[Federal Register Volume 63, Number 164 (Tuesday, August 25, 1998)]
[Rules and Regulations]
[Pages 45176-45182]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-22787]


-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 180

[OPP-300696; FRL-6021-6]
RIN 2070-AB78


Zinc Phosphide; Pesticide Tolerances for Emergency Exemptions

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This regulation establishes time-limited tolerances for 
residues of phosphine resulting from the use of the rodenticide zinc 
phosphide in or on timothy (seed, forage, hay), alfalfa (forage, hay), 
and clover (forage, hay). This action is in response to EPA's granting 
of an emergency exemption under section 18 of the Federal Insecticide, 
Fungicide, and Rodenticide Act authorizing use of the pesticide on 
timothy or timothy-alfalfa, clover stands in Washington. This 
regulation establishes a maximum permissible level for residues of 
phosphine in these food commodities pursuant to section 408(l)(6) of 
the Federal Food, Drug, and Cosmetic Act, as amended by the Food 
Quality Protection Act of 1996. The tolerances will expire and are 
revoked on February 1, 2000.

DATES: This regulation is effective August 25, 1998. Objections and 
requests for hearings must be received by EPA on or before October 26, 
1998.
ADDRESSES: Written objections and hearing requests, identified by the 
docket control number, [OPP-300696], must be submitted to: Hearing 
Clerk (1900), Environmental Protection Agency, Rm. M3708, 401 M St., 
SW., Washington, DC 20460. Fees accompanying objections and hearing 
requests shall be labeled ``Tolerance Petition Fees'' and forwarded to: 
EPA Headquarters Accounting Operations Branch, OPP (Tolerance Fees), 
P.O. Box 360277M, Pittsburgh, PA 15251. A copy of any objections and 
hearing requests filed with the Hearing Clerk identified by the docket 
control number, [OPP-300696], must also be submitted to: Public 
Information and Records Integrity Branch, Information Resources and 
Services Division (7502C), Office of Pesticide Programs, Environmental 
Protection Agency, 401 M St., SW., Washington, DC 20460. In person, 
bring a copy of objections and hearing requests to Rm. 119, Crystal 
Mall #2, 1921 Jefferson Davis Hwy., Arlington, VA.
    A copy of objections and hearing requests filed with the Hearing 
Clerk may also be submitted electronically by sending electronic mail 
(e-mail) to: [email protected]. Copies of objections and 
hearing requests must be submitted as an ASCII file avoiding the use of 
special characters and any form of encryption. Copies of objections and 
hearing requests will also be accepted on disks in WordPerfect 5.1/6.1 
file format or ASCII file format. All copies of objections and hearing 
requests in electronic form must be identified by the docket control 
number [OPP-300696]. No Confidential Business Information (CBI) should 
be submitted through e-mail. Electronic copies of objections and 
hearing requests on this rule may be filed online at many Federal 
Depository Libraries.

FOR FURTHER INFORMATION CONTACT: By mail: Libby Pemberton, Registration 
Division (7505C), Office of Pesticide Programs, Environmental 
Protection Agency, 401 M St., SW., Washington, DC 20460. Office 
location, telephone number, and e-mail address: Crystal Mall #2, 1921 
Jefferson Davis Hwy., Arlington, VA, (703) 308-9364, e-mail: 
[email protected].

SUPPLEMENTARY INFORMATION: EPA, on its own initiative, pursuant to 
section 408(e) and (l)(6) of the Federal Food, Drug, and Cosmetic Act 
(FFDCA), 21 U.S.C. 346a(e) and (l)(6), is establishing tolerances for 
phosphine resulting from the use of the rodenticide zinc phosphide in 
or on timothy (seed, forage, hay), alfalfa (forage, hay), and clover 
(forage, hay) at 0.1 part per million (ppm). These tolerances will 
expire and are revoked on February 1, 2000. EPA will publish a document 
in the Federal Register to remove the revoked tolerances from the Code 
of Federal Regulations.

I. Background and Statutory Authority

    The Food Quality Protection Act of 1996 (FQPA) (Pub. L. 104-170) 
was signed into law August 3, 1996. FQPA amends both the Federal Food, 
Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 301 et seq., and the Federal 
Insecticide, Fungicide, and Rodenticide Act (FIFRA), 7 U.S.C. 136 et 
seq. The FQPA amendments went into effect

