comments), EPA has 
assumed that all registered alternative active ingredients would 
provide adequate control of the insect pests involved with these sites.
    Comment. The Grocery Manufacturers of America (GMA) commented that 
the alternatives to dichlorvos were unsuitable because they are more 
expensive, less effective, require more frequent applications, and some 
may result in off-flavors to the stored foods.
    Agency response. The GMA did not identify the alternatives and did 
not include any data to substantiate the contentions made. The Agency 
believes that dichlorvos is used primarily as an aerosol in commercial, 
industrial, and institutional areas. In the current benefits 
assessment, the Agency has identified resmethrin and pyrethrins as 
possible aerosol alternatives for dichlorvos and chlorpyrifos, 
cypermethrin, diazinon, propetamphos, or propoxur as residual surface 
treatments that could replace the use of dichlorvos. In the absence of 
comparative efficacy or resistance data, EPA assumes that all 
registered active ingredients listed would provide adequate pest 
control. EPA has no data regarding the off-flavoring of stored foods 
for any of the alternative products.
    Comment. The National Food Processors Association (NFPA) commented 
that many of its members depend on dichlorvos for insect control in 
food processing plants, warehouses, and mushroom houses. NFPA stated 
that smaller amounts of dichlorvos are needed than the alternatives to 
control the pests, and that some pests have become resistant to the 
alternatives.
    Agency response. NFPA did not include comparative efficacy and/or 
resistance data to support their contentions. In the current EPA 
benefits assessment of dichlorvos, EPA concludes that the use of 
surface sprays (diazinon, propoxur, or pyrethrins) and larvicides 
(diflubenzuron or methoprene) are the primary methods of insect control 
currently used in mushroom houses. In the absence of comparative 
efficacy or resistance data, EPA assumes that the alternative methods 
would provide adequate levels of control.
    The Agency believes that dichlorvos is used primarily as an aerosol 
treatment in commercial, industrial, and institutional areas (including 
food processing plants and warehouses). In the current benefits 
assessment, the Agency identifies resmethrin and pyrethrins as possible 
alternatives for aerosol dichlorvos and chlorpyrifos, cypermethrin, 
diazinon, propetamphos, or propoxur as residual surface treatments that 
could replace the use of dichlorvos. In the absence of comparative 
efficacy and/or resistance data, EPA assumes that all registered active 
ingredients listed would provide adequate pest control.
    Comment. A representative from the fumigation industry commented 
that the grain, seed, popcorn, and food processing industries do not 
need dichlorvos. Alternatives to dichlorvos were listed as pyrethrins, 
resmethrin, sanitation, monitoring with pheromone traps, and the use of 
grain protectants.
    Agency response. In the current benefits assessment, EPA has 
identified several alternative active ingredients that could replace 
the use of dichlorvos in the above-mentioned areas. EPA also listed 
several non-chemical methods of insect control including sanitation, 
use of pheromone traps, predators, parasites, the use of heat or cold, 
exclusion, and irradiation. The Agency realizes that some of these 
methods may require more research before acceptance by industry and 
that many facilities would require additional construction before 
implementation could occur. In the absence of comparative efficacy or 
resistance data (none were included with the above comments), EPA 
assumes that the chemical alternatives to dichlorvos would provide 
adequate control of the insect pests. The Agency believes that the non-
chemical methods cited could aid in insect control when used alone, in 
combination with each other, or in combination with insecticides.
    Comments. Comments from the Pesticide Impact Assessment Program at 
the University of Idaho presented dichlorvos application and usage 
information for 1988 in the state of Idaho.
    Agency response. While EPA appreciates and needs this type of 
information in order to conduct a benefits assessment, EPA believes the 
data gathered in 1988 may not be accurate at this time. The Agency 
believes that the volume of dichlorvos produced and sold in the United 
States has decreased over the last 5 to 6 years and assumes that this 
trend has occurred in Idaho as well.
    Comment. Reliable Services commented that the loss of dichlorvos 
would be detrimental to the food related industries and that no 
effective alternatives exist for the use of dichlorvos strips in sewer 
catch basins for mosquito control. The alternatives identified for use 
in warehouses and food processing areas were identified as pyrethrins 
and resmethrin. Reliable Services estimates that for the alternatives, 
the number of applications are greater and the cost of materials are 
significantly higher than dichlorvos.
    Agency response. Several pest strips containing dichlorvos are 
registered for use in catch basins to control adult mosquitoes. 
Although there are no direct alternatives for these pest strips, 
different formulations of other active ingredients are available that 
provide control of the larval and pupal stages of mosquitoes occurring 
in catch basins. EPA could find no state pest control guides 
recommending the use of pest strips for mosquito control at this 
particular site. EPA lacks sufficient use, usage, and efficacy data on 
dichlorvos to conduct a benefits assessment for this site/pest 
combination.
    In the absence of comparative efficacy or resistance data, EPA 
assumes that all active ingredients listed would provide adequate pest 
control. The Agency also recognizes the importance of sanitation, 
exclusion, and trapping (pheromone traps) to control insect populations 
in storage facilities; however, EPA has no data indicating what 
percentage of insect control is accomplished by these methods.
    Comment. The National Pest Control Association (NPCA) commented 
that dichlorvos is important to the structural pest control and food 
industries (transportation, storage, and processing facilities).
    Agency response. EPA recognizes the important role dichlorvos has 
played in keeping insect populations under 

