[Federal Register Volume 69, Number 129 (Wednesday, July 7, 2004)]
[Notices]
[Pages 40909-40916]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-15208]


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ENVIRONMENTAL PROTECTION AGENCY

[OPP-2004-0180; FRL-7364-8]


Tribenuron Methyl; 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-
2004-0180, must be received on or before August 6, 2004.

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: James A. 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 are a 
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-2004-0180. 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 South Bell St., Arlington, VA. This 
docket facility is open from 8:30 a.m. to 4 p.m., Monday through 
Friday, excluding legal holidays. The docket telephone number is (703) 
305-5805.
    2. Electronic access. You may access this Federal Register document 
electronically through the EPA Internet under the ``Federal Register'' 
listings at http://www.epa.gov/fedrgstr/.
    An electronic version of the public docket is available through 
EPA's electronic public docket and comment system, EPA Dockets. You may 
use EPA Dockets at http://www.epa.gov/edocket/ to submit or view public 
comments, access the index listing of the contents of the official 
public docket, and to access those documents in the public docket that 
are available electronically. Although not all docket materials may be 
available electronically, you may still access any of the publicly 
available docket materials through the docket

[[Page 40910]]

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 EPA's Dockets. 
Information claimed as CBI and other information whose disclosure is 
restricted by statute, which is not included in the official public 
docket, will not be available for public viewing in EPA's electronic 
public docket. EPA's policy is that copyrighted material will not be 
placed in EPA's electronic public docket but will be available only in 
printed, paper form in the official public docket. To the extent 
feasible, publicly available docket materials will be made available in 
EPA's electronic public docket. When a document is selected from the 
index list in EPA Dockets, the system will identify whether the 
document is available for viewing in EPA's electronic public docket. 
Although not all docket materials may be available electronically, you 
may still access any of the publicly available docket materials through 
the docket facility identified in Unit I.B.1. EPA intends to work 
towards providing electronic access to all of the publicly available 
docket materials through EPA's electronic public docket.
    For public commenters, it is important to note that EPA's policy is 
that public comments, whether submitted electronically or in paper, 
will be made available for public viewing in EPA's electronic public 
docket as EPA receives them and without change, unless the comment 
contains copyrighted material, CBI, or other information whose 
disclosure is restricted by statute. When EPA identifies a comment 
containing copyrighted material, EPA will provide a reference to that 
material in the version of the comment that is placed in EPA's 
electronic public docket. The entire printed comment, including the 
copyrighted material, will be available in the public docket.
    Public comments submitted on computer disks that are mailed or 
delivered to the docket will be transferred to EPA's electronic public 
docket. Public comments that are mailed or delivered to the docket will 
be scanned and placed in EPA's electronic public docket. Where 
practical, physical objects will be photographed, and the photograph 
will be placed in EPA's electronic public docket along with a brief 
description written by the docket staff.

C. How and to Whom Do I Submit Comments?

    You may submit comments electronically, by mail, or through hand 
delivery/courier. To ensure proper receipt by EPA, identify the 
appropriate docket ID number in the subject line on the first page of 
your comment. Please ensure that your comments are submitted within the 
specified comment period. Comments received after the close of the 
comment period will be marked ``late.'' EPA is not required to consider 
these late comments. If you wish to submit CBI or information that is 
otherwise protected by statute, please follow the instructions in Unit 
I.D. Do not use EPA Dockets or e-mail to submit CBI or information 
protected by statute.
    1. Electronically. If you submit an electronic comment as 
prescribed in this unit, EPA recommends that you include your name, 
mailing address, and an e-mail address or other contact information in 
the body of your comment. Also include this contact information on the 
outside of any disk or CD ROM you submit, and in any cover letter 
accompanying the disk or CD ROM. This ensures that you can be 
identified as the submitter of the comment and allows EPA to contact 
you in case EPA cannot read your comment due to technical difficulties 
or needs further information on the substance of your comment. EPA's 
policy is that EPA will not edit your comment, and any identifying or 
contact information provided in the body of a comment will be included 
as part of the comment that is placed in the official public docket, 
and made available in EPA's electronic public docket. If EPA cannot 
read your comment due to technical difficulties and cannot contact you 
for clarification, EPA may not be able to consider your comment.
    i. EPA Dockets. Your use of EPA's electronic public docket to 
submit comments to EPA electronically is EPA's preferred method for 
receiving comments. Go directly to EPA Dockets at http://www.epa.gov/edocket/, and follow the online instructions for submitting comments. 
Once in the system, select ``search,'' and then key in docket ID number 
OPP-2004-0180. 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-2004-0180. 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-2004-0180.
    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 South Bell St., Arlington, VA, Attention: Docket ID 
Number OPP-2004-0180. 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.

[[Page 40911]]

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 pesticide 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 
pesticide petition. Additional data may be needed before EPA rules on 
the pesticide petition.

List of Subjects

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

    Dated: June 22, 2004.
 Lois Rossi,
Director, Registration Division, Office of Pesticide Programs.

Summary of Petition

    The petitioner's summary of the pesticide petition (PP) 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.

