[Federal Register Volume 70, Number 172 (Wednesday, September 7, 2005)]
[Notices]
[Pages 53180-53185]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-17529]


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ENVIRONMENTAL PROTECTION AGENCY

[OPP-2005-0215; FRL-7731-1]


Terbacil; Notice of Filing a Pesticide Petition to Establish a 
Tolerance for a Certain Pesticide Chemical in or on Food

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: This notice announces the initial filing of a pesticide 
petition proposing the establishment of regulations for residues of a 
certain pesticide chemical in or on various food commodities.

DATES: Comments, identified by docket identification (ID) number OPP-
2005-0215, must be received on or before October 7, 2005.

ADDRESSES: Comments may be submitted electronically, by mail, or 
through hand delivery/courier. Follow the detailed instructions as 
provided in Unit I. of the SUPPLEMENTARY INFORMATION.

FOR FURTHER INFORMATION CONTACT: Sidney Jackson, Registration Division 
(7505C), Office of Pesticide Programs,

[[Page 53181]]

Environmental Protection Agency, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460-0001; telephone number: (703) 305-7610; e-mail 
address: [email protected].

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this Action Apply to Me?

    You may be potentially affected by this action if you are an 
agricultural producer, food manufacturer, or pesticide manufacturer. 
Potentially affected entities may include, but are not limited to:
     Crop production (NAICS 111)
     Animal production (NAICS 112)
     Food manufacturing (NAICS 311)
     Pesticide manufacturing (NAICS 32532)
    This listing is not intended to be exhaustive, but rather provides 
a guide for readers regarding entities likely to be affected by this 
action. Other types of entities not listed in this unit could also be 
affected. The North American Industrial Classification System (NAICS) 
codes have been provided to assist you and others in determining 
whether this action might apply to certain entities. If you have any 
questions regarding the applicability of this action to a particular 
entity, consult the person listed under FOR FURTHER INFORMATION 
CONTACT.

B. How Can I Get Copies of this Document and Other Related Information?

    1. Docket. EPA has established an official public docket for this 
action under docket ID number OPP-2005-0215. The official public docket 
consists of the documents specifically referenced in this action, any 
public comments received, and other information related to this action. 
Although a part of the official docket, the public docket does not 
include Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. The official public docket 
is the collection of materials that is available for public viewing at 
the Public Information and Records Integrity Branch (PIRIB), Rm. 119, 
Crystal Mall 2, 1801 S. Bell St., Arlington, VA. This docket 
facility is open from 8:30 a.m. to 4 p.m., Monday through Friday, 
excluding legal holidays. The docket telephone number is (703) 305-
5805.
    2. Electronic access. You may access this Federal Register document 
electronically through the EPA Internet under the ``Federal Register'' 
listings at http://www.epa.gov/fedrgstr/.
    An electronic version of the public docket is available through 
EPA's electronic public docket and comment system, EPA Dockets. You may 
use EPA Dockets at http://www.epa.gov/edocket/ to submit or view public 
comments, access the index listing of the contents of the official 
public docket, and to access those documents in the public docket that 
are available electronically. Although not all docket materials may be 
available electronically, you may still access any of the publicly 
available docket materials through the docket facility identified in 
Unit I.B.1. Once in the system, select ``search,'' then key in the 
appropriate docket ID number.
    Certain types of information will not be placed in the EPA Dockets. 
Information claimed as CBI and other information whose disclosure is 
restricted by statute, which is not included in the official public 
docket, will not be available for public viewing in EPA's electronic 
public docket. EPA's policy is that copyrighted material will not be 
placed in EPA's electronic public docket but will be available only in 
printed, paper form in the official public docket. To the extent 
feasible, publicly available docket materials will be made available in 
EPA's electronic public docket. When a document is selected from the 
index list in EPA Dockets, the system will identify whether the 
document is available for viewing in EPA's electronic public docket. 
Although not all docket materials may be available electronically, you 
may still access any of the publicly available docket materials through 
the docket facility identified in Unit I.B.1. EPA intends to work 
towards providing electronic access to all of the publicly available 
docket materials through EPA's electronic public docket.
    For public commenters, it is important to note that EPA's policy is 
that public comments, whether submitted electronically or in paper, 
will be made available for public viewing in EPA's electronic public 
docket as EPA receives them and without change, unless the comment 
contains copyrighted material, CBI, or other information whose 
disclosure is restricted by statute. When EPA identifies a comment 
containing copyrighted material, EPA will provide a reference to that 
material in the version of the comment that is placed in EPA's 
electronic public docket. The entire printed comment, including the 
copyrighted material, will be available in the public docket.
    Public comments submitted on computer disks that are mailed or 
delivered to the docket will be transferred to EPA's electronic public 
docket. Public comments that are mailed or delivered to the docket will 
be scanned and placed in EPA's electronic public docket. Where 
practical, physical objects will be photographed, and the photograph 
will be placed in EPA's electronic public docket along with a brief 
description written by the docket staff.

