[Federal Register Volume 68, Number 158 (Friday, August 15, 2003)]
[Notices]
[Pages 48908-48913]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-20897]


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ENVIRONMENTAL PROTECTION AGENCY

[OPP-2003-0274; FRL-7322-9]


Glufosinate-Ammonium; 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 ID number OPP-2003-0274, must be

[[Page 48909]]

received on or before September 15, 2003.

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: Joanne I. Miller, Registration 
Division (7505C), Office of Pesticide Programs, Environmental 
Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460-
0001; telephone number: (703) 305-6224; 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:
    [sbull] Crop production (NAICS 111)
    [sbull] Animal production (NAICS 112)
    [sbull] Food manufacturing (NAICS 311)
    [sbull] 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 identification (ID) number OPP-2003-0274. 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, 
1921 Jefferson Davis Hwy., 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. 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.

[[Page 48910]]

    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-2003-0274. The system is an ``anonymous access'' system, which 
means EPA will not know your identity, e-mail address, or 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-2003-0274. 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-2003-0274.
    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, 1921 Jefferson Davis Hwy., Arlington, VA, Attention: Docket 
ID Number OPP-2003-0274. 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 11, 2003.
Peter Caulkins,
Acting 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.

Bayer CropScience

PP 0F06140 and PP 0F06210

    EPA has received pesticide petitions (PP 0F06140 and 0F06210) from 
Bayer CropScience, 2 T.W. Alexander Drive, Research Triangle Park, NC 
27709 proposing, pursuant to section 408(d) of the Federal Food, Drug, 
and Cosmetic Act (FFDCA), 21 U.S.C. 346a(d), to amend 40 CFR 180.473 by 
establishing a tolerance for residues of the herbicide glufosinate-
ammonium (butanoic acid, 2-amino-4-(hydroxymethylphosphinyl)-, 
monoammonium salt) and its metabolite, 3-methylphosphinicopropionic 
acid expressed as 2-amino-4-(hydroxymethylphosphinyl)butanoic acid 
equivalents in or on the raw agricultural commodities: Cotton, 
undelinted seed at 4.0 parts per million (ppm); cotton gin byproducts 
at 15 ppm; cattle, fat at 0.4 ppm; cattle, meat at 0.15 ppm; cattle 
meat byproducts at 6.0 ppm; goat, fat at 0.4 ppm; goat, meat at 0.15 
ppm; goat meat byproducts at 6.0 ppm; hog, fat at 0.4 ppm; hog, meat at 
0.15 ppm; hog meat byproducts at 6.0 ppm; horse, fat at 0.4 ppm; horse, 
meat at 0.15 ppm; horse meat byproducts at 6.0 ppm; sheep, fat at 0.4 
ppm; sheep, meat at 0.15 ppm; sheep meat byproducts at 6.0 ppm; egg at 
0.15 ppm; milk at 0.15 ppm; poultry, fat at 0.15 ppm; poultry, meat at 
0.15 ppm; and poultry meat byproducts at 0.6 ppm. Bayer CropScience 
also proposes establishing a tolerance for residues of the herbicide 
glufosinate-ammonium (butanoic acid,

[[Page 48911]]

2-amino-4-(hydroxymethylphosphinyl)-, monoammonium salt) and its 
metabolites, 3-methylphosphinicopropionic acid, and 2-acetamido-4-
methylphosphinico-butanoic acid expressed as 2-amino-4-
(hydroxymethylphosphinyl)butanoic acid equivalents in or on the raw 
agricultural commodities derived from transgenic cotton and rice 
tolerant to glufosinate-ammonium: Rice, grain at 1.0 ppm; rice, straw 
at 2.0 ppm; rice, hull at 2.0 ppm; cotton, undelinted seed at 4.0 ppm; 
and cotton, gin byproducts at 15.0 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.