E. I. du Pont de Nemours and Company

PP 0F6135

    EPA has received a pesticide petition (0F6135) from E. I. du Pont 
de Nemours and Company, DuPont Agricultural Products, Barley Mill 
Plaza, Wilmington, DE 19880-0038 proposing, pursuant to FFDCA section 
408(d), 21 U.S.C. 346a(d), to amend 40 CFR part 180 by establishing a 
tolerance for residues of tribenuron methyl (methyl 2-[[[[(4-methoxy-6-
methyl-1,3,5- triazin-2-yl)methylamino] 
carbonyl]amino]sulfonyl]benzoate) in or on the raw agricultural 
commodity imazethapyr tolerant canola at 0.02 parts per million (ppm), 
cotton seed at 0.02 ppm, cotton gin trash at 0.02 ppm, and Crop 
Development Center (CDC) triffid flax at 0.02 ppm. EPA has determined 
that the pesticide 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 pesticide petition. Additional 
data may be needed before EPA rules on the pesticide petition.

A. Residue Chemistry

    1. Plant metabolism. The qualitative nature of the residues of 
tribenuron methyl is adequately understood. Tribenuron methyl is 
rapidly metabolized in wheat plants with a half-life of less than 4 
days. A major metabolic reaction was N-demethylation of tribenuron 
methyl to form metsulfuron methyl. Metsulfuron methyl was further 
metabolized, primarily through rapid hydroxylation of the phenyl ring, 
followed by conjugation with glucose. Hydrolysis of the sulfonylurea 
bridge of tribenuron methyl to release sulfonamide and triazine amine 
was also observed. The sulfonamide may be further metabolized to 
hydroxylated sulfonamide or cyclized to saccharin. The presence of 
[alpha]-hydroxy triazine amine, N-demethyl triazine amine, and O-
demethyl N-demethyl triazine amine demonstrated that the released 
triazine moiety of tribenuron methyl was also extensively degraded in 
wheat. Metabolism studies were conducted with radioactive \14\C-
tribenuron methyl on wheat under field conditions. Wheat plants were 
treated with 72-75 gram (g) active ingredient (a.i.)/health advisory 
(ha) of \14\C-phenyl and \14\C-triazine labeled tribenuron methyl at 
the tillering stage. Samples were harvested 0, 4, 8, 14, 21, 28, and 63 
days after treatment. Total \14\C-residue levels in the foliage 
declined rapidly from 5.5 ppm at time of application to 0.55 ppm in the 
mature straw and 0.05 ppm in the grain (\14\C-phenyl), and from 4.2 ppm 
to 0.37 ppm in the mature straw and 0.01 ppm in the grain (\14\C-
triazine). Analysis of the wheat foliage and straw extracts by high 
performance liquid chromotography (HPLC) and threshold level ceiling 
(TLC) revealed that tribenuron methyl was rapidly and extensively 
metabolized. Metabolites were identified based on chromatography with 
authentic standards. The major metabolites were the glucose conjugate 
of hydroxylated metsulfuron methyl, hydroxylated saccharin, the glucose 
conjugate of hydroxylated saccharin, saccharin, triazine amine, O-
demethyl triazine amine, and O-hydroxy triazine amine.
    A metabolism study was conducted with \14\C-tribenuron methyl on 
acetolactate synthase (ALS)-tolerant canola. \14\C-tribenuron methyl 
was applied at 25 g/ha as a topical spray treatment at 2 true leaf 
stage to bolting. Whole canola plants were harvested at 0, 2 days, 35 
days, and at maturity, 78 days after treatment. Total reactive residue 
(TRR) in canola foliage, when expressed as tribenuron methyl 
equivalents, declined from, on average, 0.26 ppm at day 0 to 0.04 ppm 
at day 35. TRR in immature 35-day canola seed pods was not higher than 
0.04 ppm, and was 0.02 ppm in 78-day seed samples. \14\C-tribenuron 
methyl accounted for greater than 81% of the radioactive residue in the 
0 to 2-day foliage samples. Other minor components were polar 
metabolites or conjugates, each less than 10% of the TRR. No single 
component in the polar metabolites exceeded 0.01 ppm. In the 35-day 
foliage samples, \14\C-tribenuron methyl accounted for only about 11-
25.5% of the TRR which is less than 0.01 ppm. The average half life for 
\14\C-tribenuron methyl was 15 days. Several metabolic processes in the 
foliage are involved. They include a hydrolytic cleavage of tribenuron 
methyl as well as N-demethylation of tribenuron methyl. Other 
demethylation and hydroxylation processes continued up to final 
harvest. The results of the study suggest that the tribenuron methyl 
metabolic process in canola follows a typical plant metabolism pattern, 
and no accumulation of tribenuron methyl is anticipated in canola when 
it is used in accordance with the proposed labels.
    A metabolism study was conducted to determine the nature and 
magnitude of the residues of tribenuron methyl in