C. How and to Whom Do I Submit Comments?

    You may submit comments electronically, by mail, or through hand 
delivery/courier. To ensure proper receipt by EPA, identify the 
appropriate docket ID number in the subject line on the first page of 
your comment. Please ensure that your comments are submitted within the 
specified comment period. Comments received after the close of the 
comment period will be marked ``late.'' EPA is not required to consider 
these late comments. If you wish to submit CBI or information that is 
otherwise protected by statute, please follow the instructions in Unit 
I.D. Do not use EPA Dockets or e-mail to submit CBI or information 
protected by statute.
    1. Electronically. If you submit an electronic comment as 
prescribed in this unit, EPA recommends that you include your name, 
mailing address, and an e-mail address or other contact information in 
the body of your comment. Also include this contact information on the 
outside of any disk or CD ROM you submit, and in any cover letter 
accompanying the disk or CD ROM. This ensures that you can be 
identified as the submitter of the comment and allows EPA to contact 
you in case EPA cannot read your comment due to technical difficulties 
or needs further information on the substance of your comment. EPA's 
policy is that EPA will not edit your comment, and any identifying or 
contact information provided in the body of a comment will be included 
as part of the comment that is placed in the official public docket, 
and made available in EPA's electronic public docket. If EPA cannot 
read your comment due to technical difficulties and cannot contact you 
for clarification, EPA may not be able to consider your comment.
    i. EPA Dockets. Your use of EPA's electronic public docket to 
submit comments to EPA electronically is EPA's preferred method for 
receiving comments. Go directly to EPA Dockets at http://www.epa.gov/edocket/, and follow the online instructions for submitting comments. 
Once in the system, select ``search,'' and then key in docket ID number 
OPP-2005-0215. The system is an ``anonymous access'' system, which 
means EPA will not know your identity, e-mail address, or

[[Page 53182]]

other contact information unless you provide it in the body of your 
comment.
    ii. E-mail. Comments may be sent by e-mail to [email protected], 
Attention: Docket ID Number OPP-2005-0215. In contrast to EPA's 
electronic public docket, EPA's e-mail system is not an ``anonymous 
access'' system. If you send an e-mail comment directly to the docket 
without going through EPA's electronic public docket, EPA's e-mail 
system automatically captures your e-mail address. E-mail addresses 
that are automatically captured by EPA's e-mail system are included as 
part of the comment that is placed in the official public docket, and 
made available in EPA's electronic public docket.
    iii. Disk or CD ROM. You may submit comments on a disk or CD ROM 
that you mail to the mailing address identified in Unit I.C.2. These 
electronic submissions will be accepted in WordPerfect or ASCII file 
format. Avoid the use of special characters and any form of encryption.
    2. By mail. Send your comments to: Public Information and Records 
Integrity Branch (PIRIB) (7502C), Office of Pesticide Programs (OPP), 
Environmental Protection Agency, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460-0001, Attention: Docket ID Number OPP-2005-0215.
    3. By hand delivery or courier. Deliver your comments to: Public 
Information and Records Integrity Branch (PIRIB), Office of Pesticide 
Programs (OPP), Environmental Protection Agency, Rm. 119, Crystal Mall 
2, 1801 S. Bell St., Arlington, VA, Attention: Docket ID 
Number OPP-2005-0215. Such deliveries are only accepted during the 
docket's normal hours of operation as identified in Unit I.B.1.