[[Page 50366]]
control in the above areas. In the current benefits assessment, the 
Agency has identified alternative active ingredients (pyrethrins or 
resmethrin as aerosol sprays; chlorpyrifos, cypermethrin, diazinon, 
propetamphos, or propoxur as residual surface sprays) as well as non-
chemical practices (sanitation, exclusion, heat, cold, modified 
atmospheres, pheromones, parasites, etc,) that, alone or in 
combination, may replace the use of dichlorvos. In the absence of 
comparative efficacy or resistance data, EPA assumes that the 
registered alternative active ingredients identified would provide 
adequate levels of insect control. EPA is not certain what percentage 
of insect control can be attributed to the non-chemical control methods 
discussed.
    Comment. WHB Specialty Products Co. (WHB) commented that because of 
declining usage after 1983, any regulatory action taken by the U.S. EPA 
would have no economic impact on sales of their end-use products, which 
are used for control of insects on beef and dairy cattle and in 
livestock buildings.
    Agency response. This comment is consistent with the Agency's 
information that usage is declining.
    Comment. Consumers Union commented that the benefits of dichlorvos 
use in ``bug sprays,'' flea collars, and resin strips are negligible.
    Agency response. EPA's current benefits assessment for dichlorvos 
has identified from one to several alternatives for the use of 
dichlorvos in ``bug sprays'' (In and Around Domestic Dwellings), resin 
strips (numerous sites), and pet flea collars (Domestic Animals). Based 
on the information available at this time, it is the Agency's opinion 
that the benefits for dichlorvos use in the areas mentioned above are 
negligible. In the absence of comparative efficacy or resistance data, 
EPA assumes that available registered alternatives would provide 
adequate control of the insect pests.
    Comment. Amvac Chemical Corporation commented on the use of 
dichlorvos in warehouses and food processing areas. Amvac states that 
the alternatives are not as effective and are more expensive than 
dichlorvos.
    Agency response. The current EPA benefits assessment (commercial, 
industrial, and institutional areas) and the comments from Amvac are in 
agreement as to pests controlled, primary methods in which dichlorvos 
is applied, and the potential alternatives to dichlorvos. Amvac states 
that the alternatives are not as effective as dichlorvos and refers to 
a survey and personal communications as the source for their 
conclusions. In the absence of comparative efficacy or resistance data, 
the Agency assumes that the registered alternatives would provide 
adequate control of the insect pests in warehouses and food processing 
plants. In addition, the Agency identified several non-chemical methods 
of insect control in warehouses and food processing facilities that 
Amvac did not include in their comments. EPA believes that in recent 
years alternative methods such as sanitation, exclusion, heat, cold, 
modified atmospheres, parasites, and the use of pheromone traps have 
become more common but the Agency has no data that identifies the 
percentage of insect control that can be attributed to these methods.
    Comment. Amvac Chemical Corporation commented on the benefits and 
use of dichlorvos to control insects on dairy and beef cattle and in 
the premises housing these animals. Amvac states that resistance to 
some of the alternatives is a problem.
    Agency response. The current EPA benefits assessment for dichlorvos 
includes the following sites that relate to food or nonfood animals and 
their premises: direct application to food and nonfood animals, in and 
around premises housing food and nonfood animals, manure treatments, 
and feedlots. The pests and their potential damage to animals, the 
primary methods of using dichlorvos, and the potential alternatives 
identified are similar in both the EPA assessment and Amvac's comments. 
EPA is aware that resistance to some of the alternatives may have 
occurred; however, EPA does not have any data identifying specific 
compounds, insect species, or the extent of any resistance problem. 
Amvac relied on personal communications and surveys to support their 
statements but did not submit data to substantiate their claims 
regarding efficacy or resistance. In the absence of comparative 
efficacy or resistance data, EPA assumes that all registered products 
would provide adequate insect control.
    Comment. Amvac Chemical Corporation commented on the benefits and 
use of dichlorvos in domestic dwellings and in pet flea collars. Amvac 
states that the alternatives are not as efficacious as dichlorvos 
(based on personal communications) but includes no comparative efficacy 
and/or resistance data with their comments.
    Agency response. In the current benefits assessment, EPA addressed 
these sites under the headings in and around domestic dwellings and 
domestic animals (Cats and Dogs). The EPA list of pests, primary 
methods of dichlorvos applications, and potential alternatives for 
these two sites was similar to the information provided by Amvac. In 
the absence of efficacy and/or resistance data, the Agency assumes that 
the identified registered alternatives would provide adequate control 
of the pests.
    Comment. Amvac Chemical Corporation commented on the benefits and 
use of dichlorvos in food markets and eating establishments. Amvac 
stated that the alternatives are less effective and more costly.
    Agency response. The section titled ``Commercial, Industrial, and 
Institutional Areas'' in the current EPA benefits assessment for 
dichlorvos includes information on eating establishments. Because of 
the lack of information, EPA did not include food markets in the 
benefits assessment. The EPA assessment for eating establishments 
included many of the same pests, the same primary methods of dichlorvos 
application, and the same potential alternatives as identified in the 
Amvac comments. Although Amvac states that the alternatives are less 
effective and more costly, they did not include supporting data with 
the comments. In the absence of data, the Agency assumes that the 
identified alternatives would provide adequate control of the pests.
    Comment. Amvac Chemical Corporation commented on the benefits and 
use of dichlorvos resin strips in popcorn storage bins. Amvac 
identified the pyrethrins as a fogging treatment in bin head spaces or 
actellic (pirimiphos-methyl) as a protectant applied to the popcorn. 
Amvac states that neither the pyrethrins nor pirimiphos-methyl is as 
cost effective or efficacious as dichlorvos.
    Agency response. The Agency has no specific information regarding 
insect control in stored popcorn and did not include this specific site 
in the current assessment; however, EPA does have information for the 
treatment of other stored grain products. The Agency believes that the 
pyrethrins can be used as a head space treatment; however, EPA has no 
information concerning the number of treatments of pyrethrins it would 
take to provide the same level of control as obtained with the 
dichlorvos pest strips. The dichlorvos impregnated resin pest strips 
can provide insect control for several months.

IV. Risk/Benefit Analysis and Proposed Regulatory Decisions

A. Summary of Risk/Benefit Analysis

    EPA has concluded that the risks outweigh the benefits for most 
uses of dichlorvos, and therefore, proposes a 

[[Page 50367]]
variety of measures to reduce risks to the acceptable level, including: 
Cancellation of some uses, requiring protective clothing, specifying 
reentry intervals, and restricting use to certified applicators. Tables 
4 and 5, in this unit, summarize EPA's risk/benefit analyses and 
proposals for risk mitigation. The benefits are not expected to be 
significant for most sites, with the possible exceptions of packaged or 
bagged nonperishable raw and processed food, livestock, poultry, and 
mushroom houses. The lack of known significant benefits for most sites 
is outweighed by the potential total dietary cancer risk of 4.4 x 
10-6 from use of dichlorvos and 5.1 x 10-6 from dichlorvos 
residues due to dichlorvos plus naled, and the occupational and 
residential risks involving several MOEs less than 100 (some less than 
10) for ChE inhibition.
    EPA considered measures short of cancellation to reduce 
occupational and residential risks, such as restricted reentry 
intervals, personal protective equipment, and restricting use to 
certified applicators. Where appropriate, these measures are proposed; 
however, cancellation is proposed for several uses because risk 
mitigation measures are not expected to reduce risk sufficiently.
    There are a variety of alternatives available for dichlorvos, 
varying from use to use. EPA compared the toxicity of several 
alternatives for some major sites to understand the effect of canceling 
dichlorvos. This discussion of alternatives relates to the hazards 
posed by each pesticide in its technical form and does not take into 
account differing exposures resulting from application equipment used, 
or frequency or rate of application. The risk from a pesticide is a 
function of both the hazard or toxicity of the pesticide and the extent 
to which an individual is exposed. Alternatives fall into three 
chemical types, organophosphates, carbamates, and others. 
Organophosphates and carbamates inhibit ChE activity and result in 
neurotoxic effects. Several of the other alternatives are pyrethroids, 
including cypermethrin, permethrin, d-phenothrin and resmethrin. The 
pyrethrins and pyrethroid compounds present less of an acute hazard 
than the ChE-inhibiting alternatives. Exposure to the pyrethroids and 
pyrethrins can result in neurotoxicity, but the effects are rapidly 
reversible and only occur at much higher doses than for 
organophosphates. Pesticide poisoning incidents involving workers have 
been reported for several registered alternatives including, 
chlorpyrifos, diazinon, and malathion. Dichlorvos is a Group C 
(possible human) carcinogen, while for some alternatives there is no 
evidence of carcinogenicity or there are data gaps. Propoxur is a Group 
B2 (probable human) carcinogen and permethrin is a Group C. Dichlorvos 
has a higher cancer potency than either of these two chemicals. Also, 
the pyrethroids and pyrethrins are less toxic than dichlorvos following 
chronic exposure. Of all registered alternatives, only diazinon had an 
RfD lower than dichlorvos. Finally, no significant developmental or 
reproductive effects were reported for dichlorvos or any of the 
alternatives.