[[Page 40912]]

cotton plants after treatment with 2-\14\C-tribenuron methyl. Soil 
treatments were applied at 0.3 ounce a.i./acre as a direct spray in an 
aqueous suspension containing inert dry-flowable (DF) formulation 
ingredients. The application was performed immediately after planting 
to provide the data for the shortest anticipated time between 
application and planting. No terminal residues at or above 0.01 ppm 
were observed in any triazine-label treated fractions of mature cotton 
after treatment with tribenuron methyl. No detectable residues were 
found in the undelinted seed and very low residues of 0.028 ppm were 
observed in the gin trash after treatment. Tribenuron methyl and its 
known metabolites are not expected to be present in the terminal 
residues in gin trash or undelinted seed, when applied according to the 
proposed label.
    A confined crop rotation study with \14\C-phenyl tribenuron methyl 
was conducted using cabbage, red beets, sorghum, soybeans, and wheat 
planted in pots of sandy loam soil 30 and 120 days following a single 
application of \14\C-phenyl-labeled tribenuron methyl. For the 30-day 
aging period, samples from both treated and control crops were taken at 
28, 49, and 67 days after planting with additional samples taken from 
the sorghum and soybeans plantings at 90 and 115 days. At maturity, all 
remaining plants were harvested and subdivided into edible and 
nonedible portions. Harvest dates, in days after planting were: 90 days 
(cabbage), 115 days (beets and wheat), and 168 days (sorghum and 
soybeans). Samples from all crops from the 120-day aging study were 
taken at 28, 48, 69, and 90 days (maturity for beets, cabbage, and 
wheat,) and 120 days and 169 days (maturity for sorghum and soybeans). 
Tribenuron methyl dissipated rapidly in the soil with none of the 
intact material detected after the 30-day aging period. The major 
radiolabeled residue extracted from the soil was saccharin which 
remained in the soil at very low levels throughout the study. Some 
accumulation of total radioactive residues was apparent in the mature 
sorghum foliage, soybean, and wheat due to the dehydrated nature of 
samples harvested. The major residue in the plants was identified as 
saccharin.
    A confined crop rotation study with \14\C-triazine tribenuron 
methyl was conducted using cabbage, red beets, and sorghum. Sandy loam 
soil was treated at 32 g a.i./ha \14\C-phenyl tribenuron methyl in the 
greenhouse. Rotational crops were sown 30 and 120 days post-treatment. 
Tribenuron methyl degraded rapidly in the soil with no detectable 
intact material present 30 days post-treatment. The major radiolabeled 
metabolite was the triazine amine. No significant accumulation (less 
than 0.01 ppm) of radiolabeled materials from the soil were observed in 
the mature crops of cabbage foliage. Some accumulation of the 
radioactivity was observed in the mature beet foliage in the 30-day 
study (0.029 ppm) and the 120-day study (0.011 ppm). Major metabolites 
were N-demethyl triazine amine and O-hydroxy triazine amine. 
Accumulation of radioactivity was observed in the mature sorghum straw 
due to the dehydrated nature of this plant tissue at harvest. Levels of 
radiolabeled materials detected were 0.108 and 0.057 ppm in the 30-day 
and 120-day studies. The major metabolites were highly polar materials. 
Tribenuron methyl rapidly decomposes in soil to the triazine amine, 
which is then degraded, not accumulated, in plants.
    Based on the absence of detectable residue in food commodities 
(barley and oat grain) and on the expected low residue levels of 
individual substances in feed items (straw) under normal conditions, 
and the Residue Chemistry Test Guidelines (OPPTS 860.1300(c)(2)(D)(ii) 
which states that; one metabolism study will be required for each of 
the crop groups defined in 40 CFR 180.34(f) except for herbs and 
spices, a plant metabolism study in barley and oat was not required. 
Additionally, based on the results of three metabolism studies on 
dissimilar crops having similar metabolic routes (canola, cotton, and 
wheat), an additional metabolism study for flax is not required.
    2. Analytical method. There is an analytical method for 
determination of residues of tribenuron methyl in barley, wheat grain, 
straw, and wheat grain forage samples. The method is based on 
extraction of tribenuron methyl from crops with acetonitrile, and 
cleanup on a silica cartridge. Final determination is by normal phase 
liquid chromatography using a photoconductivity detector. Recoveries 
for grain, straw, and green forage samples fortified between 0.01 and 
0.10 ppm averaged 88% with a standard deviation of 14%. The lower level 
of quantitation (LOQ) for grain and green forage is 0.01 ppm and for 
straw it is 0.02 ppm.
    Another analytical method for determination of tribenuron methyl in 
wheat grain and straw uses 2 HPLC with ultra-violet (UV) detection at 
254 nanometer (nm). The method provides a means to quantitate 
tribenuron methyl in these matrices at levels as low as 0.05 ppm based 
on a 5-gram sample.
    An analytical method to detect tribenuron methyl at a level of 0.02 
ppm or above in grass seed, straw, and seed screenings consists of 
using gel permeation chromatography and solid-phase extraction. 
Purified column eluent is taken to dryness, dissolved in ethyl acetate, 
and analyzed by capillary gas chromatography using a mass spectral 
detector. In fortification recovery trials, an average recovery of 
87.6% with a standard deviation of 21% was obtained for 18 grass seed 
samples over a fortification range of 0.02 to 0.06 ppm. Tribenuron 
methyl residues in canola and flax samples were determined by an 
analytical method based on the use of liquid chromatography with eluent 
and column switching with photometric detection at 258 nm at levels as 
low as 0.02 ppm LOQ using a 5-gram sample.
    Residues in cotton seed and gin trash were determined based on the 
use of column-switching liquid chromatography with detection via 
positive ion electrospray mass spectroscopy. The LOQ was determined to 
be 20 nanograms (ng)/g and the LOD was estimated to be 6 ng/g, based on 
a 5-gram sample.
    3. Magnitude of residues--i. Wheat, barley, grain, and straw. A 
study was conducted to determine the extent of residues of tribenuron 
methyl in wheat when applied at the maximum use rate (0.25 ounce a.i./
acre) 40 days before maturity. Samples of mature wheat, grain, and 
straw were taken from treated and control plots at pre-harvest 
intervals (PHI) ranging from 25 to 40 days after the test substance was 
applied. A 2-step HPLC method was used to determine tribenuron methyl 
at levels as low as 0.0075 ppm in wheat grain based on a 20-gram 
sample, and 0.014 ppm in wheat straw based on a 10-gram sample. No 
grain or straw samples showed quantifiable or detectable residues of 
tribenuron methyl.
    A study was conducted to determine the extent of residues of 
tribenuron methyl in barley when applied at the maximum use rate (0.25 
ounce a.i./acre) 40 days before maturity. Samples of mature barley 
grain and straw were taken from each plot at PHI ranging from 24 to 43 
days after the test substance was applied. A 2-step HPLC method was 
used to determine tribenuron methyl at levels as low as 0.0066 ppm in 
barley grain based on a 20-gram sample, and 0.013 ppm in barley straw 
based on a 10-gram sample. One grain sample showed a detectable residue 
(0.0064 ppm) of tribenuron methyl, which is below the established grain 
tolerance of 0.05 ppm. A straw sample from one of the sites