D. How Should I Submit CBI to the Agency?

    Do not submit information that you consider to be CBI 
electronically through EPA's electronic public docket or by e-mail. You 
may claim information that you submit to EPA as CBI by marking any part 
or all of that information as CBI (if you submit CBI on disk or CD ROM, 
mark the outside of the disk or CD ROM as CBI and then identify 
electronically within the disk or CD ROM the specific information that 
is CBI). Information so marked will not be disclosed except in 
accordance with procedures set forth in 40 CFR part 2.
    In addition to one complete version of the comment that includes 
any information claimed as CBI, a copy of the comment that does not 
contain the information claimed as CBI must be submitted for inclusion 
in the public docket and EPA's electronic public docket. If you submit 
the copy that does not contain CBI on disk or CD ROM, mark the outside 
of the disk or CD ROM clearly that it does not contain CBI. Information 
not marked as CBI will be included in the public docket and EPA's 
electronic public docket without prior notice. If you have any 
questions about CBI or the procedures for claiming CBI, please consult 
the person listed under FOR FURTHER INFORMATION CONTACT.

E. What Should I Consider as I Prepare My Comments for EPA?

    You may find the following suggestions helpful for preparing your 
comments:
    1. Explain your views as clearly as possible.
    2. Describe any assumptions that you used.
     3. Provide copies of any technical information and/or data you 
used that support your views.
     4. If you estimate potential burden or costs, explain how you 
arrived at the estimate that you provide.
     5. Provide specific examples to illustrate your concerns.
     6. Make sure to submit your comments by the deadline in this 
notice.
     7. To ensure proper receipt by EPA, be sure to identify the docket 
ID number assigned to this action in the subject line on the first page 
of your response. You may also provide the name, date, and Federal 
Register citation.

II. What Action is the Agency Taking?

    EPA has received a pesticide petition as follows proposing the 
establishment and/or amendment of regulations for residues of a certain 
pesticide chemical in or on various food commodities under section 408 
of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 346a. 
EPA has determined that this petition contains data or information 
regarding the elements set forth in FFDCA section 408(d)(2); however, 
EPA has not fully evaluated the sufficiency of the submitted data at 
this time or whether the data support granting of the petition. 
Additional data may be needed before EPA rules on the petition.

List of Subjects

    Environmental protection, Agricultural commodities, Feed additives, 
Food additives, Pesticides and pests, Reporting and recordkeeping 
requirements.


    Dated: August 19, 2005.
Lois Rossi,
Director, Registration Division, Office of Pesticide Programs.

Summary of Petition

    The petitioner summary of the pesticide petition is printed below 
as required by FFDCA section 408(d)(3). The summary of the petition was 
prepared by the petitioner and represents the view of the petitioner. 
The petition summary announces the availability of a description of the 
analytical methods available to EPA for the detection and measurement 
of the pesticide chemical residues or an explanation of why no such 
method is needed.

Interregional Research Project Number 4 (IR-4)

PP 3E6640

    EPA has received a pesticide petition (PP 3E6640) from 
Interregional Research Project Number 4 (IR-4) on behalf of DuPont Crop 
Protection, P.O. Box 30, Newark, Delaware 19714-0030, proposing, 
pursuant to section 408(d) of the FFDCA, 21 U.S.C. 346a(d), to amend 40 
CFR part 180 by establishing a tolerance for residues of the herbicide, 
terbacil (3-tert-butyl-5-chloro-6-methyluracil) and its metabolites [3-
tert-butyl-5-chloro-6-hydroxymethyluracil], [6-chloro-2,3-dihydro-7-
hydroxymethyl 3,3-dimethyl-5H-oxazolo(3,2-a) pyrimidin-5-one], and [6-
chloro-2,3-dihydro-3,3,7-trimethyl-5H-oxazolo(3,2-a) pyrimidin-5-one] 
in or on the raw agricultural commodity watermelon at 1.0 parts per 
million (ppm). EPA has determined that the petition contains data or 
information regarding the elements set forth in section 408(d)(2) of 
the FFDCA; however, EPA has not fully evaluated the sufficiency of the 
submitted data at this time or whether the data supports granting of 
the petition. Additional data may be needed before EPA rules on the 
petition. This notice includes a summary of the petition that was 
prepared by DuPont Crop Protection.

