[Federal Register Volume 67, Number 235 (Friday, December 6, 2002)]
[Notices]
[Pages 72678-72683]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-30947]


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ENVIRONMENTAL PROTECTION AGENCY

[OPP-2002-0211; FRL-7283-3]


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 ID number OPP-2002-0211, must be 
received on or before January 6, 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: 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 affected by this action if you are an agricultural 
producer, food manufacturer, or pesticide manufacturer. Potentially 
affected categories and 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 the table could also be 
affected. The North American Industrial Classification System (NAICS) 
codes have been provided to assist you and others in determining 
whether or not this action might apply to certain entities. If you have 
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-2002-0211. 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

[[Page 72679]]

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-2002-0211 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-2002-0211. 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-2002-0211.
    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-2002-0211. 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

[[Page 72680]]

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: November 27, 2002.
Donald R. Stubbs,
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 6F4746

    EPA has received a pesticide petition (PP 6F4746) 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 tolerances for the sum of the 
residues of the herbicide 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 nongrass animal feed crops, forage, hay and 
seed at 3.0 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.

A. Residue Chemistry

    1. Plant metabolism. The qualitative nature of the residues of 
imazethapyr in clover is adequately understood. Based on studies 
conducted on soybean, edible and forage legumes, corn and canola, 
parent imazethapyr and common metabolites CL 288511 and CL 182704 are 
the only residues of concern for tolerance setting purposes.
    2. Analytical method. A practical analytical method for detecting 
and measuring imazethapyr residues of concern in alfalfa and clover 
commodities was submitted to EPA with the alfalfa petition. The 
analytical method for alfalfa and clover forage, hay and seed is based 
on Capillary Electrophoresis (CE) with limits of quantitation (LOQ) of 
0.50 ppm. This validated method was approved for analysis in alfalfa 
and is appropriate for the enforcement purposes of this petition.
    3. Magnitude of residues. A total of twelve field trials were 
conducted with imazethapyr and its metabolites on clover to demonstrate 
the residues in clover forage, hay and seed. In all clover residue 
studies, imazethapyr was applied at 0.094 lb ae/A, the maximum proposed 
label rate. Clover samples were cut at 15 DAT and 30 DAT, the proposed 
preharvest interval (PHI). At 30 DAT, all forage samples contained 
residues of imazethapyr and CL 288511 at less than 0.5 ppm. In most 30 
DAT forage samples, residues of CL 182704 were below the LOQ (0.5 ppm). 
No hay samples had residues of imazethapyr above the LOQ (0.5 ppm). 
There was only one hay sample containing residues of CL 288511 above 
the LOQ. In all cases, for the 15 and 30 DAT forage and hay samples, 
the primary residue was CL 182704 (the glucose conjugate of CL 288511). 
Since CL 182704 is the derivitized form of CL 288511, the residues were 
converted to a total CL 288511 equivalent residue basis. Seed and seed 
screening samples were collected from studies conducted at two sites. 
In both studies, residues of imazethapyr, CL 288511 and CL 182704 were 
less than the LOQ.
    The proposed tolerance for nongrass animal feeds is 3.0 ppm for 
imazethapyr, CL 288511 and the glucose conjugate, CL 182704. Residue 
levels of imazethapyr and CL 288511 in clover are all below the 
proposed tolerance. When residues of CL 182704 are adjusted to CL 
288511 equivalents residues, the total equivalent CL 288511 residues 
are below the proposed 3.0 tolerance level in all clover studies.

B. Toxicological Profile.

    A complete, valid and reliable database of mammalian and genetic 
toxicology studies supports the proposed tolerance for imazethapyr on 
nongrass animal feeds. This database was previously reviewed by the EPA 
in support of the tolerance petitions and registration of imazethapyr 
on soybeans, legume vegetables, corn, alfalfa and peanuts.
    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 milligrams/
kilogram/ body weight (mg/kg b.w.) 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 b.w. for both

[[Page 72681]]