A. Residue Chemistry

    1. Plant metabolism. Metabolism studies have been conducted on 
crops tolerant to glufosinate-ammonium using radiolabeled parent. As a 
result, the nature of residues found in cotton, rice, and other 
transgenic crops tolerant to glufosinate ammonium is well understood. 
The principal residue in raw agricultural commodities at harvest was 3-
methylphosphinicopropionic acid (Hoe 061517). Other relevant residues 
are N-acetyl-L-glufosinate (2-acetamido-4-methylphosphinico-butanoic 
acid, Hoe 099730) and lesser amounts of the parent compound.
    2. Analytical method. The enforcement analytical method utilizes 
gas chromatography for detecting and measuring levels of glufosinate-
ammonium and metabolites with a general limit of quantification of 0.05 
ppm. This method allows detection of residues at or above the proposed 
tolerances.
    3. Magnitude of residues. Field residue trials were conducted 
across the major regions of rice and cotton production in the United 
States. The treatment regime was selected to represent the use pattern 
that is the most likely to result in the highest residues. When sampled 
at 70 days or more after the last application glufosinate-ammonium 
derived residues did not exceed 0.74 ppm in rice grain and 1.48 ppm in 
rice straw; whereas, in cotton seed and gin by products the highest 
mean residue level was 3.2 ppm and 10.58 ppm, respectively. No 
concentration of the residues occurred when rice whole grain was 
processed into polished grain and bran, whereas a concentration factor 
of approximately 2.3 was found for rice hulls. After ginning, the 
cotton seed was processed into meal, hulls, and refined oil. No 
concentration of the residues upon processing of the cotton seed was 
observed.

B. Toxicological Profile

    1. Acute toxicity. Glufosinate-ammonium has been classified as 
toxicity category III for acute oral, dermal, and inhalation toxicity; 
and for eye irritation. Glufosinate-ammonium is not a dermal irritant 
(toxicity category IV) nor is it a dermal sensitizer. The oral 
LD50 is 2,000 milligrams/kilogram (mg/kg) in male rats and 
1,620 mg/kg in female rats.
    2. Genotoxicity. Based on results of a complete genotoxicity data 
base, there is no evidence of mutagenic activity in a battery of 
studies, including: Salmonella spp., E. coli, in vitro mammalian cell 
gene mutation assays, mammalian cell chromosome aberration assays, in 
vivo mouse bone marrow micronucleus assays, and unscheduled DNA 
synthesis assays.
    3. Reproductive and developmental toxicity. In a developmental 
toxicity study, groups of 20 pregnant female Wistar rats were 
administered glufosinate-ammonium by gavage at doses of 0, 0.5, 2.24 
10, 50, and 250 mg/kg/day from days 7 to 16 of pregnancy. The no 
observed adverse effect level (NOAEL) for maternal toxicity is 10 mg/
kg/day; the lowest observed adverse effect level (LOAEL) is 50 mg/kg/
day based on vaginal bleeding and hyperactivity in dams. In the fetus, 
the NOAEL is 50 mg/kg/day, based on dilated renal pelvis observations 
at the LOAEL of 250 mg/kg/day. In a developmental toxicity study, 
groups of 15 pregnant female Himalayan rabbits were administered 
glufosinate-ammonium by gavage at doses of 0, 2.0, 6.3, or 20.0 mg/kg/
day from days 7 to 19 of pregnancy. In maternal animals, decreases in 
food consumption and body weight gain were observed at the 20 mg/kg/day 
dose level. The NOAEL for maternal toxicity was 6.3 mg/kg/day and that 
for developmental toxicity was 20 mg/kg/day.
    In a multi-generation reproduction study, glufosinate-ammonium was 
administered to groups of 30 male and 30 female Wistar/Han rats in the 
diet at concentrations of 0, 40, 120, or 360 ppm. The LOAEL for 
systemic toxicity is 120 ppm based on increased kidney weights in both 
sexes and generations. The systemic toxicity NOAEL is 40 ppm. The LOAEL 
for reproductive/developmental toxicity is 360 ppm based on decreased 
numbers of viable pups in all generations. The NOAEL is 120 ppm.
    4. Subchronic toxicity.In a subchronic oral toxicity study, 
glufosinate-ammonium was administered to 10 NMRI mice/sex/ dose in the 
diet at levels of 0, 80, 320, or 1,280 ppm (equivalent to 0, 12, 48, or 
192 millgrams/kilogram/day (mg/kg/day)) for 13 weeks. Significant (p< 
0.05) increases were observed in serum aspartate aminotransferase and 
in alkaline phosphatase in high-dose (192 mg/kg/day) males. Also 
observed were increases in absolute and relative liver weights in mid-
(48 mg/kg/day) and high-dose males. The NOAEL is 12 mg/kg/day, the 
LOAEL is 48 mg/kg/day based on the changes in clinical biochemistry and 
liver weights.
    5. Chronic toxicity. In a combined chronic toxicity/oncogenicity 
study, glufosinate-ammonium was administered to 50 Wistar rats/sex/dose 
in the diet for 130 weeks at dose levels of 0, 40, 140, or 500 ppm 
(mean compound intake in males was 0, 1.9, 6.8, and 24.4 mg/kg/day and 
for females was 0, 2.4, 8.2, and 28.7 mg/kg/day, respectively). A dose-
related increase in mortality was noted in females at 140 and 500 ppm, 
whereas in males increased absolute and relative kidney weights were 
noted at 140 ppm and 500 ppm. The NOAEL was considered to be 40 ppm. No 
treatment-related oncogenic response was noted.
    In an oncogenicity study, glufosinate-ammonium was administered to 
50 NMRI mice/sex/dose in the diet at dose levels of 0, 80, 160 (males 
only) or 320 (females only) ppm for 104 weeks. The NOAEL for systemic 
toxicity is 80 ppm (10.82/16.19 mg/kg/day in males/females (M/F)), and 
the LOAEL is 160/320 ppm (22.60/63.96 mg/kg/day in M/F), based on 
increased mortality in males, increased glucose levels in males and 
females, and changes in glutathione levels in males. No increase in 
tumor incidence was found in any treatment group.
    In a chronic feeding study, technical glufosinate-ammonium was fed 
to male and female beagle dogs for 12 months in the diet at levels of 
2.0, 5.0, or 8.5 mg/kg/day. The NOAEL is 5.0 mg/kg/day based on 
clinical signs of toxicity, reduced weight gain and mortality 8.5 mg/
kg/day.
    In a rat oncogenicity study, glufosinate-ammonium was administered 
to Wistar rats (60/sex/group) for up to 24 months at 0, 1,000, 5,000, 
or 10,000 ppm (equivalent to 0, 45.4, 228.9, or 466.3 mg/kg/day in 
males and 0, 57.1, 281.5, or 579.3 mg/kg/day in females). The LOAEL for 
chronic toxicity is 5,000 ppm (equivalent to

