[Federal Register Volume 70, Number 124 (Wednesday, June 29, 2005)]
[Notices]
[Pages 37392-37397]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-12444]


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ENVIRONMENTAL PROTECTION AGENCY

[OPP-2005-0161; FRL-7718-5]


Imazethapyr; 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-
2005-0161, must be received on or before July 29, 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: Jim Tompkins, Registration Division 
(7505C), Office of Pesticide Programs, Environmental Protection Agency, 
1200 Pennsylvania Ave., NW., Washington, DC 20460--0001; telephone 
number: (703) 305-5697; 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 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-2005-0161. 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

[[Page 37393]]

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.
    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-2005-0161. 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-2005-0161. 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-2005-0161.
    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-2005-0161. 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

[[Page 37394]]

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 theelements 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: June 10. 2005.
Betty Shackleford,
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.

BASF Corporation

PP 5F 6947

    EPA has received a pesticide petition (5F 6947) from BASF 
Corporation, 26 Davis Drive, P.O. Box 13528, Research Triangle Park, 
North Carolina 27709-3528 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 part 180 by establishing a tolerance for residues of 
imazethapyr,2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-
imidazol-2-yl]-5-ethyl-3-pyridine-carboxylic acid) as its free acid or 
its ammonium salt (calculated as the acid), and its metabolite 2-[4, 5-
dihydro-4-methyl-4-(1-methylethyl-5-oxo-1H-imidazol-2-yl]-5-(1-
hydroxyethyl)-3-pyridinecarboxylic acid both free and conjugated] in or 
on the raw agricultural commodity rice grain at 0.3 parts per million 
(ppm) and rice straw at 0.4 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. The qualitative nature of the residues of 
imazethapyr in rice is adequately understood. Based on studies 
conducted on soybean, edible and forage legumes and corn, parent 
imazethapyr and common metabolites CL 288511 and CL 182704 are the only 
residues of concern for tolerance setting purposes.
    2. Analytical method. The analytical method for rice commodities, 
grain and straw is based on Capillary Electrophoresis with limits of 
quantitation (LOQ) of 0.05 ppm. Measurement of imazethapyr residues in 
polished rice, hull and bran are accomplished by Liquid Chromatography/
Atmospheric Pressure Ionization-Electrospray (API/ES) Mass Spectrometry 
(LC/MS). The validated LOQ of the method is 0.025 ppm. A CZE-
methodology is available for the determination of imazethapyr in 
crayfish with limits of quantitation of 50 ppb. These independently 
validated methods are appropriate for the enforcement purposes of this 
petition.
    3. Magnitude of residues. A total of nineteen field trials were 
conducted with imazethapyr and its metabolites on rice in 1997 and 1998 
at several different use rates and timing intervals to represent the 
use patterns which would result in the highest residue. In these 
trials, residues of parent compound AC 263499 in grain and straw were 
less than the limit of quantitation (0.05 ppm). The hydroxy metabolite, 
CL 288511 was detected in grain samples at a maximum value of 0.085 
ppm. All straw samples analyzed for CL 288511 residues were less than 
the limit of quantitation (0.05 ppm). The glucose conjugate, CL 182704 
was detected at a maximum value of 0.11 ppm in grain. All straw samples 
analyzed for CL 182704 residues were less than the limit of 
quantitation (0.05 ppm). The raw agricultural commodity (RAC) samples 
were also processed into polished rice, hull and bran. Results from 
these studies support the proposed tolerances of 0.3 ppm for rice grain 
and 0.4 ppm for rice straw.