[[Page 45177]]

immediately. Among other things, FQPA amends FFDCA to bring all EPA 
pesticide tolerance-setting activities under a new section 408 with a 
new safety standard and new procedures. These activities are described 
below and discussed in greater detail in the final rule establishing 
the time-limited tolerance associated with the emergency exemption for 
use of propiconazole on sorghum (61 FR 58135, November 13, 1996)(FRL-
5572-9).
    New section 408(b)(2)(A)(i) of the FFDCA allows EPA to establish a 
tolerance (the legal limit for a pesticide chemical residue in or on a 
food) only if EPA determines that the tolerance is ``safe.'' Section 
408(b)(2)(A)(ii) defines ``safe'' to mean that ``there is a reasonable 
certainty that no harm will result from aggregate exposure to the 
pesticide chemical residue, including all anticipated dietary exposures 
and all other exposures for which there is reliable information.'' This 
includes exposure through drinking water and in residential settings, 
but does not include occupational exposure. Section 408(b)(2)(C) 
requires EPA to give special consideration to exposure of infants and 
children to the pesticide chemical residue in establishing a tolerance 
and to ``ensure that there is a reasonable certainty that no harm will 
result to infants and children from aggregate exposure to the pesticide 
chemical residue. . . .''
    Section 18 of FIFRA authorizes EPA to exempt any Federal or State 
agency from any provision of FIFRA, if EPA determines that ``emergency 
conditions exist which require such exemption.'' This provision was not 
amended by FQPA. EPA has established regulations governing such 
emergency exemptions in 40 CFR part 166.
    Section 408(l)(6) of the FFDCA requires EPA to establish a time-
limited tolerance or exemption from the requirement for a tolerance for 
pesticide chemical residues in food that will result from the use of a 
pesticide under an emergency exemption granted by EPA under section 18 
of FIFRA. Such tolerances can be established without providing notice 
or period for public comment.
    Because decisions on section 18-related tolerances must proceed 
before EPA reaches closure on several policy issues relating to 
interpretation and implementation of the FQPA, EPA does not intend for 
its actions on such tolerance to set binding precedents for the 
application of section 408 and the new safety standard to other 
tolerances and exemptions.

II. Emergency Exemption for Zinc Phosphide on Timothy and Timothy-
Alfalfa/Clover and FFDCA Tolerances

    A potential population of 500 voles per acre would result in 
significant economic loss. The currently available methods of control, 
including the use of zinc phosphide bait boxes and flood irrigation, 
are inadequate and impractical. EPA has authorized under FIFRA section 
18 the use of zinc phosphide on timothy and timothy-alfalfa/clover for 
control of vole complex in Washington. After having reviewed the 
submission, EPA concurs that emergency conditions exist for this state.
    As part of its assessment of this emergency exemption, EPA assessed 
the potential risks presented by residues of phosphine in or on timothy 
(seed, forage, hay), alfalfa (forage, hay), and clover (forage, hay). 
In doing so, EPA considered the new safety standard in FFDCA section 
408(b)(2), and EPA decided that the necessary tolerances under FFDCA 
section 408(l)(6) would be consistent with the new safety standard and 
with FIFRA section 18. Consistent with the need to move quickly on the 
emergency exemption in order to address an urgent non-routine situation 
and to ensure that the resulting food is safe and lawful, EPA is 
issuing this tolerance without notice and opportunity for public 
comment under section 408(e), as provided in section 408(l)(6). 
Although these tolerances will expire and are revoked on February 1, 
2000, under FFDCA section 408(l)(5), residues of the pesticide not in 
excess of the amounts specified in the tolerance remaining in or on 
timothy (seed, forage, hay), alfalfa (forage, hay), and clover (forage, 
hay) after that date will not be unlawful, provided the pesticide is 
applied in a manner that was lawful under FIFRA, and the residues do 
not exceed a level that was authorized by these tolerances at the time 
of that application. EPA will take action to revoke these tolerances 
earlier if any experience with, scientific data on, or other relevant 
information on this pesticide indicate that the residues are not safe.
    Because this tolerance is being approved under emergency conditions 
EPA has not made any decisions about whether zinc phosphide meets EPA's 
registration requirements for use on timothy (seed, forage, hay), 
alfalfa (forage, hay), and clover (forage, hay) or whether permanent 
tolerances for this use would be appropriate. Under these 
circumstances, EPA does not believe that these tolerances serve as a 
basis for registration of zinc phosphide by a State for special local 
needs under FIFRA section 24(c). Nor does this tolerance serve as the 
basis for any State other than Washington to use this pesticide on 
these crops under section 18 of FIFRA without following all provisions 
of section 18 as identified in 40 CFR part 166. For additional 
information regarding the emergency exemption for zinc phosphide, 
contact the Agency's Registration Division at the address provided 
above.

III. Risk Assessment and Statutory Findings

    EPA performs a number of analyses to determine the risks from 
aggregate exposure to pesticide residues. First, EPA determines the 
toxicity of pesticides based primarily on toxicological studies using 
laboratory animals. These studies address many adverse health effects, 
including (but not limited to) reproductive effects, developmental 
toxicity, toxicity to the nervous system, and carcinogenicity. Second, 
EPA examines exposure to the pesticide through the diet (e.g., food and 
drinking water) and through exposures that occur as a result of 
pesticide use in residential settings.