[[Page 48912]]

228.9 mg/kg/day for male rats and 281.5 mg/kg/day for females), based 
on increased incidences of retinal atrophy. The chronic NOAEL is 1,000 
ppm. Under the conditions of this study, there was no evidence of 
carcinogenic potential. Dosing was considered adequate based on the 
increased incidence of retinal atrophy.
    6. Animal metabolism. Studies conducted in rats using 
14C- glufosinate-ammonium have shown that the compound is 
poorly absorbed (5-10%) after oral administration and is rapidly 
eliminated primarily as the parent compound. The highest residue levels 
were found in liver and kidney tissues.
    The metabolic profile and the quantitative distribution of 
metabolites were very similar in both goat and hen. The vast majority 
of the dose was excreted, primarily as parent compound. The very 
limited residues found in edible tissues, milk and eggs were comprised 
principally of glufosinate and 3-methylphosphinico-propionic acid (Hoe 
061517), with lesser amounts of N-acetyl-L-glufosinate (Hoe 099730) and 
2-methylohosphinico-acetic acid (Hoe 064619).
    7. Metabolite toxicology. Additional testing has been conducted 
with the major metabolites, 3-methylphosphinico-propionic acid, and N-
acetyl-L-glufosinate. Based on subchronic and developmental toxicity 
study results, a profile of similar or less toxicity was observed for 
the metabolites as compared to the parent compound, glufosinate-
ammonium.
    8. Endocrine disruption. No special studies have been conducted to 
investigate the potential of glufosinate-ammonium to induce estrogenic 
or other endocrine effects. However, no evidence of estrogenic or other 
endocrine effects have been noted in any of the toxicology studies that 
have been conducted with this product and there is no reason to suspect 
that any such effects would be likely.