B. Toxicological Profile

    1. Acute toxicity. Imazethapyr technical is considered to be 
nontoxic (Toxicity Category IV) to the rat by the oral route of 
exposure. In an acute oral toxicity study in rats, the LD50 
value of imazethapyr technical was greater than 5,000 mg/kg body weight 
for males and females. The results from an acute dermal toxicity study 
in rabbits indicate that imazethapyr is slightly toxic (Toxicity 
Category III) to rabbits by the dermal route of exposure. The dermal 
LD50 value of imazethapyr technical was greater than 2,000 
mg/kg bw for both male and female rabbits. Imazethapyr technical is 
considered to be non-toxic (Toxicity Category IV) to the rat by the 
respiratory route of exposure. The 4-hour LC50 value was 
greater than 3.27 mg/l (analytical) and greater than 4.21 mg/l 
(gravimetric) for both males and females. Imazethapyr technical was 
shown to be non-irritating to rabbit skin (Toxicity Category IV) and 
mildly irritating to the rabbit eye (Toxicity Category III). Based on 
the results of a dermal sensitization study (Buehler),

[[Page 37395]]

imazethapyr technical is not considered a sensitizer in guinea pigs.
    2. Genotoxicity. Imazethapyr technical was tested in a battery of 
four in vitro and one in vivo genotoxicity assays measuring several 
different endpoints of potential genotoxicity. Collective results from 
these studies indicate that imazethapyr does not pose a mutagenic or 
genotoxic risk.
    3.Reproductive and developmental toxicity. The developmental 
toxicity study in Sprague Dawley rats conducted with imazethapyr 
technical showed no evidence of developmental toxicity or teratogenic 
effects in fetuses. Thus, imazethapyr is neither a developmental 
toxicant nor a teratogen in the rat. The No-Observable-Effect-Level 
(NOEL) for maternal toxicity was 375 mg/kg bw/day, based on clinical 
signs of toxicity in the dams (e.g. excessive salivation) at 1,125 mg/
kg bw/day. Imazethapyr technical did not exhibit developmental toxicity 
or teratogenic effects at maternal dosages up to and including 1,125 
mg/kg bw/day, the highest dose tested (HDT).
    Results from a developmental toxicity study in New Zealand White 
rabbits with imazethapyr technical also indicated no evidence of 
developmental toxicity or teratogenicity. Thus, imazethapyr technical 
is neither a developmental toxicant nor a teratogen in the rabbit. The 
NOEL for maternal toxicity was 300 mg/kg bw/day, based on decreased 
food consumption and body weight gain, abortion, gastric ulceration and 
death at 1,000 mg/kg bw/day, the next HDT. The NOEL for developmental 
toxicity and teratogenic effects was determined to be <1,000 mg/kg bw/
day based on no developmental toxicity or fetal malformations 
associated with the administration of all doses.
    The results from the two-generation reproduction toxicity study in 
rats with imazethapyr technical support a NOEL for reproductive 
toxicity of 10,000 ppm (equivalent to 800 mg/kg bw/day). The NOEL for 
non-reproductive parameters (i.e. decreased weanling body weights) is 
5,000 ppm.
    4. Subchronic toxicity. A short-term (21-day) dermal toxicity study 
in rabbits was conducted with imazethapyr technical. No dermal 
irritation or abnormal clinical signs were observed at dose levels up 
to and including 1,000 mg/kg bw/day (HDT), supporting a NOEL for dermal 
irritation and systemic toxicity of 1,000 mg/kg bw/day.
    In a subchronic (13-week) dietary toxicity study in rats with 
imazethapyr technical, no signs of systemic toxicity were noted, 
supporting a NOEL of 10,000 ppm the highest concentration tested 
(equivalent to 820 mg/kg bw/day).
    In a subchronic (13-week) dietary toxicity study in dogs with 
imazethapyr technical, no signs of systemic toxicity were noted, 
supporting a NOEL of 10,000 ppm (equivalent to 250 mg/kg b.w./day), the 
highest concentration tested.
    5.Chronic toxicity. A one-year dietary toxicity study was conducted 
with imazethapyr technical in Beagle dogs at dietary concentrations of 
0, 1,000, 5,000 and 10,000 ppm. In this study, the NOEL for systemic 
toxicity was 1,000 ppm (equivalent to 25 mg/kg bw/day), based on slight 
anemia, i.e., decreased red cell parameters observed at 5,000 and 
10,000 ppm concentrations. No treatment-related histopathological 
lesions were observed at any dietary concentration, including the 