[[Page 40913]]

contained tribenuron methyl at 0.034 ppm, which is below the 
established straw tolerance of 0.10 ppm. The remaining grain and straw 
samples showed no detectable or quantifiable residues of tribenuron 
methyl.
    The results of the analyses of grain and straw from wheat and 
barley show that no residues were found in either grain or straw from 
plants treated at or below the maximum recommended application rate 
(0.25 ounce a.i./acre). The PHI ranged from 42-140 days (0.020 ppm-
0.050 ppm LOQ). A small percentage of plants treated at higher rates 
showed some residues in straw.
    ii. Forage, grass, and hay. Established plots of bluegrass, tall 
fescue, and perennial ryegrass grown for production of grass seed were 
each treated with 0.25 ounce a. i./acre and 0.50 ounce a.i./acre of 
``express'' herbicide (formulated as a 75 DF water-dispersible 
granule). A total of 4 test sites were included in the study--2 for 
bluegrass and 1 each for tall fescue and perennial ryegrass. Sampling 
PHI ranged from 56 to 85 days. Reliable detected residues of tribenuron 
methyl (0.016 ppm or above) were not found in any crop fraction from 
any test site, with one exception of a residue level of 0.004 ppm for 
the 0.25 ounce a.i./acre treatment, and 0.006 ppm for the 0.50 ounce 
a.i./acre treatment. An attempt to reconfirm this result by 
reextracting a second screening waste sample failed to confirm the 
presence of these tribenuron methyl residues.
    iii. Grain, oat, and straw. A study was conducted to determine the 
extent of residues of tribenuron methyl in oats when applied at 1 to 2 
times the maximum use rate approximately 40 days before harvest. 
Samples of mature oat grain and straw were taken from both treated and 
control plots at PHI ranging from 39 to 57 days after the application 
of the test substance. A 2-step HPLC method was used to detect 
tribenuron methyl residues in oat grain at levels as low as 0.0055 ppm 
based on a 20-gram sample and in oat straw at levels as low as 0.018 
ppm based on a 10 gram sample. Residues of tribenuron methyl in oat 
grain from oats treated at 1x and 2x were below the quantitation level 
of 0.013 ppm and 0.01 ppm, respectively. The residues of tribenuron 
methyl in oat straw were below the quantitation level of 0.018 ppm and 
0.04 ppm respectively and also below reported detection level of 0.009 
ppm and 0.018 ppm, respectively, in oat straw from oats treated at 1x 
and 2x rates.
    iv. Canola and flax. Magnitude of residue studies were conducted on 
seed fractions of canola varieties containing the SmartTM 
trait and CDC triffid flax. The post-emergent broadcast application of 
Refine Extra[reg] herbicide at a use rate of 15 to 30 g a.i./ha 
(representing 5 to 10 g a.i./ha of tribenuron methyl) which represents 
1 to 2 times the proposed use rate for Refine Extra[reg] herbicide on 
these canola and flax varieties. The study included treatment of 15 
sites for canola containing the SmartTM trait and 11 sites 
for CDC triffid flax. No tribenuron methyl residues were found above 
the LOQ of 0.02 ppm in any seed samples treated with the test substance 
at a use rate of 15 to 30 g a.i./ha Refine Extra[reg] herbicide.
    v. Cotton seed and gin trash. Magnitude of residue studies were 
also conducted to determine residues of tribenuron methyl in cotton 
seed and cotton gin trash at 9 test sites. The study consisted of 3 
treatments:
     One broadcast application at 0.45 ounce a.i./acre, applied 
approximately 14 days prior to planting.
     One broadcast application at 0.45 ounce a.i./acre, applied 
pre-plant, on the day of planting.
     One broadcast application at 2.25 ounce a.i./acre, applied 
pre-plant, the day of planting.
    The anticipated target PHI was approximately 120 days after the 
last application of the test substance; actual PHIs ranged from 123 to 
196 days. The experimentally determined LOQ was 20 parts per billion 
(ppb) for both analytes. The LOD was estimated to be 6 ppb. No 
tribenuron methyl residues were found above the LOQ of 0.02 ppm in any 
cotton seed and cotton gin trash samples treated with the test 
substance.