B. Proposed Regulatory Actions

    1. Dietary risk. EPA is proposing cancellation of dichlorvos for 
use on bulk, packaged, and bagged nonperishable raw and processed food, 
because of the unacceptable risk posed by this use. Table 4, in this 
unit, compares the dietary cancer risk before and after the actions 
proposed in this notice. The estimated upperbound excess individual 
lifetime dietary cancer risk (before EPA's proposed action) from 
application of dichlorvos is 4.4 x 10-6 and from naled-derived 
dichlorvos is 7.2 x 10-7, for a total of 5.1 x 10-6. The 
major source of estimated dietary risk is packaged, bagged or bulk 
nonperishable processed or raw food (3.4 x 10-6). The estimated 
risk from the three individual tolerances and FAR (bulk raw, packaged 
or bagged raw, and packaged or bagged processed) cannot be separated 
because, as discussed earlier, a single commodity may be treated more 
than once at different stages of production. Following EPA's proposed 
actions, discussed below, the remaining total dietary risk would be 1.7 
x 10-6, including dichlorvos derived from naled. This estimated 
dietary risk is believed to overestimate the actual risk because: (1) 
The estimated risk from naled residues is probably high because EPA 
assumed that the mosquito/fly control use (without regard to specific 
crops) would result in one percent of all commodities having residues; 
(2) EPA is assuming that 100 percent of the naled residues will 
metabolize into dichlorvos, which is probably not the case; and (3) the 
risk from milk (6.2 x 10-7 or about one-third of the risk after 
the proposed action) is believed to be an overestimate because the 
anticipated residues used in the risk assessment are based on one-half 
the limit of detection, which was used because no residues were found 
in milk following exaggerated application of dichlorvos. This dietary 
risk assessment could underestimate dietary risks from treated food in 
food handling establishments, since this risk in not included in the 
risk assessment; however, if the proposal to cancel use in commercial 
establishments, due to applicator and reentry risks, is finalized, this 
potential dietary risk will no longer exist.
    2. Use on bulk, packaged or bagged nonperishable raw and processed 
food. EPA is proposing cancellation of these uses because of 
unacceptable dietary risks, and because of the unacceptable risk to 
workers from applying dichlorvos to stored food and reentering treated 
areas. (See paragraph 3--Warehouses in this unit.)
    i. The estimated dietary risk from dichlorvos, 3.4 x 10-6, is 
of concern because it exceeds the Agency's 10-6 negligible risk 
level. This group of uses is treated as one use here for purposes of 
risk estimation because consumption data do not permit a more detailed 
breakdown. This is an unusual site in that it is not specific to a 
location such as greenhouses or tobacco warehouses. Bulk, packaged, or 
bagged food can be found in a variety of locations including food 
handling establishments (food service, food manufacturing, and food 
processing establishments), in warehouses, shipholds, trucks and any 
other location where food is stored. Since the proportion of 
commodities stored in bulk compared to packaged/bagged food is unknown, 
it is not possible to clearly separate these risks or limit the scope 
of this proposal. Also, EPA does not believe that it is possible to 
reduce the frequency or amount of dichlorvos applications to decrease 
dietary risk to an acceptable level.
    ii. There are potentially significant benefits for this use. The 
major alternatives are pyrethrins, and the absence of dichlorvos may 
require fumigant treatments. Cancellation of this use would result in 
increased costs estimated to be $12 million to replace dichlorvos with 
pyrethrins, plus, if needed, the additional cost of supplemental 
fumigations would be about $33 million with methyl bromide or $44 
million per year with aluminum phosphide. Without the use of fumigants 
in supplementing pyrethrins there could be some loss in efficacy; 
however, EPA has no basis to confirm or estimate this loss. Although 
there are potential significant economic impacts, EPA believes that the 
dietary cancer risks to the general public outweigh the benefits. 
Therefore, EPA is proposing cancellation of use on bulk, packaged or 
bagged nonperishable raw and processed food. EPA is interested in 
comments on the effect of this proposal. The dietary risk discussed may 
also be affected by the pending revocation of the section 409 FAR for 
residues of dichlorvos on packaged or bagged 

[[Page 50368]]
nonperishable processed food and the possible cancellation of the 
related uses. However, because those actions have not occurred, the 
Agency is proposing action at this time based on unacceptable dietary 
and worker risks (see warehouse discussion below).
    3. Warehouses. MOEs from applying dichlorvos in warehouses and 
reentering treated areas are unacceptable, with the exception of 
impregnated resin pest strips in closed areas such as silos. EPA is, 
therefore, proposing cancellation of this use. Even if applicator 
exposure were minimized through the use of automatic application 
equipment, the MOEs from reentry would still be unacceptable. EPA 
assumes that a variety of tasks are performed in a warehouse including 
inventory, stocking and retrieving stored commodities, all of which 
would require entry into the warehouse soon after application to 
perform these tasks, and would result in prolonged exposure to a 
worker. Therefore, EPA does not believe it is feasible to mitigate the 
risk to workers reentering treated areas.
    If dichlorvos can no longer be used in warehouses, areas where food 
is stored, due to worker risk, then the dietary risk from bulk stored, 
packaged or bagged raw and processed food would be eliminated. 
Therefore, the benefits for warehouses and for bulk stored, packaged or 
bagged food would be similar. As discussed in paragraph 2 above, there 
are potentially significant benefits for the use on bulk stored 
packaged and bagged food in warehouses. There are alternatives to 
dichlorvos for this use; however, cancellation of this use would result 
in increased costs as described in paragraph 2 above. These benefits do 
not justify MOEs of 38 for applicators and 2.8 for reentry workers. 
Based on unacceptable MOEs for applicators and reentry workers, EPA 
believes the risks outweigh the benefits, and therefore, products 
registered for the warehouse use should be canceled.
    4. Commercial, institutional, and industrial areas. The risks posed 
by these uses, which include food handling establishments, are 
estimated to be similar to risks from warehouse uses, involving MOEs of 
38 for applicators and 2.8 for persons reentering treated areas. There 
are a variety of registered alternatives in the absence of dichlorvos, 
and the benefits are not expected to be significant. EPA is, therefore, 
proposing to cancel these uses because the risks outweigh the benefits. 
Any dietary risk resulting from food handling use, although not 
estimated here, would be eliminated.
    5. Greenhouses. The estimated dietary risk from dichlorvos use in 
greenhouses is 2.0 x 10-7, which is negligible. However, the MOEs 
for workers performing most methods of application in greenhouses are 
less than 100, and about one-third are less than 50, since they involve 
the applicator remaining in the greenhouse during application. In 
addition, the MOE for reentry workers 24 hours after application is 21. 
There are a variety of registered alternatives available as a space 
treatment, surface treatment or direct treatment to plants. Assuming an 
equal number of applications to replace dichlorvos, the cancellation of 
dichlorvos should not result in significant economic impacts. These 
applicator and reentry risks are unacceptable, and thus, EPA is 
proposing to cancel registrations of products labeled for use in 
greenhouses unless the following changes are made to the label which 
will reduce risks to an acceptable level: Eliminate hand-held 
application methods and require use of automatic foggers inside the 
greenhouse or fogging through a port on the side of a greenhouse. In 
either case, no one (including the applicator) would be allowed in the 
greenhouse during the application. In addition, because of low MOEs for 
workers reentering greenhouses, the Agency is proposing to limit 
exposure by prohibiting entry by anyone, including handlers (except in 
an emergency) within the first 4 hours following application. For the 
remainder of the first 48 hours following application, the Agency is 
proposing to allow one hour per day entry into dichlorvos-treated 
greenhouses by trained pesticide handlers who are equipped with handler 
personal protective equipment (including an organic-vapor-cartridge 
respirator) and who are performing a handling task. Handling tasks are 
defined by the Worker Protection Standard (40 CFR part 170) and include 
operating ventilation equipment and checking air concentration levels. 
Entry by workers to perform non-handler tasks, such as harvesting, 
cultivation, and irrigation-related tasks would be prohibited for the 
entire 48-hour period. It is unclear what effect, if any, the reentry 
restrictions proposed in this action will have on the greenhouse 
industry, since the Agency has no information regarding the need for 
reentry tasks during the first 48 hours following application of 
dichlorvos.
    If the application and reentry restrictions proposed here are not 
feasible to implement, EPA does not believe that the loss of dichlorvos 
in greenhouses would have a significant impact on the greenhouse 
industry; benefits from the use of dichlorvos in greenhouses are 
expected to be minimal due to the availability of alternatives. 
Therefore, EPA is proposing these restrictions because, without them, 
the applicator and reentry risks outweigh the benefits. Note that the 
entry restrictions being proposed by the Agency are based on the 
assumption that the treated area would not be ventilated for the entire 
48-hour period following application. The Agency would consider data, 
if submitted, that indicate that a specified number of air exchanges or 
a specified number of hours of mechanical ventilation would reduce the 
dichlorvos air concentration level to an acceptable level for safe 
entry for workers (without respirators) in less than the proposed 48-
hour entry-restricted period. This 48-hour reentry period exceeds the 
24-hour period required in the Worker Protection Standard; however, 
based on the exposure data for dichlorvos, EPA believes that this 
longer reentry period is necessary to reduce worker risk to an 
acceptable level.
    6. Mushroom houses. The estimated dietary risk from use of 
dichlorvos in mushroom houses is 2.6 x 10-9, which is negligible. 
However, the MOEs for most methods of applying dichlorvos in mushroom 
houses are less than 100, and some are less than 10, since they involve 
the applicator remaining in the house during application. In addition, 
the MOE for reentry workers following 24 hours after application is 21. 
These applicator and reentry risks are unacceptable, and thus, EPA is 
proposing to cancel registrations of products labeled for use in 
mushroom houses unless the following changes are made to the label 
which will reduce risks to an acceptable level: Eliminate hand-held 
application methods, and require use of automatic foggers inside the 
mushroom house or fogging through a port on the side of a mushroom 
house. In either case, no one (including the applicator) would be 
allowed in the mushroom house during the application. In addition, 
because of low MOEs from reentering mushroom houses, the Agency is 
proposing to limit exposure by prohibiting entry by anyone, including 
handlers (except in an emergency) within the first 4 hours following 
application. For the remainder of the first 48 hours following 
application, the Agency is proposing to allow one hour per day entry 
into dichlorvos-treated mushroom houses by trained pesticide handlers 
who are equipped with handler personal protective equipment (including 
an 