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), 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 observed adverse effect 
level (NOAEL) for maternal toxicity was 375 mg/kg b.w./day, based on 
clinical signs of toxicity in the dams (e.g. excessive salivation) at 
1,125 mg/kg b.w./day. Imazethapyr technical did not exhibit 
developmental toxicity or teratogenic effects at maternal dosages up to 
and including 1,125 mg/kg b.w./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 
NOAEL for maternal toxicity was 300 mg/kg b.w./day, based on decreased 
food consumption and body weight gain, abortion, gastric ulceration and 
death at 1,000 mg/kg b.w./day, the next HDT. The NOAEL for 
developmental toxicity and teratogenic effects was determined to be > 
1,000 mg/kg b.w./day based on no developmental toxicity or fetal 
malformations associated with the administration of all doses.
    The results from the 2-generation reproduction toxicity study in 
rats with imazethapyr technical support a NOAEL for reproductive 
toxicity of 10,000 ppm (equivalent to 800 mg/kg b.w./day). The NOAEL 
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 b.w./day HDT, supporting a NOAEL for 
dermal irritation and systemic toxicity of 1,000 mg/kg b.w./day. In a 
subchronic (13-week) dietary toxicity study in rats with imazethapyr 
technical, no signs of systemic toxicity were noted, supporting a NOAEL 
of 10,000 ppm the highest concentration tested (HCT) (equivalent to 820 
mg/kg b.w./day).
    In a subchronic (13-week) dietary toxicity study in dogs with 
imazethapyr technical, no signs of systemic toxicity were noted, 
supporting a NOAEL of 10,000 ppm (equivalent to 250 mg/kg b.w./day), 
the (HCT).
    5. Chronic toxicity. A 1-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 NOAEL for systemic 
toxicity was 1,000 ppm (equivalent to 25 mg/kg b.w./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 HCT 
(10,000 ppm).
    In a 2-year chronic dietary oncogenicity and toxicity study in rats 
conducted with imazethapyr technical, the NOAEL for oncogenicity and 
chronic systemic toxicity was 10,000 ppm (equivalent to 500 mg/kg b.w./
day), the HCT. An 18-month chronic dietary oncogenicity and toxicity 
study in mice with imazethapyr technical supports a NOAEL for 
oncogenicity of 10,000 ppm, the HCT (equivalent to 1,500 mg/kg b.w./
day), and a NOAEL for chronic systemic toxicity of 5,000 ppm 
(equivalent to 750 mg/kg b.w./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 a-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 a-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

[[Page 72682]]