A. Residue Chemistry

    1. Plant metabolism. The metabolism and chemical nature of residues 
of terbacil in plants and animals are adequately understood. The fate 
of terbacil has been extensively studied using radioactive tracers in 
plant and animal metabolism/nature of the residue studies.
    2. Analytical method. There is a practical analytical method 
utilizing microcoulometric gas chromatography with thermionic or 
nitrogen

[[Page 53183]]

phosphorous detection available for enforcement with a limit of 
detection that allows monitoring food with residues at or above 
tolerance levels. The limit of detection for the method determined by 
the lowest standard of 0.5 nanogram per microliter (ng/[mu]l) was 0.05 
ppm.
    3. Magnitude of residues. Crop field trial residue data from a 69- 
to 94-day preharvest interval (PHI) study show that the proposed 
tolerance in or on watermelon at 1.0 ppm will not be exceeded when 
DuPont Sinbar (trade name) herbicide is used as directed.

B. Toxicological Profile

    1. Acute toxicity. Terbacil technical has been placed in EPA 
Toxicity Category III for acute oral toxicity (rat lethal dose 
(LD50) 934 milligram/kilogram (mg/kg) in female rats; 1,255 
mg/kg in male rats); Category IV for acute inhalation lethal 
concentration (LC50) >4.4 milligrams per liter (mg/L) in 
rats); Category IV for acute dermal (rabbit LD50 >5,000 mg/
kg); and Category III for primary eye irritation (mild conjunctival 
effects clearing in 72 hours in rabbits). Although a primary dermal 
irritation study is not available on terbacil technical, the Agency 
indicated to the Registrant that if no dermal irritation was observed 
in a 21-day sub-chronic dermal study, then the requirements for the 
primary dermal irritation study would be satisfied. No dermal 
irritation was reported in that study. A dermal sensitization test on 
terbacil in guinea pigs showed no dermal sensitization.
    2. Genotoxicity. Terbacil technical was tested and found negative 
in a Chinese hamster ovary (CHO) Hypoxanthine guanine phophoribosyl 
transferase (HGPRT) gene mutation assay when tested up to cytotoxic 
levels, with and without S-9 activation (cytotoxicity >3.0 micromolar 
(mM) without activation; >2.75 mM with activation). Terbacil technical 
was also negative for unscheduled DNA synthesis when tested up to 
cytotoxic levels (5 mM) in the rat. It was also negative for 
clastogenicity in a chromosomal aberration study in rat bone marrow 
cells, at doses up to 500 mg/kg.
    3. Reproductive and developmental toxicity. Terbacil was tested in 
male and female rats at control and dietary levels of 50 or 250 ppm 
(equivalent to 2.5 or 12.5 mg/kg/day, over three generations. The first 
litter of each generation was discarded, and the second litter bred to 
produce the next generation. No reproductive effects were seen at the 
highest dose tested. Therefore, the no observed adverse effect level 
(NOAEL) for reproductive toxicity was equal to or greater than 250 ppm 
(12.5 mg/kg/day).
    Terbacil has been tested in rats and rabbits for its potential to 
produce developmental toxicity. Rats were fed 0, 250, 1,250 or 5,000 
ppm (equivalent to 0, 12.5, 62.5, or 250 mg/kg/day) of terbacil in the 
diet from days 6 through 15 of gestation. The developmental NOAEL was 
250 ppm (12.5 mg/kg/day); the developmental LOAEL of 1,250 ppm (62.5 
mg/kg/day) was based upon significantly decreased numbers of live 
fetuses per litter, apparently due to fetal loss occurring before or 
near the time of implantation. The maternal NOAEL was 250 ppm (12.5 mg/
kg/day), based on decreased body weight at 1,250 ppm (62.5 mg/kg/day). 
Teratogenicity in pregnant rats was not demonstrated.
    Rabbits were given doses of terbacil of 0, 30, 200, or 600 mg/kg/
day by gavage, on gestation days 7 through 19. The maternal NOAEL was 
200 mg/kg/day, based on maternal deaths (5 died and 2 were sacrificed 