[[Page 50369]]
organic-vapor-cartridge respirator) and who are performing a handling 
task. Handling tasks are defined by the Worker Protection Standard (40 
CFR part 170) and include operating ventilation equipment and checking 
air concentration levels. Entry by workers to perform non-handler 
tasks, such as harvesting, cultivation, and irrigation-related tasks 
would be prohibited for the entire 48-hour period. The economic impact 
resulting from these restrictions is not expected to be significant 
since dichlorvos is only used for insect control after surface sprays 
and larvacides have been used, and permethrin is available as a direct 
alternative to dichlorvos. It is unclear what effect, if any, the 
reentry restrictions proposed in this action will have on the mushroom 
industry, since the Agency has no information showing whether reentry 
to perform crop cultivation tasks is necessary during the first 48 
hours following application. EPA acknowledges that there may be impacts 
due to these restrictions; however in the absence of data, EPA is 
assuming no impact. Therefore, EPA is proposing these restrictions 
because, without them, the applicator and reentry risks outweigh the 
benefits. Note that the entry restrictions being proposed by the Agency 
are based on the assumption that the treated area would not be 
ventilated at all during the entire 48-hour period following 
application. The Agency would consider data, if submitted, that 
indicate that a specified number of air exchanges or a specified number 
of hours of mechanical ventilation would reduce the dichlorvos air 
concentration level to an acceptable level for safe entry for workers 
(without respirators) in less than the proposed 48-hour entry-
restricted period. This 48-hour reentry period exceeds the 24-hour 
period required in the Worker Protection Standard; however, based on 
exposure data for dichlorvos, EPA believes that this longer reentry 
period is necessary to reduce worker risk to an acceptable level.
    7. Direct treatment to domestic food and non-food animals (non-
poultry). EPA is proposing cancellation of all products registered for 
hand-held application methods to domestic animals. The MOE for hand 
application is approximately 6. Other direct application methods that 
do not involve hand-held application are not expected to exceed the 
Agency's level of concern and would still be allowed. These include: 
face and back rubbers, and devices which automatically apply dichlorvos 
to the animals. The loss of dichlorvos for hand-held treatment of 
animals should not have a major economic impact since there are easily 
available alternatives similar in cost to dichlorvos, and dichlorvos 
can still be used by other methods. Therefore, EPA believes that the 
risks outweigh the benefits for hand-held methods of application to 
food and non-food animals, excluding poultry.
    8. Direct treatment to domestic food and non-food animals 
(poultry). EPA is proposing to retain the use of dichlorvos on poultry 
because the risks from application are not unreasonable. Dichlorvos is 
mainly used as a space spray to treat poultry premises, but it is also 
used for direct animal treatment. EPA does not have data to estimate 
risk from treating poultry; however, the Agency believes that both the 
application method and fewer number of applications will result in much 
lower exposure and risk than for cattle treatment. The benefits for 
poultry treatment cannot be separated out from the use on domestic 
animals and their premises. However, EPA believes there is a benefit 
for controlling mites on laying hens. As a result EPA is believes the 
benefits of dichlorvos use exceeds the risks and is proposing retention 
of this use.
    9. Treatment of domestic animal (food and non-food) premises. EPA 
is proposing to retain the use of dichlorvos for treatment of domestic 
animal premises. The Agency estimates that MOEs for applying dichlorvos 
are greater than 100. Because there may be some benefits for the 
combined direct animal and premise treatment, and the estimated risk is 
very low, EPA believes that the benefits of this use outweigh the 
risks. Therefore, EPA is proposing retention of this use.
    10. Feedlots (including around feedlots, stockyards, corrals, and 
holding pens). EPA proposes to retain the use of dichlorvos in 
feedlots. The Agency estimates that the MOEs for applying dichlorvos 
are greater than 100. Also application of dichlorvos in feedlots 
generally involves application over a short period of time in a well 
ventilated area, which together, further reduces the risk of exposure. 
There are various alternatives to dichlorvos for controlling flies in 
feedlots. Because there are probable regional impacts resulting from 
cancellation of this use, and the MOEs are greater than 100, EPA is 
proposing to retain this use. Therefore, the benefits outweigh the 
risks in this case.
    11. Manure. EPA proposes retaining the use of dichlorvos on manure. 
The Agency estimates that the MOEs for applying dichlorvos on manure 
are greater than 100. In addition, manure is generally located outdoors 
or in well-ventilated areas, thereby reducing exposure to dichlorvos. 
There are various alternatives to dichlorvos for controlling flies on 
manure. There may be some benefits from the use of dichlorvos on 
manure, although not significant, and because this use is not a risk of 
concern, EPA is proposing to retain the use on manure.
    12. Tobacco warehouse. EPA is proposing cancellation of products 
registered for this use because both applicator and reentry MOEs are 
low: 2 for application and 0.3 for reentry. Although EPA did not 
conduct a benefits analysis for this use site, EPA believes that little 
or no dichlorvos is used for tobacco warehouses, and Amvac has 
requested voluntary cancellation for this use site. The Agency does not 
anticipate a significant economic impact from cancellation; therefore, 
the risks of this use outweigh its benefits.
    13. Residential uses. The Agency is proposing cancellation of all 
products registered for residential uses, including use by residents 
and by professional applicators, and for use on pets. EPA has 
determined that the MOEs are significantly less than 100 for all 
methods of application in the home and for post-application exposure to 
residents. The animal health and safety data discussed earlier also 
indicate an unacceptable risk for pets. Overall, the effect of 
cancellation of all residential uses is not expected to be significant, 
since there are several alternatives available. Therefore, EPA believes 
that the risks to residents and pets outweigh the benefits of this use.
    14. Ornamental lawns, turf and plants. EPA is proposing to cancel 
dichlorvos products registered for these uses. The estimated risks from 
application of dichlorvos to ornamental lawns, turf, and plants are low 
(32 - similar to a greenhouse power sprayer). The economic impact 
resulting from the cancellation of this use is not expected to be 
significant since there are alternatives available which, in some 
cases, cost less than dichlorvos. Therefore, the risks outweigh the 
benefits.
    15. Kennels. EPA is proposing to retain use in kennels. The Agency 
estimates that the MOE for applying dichlorvos in kennels is similar to 
that of a dairy barn or at least 225. There may be some benefits from 
the use of dichlorvos in kennels, although not significant, and because 
this use is not a risk of concern, EPA is proposing to retain this use. 