highest concentration tested (10,000 ppm).
    In a two-year chronic dietary oncogenicity and toxicity study in 
rats conducted with imazethapyr technical, the NOEL for oncogenicity 
and chronic systemic toxicity was 10,000 ppm (equivalent to 500 mg/kg 
bw/day), the highest concentration tested. An 18-month chronic dietary 
oncogenicity and toxicity study in mice with imazethapyr technical 
supports a NOEL for oncogenicity of 10,000 ppm, the highest 
concentration tested (equivalent to 1,500 mg/kg bw/day), and a NOEL for 
chronic systemic toxicity of 5,000 ppm (equivalent to 750 mg/kg bw/
day), based on decreased body weight gain in both sexes).
    The EPA has classified imazethapyr as negative for carcinogenicity 
(evidence of non-carcinogenicity for humans) based on the absence of 
treatment-related tumors in acceptable carcinogenicity studies in both 
rats and mice.
    6. Animal metabolism. The rat, goat and hen metabolism studies 
indicate that the qualitative nature of the residues of imazethapyr in 
animals is adequately understood.
    In three rat metabolism studies conducted with radiolabeled 
imazethapyr technical the major route of elimination of the herbicide 
was through rapid excretion in urine and to a much lesser extent in 
feces. In the first study, almost 100% of the administered material was 
recovered in excreta within 96 hours (89-95% in urine, 6-11% in feces). 
The major residue in urine and feces was parent compound. Approximately 
2% of the dose was metabolized and excreted as the [alpha]-hydroxyethyl 
derivative of imazethapyr. In the second study, the test material was 
rapidly and completely eliminated unchanged in the urine within 72 
hours of dosing. After 24 hours, 92.1% of radioactivity was excreted in 
the urine with 4.67% in the feces. There was no significant 
bioaccumulation of radioactivity in the tissues from this rat 
metabolism study (<0.01 ppm after 24 hours). In the third study, four 
groups treated with radiolabeled imazethapyr readily excreted <95% of 
the test material in the urine and feces within 48 hours. A high 
percentage (97-99%) of the test material was excreted in the urine as 
unchanged parent, the remainder as the [alpha]-hydroxyethyl derivative 
of imazethapyr. For all three studies, the major route of elimination 
of the herbicide in rats was through rapid excretion of unchanged 
parent compound in urine. It is clear that imazathapyr and its related 
residues do not accumulate in tissues and organs.
    In the goat metabolism study, parent 14C-imazethapyr was 
dosed to lactating goats at 0.25 ppm and 1.25 ppm. Results showed 
14C-residues of <0.01 ppm in milk and <0.05 ppm in leg 
muscle, loin muscle, blood, fat, liver and kidney. Laying hens dosed at 
0.5 ppm and 2.5 ppm with 14C-imazethapyr showed 
14C-residues of <0.05 ppm in eggs and all tissues (blood, 
muscle, skin/fat, liver and kidney).
    Additional animal metabolism studies have been conducted with CL 
288511 (main metabolite in treated crops fed to livestock) in both 
laying hens and lactating goats. These studies have been repeated to 
support subsequent use extensions on crops used as livestock feed items 
which would theoretically result in a higher dosing of imazethapyr-
derived residues to livestock ( i.e., corn, alfalfa). In these studies, 
lactating goats dosed at 42 ppm of 14C-CL 288511 showed 
14C-residues of <0.01 ppm in milk, leg muscle, loin muscle 
and omental fat. 14C-Residues in blood were mostly <0.01 ppm 
but reached 0.01 ppm on two of the treatment days. 14C-
Residue levels in the liver and kidney were 0.02 and 0.09 ppm, 
respectively. Laying hens dosed at 10.2 ppm of 14C-
imazethapyr showed 14C-residues of <0.01 ppm in eggs and all 
tissues (blood, muscle, skin/fat, liver and kidney). 14C-
imazethapyr or 14C-CL 288511 ingested by either laying hens 
or lactating goats was excreted within 48 hours of dosing. These 
studies indicate that parent imazethapyr and CL 288511-related residues 
do not accumulate in milk or edible tissues of the ruminant.
    7. Metabolite toxicology. Metabolism studies in soybean, peanut, 
corn and alfalfa indicate that the only significant metabolites are the 
[alpha]-hydroxyethyl derivative of imazethapyr, CL 288511 and its 
glucose conjugate CL 182704. The [alpha]-hydroxyethyl metabolite has 
also