A. Toxicity

    1. Threshold and non-threshold effects. For many animal studies, a 
dose response relationship can be determined, which provides a dose 
that causes adverse effects (threshold effects) and doses causing no 
observed effects (the ``no-observed effect level'' or ``NOEL'').
    Once a study has been evaluated and the observed effects have been 
determined to be threshold effects, EPA generally divides the NOEL from 
the study with the lowest NOEL by an uncertainty factor (usually 100 or 
more) to determine the Reference Dose (RfD). The RfD is a level at or 
below which daily aggregate exposure over a lifetime will not pose 
appreciable risks to human health. An uncertainty factor (sometimes 
called a ``safety factor'') of 100 is commonly used since it is assumed 
that people may be up to 10 times more sensitive to pesticides than the 
test animals, and that one person or subgroup of the population (such 
as infants and children) could be up to 10 times more sensitive to a 
pesticide than another. In addition, EPA assesses the potential risks 
to infants and children based on the weight of the evidence of the 
toxicology studies and determines whether an additional uncertainty 
factor is warranted. Thus, an aggregate daily exposure to a pesticide 
residue at or below the RfD (expressed as 100% or less of the RfD) is 
generally considered

[[Page 45178]]

acceptable by EPA. EPA generally uses the RfD to evaluate the chronic 
risks posed by pesticide exposure. For shorter term risks, EPA 
calculates a margin of exposure (MOE) by dividing the estimated human 
exposure into the NOEL from the appropriate animal study. Commonly, EPA 
finds MOEs lower than 100 to be unacceptable. This 100-fold MOE is 
based on the same rationale as the 100-fold uncertainty factor.
    Lifetime feeding studies in two species of laboratory animals are 
conducted to screen pesticides for cancer effects. When evidence of 
increased cancer is noted in these studies, the Agency conducts a 
weight of the evidence review of all relevant toxicological data 
including short-term and mutagenicity studies and structure activity 
relationship. Once a pesticide has been classified as a potential human 
carcinogen, different types of risk assessments (e.g., linear low dose 
extrapolations or MOE calculation based on the appropriate NOEL) will 
be carried out based on the nature of the carcinogenic response and the 
Agency's knowledge of its mode of action.
    2. Differences in toxic effect due to exposure duration. The 
toxicological effects of a pesticide can vary with different exposure 
durations. EPA considers the entire toxicity data base, and based on 
the effects seen for different durations and routes of exposure, 
determines which risk assessments should be done to assure that the 
public is adequately protected from any pesticide exposure scenario. 
Both short and long durations of exposure are always considered. 
Typically, risk assessments include ``acute,'' ``short-term,'' 
``intermediate term,'' and ``chronic'' risks. These assessments are 
defined by the Agency as follows.
    Acute risk, by the Agency's definition, results from 1-day 
consumption of food and water, and reflects toxicity which could be 
expressed following a single oral exposure to the pesticide residues. 
High end exposure to food and water residues are typically assumed.
    Short-term risk results from exposure to the pesticide for a period 
of 1-7 days, and therefore overlaps with the acute risk assessment. 
Historically, this risk assessment was intended to address primarily 
dermal and inhalation exposure which could result, for example, from 
residential pesticide applications. However, since enaction of FQPA, 
this assessment has been expanded to include both dietary and non-
dietary sources of exposure, and will typically consider exposure from 
food, water, and residential uses when reliable data are available. In 
this assessment, risks from average food and water exposure, and high-
end residential exposure, are aggregated. High-end exposures from all 
three sources are not typically added because of the very low 
probability of this occurring in most cases, and because the other 
conservative assumptions built into the assessment assure adequate 
protection of public health. However, for cases in which high-end 
exposure can reasonably be expected from multiple sources (e.g. 
frequent and widespread homeowner use in a specific geographical area), 
multiple high-end risks will be aggregated and presented as part of the 
comprehensive risk assessment/characterization. Since the toxicological 
endpoint considered in this assessment reflects exposure over a period 
of at least 7 days, an additional degree of conservatism is built into 
the assessment; i.e., the risk assessment nominally covers 1-7 days 
exposure, and the toxicological endpoint/NOEL is selected to be 
adequate for at least 7 days of exposure. (Toxicity results at lower 
levels when the dosing duration is increased.)
    Intermediate-term risk results from exposure for 7 days to several 
months. This assessment is handled in a manner similar to the short-
term risk assessment.
    Chronic risk assessment describes risk which could result from 
several months to a lifetime of exposure. For this assessment, risks 
are aggregated considering average exposure from all sources for 
representative population subgroups including infants and children.