[[Page 50370]]

    16. Insect traps. EPA is proposing to retain the use of dichlorvos 
in insect traps. The risk to applicators is expected to be negligible 
because of the short amount of time that the applicator is in contact 
with the trap, and because the traps are located outside away from 
people. The only alternative, adhesive strips, may not be as effective 
as dichlorvos in cases where there are heavy insect populations. 
Although the overall benefits are not expected to be significant, the 
benefits for heavy insect problems outweigh the negligible risks.
    17. Garbage dumps. EPA proposes retaining the use of dichlorvos on 
garbage dumps. The Agency estimates that the MOE for applying 
dichlorvos on a garbage dump are greater than 100. In addition, garbage 
is generally located outdoors or in a separate room, thereby reducing 
exposure. There are various alternatives to dichlorvos for controlling 
flies on garbage. There may be some benefits from the use of dichlorvos 
on garbage dumps, although not significant, and because this use is not 
a risk of concern, EPA is proposing to retain the use on garbage dumps.
    18. Commercial transportation vehicles. There are unacceptable 
applicator and reentry risks for all commercial transportation uses. 
Due to a very low MOE of 14 for applicators on airplanes, EPA is 
proposing to cancel dichlorvos products registered for this use. EPA 
does not believe it is possible to reduce this risk. The benefits are 
not expected to be significant, since EPA estimates the use to be 
minimal and Amvac has requested voluntary cancellation of this use. 
Therefore, EPA believes the risks outweigh the benefits of continued 
use in airplanes.
    The Agency believes that risk mitigation measures are possible for 
use of dichlorvos in buses. For passenger buses, EPA is proposing to 
eliminate applicator exposure by limiting application to only foggers, 
and requiring a 6-hour ventilation period following treatment. With 
these measures required, the benefits of use of dichlorvos in buses 
would outweigh its risk.
    EPA is proposing to cancel products registered for use in other 
vehicles (trucks/shipholds/railroad cars). EPA does not believe it is 
feasible to mitigate the risk from reentry. A 36-hour reentry period 
would be required to achieve an MOE above 100, which is not practical 
for commercial vehicles. The economic impact resulting from the 
cancellation of this use is not expected to be significant since there 
are alternatives available which would result in similar treatment 
costs. Therefore, the risks outweigh the benefits.
    19. Restricted use. With the exception of certain uses listed 
below, EPA is proposing that all registered products be restricted to 
use by certified applicators only. This proposal is based on the acute 
toxicity of dichlorvos (Toxicity Category I, the most toxic 
classification) and the existence of poisoning incidents. This is not 
expected to be a major burden since most commercial use products 
already have a label statement limiting sale and use to pest control 
operators. In addition, the Registration Standard recommended 
classification of all products, except those labeled for household use 
only, as restricted use. EPA is therefore proposing to restrict the use 
of all products except those registered for only the following uses: 
impregnated strips in enclosed spaces within a museum and insect traps.
    20. PPE requirements. EPA proposes to cancel the registration of 
all remaining dichlorvos products unless the labels are amended to 
require users to wear: a long sleeved shirt, long pants, gloves, socks 
and shoes. EPA estimates of acceptable MOEs for some uses are based on 
wearing these protective clothing. The PPE proposed in this Notice are 
the minimum needed to eliminate unreasonable risks from use of 
dichlorvos. If the presence of additional active ingredients in 
specific end-use products result in more restrictive PPE requirements 
then the more restrictive requirements must be placed on the end-use 
label.
    If the acute inhalation toxicity of the end-use product is in 
category I or II, and therefore, a respirator is required for pesticide 
handlers, the following type of respirator is appropriate to mitigate 
dichlorvos inhalation concerns: a respirator with either an organic-
vapor-removing cartridge with a prefilter approved for pesticides 
(MSHA/NIOSH approval number prefix TC-23C), or a canister approved for 
pesticides (MSHA/NIOSH approval number prefix TC-14G).
    21. Retained uses. EPA is proposing to retain the following uses; 
however, the related registrations will be canceled unless the labels 
conform to the above cancellations, restricted use, reentry and 
protective clothing requirements: mushroom houses and greenhouses (only 
automatic foggers or fogging through a port), kennels, feedlots, insect 
traps, garbage dumps, direct application to poultry, automated 
application to livestock, animal premises, manure, and buses.

 Table 4.--Upper Bound Cancer Risk Estimates from use of Dichlorvos and 
                                  Naled                                 
------------------------------------------------------------------------
                                  Risk Before Agency   Risk After Agency
               Use                  Proposed Action     Proposed Action 
------------------------------------------------------------------------
Packaged or bagged, non-          3.4 x 10-6          0                 
 perishable processed food and                                          
 RACs (including bulk stored,                                           
 regardless of fat content)                                             
                                                                        
------------------------------------------------------------------------
Milk                              6.2 x 10-7          6.2 x 10-7        
------------------------------------------------------------------------
                                                                        
Eggs                              7.1 x 10-8          7.1 x 10-8        
------------------------------------------------------------------------
                                                                        
Red Meat                          1.1 x 10-7          1.1 x 10-7        
------------------------------------------------------------------------
                                                                        
Poultry                           3.7 x 10-8          3.7 x 10-8        
------------------------------------------------------------------------
                                                                        
Agricultural uses                 2.1 x 10-7          2.1 x 10-7        
  Lettuce                           1.6 x 10-7          1.6 x 10-7      
  Cucumbers                         2.6 x 10-8          2.6 x 10-8      
  Tomatoes                          1.4 x 10-8          1.4 x 10-8      

[[Page 50371]]
                                                                        
  Mushrooms                         2.6 x 10-9          2.6 x 10-9      
  Radishes                          9.8 x 10-10         9.8 x 10-10     
------------------------------------------------------------------------
                                                                        
Dichlorvos from application of:                                         
  Dichlorvos                      4.4 x 10-6          1 x 10-6          
  Naled                           7.2 x 10-7          7.2 x 10-7        
                                                                        
Total                             5.1 x 10-6          1.7 x 10-6        
------------------------------------------------------------------------



                               Table 5.--Summary of Dichlorvos Risks and Benefits                               
----------------------------------------------------------------------------------------------------------------
                       Non-Dietary Margin of                                                                    
                             Exposure:         Dietary Upper Bound                                              
         Uses              Cholinesterase          Cancer Risk              Benefits           Proposed Action  
                             Inhibition                                                                         
----------------------------------------------------------------------------------------------------------------
Domestic Dwellings                                                                                              
 (Application)                                                                                                  
  Pressurized Aerosol  47                     N/A                    Benefits in and        Cancel              
                                                                      around domestic                           
                                                                      dwellings are not                         
                                                                      expected to be                            
                                                                      significant                               
  Crack and crevice    23                     N/A                                           Cancel              
   treatment                                                                                                    
----------------------------------------------------------------------------------------------------------------
Domestic Dwellings                                                                                              
 (Post-Application)                                                                                             
  Total release        17                     N/A                    Benefits in and        Cancel              
   fogger                                                             around domestic                           
                                                                      dwellings are not                         
                                                                      expected to be                            
                                                                      significant                               
  Pressurized Aerosol  17                     N/A                                           Cancel              
  Crack and crevice    2                      N/A                                           Cancel              
   treatment                                                                                                    
  Resin Pest strips    20                     N/A                                           Cancel              
  Pet Flea collars     240                    N/A                                           Cancel              
----------------------------------------------------------------------------------------------------------------
Occupational Exposure                                                                                           
----------------------------------------------------------------------------------------------------------------
Mushroom House                                                                                                  
  Applicator           Majority of MOEs less  2.6 x 10-9             Benefits are not       Allowable           
                        than 50 and some                              expected to be         Application Methods
                        less than 10                                  significant           -Automatic foggers  
                                                                                            -Thermal foggers    
                                                                                             through a port     
                                                                                                                

[[Page 50372]]
                                                                                                                
  Reentry                                                                                                       
    After 24 hours     21 (no respirator)                                                   Reentry Restrictions
    After 48 hours     289 (no respirator)                                                  Limited reentry     
                                                                                             during first 48    
                                                                                             hours following    
                                                                                             treatment. No entry
                                                                                             within first 4     
                                                                                             hours; limited     
                                                                                             reentry (one hour  
                                                                                             per 24 hours) for  
                                                                                             handling activities
                                                                                             only.              
----------------------------------------------------------------------------------------------------------------
Greenhouse                                                                                                      
  Applicator           Majority of MOEs less  1.6 x 10-7 (lettuce)   Not expected to be     Allowable           
                        than 100 and 30%      2.6 x 10-8              significant            Application Methods
                        less than 50           (cucumbers)                                  -Automatic foggers  
                                              1.4 x 10-8 (tomatoes)                         -Thermal foggers    
                                              8.8 x 10-10                                    through a port     
                                               (radishes)                                                       
                                                                                                                