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, alfalfa and canola indicate that the only significant metabolites 
are the a-hydroxyethyl derivative of imazethapyr, CL 288511 and its 
glucose conjugate CL 182704. The a-hydroxyethyl metabolite has also 
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 2-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. The potential dietary exposure to imazethapyr 
has been calculated from the proposed tolerance for use on rice and 
previously established tolerances for peanuts, legume vegetables, 
soybeans, alfalfa, endive, lettuce, and corn. This very conservative 
chronic dietary exposure estimate used the proposed tolerance of 0.5 
parts per million (ppm) for rice, and tolerance values of 0.1 ppm for 
peanuts, 0.1 ppm for legume vegetables, 0.1 ppm for soybeans, 3.0 ppm 
for alfalfa, 0.1 ppm for endive (escarole), 0.1 ppm for lettuce, and 
0.1 ppm for corn. In addition, these estimates assume that 100% of 
these crops contain imazethapyr residues. In support of this tolerance 
petition, a proposed tolerance of 3.0 ppm for nongrass animal feeds 
would not be expected to contribute significantly to this dietary risk 
assessment.
    2. Food. Potential exposure to residues of imazethapyr in food will 
be restricted to intake of rice, peanuts, legume vegetables, soybeans, 
alfalfa (sprouts), endive, lettuce, and corn. Using the assumptions 
discussed above, the Theoretical Maximum Residue Concentration (TMRC) 
values of imazethapyr were calculated for the U.S. general population 
and subgroups. Based on the tolerances given above, the TMRC values for 
each group are:
    [sbull] 0.000419 mg/kg b.w./day for the general U.S. population.
    [sbull] 0.001104 mg/kg b.w./day for all infants (> 1 year).
    [sbull] 0.001298 mg/kg b.w./day for non-nursing infants.
    [sbull] 0.000870 mg/kg b.w./day for children 1 to 6 years of age.
    [sbull] 0.000610 mg/kg b.w./day for children 7 to 12 years of age.
    The TMRC values indicate that non-nursing infants are the most 
highly exposed population subgroup.
    3. Drinking water. As a screening-level assessment for aggregate 
exposure, the U.S. EPA evaluates a drinking water level of comparison 
(DWLOC), which is the maximum concentration of a chemical in drinking 
water that would be acceptable in light of total aggregate exposure to 
that chemical. In 1990, the EPA set the reference dose (RfD) for 
imazethapyr at 0.25 mg/kg b.w./day, based on the NOAEL from the 1-year 
dietary toxicity study in dogs of 25 mg/kg b.w./day and a 100-fold 
uncertainty factor. Based on the cRfD of 0.25 mg/kg b.w./day and the 
EPA's default factors for body weight and drinking water consumption, 
the DWLOCs have been calculated to assess the potential dietary 
exposure from residues of imazethapyr in water. For the adult 
population the chronic DWLOC was 8735 ppb and for children the DWLOC 
was estimated to be 2491 parts per billion (ppb).
    Chronic drinking water exposure analyses were calculated for 
imazethapyr using EPA screening concentration in ground water (SCI-
GROW), and genetic expected environmental concentration (GENEEC) for 
surface water. The SCI-GROW value is 16.54 ppb and the calculated peak 
GENEEC value is 5.96 ppb by aerial application. For the U.S. adult 
population, the estimated exposures of imazethapyr residues in ground 
water and surface water are approximately 0.19% and 0.07%, 
respectively, of the DWLOC. The estimated exposures of children to 
imazethapyr residues in groundwater and surface water are approximately 
0.66%, and 0.24%, respectively, of the DWLOC. Therefore, the exposures 
to drinking water from imazethapyr use are negligible.
    4. Non-dietary exposure. Imazethapyr products are not currently 
registered or 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 U.S. 
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. The RfD represents the level at or below which 
daily aggregate exposure over a lifetime will not pose appreciable 
risks to human health. In 1990, the EPA set the RfD for imazethapyr at 
0.25 mg/kg b.w./day, based on the NOAEL from the 1-year dietary 
toxicity study in dogs of 25 mg/kg b.w./day and a 100-fold uncertainty 
factor. The chronic dietary exposure of 0.000419 mg/kg b.w./day for the 
general U.S. population will utilize only 0.2% of the RfD of 0.25 mg/kg 
b.w./day. EPA generally has no concern for exposures below 100% of the 
RfD. Due to the low toxicity of imazethapyr, an acute exposure dietary 
risk assessment is not warranted. The complete and reliable toxicity 
database, the low toxicity of the active ingredient, and the results of 
the chronic dietary exposure risk assessment support the conclusion 
that there is a ``reasonable certainty of no harm'' from the proposed 
use of imazethapyr on imidazolinone tolerant rice, canola and nongrass 
animal feeds.
    2. Infants and children. The conservative dietary exposure 
estimates of all registered uses including the proposed tolerance for 
rice show exposures of 0.001104, 0.000440, 0.000870, and 0.000610 mg/kg 
b.w./day which will utilize 0.4, 0.2, 0.3, and 0.2% of the RfD for all 
infants (< 1 year), nursing infants, children 1-6 years, and children 
7-12 years, respectively. The chronic dietary exposures for non-nursing 
infants, the most highly exposed subgroup, will utilize only 0.5% of 
the RfD. Results from the 2-generation reproduction study in rats and 
the developmental toxicity studies in rabbits and rats indicate no 
increased sensitivity to developing offspring when compared to parental 
toxicity. These results also indicate that imazethapyr is neither a 
developmental toxicant nor a teratogen in either the rat or rabbit.

[[Page 72683]]

 Therefore, an additional safety factor is not warranted, and the RfD 
of 0.25 mg/kg b.w./day, which utilizes a 100-fold safety factor is 
appropriate to ensure a reasonable certainty of no harm to infants and 
children.

F. International Tolerances

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

[FR Doc. 02-30947 Filed 12-5-02; 8:45 a.m.]
BILLING CODE 6560-50-S