in extremis) at the LOAEL of 600 mg/kg/day. The developmental NOAEL was 
also 200 mg/kg/day based on decreased live fetal weights in the high 
dose group. Teratogenicity in pregnant rabbits was not demonstrated.
    4. Subchronic toxicity. Subchronic oral toxicity was tested in a 
90-day feeding study in rats. A NOAEL of 100 ppm (equivalent to 5 mg/
kg/day) and a LOAEL of 500 ppm, equivalent to 25 mg/kg/day highest dose 
tested (HDT) were established, based on increased absolute and relative 
liver weights, vacuolization and hypertrophy of hepatocytes. The data 
requirement for subchronic oral toxicity in a nonrodent was satisfied 
by a 2-year feeding study in beagle dogs, in which a NOAEL of 50 ppm 
(equivalent to 1.25 mg/kg/day) and a LOAEL of 250 ppm (equivalent to 
7.2 mg/kg/day) were established, based on increased thyroid to body 
weight ratios, slight increase in liver weights, and elevated alkaline 
phosphatase levels.
    Subchronic dermal toxicity was tested in a 21-day study in rabbits. 
Terbacil (80% active ingredient (a.i.)) was applied to prepared skin of 
male and female rabbits at 5,000 mg/kg/day, 5 hours/day, 5 days/week. 
No systemic toxicity was observed; mild scaling and staining were 
reported at the test sites.
    5. Chronic toxicity. Terbacil 80% a.i. was administered to beagle 
dogs (4/sex/group) in the diet for 2 years, at doses of 50, 250, or 
2,500/10,000 ppm (equivalent to 1.25, 6.25, 62.5/250 mg/kg/day). The 
NOAEL was 50 ppm (1.25 mg/kg/day) and the LOAEL was 250 ppm (6.25 mg/
kg/day) based on increased thyroid to body weight ratios, slight 
increase in liver weights, and elevated alkaline phosphatase levels. 
Relative liver weights were also increased at 2,500 and 10,000 ppm in 
dogs sacrificed at 1 year and 2 years, respectively.
    A 2-year rat study was conducted using terbacil 97.4% a.i. 
administered to male and female rats at dietary levels of 0, 25, 1,500, 
or 7,500 ppm (approximate doses for males of 0,0.9, 58, and 308 mg/kg/
day and for females of 0, 1.4, 83/484 mg/kg/day). The systemic NOAEL is 
25 ppm and the LOAEL is 1,500 ppm based on liver weight and 
centrilobular hypertrophy. The study was conducted at adequate dosages 
as demonstrated by the decrement in body weight gain in both sexes. 
There was no evidence of increased tumor incidence in the treated 
animals when compared to the controls.
    Terbacil has been tested in a chronic 2-year feeding/oncogenicity 
study in mice at doses of 0, 50, 1,250, or 5,000/7,500 ppm (equivalent 
to 7, 179, 714/1,071 mg/kg/day). The increase in dose occurred after 
week 54. A systemic NOAEL of 50 ppm is based on the LOAEL of 1,250 ppm 
that resulted in mild hypertrophy of the centrilobular hepatocytes and 
decreased pituitary weights in males. Pituitary weight was also 
decreased in high-dose females. There was an increased incidence of 
lung neoplasms (adenomas and adenocarcinomas) in all treated male mice, 
which was not dose-related; in addition, these tumors were within the 
range of similar tumors observed in historical control mice.
    6. Animal metabolism. Radiolabeled terbacil was tested in rats in 
single doses of 6.5 or 500 mg/kg; 97-103% of radioactivity was 
recovered within 5 days: 70-86% in urine, and 28% in feces. The major 
metabolites were glucuronide, sulfate, and N-acetylcysteine conjugates. 
The primary metabolic pathway is hydroxylation of the 6-methyl group to 
form the alcohol, which is conjugated to form the glucuronide (35% of 
the dose) and the sulfate derivatives (11%). Terbacil is also 
metabolized to the 5-hydroxy intermediate, which is further conjugated 
to form a sulfate derivative (17%).
    7. Metabolite toxicology. The parent molecule is the only moiety of 
toxicological significance appropriate for regulation in plant and 
animal commodities.
    8. Endocrine disruption. No observed effects reported.