  Reentry                                                                                                       
    After 24 hours     21 (no respirator)                                                   Reentry Restrictions
    After 48 hours     289 (no respirator)                                                  Limited reentry     
                                                                                             during first 48    
                                                                                             hours following    
                                                                                             treatment. No entry
                                                                                             within first 4     
                                                                                             hours; limited     
                                                                                             reentry (one hour  
                                                                                             per 24 hours) for  
                                                                                             handling activities
                                                                                             only.              
----------------------------------------------------------------------------------------------------------------
Domestic food/nonfood                                                                                           
 animals (non-                                                                                                  
 poultry)                                                                                                       
  Applicator           6.1                    6.2 x 10-7 (milk)      Probable regional      Cancel all hand     
                                                                      impacts                application methods
                                                                                             to both food and   
                                                                                             nonfood animals    

[[Page 50373]]
                                                                                                                
                                              1.1 x 10-7 (red meat)                         Other uses are      
                                                                                             permitted such as  
                                                                                             back and face      
                                                                                             rubbers, and       
                                                                                             automatic          
                                                                                             application        
                                                                                             systems.           
----------------------------------------------------------------------------------------------------------------
Domestic food/nonfood  > 100                  7.1 x 10-8 (eggs)      Possible regional      Retain Use          
 animals (poultry)                                                    impacts                                   
                                              3.7 x 10-8 (poultry)                                              
----------------------------------------------------------------------------------------------------------------
Domestic animal                                                                                                 
 premises (food and                                                                                             
 non-food) (includes                                                                                            
 dairy barns, mink                                                                                              
 farms, barns,                                                                                                  
 stables, poultry                                                                                               
 houses)                                                                                                        
  Applicator           > 100                  N/A                    Probable regional      Retain uses         
                                                                      impacts                                   
  Reentry              > 100                  N/A                                                               
----------------------------------------------------------------------------------------------------------------
Feedlots               >100                   N/A                    Probable regional      Retain use          
                                                                      impacts                                   
----------------------------------------------------------------------------------------------------------------
Manure                 >100                   N/A                    Benefits not expected  Retain use          
                                                                      to be significant                         
----------------------------------------------------------------------------------------------------------------
Tobacco warehouse                             N/A                    Benefits not expected  Cancel              
                                                                      to be significant                         
  Applicator-          2                                                                                        
   sprinkling                                                                                                   
  Mixer-loader         32,500                                                                                   
  Warehouse worker     0.3                                                                                      
   (reentry)                                                                                                    
----------------------------------------------------------------------------------------------------------------
Ornamental lawns,      32 (similar to         N/A                    Not expected to be     Cancel              
 turf and plants        greenhouse power                              significant                               
                        sprayer)                                                                                
----------------------------------------------------------------------------------------------------------------
Warehouse treatment                                                                                             
 (affects                                                                                                       
 nonperishable bulk,                                                                                            
 packaged and bagged                                                                                            
 raw and processed                                                                                              
 commodities)                                                                                                   
  Application          38                     3.4 x 10-6             $12 million for both   Cancel all          
                                                                      raw and processed      application methods
                                                                      nonperishable bulk,    except for         
                                                                      packaged, or bagged    impregnated resin  
                                                                      agricultural           strips which are   
                                                                      commodities plus the   limited to closed  
                                                                      cost of additional     areas such as      
                                                                      fumigations if         silos.             
                                                                      needed.                                   
  Reentry              2.8                                                                                      
----------------------------------------------------------------------------------------------------------------
Kennels                > 100 (similar to      N/A                    Not expected to be     Retain use          
                        dairy barn)                                   significant                               

[[Page 50374]]
                                                                                                                
                                                                                                                
----------------------------------------------------------------------------------------------------------------
Insect traps           negligible risk        N/A                    Not expected to be     Retain use          
                                                                      significant                               
  Applicator                                                                                                    
----------------------------------------------------------------------------------------------------------------
Garbage dumps          > 81 (less than        N/A                    Not expected to be     Retain use          
                        greenhouse risk)                              significant                               
                                                                                                                
----------------------------------------------------------------------------------------------------------------
Commercial,                                                                                                     
 institutional and                                                                                              
 industrial areas                                                                                               
 (includes food                                                                                                 
 service, food                                                                                                  
 processing, end food                                                                                           
 manufacturing                                                                                                  
 possibilities)                                                                                                 
  Applicator           38                     Potential dietary      Not expected to be     Cancel all uses     
                                               risks                  significant                               
  Reentry              2.8                                                                                      
----------------------------------------------------------------------------------------------------------------
Commercial                                                                                                      
 transportation                                                                                                 
 vehicles                                                                                                       
----------------------------------------------------------------------------------------------------------------
Airplanes                                     N/A                    Not expected to be     Cancel use on       
 (disinsection of                                                     significant            airplanes          
 aircraft)                                                                                                      
  Passenger - post-    135                                                                                      
   application                                                                                                  
  Applicator           14                                                                                       
----------------------------------------------------------------------------------------------------------------
  Buses-passenger      55                     N/A                    Not expected to be     Retain only fogger  
                                                                      significant            use on buses and   
                                                                                             require a 6-hour   
                                                                                             ventilation period 
                                                                                             before reentry.    
----------------------------------------------------------------------------------------------------------------
Truck, shipholds,                                                                                               
 rail cars                                                                                                      
  Application          > warehouse            Potential dietary      Not expected to be     Cancel use          
                                               risk                   significant                               
  Reentry              20                                                                                       
----------------------------------------------------------------------------------------------------------------



    Note: Amvac has requested voluntary deletion of the following 
uses from their technical and end-use labels. In response to the 
Federal Register Notice announcing Amvac's request, no one expressed 
interest in retaining these uses, with the exception of greenhouses 
and outdoor household use. Therefore, the Agency intends to follow 
through with Amvac's request to delete these uses, excluding the two 
exceptions. Any risks associated with these uses will be eliminated.
    - Domestic dwellings (except for impregnated resin pest strips, 
total release foggers, and crack and crevice treatment). There is 
interest in supporting outdoor household use and this use will not 
be immediately deleted. However, based on risk/benefit 
considerations, the Agency is proposing to cancel this use.
    - Greenhouses. Because there is interest in supporting use in 
greenhouses, this use will not be immediately deleted. However, 
based on risk/benefit considerations, the Agency is proposing to 
cancel this use, unless certain use restrictions are put into place.
    - Tobacco and tobacco warehouses
    - Food service establishments, food manufacturing establishments 
and food processing establishments, with the exception of nonfood-
processing areas. - Aircraft and buses
The following uses which Amvac is requesting to delete are not 
included in the above risk/benefit table: tomatoes, rangeland 
grasses, and aerial application.

V. Existing Stocks

    Under the authority of FIFRA section 6(a)(1), EPA will establish 
certain limitations on the distribution and use of existing stocks of 
dichlorvos products subject to any final cancellation notice. EPA 
defines the term ``existing stock'' to mean any quantity of dichlorvos 
products in the United States on the effective date of the Final Notice 
of Intent To Cancel certain registrations, or on the effective date an 
application for amendment of registration is granted by the Agency. 
Such existing stocks include dichlorvos products that have been 
formulated, packaged, and labeled and are being held for shipment or 
release or have been shipped or released into commerce.
    EPA is proposing not to permit the continued sale, distribution, or 
use of dichlorvos products affected by this Notice after the effective 
date of the Final Cancellation Notice. EPA reserves the right to amend 
this existing stocks provision, should conditions warrant 

[[Page 50375]]
such amendment. The final cancellation notice may amend the existing 
stocks provisions in the Use Deletion Notice published on April 19, 
1995 (60 FR 19580).

