sulfentrazone (Authority) Pesticide Tolerance Petition 11/96
ENVIRONMENTAL PROTECTION AGENCY
Pesticide Tolerance Petition; Notice of Filing
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of filing.
SUMMARY: This notice is a summary of a pesticide petition proposing the
establishment of a regulation for residues of sulfentrazone in or on
DATES: Comments, identified by the docket number [PF-670], must be
received on or before, December 6, 1996.
ADDRESSES: By mail, submit written comments to Public Response and
Program Resources Branch, Field Operations Division (7506C), Office of
Pesticide Programs, Environmental Protection Agency, 401 M St. SW.,
Washington, DC 20460. In person, bring comments to Rm 1132, CM #2, 1921
Jefferson Davis Highway, Arlington, VA 22202.
Comments and data may also be submitted electronically by sending
electronic mail (e-mail) to: email@example.com. Electronic
comments must be submitted as an ASCII file avoiding the use of special
characters and any form of encryption. Comments and data will also be
accepted on disks in WordPerfect in 5.1 file format or ASCII file
format. All comments and data in electronic form must be identified by
the docket number [PF-670]. Electronic comments on this proposed rule
may be filed online at many Federal Depository Libraries. Additional
information on electronic submissions can be found below in this
Information submitted as a comments concerning this document may be
claimed confidential by marking any part or all of that information as
``Confidential Business Information'' (CBI). CBI should not be
submitted through e-mail. Information marked as CBI will not be
disclosed except in accordance with procedures set forth in 40 CFR part
2. A copy of the comment that does not contain CBI must be submitted
for inclusion in the public record. Information not marked confidential
may be disclosed publicly by EPA without prior notice. All written
comments will be available for public inspection in Rm. 1132 at the
address given above, from 8 a.m. to 4:30 p.m., Monday through Friday,
excluding legal holidays.
FOR FURTHER INFORMATION CONTACT: Joanne Miller (PM23) Rm., 237, CM #2,
1921 Jefferson Davis Highway, Arlington, VA. 703-305-6224, e-mail:
SUPPLEMENTARY INFORMATION: EPA has received a pesticide petition (PP
4F4407) from FMC Corporation, 1735 Market Street, Philadelphia, PA
19103, proposing pursuant to section 408(d) of the Federal Food, Drug
and Cosmetic Act (FFDCA), 21 U.S.C. section 346a(d), to amend 40 CFR
part 180 by establishing a tolerance for residues of the herbicide
methyl-5-oxo-lH-1,2,4-triazol-1-yl]phenyl]-methanesulfonamide in or on
the raw agricultural commodity soybeans at 0.05 ppm and rotational crop
tolerances in cereal grains from 0.1 to 0.5 ppm. The proposed
analytical method is gas chromatography with electron detection.
Pursuant to section 408(d)(2)(A)(I) of the FFDCA, as amended, FMC
Corporation has submitted the following summary of information, data
and arguments in support of their pesticide petition. This summary was
prepared by FMC Corporation and EPA has not fully evaluated the merits
of the petition. EPA edited the summary to clarify that the conclusions
and arguments were the petitioner's and not necessarily EPA's and to
remove certain extraneous material.
I. FMC Petition Summary
1. Sulfentrazone uses. Sulfentrazone is the first herbicide in a
new aryl triazolinone chemical class. Weeds found resistant to other
herbicides are not cross resistant to sulfentrazone. The unique mode of
action of sulfentrazone provides economic control for a wide spectrum
of grass and broadleaf weeds, with exceptional strength on morningglory
and nutsedge species.
Sulfentrazone will be used on soybeans to control Broadleafs
(including cocklebur, lambsquarter, morningglory, pigweed and
velvetleaf); Grasses (including barnyardgrass, crabgrasses, foxtail,
goose grass, johnsongrass and panicum); Sedges (including purple and
yellow nutsedge and annual sedge).
Sulfentrazone will be applied to the soil preemergent to the
soybean crop. The product controls emerging weeds and also has
postemergent burn-down activity to small exposed weeds. A single
application will be made using standard low pressure ground herbicide
boom sprayer equipped with suitable nozzles and screens. Application
rates for sulfentrazone alone range from 0.25 to 0.375 lb active
ingredient per acre dependent on soil texture, organic matter, and
geography. Combinations with selected products may further reduce the
application rate to 0.15 lb active ingredient per acre. Applications
can be made up to 30 days before crop emergence in either conventional
or no-till situations. Authority 75DF or 4F may be applied early
preplant, preplant incorporated or preemergence.
2. Sulfentrazone safety. FMC has submitted over 40 separate
toxicology studies in support of tolerances for sulfentrazone.
According to FMC, sulfentrazone is not a carcinogen or a mutagen and
has low oral and dermal toxicity to mammals. Although laboratory
experiments at the higher rates tested have shown some developmental
and reproductive effects, risk assessment calculations indicate the
margins of safety for agricultural
workers and the population in general far exceed the EPA required level
The following mammalian toxicity studies have been conducted to
support the tolerance of sulfentrazone:
A rat acute oral study with an LD<INF>50 of 3,034 mg/kg (male) and
2,689 mg/kg (female).
A rabbit acute dermal LD<INF>50 of >2,000 mg/kg.
A rat acute inhalation LC<INF>50 of >4.13 mg/L.
A primary eye irritation study in the rabbit which showed mild
A primary dermal irritation study which showed no irritation.
A primary dermal sensitization study which showed no sensitization.