C. Aggregate Exposure

    1. Dietary exposure. Tolerances have been established (40 CFR 
180.473) for the combined residues of glufosinate-ammonium and 
metabolites in or on a variety of raw agricultural commodities. No 
appropriate toxicological endpoint attributable to a single exposure 
was identified in the available toxicity studies. EPA has, therefore, 
not established an acute reference dose (RfD) for the general 
population including infants and children. An acute population adjusted 
dose (aPAD - 95th percentile) of 0.021 mg/kg/day was established, 
however, for the females 13+ subgroup based on the results of the 
developmental toxicity study in rabbits with an uncertainty factor of 
300. Therefore, an acute dietary analysis was conducted for this sub-
population; whereas, chronic dietary analysis was conducted for the 
usual populations. A chronic population adjusted dose (cPAD) of 0.007 
mg/kg/day (based on the 2-year chronic study in rats and an uncertainty 
factor of 300) was used to perform the chronic dietary analysis.
    i. Food. An acute dietary analysis was conducted using the Dietary 
Exposure Evaluation Model (DEEMTM) software version 7.6 and 
the 1994-1998 Continuing Survey of Food Intake by Individuals (CSFII) 
consumption data base. The Tier I acute dietary assessment was modified 
by incorporating percent crop treated (PCT) values for blended items 
only. Thus, the following PCT values were used: Soybean, 6%; canola, 
11%; cotton, 15%, rice, 2%; sugar beet, 1%; and sugar beet molasses, 
1%. Tolerance values of blended feed items in the animal diets were 
also multiplied by PCT. Dietary burdens were then multiplied by the 
maximum tissue to feed ratios observed in the animal feeding studies. 
This Tier I analysis resulted in an exposure of 0.002746 mg/kg bw/day 
(95th percentile) for the female 13+ sub-population (the only 
population of concern) representing 13% utilization of the aPAD.
    Chronic dietary analysis was conducted to estimate exposure to 
potential glufosinate-ammonium residues in or on registered and 
proposed commodities. The DEEMTM software (version 7.6) and 
the 1994-1998 USDA food consumption data were used. Tolerance level 
residues were assumed for all commodities. Percent crop treated values 
generated by EPA/BEAD and Bayer CropScience were incorporated as 
follows: Tree nuts, 1%; apples, 1%; field corn, 3%; grapes, 1%; 
soybeans, 6%; potatoes, 1%; canola, 11%; and sugar beet, 1%. Bayer 
CropScience estimates that an upper bound value for cotton at market 
maturity is 15% and that for rice is 2%. All other crops are included 
at 100% of crop treated. For the chronic dietary risk assessment, 
secondary residues that could occur as a result of residues of 
glufosinate-ammonium and metabolites in the diet of ruminants and 
poultry were adjusted for percent of the crop treated as indicated 
above. Chronic dietary exposure estimates from residues of glufosinate-
ammonium for the U.S. population represented approximately 3.2% of the 
chronic PAD; whereas that for children 1-2, the sub-population with the 
highest exposure, represented approximately 12% of the chronic PAD. The 
approach used is very conservative, yet still indicates that dietary 
exposures for all segments of the population are well within the 
chronic reference doses. This analysis was based on highly conservative 
assumptions. The Agency has no concerns with PAD utilization up to 
100%.
    ii. Drinking water. U.S. EPA's Standard Operating Procedure (SOP) 
for Drinking Water Exposure and Risk Assessments was used to perform 
the drinking water assessment. The models Screening Concentrations in 
Ground Water (SCI-GROW) and EPA's Pesticide Root Zone Model/Exposure 
Analysis Modeling System (PRZM/EXAMS) were used to estimate the 
concentration of glufosinate-ammonium that might occur in water. The 
acute drinking water level of comparison (DWLOC) for females 13+ is 548 
parts per billion (ppb). In comparison, the acute estimated drinking 
water concentrations (EDWC) calculated by PRZM/EXAMS is 67 ppb.
    The chronic DWLOC calculated for adults is 237 ppb and that for 
children/toddlers is 62 ppb. The chronic EDWC calculated using a worst 
case scenario is 17 ppb PRZM/EXAMS. The DWLOCs are based on highly 
conservative dietary (food) exposures and are expected to be much 
higher in real world situations reducing further the percent 
utilization of the DWLOC.
    2. Non-dietary exposure. U.S. EPA's SOP for Drinking Water Exposure 
and Risk Assessments was used to perform the drinking water assessment. 
The models SCI-GROW and PRZM/EXAMS were used to estimate the 
concentration of glufosinate-ammonium that might occur in water. The 
acute DWLOC for females 13+ is 548 ppb. In comparison, the acute EDWC 
calculated by PRZM/EXAMS is 67 ppb.
    The chronic DWLOC calculated for adults is 237 ppb and that for 
children/toddlers is 62 ppb. The chronic EDWC calculated using a worst 
case scenario is 17 ppb PRZM/EXAMS. The DWLOCs are based on highly 
conservative dietary (food) exposures and are expected to be much 
higher in real world situations reducing further the percent 
utilization of the DWLOC.