C. Aggregate Exposure

    1. Dietary exposure--i. Food. Tolerances have been established for 
the residues of terbacil in or on a variety of agricultural 
commodities. For purposes

[[Page 53184]]

of assessing dietary exposure, chronic and acute dietary assessments 
have been conducted using all existing and pending tolerances for 
terbacil. To estimate acute dietary risk, the endpoint selected was 
based on a rat development toxicity study in which the maternal and 
fetal NOAEL were 12.5 mg/kg/day. The reference dose (RfD) for systemic 
toxicity was determined for terbacil as 0.013 mg/kg/day, by the 
Agency's RfD committee in 1986. The RfD was calculated from a 2-year 
feeding study in dogs in which the NOAEL was 1.25 mg/kg/day (based on 
increased relative liver weights and increased serum alkaline 
phosphatase, seen at 7.25 mg/kg/day), and an uncertainty factor of 100. 
The RfD of 0.013 mg/kg/day was reaffirmed by the Agency's RfD Committee 
on September 1, 1994.
    A Tier 1 (screening) assessment was conducted by DuPont; tolerance 
values, indicated below, were used in the assessment with no 
adjustments for processing or usage. (Alfalfa feed commodities are not 
included in the assessment because they are not consumed by humans.)

------------------------------------------------------------------------
                                                              Tolerance
                         Commodity                              (ppm)
------------------------------------------------------------------------
Apple                                                                0.3
------------------------------------------------------------
Asparagus                                                            0.4
------------------------------------------------------------
Blueberry                                                            0.2
------------------------------------------------------------
Caneberry Crop Subgroup 13B                                          0.2
------------------------------------------------------------
Peach                                                                0.2
------------------------------------------------------------
Peppermint                                                           2.0
------------------------------------------------------------
Spearmint                                                            2.0
------------------------------------------------------------
Strawberry                                                           0.1
------------------------------------------------------------
Sugarcane                                                            0.4
------------------------------------------------------------
Watermelon                                                           1.0
                                                              (proposed)
------------------------------------------------------------------------

    The chronic risk values were calculated with a chronic reference 
dose (cRfD) of 0.013 mg/kg body weight (bwt)/day. The chronic dietary 
exposure for the U.S. population was 0.000725 mg/kg bwt/day (5.6% of 
the cRfD). The most sensitive subpopulation was children 1-6 years old 
with a chronic dietary exposure of 0.002991 mg/kg bwt/day (23.0% of the 
cRfD).
    The acute risk values were calculated with an acute reference dose 
(aRfD) of 0.125 mg/kg bwt/day. The acute dietary exposure (at the 95th 
percentile) for the U.S. population was 0.003071 mg/kg bwt/day (2.5% of 
aRfD). The most sensitive subpopulation was children 1-2 years old with 
an acute dietary exposure (at the 95th percentile) of 0.015641 mg/kg 
bwt/day(12.5% aRfD).
    These results of Tier 1 (screening) assessments support the 
registrant's view that there is reasonable certainty of no harm from 
the use of this product as labeled/proposed.
    Terbacil is classified as a Group E carcinogen--no evidence of 
carcinogenicity in either rats or mice. Therefore, a carcinogenicity 
risk analysis for humans is not required.
    ii. Drinking water. Other potential dietary sources of exposure of 
the general population to pesticides are residues in drinking water.
    For acute drinking water risk, the Drinking Water Levels of Concern 
(DWLOCs) were calculated using an aRfD (acute) endpoint of 0.125 mg/kg 
and compared to surface water or ground water EEC (estimated 
environmental concentration) values of 0.154 ppm and 0.125 ppm, 
respectively. The DWLOC values are as follows:

------------------------------------------------------------------------
                                                                DWLOC
                    Population Subgroups                        Values
                                                                (ppm)
------------------------------------------------------------------------
U.S. Population                                                      4.3
------------------------------------------------------------
Non-Nursing Infants                                                  1.1
------------------------------------------------------------
Children 1-6 Years                                                   1.1
------------------------------------------------------------
Children 7-12 Years                                                  1.2
------------------------------------------------------------
Females 13+ Nursing                                                  3.6
------------------------------------------------------------
Males 13-19 Years                                                    4.3
------------------------------------------------------------
Seniors 55+                                                          4.3
------------------------------------------------------------------------

    For chronic drinking water risk, the DWLOCs were calculated using a 
cRfD (chronic) endpoint of 0.013 mg/kg and compared to surface water or 
ground water EEC values of 0.105 ppm and 0.0089 ppm, respectively. The 
DWLOC values are as follows:

------------------------------------------------------------------------
                                                                DWLOC
                    Population Subgroups                        Values
                                                                (ppm)
------------------------------------------------------------------------
U.S. Population                                                     0.43
------------------------------------------------------------
Non-Nursing Infants                                                 0.10
------------------------------------------------------------
Children 1-6 years                                                  0.10
------------------------------------------------------------
Children 7-12 Years                                                 0.12
------------------------------------------------------------
Females 13+ Nursing                                                 0.36
------------------------------------------------------------
Males 13-19 years                                                   0.43
------------------------------------------------------------
Seniors 55+                                                         0.44
------------------------------------------------------------------------

    The estimated environmental concentrations are within acceptable 
ranges. Because of the conservative nature of the screening level 
dietary assessments performed, and the fact that actual ground water 
monitoring data, although limited, are not showing large amounts of 
terbacil present, DuPont does not believe that drinking water sources 
of terbacil are of concern.
    2. Non-dietary exposure. Terbacil is not registered for any use 
that could result in non-occupational, non-dietary exposure to the 
general population. Alfalfa feed commodities were not included in the 
assessment because they are not consumed by humans.

D. Cumulative Effects

    Section 408(b)(2)(D)(v) requires that, when considering whether to 
establish, modify, or revoke a tolerance, the Agency considers 
``available information'' concerning the cumulative effects of a 
particular pesticide's residues and ``other substances that have a 
common mechanism of toxicity.'' 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.
    In assessing the potential risk from cumulative effects of terbacil 
and other chemical substances, the Agency has considered structural 
similarities that exist between terbacil and other substituted uracil 
compounds such as bromacil and lenacil.
    A comparison of the available toxicological database for terbacil 
and bromacil revealed no clear common mode of toxicity for these 
chemicals. The toxicology database for lenacil was not considered 
because there are currently no registered uses of lenacil. A summary of 
the most prominent clinical

[[Page 53185]]

signs from terbacil and bromacil follows.
    The following clinical signs were observed in the terbacil 
toxicology database: Decrease in body weight, increase in liver 
weights, vacuolization and hypertrophy of hepatocytes, hypertrophy of 
centrilobular hepatocytes in males, decreased pituitary weights in 
males and females, increase in thyroid/body weight ratio, and elevated 
alkaline phosphatase.
    The following clinical signs were observed in the bromacil 
toxicology database: Decreased body weight, focal atrophy of 
seminiferous tubules (testicular abnormalities), hydronephrosis, 
suggestive histological evidence for antithyroid activity (cystic 
follicles in the thyroid and enlargement of centrilobular cells of the 
liver), and a positive trend in thyroid tumors for male rats (basis of 
C classification for carcinogenicity).
    Based on these data, DuPont concludes that there is no clear common 
mode of toxicity (thyroid or liver) between terbacil and bromacil. With 
both chemicals, there is marginal evidence of liver effects 
(principally enlargement of centrilobular cells). Enlargement of liver 
cells is not a specific enough effect to be considered a common mode of 
toxicity. The thyroid effects observed with bromacil were cystic 
follicles. Terbacil induced an increase in relative thyroid weights but 
no increase in absolute thyroid weights. An increase in relative weight 
without a corresponding increase in absolute weight has very little 
meaning, especially without any supporting histological or hormonal 
evidence. This conclusion was based on the marginal liver effects noted 
in the databases, and the absence of thyroid effects in the terbacil 
database (with the exception of increases in relative thyroid weights).
    DuPont has no information indicating that any other chemical has a 
common mode of toxicity with terbacil and, therefore concludes that an 
aggregate risk assessment will indicate risks resulting only from 
terbacil.