[[Page 37396]]

been identified in minor quantities in the previously submitted rat 
metabolism studies and in goat and hen metabolism studies. No 
additional toxicologically significant metabolites were detected in any 
of the plant or animal metabolism studies.
    8. Endocrine disruption. Collective organ weight data and 
histopathological findings from the two-generation rat reproductive 
study, as well as from the subchronic and chronic toxicity studies in 
three different animal species demonstrate no apparent estrogenic 
effects or treatment-related effects of imazethapyr on the endocrine 
system.

C. Aggregate Exposure

    1. Dietary exposure--i. Food. BASF has determined that there are no 
toxic effects attributable to a single dose of imazethapyr. Therefore, 
a quantitative acute dietary exposure and risk assessment was not 
required.
    Assessments were conducted to evaluate the potential risk due to 
chronic dietary exposure of the U.S. population to residues of 
imazethapyr. This herbicide and its metabolites (CL 288511, CL 182704) 
were expressed as the parent compound (imazethapyr). A dietary exposure 
analysis was conducted for all current crops, including the increased 
tolerance for rice grain and straw, and secondary residues in meat, 
meat byproducts, and fat. The commodities include canola, field corn, 
crop group 6, soybeans, alfalfa, nongrass animal feed group, peanuts, 
endive, crayfish, head lettuce, and leaf lettuce.
    The tier 1 chronic dietary exposure estimates were based on the 
tolerance values, 100 percent crop treated values, default 
concentration/processing factors and consumption data from the USDA 
Continuing Survey of Food Intake by Individuals (CSFII 1994 - 1996, 
1998) and the EPA Food Commodity Ingredient Database (FCID) using 
Exponent's Dietary Exposure Evaluation Module (DEEM-FCID) software. 
Resulting exposure estimates were compared against the imazethapyr 
chronic Population Adjusted Dose (cPAD) of 2.5 mg/kg bw/day.
    Exposure estimates for the imazethapyr chronic dietary assessments 
were well below U.S. EPA's level of concern (See Table 1). The 
estimated chronic dietary exposure was <0.1% of the cPAD for all 
subpopulations. Additional refinements such as the use of anticipated 
residues and predicted percent crop treated would further reduce the 
estimated chronic dietary exposure.

           Table 1.--Summary of Chronic Dietary Exposure and Risk for Imazethapyr Considering All Current Crops and Secondary Animal Residues
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                   Population Subgroups                            Exposure Estimate (mg/kg bw/day)               %cPAD (cPAD = 2.5 mg/kg bw/day)
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U.S. Population                                                                                  0.000476                                          0.019
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    ii. Drinking water. Because the Agency does not have monitoring 
data, drinking water concentration estimates are made by reliance on 
simulation or modeling taking into account data on the physical 
characteristics of imazethapyr. EPA determined that the residue of 
concern in drinking water is only imazethapyr. Surface water (rice 
paddy model; peak and average 126 [mu]g/l) estimated drinking water 
concentrations (EDWCs) for imazethapyr were calculated. The surface 
water EDWCs were generated assuming two applications of imazethapyr at 
0.188 lbs ae/acre (highest registered/proposed multiple application 
rate). Based on several prospective ground water studies the upper 
bound ground water exposure would not be expected to exceed 1 [mu]g/L. 
The estimated drinking water concentrations (EDWC) for both surface 
water and ground water are well below the allowable level. Drinking 
water level of comparison (DWLOC) calculations and comparisons to 
surface water estimations are given as follows in Table 2.