B. Aggregate Exposure

    In examining aggregate exposure, FFDCA section 408 requires that 
EPA take into account available and reliable information concerning 
exposure from the pesticide residue in the food in question, residues 
in other foods for which there are tolerances, residues in groundwater 
or surface water that is consumed as drinking water, and other non-
occupational exposures through pesticide use in gardens, lawns, or 
buildings (residential and other indoor uses). Dietary exposure to 
residues of a pesticide in a food commodity are estimated by 
multiplying the average daily consumption of the food forms of that 
commodity by the tolerance level or the anticipated pesticide residue 
level. The Theoretical Maximum Residue Contribution (TMRC) is an 
estimate of the level of residues consumed daily if each food item 
contained pesticide residues equal to the tolerance. In evaluating food 
exposures, EPA takes into account varying consumption patterns of major 
identifiable subgroups of consumers, including infants and children. 
The TMRC is a ``worst case'' estimate since it is based on the 
assumptions that food contains pesticide residues at the tolerance 
level and that 100% of the crop is treated by pesticides that have 
established tolerances. If the TMRC exceeds the RfD or poses a lifetime 
cancer risk that is greater than approximately one in a million, EPA 
attempts to derive a more accurate exposure estimate for the pesticide 
by evaluating additional types of information (anticipated residue data 
and/or percent of crop treated data) which show, generally, that 
pesticide residues in most foods when they are eaten are well below 
established tolerances.
    Percent of crop treated estimates are derived from federal and 
private market survey data. Typically, a range of estimates are 
supplied and the upper end of this range is assumed for the exposure 
assessment. By using this upper end estimate of percent of crop 
treated, the Agency is reasonably certain that exposure is not 
understated for any significant subpopulation group. Further, regional 
consumption information is taken into account through EPA's computer-
based model for evaluating the exposure of significant subpopulations 
including several regional groups, to pesticide residues. For this 
pesticide, the most highly exposed population subgroup (children 1-6 
years old) was not regionally based.

IV. Aggregate Risk Assessment and Determination of Safety

    Consistent with section 408(b)(2)(D), EPA has reviewed the 
available scientific data and other relevant information in support of 
this action, EPA has sufficient data to assess the hazards of zinc 
phosphide and to make a determination on aggregate exposure, consistent 
with section 408(b)(2), for a time-limited tolerance for phosphine 
resulting from the use of the rodenticide zinc phosphide of zinc 
phosphide on timothy (seed, forage, hay), alfalfa (forage, hay), and 
clover (forage, hay) at 0.1 ppm. EPA's assessment of the dietary 
exposures and risks associated with establishing the tolerances 
follows.

A. Toxicological Profile

    EPA has evaluated the available toxicity data and considered its 
validity, completeness, and reliability as well as the relationship of 
the results of the studies to human risk. EPA has also considered 
available information concerning the variability of the

[[Page 45179]]

sensitivities of major identifiable subgroups of consumers, including 
infants and children. The nature of the toxic effects caused by zinc 
phosphide are discussed below.
    1. Acute toxicity. No toxicology studies were identified by OPP 
which demonstrated the need for an acute dietary risk assessment.
    2. Short - and intermediate - term toxicity. Since 10% zinc 
phosphide tracking powder has been classified in Toxicity Category IV 
(LC50 > 19.6 mg/L), inhalation exposure resulting from this 
section 18 action is not considered toxicologically significant. For 
short-term and intermediate dermal MOE calculations, Health Effects 
Division (HED), OPP recommended use of the adjusted acute dermal 
LD50 NOEL of 1,000 milligrams/kilogram (mg/kg) from the 
acute dermal toxicity study in rabbits. In the absence of other dermal 
toxicity data, the acute NOEL dose of 1,000 mg/kg was divided by a 100-
fold uncertainty factor to approximate a 3-month dermal NOEL for worker 
dermal exposure. The 3-month dermal NOEL is 10 mg/kg/day. At the lowest 
effect level (LEL) of 2,000 mg/kg in the rabbit dermal LD50 
study, the animals lost weight, but no mortalities were observed up to 
5,000 mg/kg highest dose tested (HDT). Actual risk from dermal exposure 
is likely to be significantly less, since zinc phosphide reacts with 
water and stomach acid to produce the toxic gas phosphine from oral, 
but not dermal, exposure.
    3. Chronic toxicity. EPA has established the RfD for zinc phosphide 
at 0.003 (mg/kg/day). This RfD is based on an LEL of 3.48 mg/kg/day 
from an open literature 90-day rat feeding study. Effects observed at 
the LEL were decreased food consumption and body weight. An uncertainty 
factor of 10,000 was used due to data gaps and the absence of a NOEL in 
the study. The Agency has reviewed a 90-day gavage study in rats which 
had a NOEL of 0.1 mg/kg/day and a LEL of 1.0 mg/kg/day. The LEL of 1.0 
mg/kg/day was based on increased mortality and kidney-nephrosis in male 
rats.
    4. Carcinogenicity. Zinc phosphide has not been reviewed for 
carcinogenicity. OPP has waived carcinogenicity data requirements for 
zinc phosphide on the basis that exposures to zinc phosphide are 
controlled to prevent exposures to humans. Applications to crop areas 
are such that the zinc phosphide will dissipate.