E. Safety Determination

    1. U.S. population. EPA has determined that the established 
tolerances for terbacil meet the safety standards under the FQPA 
amendments to section 408(b)(2)(D) for the general population. In 
reaching this determination, EPA has considered available information 
on aggregate exposures (both acute and chronic) from non-occupational 
sources, food and drinking water, as well as the possibility of 
cumulative effects from terbacil and other chemicals with similar 
mechanism of toxicity.
    Since there are no residential or lawn uses of terbacil, no dermal 
or inhalation exposure is expected in and around the home.
    In assessing acute dietary risk from food, the endpoint selected 
was developmental toxicity. Because the endpoint of concern is a 
developmental effect, the only sub-population of concern is females of 
child-bearing age (i.e., females, 13+ years old).
    The acute risk values were calculated by DuPont with an aRfD of 
0.125 mg/kg bwt/day. The acute dietary exposure (at the 95th 
percentile) for the U.S. population was 0.003071 mg/kg bwt/day (2.5% of 
aRfD). The most sensitive subpopulation was children 1-2 years old with 
an acute dietary exposure (at the 95th percentile) of 0.015641 mg/kg 
bwt/day (12.5% aRfD).
    The chronic risk values were calculated by DuPont with a cRfD of 
0.013 mg/kg bwt/day. The chronic dietary exposure for the U.S. 
population was 0.000725 mg/kg bwt/day (5.6% of the cRfD). The most 
sensitive subpopulation was children 1-6 years old with a chronic 
dietary exposure of 0.002991 mg/kg bwt/day (23.0% of the cRfD).
    In evaluating the potential for cumulative effects, EPA compared 
terbacil with other structurally similar substituted uracil compounds, 
such as bromacil and lenacil, and then with other compounds producing 
similar effects. A comparison of the available toxicological database 
for terbacil and bromacil revealed no clear common mode of toxicity for 
the chemicals. The toxicology database for lenacil was not considered 
because there are currently no registered uses of lenacil. Based on the 
available data, the Agency has determined that there is no clear common 
mode of toxicity between terbacil and bromacil.
    2. Infants and children. EPA has determined that the established 
tolerances for terbacil meet the safety standard under the FQPA 
amendment to section 408(b)(2)(C) for infants and children. The safety 
determination for infants and children considers the factors noted 
above for the general population, but also takes into account the 
possibility of increased dietary exposure due to the specific 
consumption patterns of infants and children, as well as the 
possibility of increased susceptibility to the toxic effects of 
terbacil residues in this population subgroup.
    In determining whether or not infants and children are particularly 
susceptible to toxic effects from terbacil residues, EPA considered the 
completeness of the database for developmental and reproductive 
effects, the nature of the effects observed, and other information.
    Based on current data requirements, terbacil has a complete 
database for developmental and reproductive toxicity. Because the 
developmental NOAELs were the same as those for maternal toxicity, and 
the NOAEL for systemic (parental) toxicity was higher than the NOAEL 
for reproductive toxicity, DuPont believes that these data do not 
suggest an increased pre- or post-natal sensitivity of children and 
infants to terbacil exposure. Therefore, DuPont concludes that the 
available toxicology data do not support an uncertainty factor of 1,000 
as specified in FQPA and that the present uncertainty factor of 100 is 
adequate to ensure the protection of infants and children from exposure 
to terbacil.
    It is estimated by DuPont that terbacil exposure from the chronic 
diet is as follows: All infants less than 1 year--18% of the cRfD; 
Nursing infants--9.7% of the cRfD; Non-nursing infants--21.2% of the 
cRfD; Children 1-6 years--23% of the cRfD.

F. International Tolerances

    There are no established Codex maximum residue levels (MRL's) or 
international tolerances for terbacil on watermelon.

[FR Doc. 05-17529 Filed 9-6-05; 8:45 am]
BILLING CODE 6560-50-S