VI. Procedural Matters

    As required by FIFRA sections 6(b) and 25(d), and 40 CFR 154.31(b), 
EPA has transmitted copies of a draft Notice of Intent to Cancel based 
on this Notice, together with the support documents, to the Secretary 
of Agriculture and the Scientific Advisory Panel for comment. EPA will 
publish any comments received from the Secretary or the Panel, and 
EPA's responses, in the Notice of Final Determination.

VII. Public Record and Opportunity for Comment

    The Agency is providing a 90-day period for the public to comment 
on this Notice and on the dichlorvos Special Review Docket. Comments 
must be submitted by December 27, 1995. All comments and information 
should be submitted in triplicate to the address given in the Notice 
under ``ADDRESSES.'' All comments should be identified with the public 
docket number (OPP-30000/56). All comments, information, and analyses 
which come to the attention of EPA may serve as a basis for final 
determination of regulatory action during the Special Review.
    A public version of this record, including printed, paper versions 
of electronic comments, which does not include any information claimed 
as CBI, is available for inspection from 8 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The public record is located 
in Rm. 1132 of the Public Response and Program Resources Branch, Field 
Operations Division (7506C), Office of Pesticide Programs, 
Environmental Protection Agency, Crystal Mall #2, 1921 Jefferson Davis 
Highway, Arlington, VA.
    Electronic comments can be sent directly to EPA at:

    [email protected]

    Electronic comments must be submitted as an ASCII file avoiding the 
use of special characters and any form of encryption.
    The official record for this Notice, as well as the public version, 
as described above will be kept in paper form. Accordingly, EPA will 
transfer all comments received electronically into printed, paper form 
as they are received and will place the paper copies in the official 
record which will also include all comments submitted directly in 
writing. The official record is the paper record maintained at the 
address in ``ADDRESSES'' at the beginning of this document.

VIII. Public Docket

    Pursuant to 40 CFR 154.15, the Agency has established a public 
docket [OPP-30000/56] for the dichlorvos Special Review. This public 
docket will include: (1) This Notice; (2) any other notices pertinent 
to the dichlorvos Special Review; (3) non-CBI documents and copies of 
written comments submitted to the Agency in response to the pre-Special 
Review registrant notification, the Federal Register Notice initiating 
Special Review, this Notice, any other Notice regarding dichlorvos 
submitted at any time during the Pre-Special Review process by persons 
outside government; (4) a transcript of any public meetings held by EPA 
for the purpose of gathering information on dichlorvos; (5) memoranda 
describing each meeting held during the Special Review process between 
Agency personnel and persons outside government pertaining to 
dichlorvos; and (6) a current index of materials in the public docket.

IX. References

    1. U.S. EPA, George Z. Ghali, Fourth Peer Review of Dichlorvos 
(DDVP), memorandum to George LaRocca (September 18, 1989).
    2. National Toxicology Program (NTP), Pathology Working Group 
Report (1986), Dichlorvos Two Year B6C3f1 Mouse Corn Oil Gavage Study 
(Southern Research Institute, No. 5049, Test 2, NTP C#00113b). MRID 
006019.
    3. NTP (National Toxicology Program), Pathology Working Group 
Report (1986), Two Year Gavage Study of Dichlorvos in F344 Rats, 
(Southern Research Institute, Number 504).
    4. U.S. EPA., FIFRA Scientific Advisory Panel, Transmittal of FIFRA 
Scientific Advisory Panel Reports on the September 23, 1987 Meeting 
Regarding the Peer Review Classification of Dichlorvos as a B2 Oncogen, 
to Douglas D. Campt, October 1, 1987.
    5. U.S. EPA, Judith W. Hauswirth, Second Peer Review of Dichlorvos 
Reevaluation Following the September 23, 1987 Science Advisory Panel 
Review, Memorandum to George LaRocca, March 16, 1988.
    6. U.S. EPA, Memorandum, Judith W. Hauswirth, Third Peer Review of 
Dichlorvos - Reevaluation Following the April 18, 1988 Meeting of the 
NTP Panel of Experts, to George LaRocca, August 17, 1988.
    7. U.S. EPA, Memorandum, George Z. Ghali, Fourth Peer Review of 
Dichlorvos (DDVP), to George LaRocca, September 18, 1989.
    8. Shirasu, U. et. al. (1976) Mutagenicity Screening of Pesticides 
in the Microbial System. Mutation Research 40: 19-30; also in 
submission to EPA received May 28, 1980, submitted by Upjohn Co.
    9. Bridges, B. (1978) On the detection of volatile liquid mutagens 
with bacteria; experiments with dichlorvos and epichlorhydrin, Mutation 
Research 54:367-371. MRID 40303301.
    10. Rosenkranz, H. (1973) Preferential effect of dichlorvos 
(Vapona) on bacteria deficient in DNA polymerase, Cancer Research 
33:458-459, MRID 40304402.
    11. Sobels, F., et al. (1979) Absence of a mutagenic effect of 
dichlorvos in Drosophilla melanogaster, Mutation Research 67:89-92, 
MRID 40304403.
    12. Moriya, M., et al. (1978) Effects of cysteine and a liver 
metabolic activation system on the activities of mutagenic pesticides, 
Mutation Research 57:259-263.
    13. Wile, D. (1973) Chemical induction of Streptomycin-resistant 
mutation in Escherichia coli; Dose and mutagenic effects of dichlorvos 
and methyl methanesulfonate, Mutation Research 19:33-41, MRID 40303306.
    14. Hanna, P., et al., (1975) Mutagenicity of organophosphorus 
compounds in bacteria and Drosophila, Mutation Research, 28:405-420, 
MRID # 00142663.
    15. Mohn, G. (1973) 5-Methyltryptophan resistance mutations in 
Escherichia coli K-12: Mutagenic activity of monofunctional alkylating 
agents including organophosphorus insecticides, Mutation Research. 
20:7-15, MRID # 001146101.
    16. SDS Biotech Corporation, D-5455c, Report undated. L5178YTK+/- 
Mouse Lymphoma Forward Mutation Assay with T=169-1.
    17. SDS Biotech Corporation, D-5456C, Report undated. A dominant 
lethal assay in Mice with T-169-1.
    18. Lofroth, A. Naturforsch, C:biosci.:33c:783-5, 1978; and 
Fischer, et al. Chem.-Biol. Interact. 19:205214, 1977.
    19. U.S. EPA, Stephen A. Schaible , Addendum to DDVP Chronic 
Exposure Analyses and Cancer Risk Assessments Evaluating Dietary Risk 
for the DDVP PD 2/3, memorandum to Dennis Utterback, March 6, 1995.
    20. U.S. EPA, George Ghali, Dichlorvos (DDVP): Reconsideration of 
Quantification of Human Risk, Memorandum to George LaRocca and Dennis 
Utterback (July 7, 1993).
    21. I.C. Lamb, An Acute Neurotoxicity Study of Dichlorvos in Rats, 
Unpublished report submitted by 