B. Exposures and Risks

    1. From food and feed uses. Tolerances have been established (40 
CFR 180.284(a) and (b)) for residues of the phosphine resulting from 
the use of the rodenticide zinc phosphide in or on a variety of raw 
agricultural commodities. There is no reasonable expectation of 
secondary residues in meat, milk, poultry, or eggs (Category 3 of 40 
CFR 180.6(a)). Any residues of zinc phosphide ingested by livestock 
would be metabolized to naturally occurring phosphorous compounds. No 
human food items are derived from timothy grown for seed or mixed 
stands of timothy-alfalfa-clover produced for hay. Therefore, humans 
will receive no additional dietary exposure to phosphine as a result of 
establishment of these tolerances. Risk assessments were conducted by 
EPA to assess dietary exposures and risks from zinc phosphide as 
follows:
    i.  Acute exposure and risk. Acute dietary risk assessments are 
performed for a food-use pesticide if a toxicological study has 
indicated the possibility of an effect of concern occurring as a result 
of a one day or single exposure.
    ii. Chronic exposure and risk. For the purpose of assessing chronic 
dietary exposure from zinc phosphide, EPA assumed tolerance level 
residues and 100% of crop treated for the proposed and existing food 
uses of zinc phosphide. These conservative assumptions result in 
overestimation of human dietary exposures.
    2. From drinking water. Zinc phosphide degrades rapidly to Zn2+ and 
phosphine gas which absorp strongly to soil and are common nutrients in 
soil. Zinc phosphide and its degradation products appear to have a low 
potential for ground water and surface water contamination. There is no 
information on zinc phosphide (phosphine) residues in ground water and 
runoff in the EFED One-Liner Data Base. There is no established Maximum 
Concentration Level (MCL) for residues of zinc phosphide (phosphine) in 
drinking water. No drinking water health advisory levels have been 
established for zinc phosphide (phosphine). There is no entry for zinc 
phosphide (phosphine) in the ``Pesticides in Groundwater Database'' 
(EPA 734-12-92-001, September 1992). Based on the available studies 
used in EPA's assessment of environmental risk, EPA does not anticipate 
exposure to residues of zinc phosphide (phosphine) in drinking water.
    3. From non-dietary exposure. Zinc phosphide is currently 
registered for use on the following residential non-food sites: hand-
applied bait to underground burrows in/on the following sites/settings: 
bulb crops, golf course turfgrass, lawns, ornamentals, nurseries, 
parks, homes, industrial, commercial, and agricultural buildings.
    These registrations could result in non-occupational exposure and 
EPA acknowledges that there may be short-, intermediate-, and long-term 
non-occupational, non-dietary exposure scenarios. At this time, the 
Agency has insufficient information to assess the potential risks from 
such exposure.
    4. Cumulative exposure to substances with common mechanism of 
toxicity. Section 408(b)(2)(D)(v) requires that, when considering 
whether to establish, modify, or revoke a tolerance, the Agency 
consider ``available information'' concerning the cumulative effects of 
a particular pesticide's residues and ``other substances that have a 
common mechanism of toxicity.'' The Agency believes that ``available 
information'' in this context might include not only toxicity, 
chemistry, and exposure data, but also scientific policies and 
methodologies for understanding common mechanisms of toxicity and 
conducting cumulative risk assessments. For most pesticides, although 
the Agency has some information in its files that may turn out to be 
helpful in eventually determining whether a pesticide shares a common 
mechanism of toxicity with any other substances, EPA does not at this 
time have the methodologies to resolve the complex scientific issues 
concerning common mechanism of toxicity in a meaningful way. EPA has 
begun a pilot process to study this issue further through the 
examination of particular classes of pesticides. The Agency hopes that 
the results of this pilot process will increase the Agency's scientific 
understanding of this question such that EPA will be able to develop 
and apply scientific principles for better determining which chemicals 
have a common mechanism of toxicity and evaluating the cumulative 
effects of such chemicals. The Agency anticipates, however, that even 
as its understanding of the science of common mechanisms increases, 
decisions on specific classes of chemicals will be heavily dependent on 
chemical specific data, much of which may not be presently available.
    Although at present the Agency does not know how to apply the 
information in its files concerning common mechanism issues to most 
risk assessments, there are pesticides as to which the common mechanism 
issues can be resolved. These pesticides include pesticides that are 
toxicologically dissimilar to existing chemical substances (in which 
case the Agency can conclude that it is unlikely that a pesticide 
shares a common mechanism of activity with other