B. Toxicological Profile

    1. Acute toxicity. Based on EPA criteria, technical tribenuron 
methyl is in acute toxicity category IV for oral and inhalation routes 
of exposure, and for skin irritation. Tribenuron methyl is in acute 
toxicity category III for the dermal route of exposure, and for eye 
irritation. It is not a skin sensitizer.

------------------------------------------------------------------------
 
------------------------------------------------------------------------
Acute oral toxicity in rats                 Lethal dose (LD)50 >5,000
                                             milligrams/kilogram (mg/kg)
------------------------------------------------------------------------
Acute dermal toxicity in rabbits            LD50 >2,000 mg/kg
------------------------------------------------------------------------
Acute inhalation toxicity in rats           Lethal concentration (LC)50
                                             >5.0 mg/Liter (L)
------------------------------------------------------------------------
Primary eye irritation in rabbits           Moderate effects reversed
                                             within 3 days
------------------------------------------------------------------------
Primary dermal irritation in rabbits        Slight skin irritant
------------------------------------------------------------------------
Dermal sensitization                        Non-sensitizer
------------------------------------------------------------------------

    >2. Genotoxicity. Technical tribenuron methyl has shown no 
genotoxic or mutagenic activity in the following in vitro and in vivo 
tests:

------------------------------------------------------------------------
 
------------------------------------------------------------------------
In vitro mutagenicity Ames Assay            Negative
------------------------------------------------------------------------
In vitro mutagenicity chinese hampster      Negative
 ovary/hypoxanthine guanine phophoribosyl
 transferase (CHO/HGPRT) Assay
------------------------------------------------------------------------
In vitro unscheduled deoxyribonucleic acid  Negative
 (DNA) synthesis
------------------------------------------------------------------------
In vivo Cytogenetic                         Negative
------------------------------------------------------------------------
In vivo micronuclei induction (mouse)       Negative
------------------------------------------------------------------------

    Tribenuron methyl was negative for mutagenicity in an in vitro 
bacterial gene mutation assay using Salmonella typhimurium and in an in 
vitro mammalian cell gene mutation assay using chinese hampster ovary 
(CHO) cells. In cultured primary rat hepatocytes in vitro, 
thifensulfuron methyl was negative for the induction of unscheduled DNA 
synthesis.
    In a test measuring clastogenic damage in vivo, tribenuron methyl 
was negative for the induction of chromosome aberrations in male and 
female rat bone marrow cells. A study measuring chromosome damage in 
vivo was conducted. The study included the evaluation of micronuclei in 
bone marrow polychromatic erythrocytes of male and female mice. The 
result was negative when exposures were conducted at 5,000 mg/kg body 
weight.
    3. Reproductive and developmental toxicity. On long-term dietary 
administration, tribenuron methyl did not affect the reproduction or 
lactation performance of rats. Developmental studies in the rat and 
rabbit by gavage administration indicated that tribenuron methyl did 
not present a unique toxic risk to the fetus. Embryo-fetal and maternal 
NOAELs were equivalent in all cases.
    There were no effects in reproduction or lactation in rats in a 1-
generation reproduction study with rats fed for 90 days with diets that 
contained 0; 100; 1,750; or 5,000 ppm a.i. The no observed effect level 
(NOEL) was 100 ppm (7 mg/kg/day for males and 8 mg/

[[Page 40914]]

