[Federal Register Volume 68, Number 2 (Friday, January 3, 2003)]
[Notices]
[Pages 370-374]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-7]


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

ENVIRONMENTAL PROTECTION AGENCY

[OPP-2002-0212; FRL-7283-4]


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.

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

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

DATES: Comments, identified by docket ID number OPP-2002-0212, must be 
received on or before February 3, 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-2002-0212. 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.

[[Page 371]]

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-2002-0212. 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-2002-0212. 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-2002-0212.
    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-2002-0212. 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

[[Page 372]]

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: December 20, 2002.
Debra Edwards,
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 1E6268

    EPA has received a pesticide petition (PP 1E6268) from BASF 
Corporation, P.O. Box 400, Princeton, NJ 08543-0400 proposing pursuant 
to section 408(d) of the Federal Food, Drug, and Cosmetic Act, 21 
U.S.C. 346a(d), to amend 40 CFR part 180 by establishing an import 
tolerance 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 in or on the raw agricultural commodity canola 
seed at 0.1 part 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 
support 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 canola is adequately understood. Based on studies 
conducted on soybean, edible and forage legumes, corn and canola, 
parent imazethapyr and common metabolite CL 288511 are the only 
residues of concern for tolerance setting purposes.
    2. Analytical method. Practical analytical methods for detecting 
and measuring imazethapyr residues of concern in canola are submitted 
to EPA with this petition. The analytical methods for canola seed are 
based on gas chromatography and capillary electrophoresis with limits 
of quantitation (LOQ) of 0.05 ppm. Measurement of imazethapyr residues 
in canola oil and meal are accomplished by gas chromatography with LOQ 
of 0.05 ppm. These validated methods are appropriate for the 
enforcement purposes of this petition.
    3. Magnitude of residues. A total of 13 field trials were conducted 
with imazethapyr and its metabolite on canola in 1992, 1993, 1994, and 
1999 at several different use rates and timing intervals to represent 
the use patterns, conditions and areas of use of this product in 
Canada. Apparent residues of imazethapyr (CL 263499) and metabolite CL 
288511 in all canola seed samples were below the LOQ of 0.05 ppm 
regardless of rate or days after treatment sampled.

B. Toxicological Profile

    A complete, valid and reliable database of mammalian and genetic 
toxicology studies supports the proposed tolerance for imazethapyr on 
canola. This database was previously reviewed by 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 bwt) 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 bwt 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 milligram/liter 
(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 observable adverse effect 
level (NOAEL) for maternal toxicity was 375 mg/kg bwt/day, based on 
clinical signs of toxicity in the dams (e.g., excessive salivation) at 
1,125 mg/kg bwt/day. Imazethapyr technical did not exhibit 
developmental toxicity or teratogenic effects at maternal dosages up to 
and including 1,125 mg/kg bwt/day, the highest dose tested.
    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 bwt/day, based on decreased 
food consumption and body weight gain, abortion, gastric ulceration and 
death at 1,000 mg/kg bwt/day, the next highest dose tested. The NOAEL 
for developmental toxicity and teratogenic effects was determined to be 
> 1,000 mg/kg bwt/day based on no developmental toxicity or fetal 
malformations associated with the administration of all doses.

[[Page 373]]

    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 bwt/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 bwt/day (highest dose tested), supporting 
a NOAEL for dermal irritation and systemic toxicity of 1,000 mg/kg bwt/
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 
(equivalent to 820 mg/kg bwt/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 bwt/day), the 
highest concentration tested.
    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 bwt/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 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 bwt/
day), the highest concentration tested. An 18-month chronic dietary 
oncogenicity and toxicity study in mice with imazethapyr technical 
supports a NOAEL for oncogenicity of 10,000 ppm, the highest 
concentration tested (equivalent to 1,500 mg/kg bwt/day), and a NOAEL 
for chronic systemic toxicity of 5,000 ppm (equivalent to 750 mg/kg 
bwt/day), based on decreased body weight gain in both sexes).
    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, alfalfa, and canola 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 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 
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 import tolerance petition, a 
proposed tolerance of 0.1 ppm for canola would not be expected to 
contribute significantly to this dietary risk assessment.
    i. 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

[[Page 374]]

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 bwt/day for the general U.S. population;
    [sbull] 0.001104 mg/kg bwt/day for all infants (< 1 year);
    [sbull] 0.001298 mg/kg bwt/day for non-nursing infants;
    [sbull] 0.000870 mg/kg bwt/day for children 1 to 6 years of age; 
and
    [sbull] 0.000610 mg/kg bwt/day for children 7 to 12 years of age.
    The TMRC values indicate that non-nursing infants are the most 
highly exposed population subgroup.
    ii. Drinking water. As a screening-level assessment for aggregate 
exposure, 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, EPA set the Reference Dose (RfD) for imazethapyr at 
0.25 mg/kg bwt/day, based on the NOAEL from the 1-year dietary toxicity 
study in dogs of 25 mg/kg bwt/day and a 100-fold uncertainty factor. 
Based on the chronic RfD of 0.25 mg/kg bwt/day and 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 8,735 parts per billion (ppb) and for children the DWLOC was 
estimated to be 2,491 ppb.
    Chronic drinking water exposure analyses were calculated for 
imazethapyr using EPA screening models Screening Concentration in 
Ground Water (SCI-GROW) for ground water and Generic 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 ground water 
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.
    2. 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. BASF is 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, EPA set the RfD for imazethapyr at 0.25 
mg/kg bwt/day, based on the NOAEL from the 1-year dietary toxicity 
study in dogs of 25 mg/kg bwt/day and a 100-fold uncertainty factor. 
The chronic dietary exposure of 0.000419 mg/kg bwt/day for the general 
U.S. population will utilize only 0.2% of the RfD of 0.25 mg/kg bwt/
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 and canola.
    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 
bwt/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. 
Therefore, an additional safety factor is not warranted, and the RfD of 
0.25 mg/kg bwt/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 canola.

[FR Doc. 03-7 Filed 1-2-03; 8:45 am]
BILLING CODE 6560-50-S