[[Page 45180]]

substances) and pesticides that produce a common toxic metabolite (in 
which case common mechanism of activity will be assumed).
    EPA does not have, at this time, available data to determine 
whether zinc phosphide has a common mechanism of toxicity with other 
substances or how to include this pesticide in a cumulative risk 
assessment. Unlike other pesticides for which EPA has followed a 
cumulative risk approach based on a common mechanism of toxicity, zinc 
phosphide does not appear to produce a toxic metabolite produced by 
other substances. For the purposes of this tolerance action, therefore, 
EPA has not assumed that zinc phosphide has a common mechanism of 
toxicity with other substances.

C. Aggregate Risks and Determination of Safety for U.S. Population

    1. Chronic risk. Using the TMRC exposure assumptions described 
above, EPA has concluded that aggregate exposure to zinc phosphide from 
food will utilize 27.5% of the RfD for the U.S. population. The major 
identifiable subgroup with the highest aggregate exposure is children 1 
to 6 years old ``discussed below.'' EPA generally has no concern for 
exposures below 100% of the RfD because the RfD represents the level at 
or below which daily aggregate dietary exposure over a lifetime will 
not pose appreciable risks to human health. Despite the potential for 
exposure to zinc phosphide from non-dietary, non-occupational exposure, 
EPA does not expect the aggregate exposure to exceed 100% of the RfD. 
EPA concludes that there is a reasonable certainty that no harm will 
result from aggregate exposure to zinc phosphide residues.
    2. Short- and intermediate-term risk. Short- and intermediate-term 
aggregate exposure takes into account chronic dietary food and water 
(considered to be a background exposure level) plus indoor and outdoor 
residential exposure.

D. Aggregate Cancer Risk for U.S. Population

    Zinc phosphide has not been reviewed for carcinogenicity. OPP has 
waived carcinogenicity data requirements for zinc phosphide on the 
basis that exposures to zinc phosphide are controlled to prevent 
exposures to humans. Applications to crop areas are such that the zinc 
phosphide will dissipate.

E. Aggregate Risks and Determination of Safety for Infants and Children

    1. Safety factor for infants and children--In general. In assessing 
the potential for additional sensitivity of infants and children to 
residues of zinc phosphide, EPA considered data from developmental 
toxicity studies in the rat and mouse. The developmental toxicity 
studies are designed to evaluate adverse effects on the developing 
organism resulting from maternal pesticide exposure during gestation. 
Reproduction studies provide information relating to effects from 
exposure to the pesticide on the reproductive capability of mating 
animals and data on systemic toxicity.
    FFDCA section 408 provides that EPA shall apply an additional 
tenfold margin of safety for infants and children in the case of 
threshold effects to account for pre-and post-natal toxicity and the 
completeness of the database unless EPA determines that a different 
margin of safety will be safe for infants and children. Margins of 
safety are incorporated into EPA risk assessments either directly 
through use of a MOE analysis or through using uncertainty (safety) 
factors in calculating a dose level that poses no appreciable risk to 
humans. EPA believes that reliable data support using the standard MOE 
and uncertainty factor (usually 100 for combined inter- and intra-
species variability)) and not the additional tenfold MOE/uncertainty 
factor when EPA has a complete data base under existing guidelines and 
when the severity of the effect in infants or children or the potency 
or unusual toxic properties of a compound do not raise concerns 
regarding the adequacy of the standard MOE/safety factor.
    There were no developmental findings in rats up to a maternally 
toxic dose of 4.0 mg/kg/day zinc phosphide nor in mice at 4.0 mg/kg/day 
(HDT). A comparison of the NOEL of 0.1 mg/kg/day in the recent 90-day 
rat gavage study and the NOELs for developmental toxicity in rats and 
mice (4.0 mg/kg/day) provides a 40-fold difference, which demonstrates 
that there are no special pre-natal sensitivities for infants and 
children. OPP has waived teratogenicity in the rabbit and the 2-
generation reproduction study in the rat data requirements for zinc 
phosphide on the basis that exposures to zinc phosphide are controlled 
to prevent exposures to humans. Applications to crop areas are such 
that the zinc phosphide will dissipate. Since there are no reproduction 
studies with zinc phosphide, the post-natal potential for effects from 
zinc phosphide in infants and children cannot be fully evaluated. 
However, the above information, together with the uncertainty factor of 
10,000 utilized to calculate the RfD for zinc phosphide, is considered 
adequate protection for infants and children with respect to prenatal 
and postnatal development against dietary exposure to zinc phosphide 
residues, and therefore, EPA has determined that an additional 10-fold 
safety factor is not appropriate.
    2. Chronic risk. Using the conservative exposure assumptions 
described above, EPA has concluded that aggregate exposure to zinc 
phosphide from food will utilize from 6.8% of the RfD for nursing 
infants (<1 year old) and up to 59.9% children 1 to 6 years old. EPA 
generally has no concern for exposures below 100% of the RfD because 
the RfD represents the level at or below which daily aggregate dietary 
exposure over a lifetime will not pose appreciable risks to human 
health. Despite the potential for exposure to zinc phosphide from non-
dietary, non-occupational exposure, EPA does not expect the aggregate 
exposure to exceed 100% of the RfD. EPA concludes that there is a 
reasonable certainty that no harm will result to infants and children 
from aggregate exposure to zinc phosphide residues.