kg/day for females) based on lower mean dam and pup body weights for 
the intermediate and high dose groups.
    There were no effects on fertility observed in a 2-generation 
reproduction study, in rats fed for at least 90 days with diets that 
contained 0, 25, 250, or 1,000 ppm a.i. The NOEL was 25 ppm based on 
lower body weights for the dams and offspring at 250 and 1,000 ppm. 
There were no differences attributed to administration of tribenuron 
methyl in the number of litters produced or other indices of 
reproductive performance. No compound-related effects on male fertility 
were noted. No effect on the number of pups born or pup survival were 
observed in any tribenuron methyl treated group.
    In a study to evaluate developmental toxicity potential in rats, 
tribenuron methyl did not produce birth defects after administering via 
oral intubation to pregnant rats dosage levels of 0, 20, 125, and 500 
mg/kg/day. The NOEL for this study was 20 mg/kg/day for both maternal 
and developmental toxicity. This was based on maternal effects at the 
125 and 500 mg/kg/day. The effects included decreased body weight gain 
and food consumption and an increased incidence of excess salivation. 
Fetal effects included decreased body weights and increased number of 
resorptions (only at (hightest dose tested HDT)). In the rabbit 
developmental toxicity study, rabbits were fed dosage levels of 0, 5, 
20, and 80 mg/kg/day. The NOEL for maternal and developmental toxicity 
was 20 mg/kg/day. This was based on maternal effects which included 
decreased feed consumption and an increased incidence of abortions (at 
the HDT). Fetal effects included slightly reduced body weights at 80 
mg/kg/day.
    4. Subchronic toxicity. The most sensitive species to subchronic 
exposure of tribenuron methyl was the rat. In the rat study, rats were 
fed dosage levels of 0; 100; 1,750; or 5,000 ppm tribenuron methyl for 
90 days. The findings show that the NOEL for tribenuron methyl was 100 
ppm for both male and female rats (90-day dietary). This concentration 
is equivalent to 7 and 9 mg/kg/day in male and female rats, 
respectively. The NOEL was based on the decreased body weight and 
decreased feed consumption noted in the 1,750 and 5,000 ppm groups. The 
NOEL for the 90-day mouse feeding study was 500 ppm (70 mg/kg/day for 
males and 90 mg/kg/day for females) based on liver and spleen effects 
at 1,250; 2,500; and 5,000 ppm at 4 weeks. An increase in liver weights 
at 2,500 ppm was noted with no histologic effects at any level. The 
NOEL for subchronic (90-day dietary) exposure in dogs was 500 ppm (15.1 
mg/kg/day for male and 14.9 mg/kg/day for female dogs). This was based 
on lower mean body weights of male dogs fed the 2,500 ppm diet. A 
specific target organ was not identified in any of the species studied.
    5. Chronic toxicity. The NOEL for chronic (18-month dietary) 
exposure in mice was 200 ppm (equivalent to 25 and 31 mg/kg/day in male 
and female mice, respectively). This was based on lower body weights 
for mice in the high-dose group (1,500 ppm). There were no neoplastic 
or other histopathological effects associated with this compound and no 
target organ was identified. Additionally, no evidence of tribenuron 
methyl induced oncogenicity was observed in the mouse.
    The NOEL for chronic (2-year dietary) exposure in rats was 25 ppm 
(0.95 and 1.2 mg/kg/day for male and female rats, respectively). Lower 
body weights, which paralleled lower food consumption and organ weight 
effects, were observed in the 250 and 1,250 ppm groups. There were no 
clinical or histopathological effects associated with these organ 
weight effects. The incidence of mammary adenocarcinomas was greater 
than controls for female rats in the 1,250 ppm group. This effect was 
only observed in this high-dose group and under conditions of 
significant physiological stress (body weights for female rats were 42% 
lower than the controls).
    In a 1-year feeding study in dogs, the NOEL was determined by 
DuPont to be 250 ppm (8.16 and 8.18 mg/kg/day for male and female dogs, 
respectively). This was based on slightly lower body weights and 
increased serum creatinine concentrations for dogs in the high-dose 
group (1,500 ppm). Upon review by EPA, the NOEL was set at 25 ppm (0.79 
mg/kg/day). There were no neoplastic or other histopathological effects 
associated with compound administration.
    6. Animal metabolism. Metabolism of tribenuron methyl was evaluated 
in rats using both phenyl and triazine labeling. Tribenuron methyl was 
extensively and rapidly converted to polar metabolites and primarily 
excreted in the urine and feces. Urinary excretion accounted for 2 to 4 
times the amount of radiolabel excreted via feces in all groups. 
Essentially all of the tribenuron methyl and its metabolites were 
excreted in the urine and feces of the rat within 96 hours after 
dosing. Levels of radiolabeled residues in tissues were correspondingly 
higher in those groups with slower elimination kinetics, but no 
evidence of bioconcentration was seen. None of the dosed label was 
expired as carbon dioxide or volatile metabolites.
    The average excretion half-life values for male and female rats in 
the low-dose group (20 mg/kg) were approximately the same (26-33 hours) 
and independent of dietary preconditioning. The average excretion half-
lives for male and female rates in the high-dose groups (1,700; 1,800; 
and 2,000 mg/kg) were approximately 51-54 hours (males) and 68-96 hours 
(females). These results indicate that the metabolism of tribenuron 
methyl in male and female rats is qualitatively similar; however, 
female rats metabolize and excrete this product much slower than male 
rats at the high doses. The low residual radioactivity in the rat 
indicated that tribenuron methyl does not covalently bind to tissue 
macromolecules. Based on these data, the body burden of this compound 
is not expected to increase significantly upon repeated, long-term 
administration.
    The major metabolites of tribenuron methyl are those expected from 
the enzymatic hydroxylation and dealkylation activities of the hepatic 
microsomal mixed function oxidase system. The major urinary metabolites 
were identified as metsulfuron methyl and saccharin (phenyl labeled 
groups) and metsulfuron methyl and O-demethyl triazine amine (triazine 
labeled groups); no evidence of glucuronide or sulfate conjugation was 
seen.
    Results from a metabolism study with 2 radioactive forms of 
tribenuron methyl (\14\C-triazine and \14\C-phenyl) in lactating goats 
show that most of the dosed radioactivity was recovered in the urine 
(61-71%) and feces (15-20%). In the urine, intact tribenuron methyl and 
metsulfuron methyl accounted for 17-23% and 20-22% of the administered 
dose, respectively. The third major component in phenyl-dosed goat 
urine was saccharin (23.5% of the dose); the third major metabolite in 
the triazine-dosed goat urine was O-demethyl N-demethyl triazine amine 
(10.9%). The highest levels of residues observed in the milk were 0.09 
ppm (tribenuron methyl equivalents) from the triazine-dosed goat, and 
0.006 ppm from the phenyl-dosed goat. Recoveries of the administered 
dose were 82.2% for the goat given the triazine label, and 86.8% for 
the goat dosed with the phenyl label. Throughout the dosing phase, the 
goats did not display any signs of toxicity, and there was no effect on 
milk production.
    There were no significant levels of unique plant metabolites of 
thifensulfuron methyl found in food or feed products at crop maturity. 
Hence,