[[Page 50376]]
Amvac Chemical Corp. and conducted at Wil Research Labs., Inc., 
Ashland, Oh, Study No. Wil 188003, Study date January 1, 1993, MRID # 
426553-01.
    22. J. Beavers, C.P. Driscoll, V. Dukes and M. Jaber. DDVP: An 
Acute Delayed Neurotoxicity Study in Laying Hens, Unpublished report 
submitted by Amvac Chemical Corp. and conducted at Wildlife 
International Ltd., Easton, Md, Study No. 246-103. Study date - 
December 29, 1988, MRID # 410047-02.
    23. A 2-week Range-Finding Study on DDVP in Dogs, Unpublished 
report submitted by Amvac Chemical Corp. and conducted at Hazleton 
Laboratories America, Inc., Vienna, VA. HLA Study No. 2534-101, Study 
date - August 6, 1990, MRID # 415931-01.
    24. J.M. Kleeman, Thirteen Week Gavage Toxicity Study with DDVP in 
Rats, Unpublished study submitted by Amvac Chemical Corp. and conducted 
at Hazleton Laboratories America, Madison, WI, Study No. HLA 6274-102, 
Study date - December 28, 1988, Mrid #410047-01.
    25. I.C. Lamb, Subchronic Neurotoxicity Study (13 Week) of 
Dichlorvos in Rats, Unpublished report submitted by Amvac Chemical 
Corp. and conducted at Wil Research Labs, Inc., Ashland, Oh, Study No. 
WIL 188003, Study date September 30, 1993. MRID # 429581-01.
    26. Tyl, R.W., M.C. Marr and C.B. Myers, Developmental Toxicity 
Evaluation of DDVP Administered by Gavage to New Zealand White Rabbits, 
Unpublished report submitted by Amvac Chemical Corp. and conducted at 
Research Triangle Institute, Research Triangle Park, NC, Study No. 60C-
4629-30/40, Study date - February 22, 1991, MRID # 418024-01.
    27. E. Thorpe, A.b. Wilson, K.M. Dix and D. Blair, Teratological 
Studies with Dichlorvos Vapour and in Rabbits and Rats, Archives of 
Toxicology 30:29-38 (1972).
    28. Dichlorvos (DDVP) 28-Day Neurotoxicity Study in Hens (6(a)(2) 
Notification), Unpublished report submitted by Amvac Chemical Corp. and 
conducted at Huntingdon Research Centre, Cambridgeshire, England, MRID 
# 42586200-01.
    29. Blair, D., K.M. Dix and P.F. Hunt, Two Year Inhalation Exposure 
of Rats to Dichlorvos Vapor, Unpublished report submitted by Fermenta 
Animal Health Company and conducted at Tunstall Laboratory, 
Sittingbourne Research Center, Study No. TLGR. 0026. 74, Study date - 
June 1974, MRID # 00057695 00632569.
    30. V.R. Markiewicz, A 52-Week Chronic Toxicity Study on DDVP in 
Dogs, Unpublished report submitted by Amvac Chemical Corp. and 
conducted at Hazleton Laboratories America, Inc., Vienna, VA, HLA Study 
No. 2534-102, Study date - August 6, 1990, MRID #415931-01.
    31. R.W. Tyl, C.B. Myers, and M.C. Marr, Two-Generation 
Reproductive Toxicity Study of DDVP Administered in the Drinking Water 
to CD (Sprague-Dawley Rats), Unpublished report submitted by Amvac 
Chemical Corp. and conducted at Reproductive and Developmental 
Toxicology Laboratory, Research Triangle Park, NC, Report No. 60C-4629-
170, Study date - August 31, 1992, MRID # 424839-01.
    32. U.S. EPA. J.E. Stewart, Review of Human Toxicology Data on 
Dichlorvos (DDVP), Memorandum to the Toxicology Branch Files (April 8, 
1993).
    33. U.S. EPA, Guidance for the Reregistration of Pesticide Products 
Containing DDVP as the Active Ingredient, September 1987: p. 35.
    34. Mehler, L. Case Reports Received by the California Surveillance 
Program in which Health Effects were Attributed to DDVP, April 1993.
    35. American Association of Poison Control Centers. 1993-1994. DDVP 
Exposure Experience Data 1985 through 1992. American Association of 
Poison Control Centers, Washington, DC.
    36. U.S. EPA. Jerome Blondell, Review of Poison Control Center Data 
Call-In, December 5, 1994.
    37. U.S. EPA, B.T. Backus, EPA File Symbol: 778-IG Seargant's Fast-
Acting Flea Tick Collar for Dogs, Memorandum to George LaRocca, 
September 21, 1983.
    38. U.S. EPA, Byron T. Backus, A.H. Robins DDVP Dog Collar, 
Memorandum to George LaRocca, September 18, 1984.
    39. U.S. EPA, Byron T. Backus, Data Evaluation Report VII: 
Cholinesterase (98 day collar exposure) - dog, May 27, 1986.
    40. Letter from Amvac Chemical Corporation to George Larocca, 
November 2, 1994.
    41. U.S. EPA. Report of EPA Cancer Peer Review Committee on 
Trichlorfon, February 28, 1995.
    42. U.S. EPA. Report of Reference Dose Committee on Naled, August 
31, 1994.
    43. U.S. EPA, Susan V. Hummel, Dichlorvos (DDVP; 084001): 
Registration Case No. 0310 Anticipated Residues Resulting From Use of 
Dichlorvos and Naled for Carcinogenic Dietary Exposure Assessment, 
memorandum to Dennis Utterback, September 12, 1994.
    44. U.S. EPA, Susan V. Hummel, Dichlorvos (084001) Reregistration 
Case No. 0310, Processing studies on field corn, wheat, rice, 
cottonseed and soybeans, memorandum to Brigid Lowery, July 18, 1994.
    45. U.S. EPA, John Faulkner and Douglas Sutherland. DDVP and Naled 
Usage and Use Patterns, memorandum to Debra Edwards, October 26, 1994.
    46. U.S. EPA, Note from Doug Sutherland and John Faulkner to Dennis 
Utterback, January 27, 1995.
    47. U.S. EPA, Doug Sutherland and John Faulkner, Usage of DDVP 
applied to dairy cattle and their premises in California, Note to 
Dennis Utterback, February 1, 1995.
    48. U.S. EPA, David Jacquith, Revisions to Exposure Assessment for 
DDVP, memorandum to Dennis Utterback, April 15, 1993.
    49. U.S. EPA, David Jaquith, Amendments/Clarifications of Exposure 
Assessments for DDVP, Memorandum to Mike Beringer, September 2, 1993.
    50. EPA, David Jaquith, Documentation of Reentry Intervals for Use 
of DDVP in Mushroom Houses, for Use in Buses, and in Trucks/Shipholds/
Railroad Cars, Memorandum to Dennis Utterback, August 25, 1994.
    51. U.S. EPA, Michael J. Beringer, Updated DDVP Occupational/
residential Risk Assessment, Memorandum to Dennis Utterback, February 
23, 1994.
    52. U.S. EPA, Stephen A. Schaible, Acute and Chronic Dietary 
Exposure Analyses for DDVP, Memorandum to Dennis Utterback and Michael 
Beringer, December 2, 1994.
    53. U.S. EPA, Stephen A. Schaible, Addendum to DDVP Chronic 
Exposure Analyses and Cancer Risk Assessments Evaluating Dietary Risk 
for the DDVP PD 2/3, Memorandum to Dennis Utterback, March 6, 1995.
    54. U.S. EPA, G. Ghali memorandum to G. LaRocca and L. Rossi, June 
10, 1992.
    55. U.S. EPA, Mike Beringer, Occupational and Residential Risk 
Assessment for DDVP, memorandum to Dennis Utterback, September 8, 1993.
    56. U.S. EPA, Allen Jennings, Transmittal of Dichlorvos PD2/3 and 
Supporting Benefits Assessments, memorandum to Daniel Barolo, November 
16, 1993.
    57. U.S. EPA, Douglas W. S. Sutherland, DDVP Use in Mushroom 
Houses, Note to Michael Beringer, February 23, 1994.
    58. Mary S. Partridge, William G. Smith and Donald A. Rutz, Pest 
and Pesticide Use Assessment for Poultry Production Systems in New York 
State and the Commonwealth of Pennsylvania for 1992, Pesticide 
Management Program, Cornell University, Ithaca, NY.
    59. Mary S. Partridge, William G. Smith and Donald A. Rutz, Pest 
and Pesticide Use Assessment for Dairy Cattle and Cabbage Production 
Systems 

[[Page 50377]]
in New York State for 1991, Pesticide Management Education Program, 
Cornell University, Ithaca, NY.
    60. U.S. EPA, Douglas Sutherland, Note regarding a Variety of 
Sites, to Mike Beringer, March 29, 1994.

List of Subjects

    Environmental protection.

    Dated: September 22, 1995.
Lynn R. Goldman,
Assistant Administrator for Prevention, Pesticides and Toxic 
Substances.

[FR Doc. 95-24112 Filed 9-27-95; 8:45 am]
BILLING CODE 6560-50-F