V. Other Considerations

A. Metabolism In Plants and Animals

    The metabolism of zinc phosphide in plants and animals is 
adequately understood for the purposes of these tolerances. The residue 
of concern is unreacted zinc phosphide, measured as phosphine, that may 
be present.

B. Analytical Enforcement Methodology

    Adequate methods for purposes of data collection and enforcement of 
tolerances for zinc phosphide residues as phosphine gas are available. 
Methods for determining zinc phosphide residues of as phosphine gas are 
described in PAM, Vol. II, as Method A.

C. Magnitude of Residues

    Residues of phosphine resulting from this use of zinc phosphide in 
timothy (seed, forage, hay), alfalfa (forage, hay) and clover (forage, 
hay) will not exceed 0.1 part per million (ppm).

D. International Residue Limits

    There are no Codex tolerances for timothy (seed, forage, hay), 
alfalfa (forage, hay) and clover (forage, hay).

VI. Conclusion

    Therefore, these tolerances are established for phosphine resulting 
from the use of the rodenticide zinc phosphide in timothy (seed, 
forage,

[[Page 45181]]

hay), alfalfa (forage, hay), and clover (forage, hay) at 0.1 ppm.

VII. Objections and Hearing Requests

    The new FFDCA section 408(g) provides essentially the same process 
for persons to ``object'' to a tolerance regulation issued by EPA under 
new section 408(e) and (l)(6) as was provided in the old section 408 
and in section 409. However, the period for filing objections is 60 
days, rather than 30 days. EPA currently has procedural regulations 
which govern the submission of objections and hearing requests. These 
regulations will require some modification to reflect the new law. 
However, until those modifications can be made, EPA will continue to 
use those procedural regulations with appropriate adjustments to 
reflect the new law.
    Any person may, by October 26, 1998, file written objections to any 
aspect of this regulation and may also request a hearing on those 
objections. Objections and hearing requests must be filed with the 
Hearing Clerk, at the address given above (40 CFR 178.20). A copy of 
the objections and/or hearing requests filed with the Hearing Clerk 
should be submitted to the OPP docket for this rulemaking. The 
objections submitted must specify the provisions of the regulation 
deemed objectionable and the grounds for the objections (40 CFR 
178.25). Each objection must be accompanied by the fee prescribed by 40 
CFR 180.33(i). If a hearing is requested, the objections must include a 
statement of the factual issues on which a hearing is requested, the 
requestor's contentions on such issues, and a summary of any evidence 
relied upon by the requestor (40 CFR 178.27). A request for a hearing 
will be granted if the Administrator determines that the material 
submitted shows the following: There is genuine and substantial issue 
of fact; there is a reasonable possibility that available evidence 
identified by the requestor would, if established, resolve one or more 
of such issues in favor of the requestor, taking into account 
uncontested claims or facts to the contrary; and resolution of the 
factual issues in the manner sought by the requestor would be adequate 
to justify the action requested (40 CFR 178.32). Information submitted 
in connection with an objection or hearing request may be claimed 
confidential by marking any part or all of that information as CBI. 
Information so marked will not be disclosed except in accordance with 
procedures set forth in 40 CFR part 2. A copy of the information 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.

VIII. Public Record and Electronic Submissions

    EPA has established a record for this rulemaking under docket 
control number [OPP-300696] (including any comments and data submitted 
electronically). 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 8:30 a.m. 
to 4 p.m., Monday through Friday, excluding legal holidays. The public 
record is located in Room 119 of the Public Information and Records 
Integrity Branch, Information Resources and Services Division (7502C), 
Office of Pesticide Programs, Environmental Protection Agency, Crystal 
Mall #2, 1921 Jefferson Davis Highway, Arlington, VA.
    Electronic comments may be sent directly to EPA at:
    [email protected].