                                           Table 2. -- Estimated Chronic Drinking Water Values for Imazethapyr
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            DWLOCchronic               U.S. Population\1\     All Infants <1 year)    Children (1-6 years)  Females (13-49 years)   Adults (20-49 years)
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DWLOC chronic ([mu]g/L)              87483                   24993                   24991                  74989                  87485
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*acute value for surface water


[[Page 37397]]

    iii. Aggregate exposure (diet + water). The estimated chronic 
aggregate exposure of imazethapyr from potential residues in food and 
water are summarized in Table 3 as follows. Imazethapyr is not 
registered for residential use and therefore residential exposure was 
not considered.

                                      Table 3. -- Estimated Chronic Aggregate Exposure From the Use of Imazethapyr
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                                                                                Chronic Drinking Water  Aggregate Exposure2 (mg/
           Population Subgroup              Chronic Food Exposure (mg/kg/day)   Exposure1 (mg/kg/day)           kg/day)              Aggregate %cPAD
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U.S. Population                                                      0.000476                 0.003600                 0.004076                     0.16
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\1\ Aggregate Exposure = Food Exposure + Drinking Water Exposure
\2\ Drinking Water Exposure (mg/kg/day) = [Drinking Water Concentration ([mu]g/L) * Water Consumed (L/day)/ Body weight (kg)]/1,000

    The assessment results indicate the aggregate exposure of 
imazethapyr from potential residues in food and drinking water will not 
exceed the U.S. EPA's level of concern (100% of PAD). The percent 
chronic PAD was <1% for all subpopulations. Additional refinements such 
as the use of anticipated residues and predicted percent crop treated 
would further reduce the estimated chronic dietary exposure and %cPAD. 
Overall, considering a ``worst-case'' scenario, we can conclude with 
reasonable certainty that no harm will occur from chronic aggregate 
exposure of imazethapyr residues from the current crops, including the 
higher proposed tolerance values.
    2. Non-dietary exposure . Imazethapyr products are not currently 
registered for requested to be registered for residential use; 
therefore the estimate of residential exposure is not relevant to this 
tolerance petition.

D. Cumulative Effects

    Imazethapyr is a member of the imidazolinone class of herbicides. 
Other compounds of this class are registered for use in the United 
States However, the herbicidal activity of the imidazolinones is due to 
the inhibition of acetohydroxyacid synthase (AHAS), an enzyme only 
found in plants. AHAS is part of the biosynthetic pathway leading to 
the formation of branched chain amino acids. Animals lack AHAS and this 
biosynthetic pathway. This lack of AHAS contributes to the low toxicity 
of the imidazolinone compounds in animals. We are aware of no 
information to indicate or suggest that imazethapyr has any toxic 
effects on mammals that would be cumulative with those of any other 
chemical. Therefore, for the purposes of this tolerance petition no 
assumption has been made with regard to cumulative exposure with other 
compounds having a common mode of action.

E. Safety Determination

    1. U.S. population. Using the conservative exposure assumptions 
described above and based on the completeness and the reliability of 
the toxicity data, BASF has estimated the aggregate exposure to 
imazethapyr will utilize less than 1% of the cPAD for the U.S. 
population and all subpopulations, respectively.
    2. Infants and children. All subpopulations based on age were 
considered. Infants and children remained below 1% of the aggregate 
cPAD for food and water. BASF, considering a worst-case situation, 
concludes with reasonable certainty that no harm will result to infants 
or children from aggregate exposure to imazethapyr residues.
    No additional FQPA safety factor(s) are considered to be 
appropriate for imazethapyr. There is a complete toxicity database for 
imazethapyr and the exposure data are complete or are estimated based 
on data that reasonably accounts for potential exposures. Based on the 
toxicology data and conclusions, a FQPA safety factor of 1X appears to 
be appropriate for imazethapyr.

F. International Tolerances

    There are no Codex maximum residue levels established or proposed 
for residues of imazethapyr on rice.

[FR Doc. 05-12444 Filed 6-28-05; 8:45 am]
BILLING CODE 6560-50-S