D. Cumulative Effects

    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.'' EPA has indicated that, at this time, 
the Agency does not have available data to determine whether 
glufosinate-

[[Page 48913]]

ammonium 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, glufosinate-ammonium does not 
appear to produce a toxic metabolite produced by other substances. For 
the purposes of this tolerance petition, therefore, it has not been 
assumed that glufosinate-ammonium has a common mechanism of toxicity 
with other substances.

E. Safety Determination

    1. U.S. population. Using the conservative assumptions described 
above and based on the completeness and reliability of the toxicity 
data, it is concluded that chronic dietary exposure to the registered 
and proposed uses of glufosinate-ammonium will utilize at most 3.2% of 
the chronic population adjusted dose for the U.S. population. The 
actual exposure is likely to be significantly less than predicted by 
this analysis as data and models that are more realistic are developed. 
Exposures below 100% of the PAD are generally assumed to be of no 
concern because the PAD represents the level at or below which daily 
aggregate exposure over a lifetime will not pose appreciable risk to 
human health.
    The acute population of concern, female 13+ utilizes 13% of the 
aPAD. This is a Tier I highly conservative assessment and actual 
exposure is likely to be far less. DWLOCs based on dietary exposures 
are greater than the conservative estimated levels, and would be 
expected to be well below the 100% level of the reference dose, if they 
occur at all.
    EPA has concluded that it is not appropriate to aggregate non-
dietary exposures with dietary exposures in a risk assessment because 
the toxicity end-points are different.
    Therefore, there is a reasonable certainty that no harm will occur 
to the U.S. population from aggregate exposure (food, drinking water 
and nonresidential) to residues of glufosinate-ammonium and 
metabolites.
    2. Infants and children. The toxicological data base is sufficient 
for evaluating prenatal and postnatal toxicity for glufosinate-
ammonium. There are no prenatal or postnatal susceptibility concerns 
for infants and children, based on the results of the rat and rabbit 
developmental toxicity studies and the 2-generation reproduction study. 
Based on clinical signs of neurological toxicity in short and 
intermediate dermal toxicity studies with rats, EPA has determined that 
an added FQPA safety factor of 3x is appropriate of assessing the risk 
of glufosinate-ammonium derived residues in crop commodities.
    Using the conservative assumptions described in the exposure 
section above, the percent of the chronic population adjusted dose that 
will be used for exposure to residues of glufosinate-ammonium in food 
for children 1-2 (the most highly exposed sub-group) is 12%. Infants 
utilize 11.6% of the chronic PAD. As in the adult situation, DWLOCs are 
higher than the worst case EDWC and are expected to use well below 100% 
of the PAD, if they occur at all.
    Therefore, there is a reasonable certainty that no harm will occur 
to infants and children from aggregate exposure to residues of 
glufosinate-ammonium.

F. International Tolerances

    Maximum residue limits for glufosinate-ammonium and metabolites in 
or on rice commodities have not been established by the Codex 
Alimentarius Commission.

[FR Doc. 03-20897 Filed 8-14-03; 8:45 am]
BILLING CODE 6560-50-S