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

IX. Regulatory Assessment Requirements

    This final rule establishes tolerances under FFDCA section 408(d) 
in response to a petition submitted to the Agency. The Office of 
Management and Budget (OMB) has exempted these types of actions from 
review under Executive Order 12866, entitled Regulatory Planning and 
Review (58 FR 51735, October 4, 1993). This final rule does not contain 
any information collections subject to OMB approval under the Paperwork 
Reduction Act (PRA), 44 U.S.C. 3501 et seq., or impose any enforceable 
duty or contain any unfunded mandate as described under Title II of the 
Unfunded Mandates Reform Act of 1995 (UMRA) (Pub. L. 104-4). Nor does 
it require any prior consultation as specified by Executive Order 
12875, entitled Enhancing the Intergovernmental Partnership (58 FR 
58093, October 28, 1993), or special considerations as required by 
Executive Order 12898, entitled Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations (59 FR 7629, February 16, 1994), or require OMB review in 
accordance with Executive Order 13045, entitled Protection of Children 
from Environmental Health Risks and Safety Risks (62 FR 19885, April 
23, 1997).
    In addition, since these tolerances and exemptions that are 
established under FFDCA section 408 (l)(6), such as the tolerances in 
this final rule, do not require the issuance of a proposed rule, the 
requirements of the Regulatory Flexibility Act (RFA) (5 U.S.C. 601 et 
seq.) do not apply. Nevertheless, the Agency has previously assessed 
whether establishing tolerances, exemptions from tolerances, raising 
tolerance levels or expanding exemptions might adversely impact small 
entities and concluded, as a generic matter, that there is no adverse 
economic impact. The factual basis for the Agency's generic 
certification for tolerance acations published on May 4, 1981 (46 FR 
24950), and was provided to the Chief Counsel for Advocacy of the Small 
Business Administration.

X. Submission to Congress and the Comptroller General

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this rule and other 
required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. This rule is not a 
``major rule'' as defined by 5 U.S.C. 804(2).

List of Subjects in 40 CFR Part 180

    Environmental protection, Administrative practice and procedure, 
Agricultural commodities, Pesticides and pests, Reporting and 
recordkeeping requirements.


[[Page 45182]]


    Dated: August 11, 1998.

James Jones,

Director, Registration Division, Office of Pesticide Programs.
    Therefore, 40 CFR chapter I is amended as follows:

PART 180--[AMENDED]

    1. The authority citation for part 180 continues to read as 
follows:

    Authority: 21 U.S.C. 346a and 371.

    2. Section 180.284 is revised to read as follows:


Sec. 180.284   Zinc phosphide; tolerances for residues.

    (a) General. Tolerances are established for residues of the 
phosphine resulting from the use of the rodenticide zinc phosphide in 
or on the raw agricultural commodities as follows:

                                                                        
------------------------------------------------------------------------
                                                              Parts per 
                         Commodity                             million  
------------------------------------------------------------------------
Grapes.....................................................         0.01
Grasses (rangeland)........................................          0.1
Sugarcane..................................................         0.01
------------------------------------------------------------------------

    (b) Section 18 emergency exemptions. Time-limited tolerances are 
established for residues of phosphine resulting from the use of the 
rodenticide zinc phosphide in connection with use of the pesticide 
under FIFRA section 18 emergency exemptions granted by EPA. The 
tolerances are specified in the following table. The tolerances expire 
on the date specified in the table.


                                                                        
------------------------------------------------------------------------
                                           Parts per      Expiration/   
                Commodity                   million      RevocationDate 
------------------------------------------------------------------------
Alfalfa (forage)........................          0.1           02/01/00
Alfalfa (hay)...........................          0.1           02/01/00
Clover (forage).........................          0.1           02/01/00
Clover (hay)............................          0.1           02/01/00
Timothy (forage)........................          0.1           02/01/00
Timothy (hay)...........................          0.1           02/01/00
Timothy (seed)..........................          0.1           02/01/00
------------------------------------------------------------------------

    (c) Tolerances with regional registrations. Tolerances with 
regional registration, as defined in Sec. 180.1(n), are established for 
residues of phosphine resulting from the use of the rodenticide zinc 
phosphide in or on the following raw agricultural commodities as 
follows:

------------------------------------------------------------------------
                                                              Parts per 
                         Commodity                             million  
------------------------------------------------------------------------
Artichoke (globe)..........................................         0.01
Sugar beet (roots).........................................         0.04
Sugar beet (tops)..........................................         0.02
------------------------------------------------------------------------

    (d) Indirect or inadvertent residues. [Reserved]

[FR Doc. 98-22787 Filed 8-24-98; 8:45 am]
BILLING CODE 6560-50-F