[[Page 40915]]

toxicity testing of other degradation products of thifensulfuron methyl 
is not needed.
    7. Metabolite toxicology. There is no evidence that the metabolites 
of tribenuron methyl as identified in either the plant or animal 
metabolism studies are of any toxicological significance.
    8. Endocrine disruption. In a previous 2-year feeding study, female 
rats fed, 1,250 ppm tribenuron methyl had an approximately 3-fold 
increase in mammary adenocarcinoma incidence when compared to control. 
This concentration of tribenuron methyl exceeded the maximum tolerated 
dose, producing a 43% decrease in body weight. In contrast, an 18-month 
feeding study demonstrated that tribenuron methyl was not oncogenic in 
mice. Because tribenuron methyl is also negative in five short-term 
tests for genotoxicity, a non-genotoxic mechanism was investigated. A 
study was designed to investigate whether tribenuron methyl can alter 
the hormonal system of female rats, which would support a non-genotoxic 
mechanism for the tribenuron methyl-induced mammary adenocarcinoma. The 
integrity of the endocrine system was assessed by monitoring the 
estrous cycle, measuring serum hormone levels, characterizing the 
estrogen and progesterone receptors from the uterus and mammary gland, 
and weighing reproductive organs.
    The data from this study indicate that the endocrine system may 
have been affected at a relatively high dose, 5,000 ppm. These data 
further suggest that the hormonal effects served to enhance the growth 
of preinitiated mammary cells in this susceptible rat strain. Such 
hormone-mediated effects are considered to have a threshold below which 
growth of mammary tissue will not be affected. Adequate margins of 
safety protect humans from these threshold effects.

C. Aggregate Exposure

    1. Dietary exposure. The chronic reference dose (RfD) of 0.008 mg/
kg/day is based on the NOEL of 0.79 mg/kg/day from a 1-year dog feeding 
study and a 100X safety factor (SF). The acute RfD of 0.20 mg/kg/day is 
based the NOEL of 20 mg/kg/day from the rabbit and rat developmental 
studies and a 100X safety factor.
    i. Food. Chronic dietary exposure assessment. Chronic dietary 
exposure, resulting from the proposed use of tribenuron methyl on 
barley, canola, cotton, flax, grass, oats, and wheat, is well within 
the acceptable limits for all sectors of the population, as predicted 
by the chronic module of the Dietary Exposure Evaluation Model ((DEEM), 
Novigen Sciences, Inc., 1999 Version 6.74). The percentage or 
proportion of a crop that is treated can have a significant effect on 
the exposure profile. In this case, it was assumed for the crop that 
100% was treated with tribenuron methyl. Based on a comparison with the 
use profile for most other herbicides, this is an extremely 
conservative estimate. The predicted chronic exposure for the U.S. 
population subgroup was 0.000094 mg/kg body weight/day (bwt/day). The 
population subgroup with the highest predicted level of chronic 
exposure was the children 1 to 6 years subgroup with an exposure of 
0.000213 mg/kg bwt/day. Based on a chronic NOEL of 0.79 mg/kg bwt/day 
and a 100-fold (SF), the chronic RfD would be 0.008 mg/kg bwt/day. For 
the U.S. population, the predicted exposure is equivalent to 1.2% of 
the chronic RfD. For the population subgroup with the highest level of 
exposure (children 1 to 6 years), the exposure would be equivalent to 
2.7% of the chronic RfD. Because the predicted exposures, expressed as 
percentages of the chronic RfD, are well below 100%, there is 
reasonable certainty that no chronic effects would result from dietary 
exposure to tribenuron methyl.
    ii. Acute dietary exposure. The predicted acute exposure for the 
U.S. population subgroup was 0.000262 mg/kg bwt/day (95\th\ 
percentile). The population subgroup with the highest predicted level 
of acute exposure was the children 1 to 6 years subgroup with an 
exposure of 0.000475 mg/kg bwt/day (95\th\ percentile). Based on an 
acute NOEL of 20 mg/kg bwt/day and a 100-fold SF, the acute RfD would 
be 0.20 mg/kg bwt/day. For the U.S. population the predicted exposure 
(at the 95\th\ percentile) is equivalent to 0.13% of the acute RfD. For 
the population subgroup with the highest level of exposure (children 1 
to 6 years), the exposure (at the 95\th\ percentile) would be 0.24% of 
the acute RfD. Because the predicted exposures, expressed as 
percentages of the acute RfD, are well below 100%, there is reasonable 
certainty that no acute effects would result from dietary exposure to 
tribenuron methyl.
    iii. Drinking water. Surface water exposure was estimated using the 
Generic Expected Environmental Concentration (GENEEC) model. Ground 
water exposures were estimated using screening concentration in ground 
water (SCI-GROW).
    EPA uses drinking water levels of comparisons (DWLOCs) as a 
surrogate measure to capture risk associated with exposure to 
pesticides in drinking water. A DWLOC is the concentration of a 
pesticide in drinking water that would be acceptable as an upper limit 
in light of total aggregate exposure to that pesticide from food, 
water, and residential uses. A DWLOC will vary depending on the residue 
level in foods, the toxicity endpoint and with drinking water 
consumption patterns and body weights for specific subpopulations.
    The acute DWLOCs are 7 ppm for the U.S. population and 2 ppm for 
the subpopulation with the highest exposure (children 1 to 6 years). 
The estimated maximum concentration of tribenuron methyl in surface 
water 0.7 ppb are derived from GENEEC is much lower than the acute 
DWLOCs. Therefore, one can conclude with reasonable certainty that 
residues of tribenuron methyl in drinking water do not contribute 
significantly to the aggregate acute human health risk.
    The chronic DWLOCs are 0.3 ppm for the U.S. population and 0.01 ppm 
for the subpopulation with the highest exposure (children 1 to 6 
years). These DWLOC values are substantially higher than the GENEEC 56-
day estimated environmental concentration of 0.3 ppb for tribenuron 
methyl in surface water. Therefore, one can conclude with reasonable 
certainty that residues of tribenuron methyl in drinking water do not 
contribute significantly to the aggregate chronic human health risk.
    2. Non-dietary exposure. Tribenuron methyl is not registered for 
any use which could result in non-occupational or non-dietary exposure 
to the general population.

D. Cumulative Effects

    Tribenuron methyl belongs to the sulfonylurea class of crop 
protection chemicals. Other structurally similar compounds in this 
class are registered herbicides. However, the herbicidal activity of 
sulfonylureas is due to the inhibition of ALS, an enzyme found only in 
plants. This enzyme is part of the biosynthesis pathway leading to the 
formation of branched chain amino acids. Animals lack ALS and this 
biosynthetic pathway. This lack of ALS contributes to the relatively 
low toxicity of sulfonylurea herbicides in animals. There is no 
reliable information that would indicate or suggest that thifensulfuron 
methyl has any toxic effects on mammals that would be cumulative with 
those of any other chemical.

E. Safety Determination

    1. U.S. population. Tribenuron methyl is the active ingredient in 
two DuPont herbicides with new proposed uses on the following 
commercial crops:

[[Page 40916]]

Imazethapyr tolerant canola, cotton, and CDC triffid flax. There are no 
residential uses for any tribenuron methyl containing herbicides.
    Based on data and information submitted by DuPont, EPA previously 
determined that the establishment of tolerances of tribenuron methyl on 
the following raw agricultural commodities would protect the public 
health, including the health of infants and children:

----------------------------------------------------------------------------------------------------------------
                Wheat                           Barley                   Grass                     Oats
----------------------------------------------------------------------------------------------------------------
Grain                                  Grain                    Forage                   Grain
 
Straw                                  Straw                    Hay                      Straw
----------------------------------------------------------------------------------------------------------------

    Establishment of new tolerances for tribenuron methyl on 
imazethapyr tolerant canola seed at 0.02 ppm, cotton seed at 0.02 ppm, 
cotton gin trash at 0.02 ppm, and CDC triffid flax at 0.02 ppm, will 
not adversely impact public health.
    Using the conservative exposure assumptions described in this unit, 
and based on the most sensitive chronic NOEL of 0.79 mg/kg/day and an 
RfD of 0.008 mg/kg/day, the aggregate dietary exposure will utilize 
2.7% of the RfD for the U.S. population. Generally, exposure below 100% 
of the RfD are of no concern because the RfD represents the level at or 
below which daily dietary exposure over a lifetime will not pose risk 
to human health. We therefore conclude that there is reasonable 
certainty that no harm will result from aggregate exposure to 
tribenuron methyl residues.
    2. Infants and children. Chronic dietary exposure of the most 
highly exposed subgroup in the population, children 1 to 6, is 0.000213 
mg/kg/day or 2.7% of the chronic RfD. The acute dietary exposure of the 
most exposed subgroup, children 1 to 6, is 0.24% of the acute RfD 
(95th percentile). For non-nursing infants (<1-year), the 
acute dietary exposure is 0.15% acute RfD (95th percentile).
    There are no residential uses of tribenuron methyl and 
contamination of drinking water is extremely unlikely. Based on the 
completeness and reliability of the toxicity data, the lack of 
toxicological endpoints of special concern, the lack of any indication 
of greater sensitivity of children, and the conservative exposure 
assessment, there is a reasonable certainty that no harm will result to 
infants and children from the aggregate exposure to residues of 
tribenuron methyl from all anticipated sources of dietary and non-
occupational exposure. Accordingly, there is no need to apply an 
additional safety factor for infants and children.

F. International Tolerances

    The maximum residue level (MRL) in Canada for tribenuron methyl on 
canola is 0.1 ppm. No Mexican or Codex MRLs exist for tribenuron methyl 
on canola. There are no Canadian, Mexican or Codex MRLs for tribenuron 
methyl on cotton and flax.
[FR Doc. 04-15208 Filed 7-6-04; 8:45 am]
BILLING CODE 6560-50-S