An acute neurotoxicity study with a No-Observed Effect Level (NOEL)
of 250 mg/kg and no neuropathological findings at any dose.
A 28-day feeding study in the rat with a NOEL of 1,000 ppm based on
A 90-day feeding study in the rat with a NOEL of 1,000 ppm based on
A 28-day feeding study in the mouse with a NOEL of 800 ppm based on
effects on hematology parameters.
A 90-day feeding study in the mouse with a NOEL of 300 ppm based on
A 90-day subchronic neurotoxicity study in the rat with a
neurotoxicity and overall NOEL of 500 ppm; no histopathological effects
on the peripheral or central nervous system were observed.
A 24-month chronic feeding/oncogenicity study in the rat with an
overall NOEL of 600 ppm in females and 1,000 ppm in males based on
hematology effects and reduced body weights. There was no evidence of
an oncogenic response.
A 4 week range-finding study in dogs with a NOEL of 900 ppm based
on hematology effects.
A 90-day feeding study in dogs with a NOEL of 300 ppm based on
A 12-month feeding study in dogs with a NOEL of 800 ppm based on
hematology effects and microscopic liver changes.
A mouse oncogenicity study with a NOEL of 600 ppm based on
decreased hemoglobin. There was no evidence of oncogenicity.
An oral teratology study in the rat with a maternal NOEL of 25 mg/
kg/day based on body weight effects and a fetal NOEL of 10 mg/kg/day
based on reduced body weights and delayed skeletal effects at higher
A supplemental teratology study conducted to test for cardiac
effects at the request of the EPA did not reveal any significant
effects on fetal cardiac development.
A dermal teratology study in the rat with a maternal NOEL of 250
mg/kg/day and a fetal NOEL of 100 mg/kg/day based on an increase in
fetal and litter incidence of skeletal effects.
An oral teratology study in the rabbit with a maternal and fetal
NOEL of 100 mg/kg/day based on decreased body weights for the does and
fetal effects at higher doses.
A two generation reproduction study in the rat with a NOEL for
systemic and reproductive/developmental parameters of 200 ppm. Male
fertility in the Fl generation was reduced at higher doses; litter
size, pup survival and pup bodyweight for both generations were also
effected at higher doses.
A supplemental rat reproduction study with a NOEL for reproductive
parameters of 200 ppm.
Ames Assay: Negative; Mouse lymphoma: Negative with activation,
equivocal without activation.
Mouse Micronucleus Assay: Negative.
3. Threshold effects--chronic effects. Based on the available
chronic toxicity data, FMC believes the Reference Dose (RfD) for
sulfentrazone should be 0.05 mg/kg/day. The RfD for sulfentrazone is
based on a multigeneration reproduction study in rats with a threshold
No-observed Effect Level (NOEL) of 14 mg/kg/day and an uncertainty
factor of 100, with an additional modifying factor of 3 to account for
the nature of the effects.
Acute toxicity. EPA recently proposed a tiered approach to estimate
acute dietary exposure. The methods proposed by the EPA were reviewed
and supported by the FIFRA scientific advisory panel (SAP, 1995). EPA's
Tier 1 method is based on the assumption that residue concentrations do
not vary. The analysis assumes that all residues have the same
magnitude, typically the highest field trial residue or tolerance
value. This value is assumed for all points along the consumption
distribution, resulting in a distribution of dietary exposure.
For the acute analysis for sulfentrazone, a Tier 1 analysis was
conducted for the overall U.S. population, infants, children 1 to 6
years of age, females 13 years and older, and males 13 years and older.
Using the NOEL of 10 mg/kg/day derived from the oral teratology study
in rats, the following margins of exposure were calculated (Margins of
exposure of 100 or more are considered satisfactory):
Population Group Margin of Exposure
U.S. Population................................ 2,180
Children 1 to 6................................ 2,052
Females 13 years and older..................... 3,640
Males 13 years and older....................... 3,219
4. Non-threshold effects--Carcinogenicity. Using the Guidelines for
Carcinogen Risk Assessment, FMC believes sulfentrazone to be in Group E
for carcinogenicity -- no evidence of carcinogenicity -- based on the
results of carcinogenicity studies in two species. There was no
evidence of carcinogenicity in an 18-month feeding study in mice and a
2-year feeding study in rats at the dosage levels tested. The doses
tested are adequate for identifying a cancer risk. Thus, a cancer risk
assessment should not be necessary.
5. Aggregate exposure. For purposes of assessing the potential
dietary exposure, FMC has estimated aggregate exposure based on the
Theoretical Maximum Residue Contribution (TMRC) from the tolerances for
sulfentrazone on soybeans at 0.05 ppm and rotational crop tolerances in
cereal grains from 0.1 to 0.5 ppm. (The TMRC is a worse case estimate
of dietary exposure since it is assumed that 100 percent of all crops
for which tolerances are established are treated and that pesticide
residues are present at the tolerance levels.) Dietary exposure to
residues of sulfentrazone in or on food will be limited to residues on
soybeans and cereal grains. Forage and straw from cereal grains are fed
to animals; thus exposure of humans to residues might result if such
residues carry through to meat, milk, poultry or eggs. However, FMC
believes that there is no reasonable expectation that measurable
residues of sulfentrazone will occur in meat, milk, poultry or eggs
from this use. There are no other established U.S. tolerances for
sulfentrazone, and there are no registered uses for sulfentrazone on
food or feed crops in the U.S. In conducting this exposure assessment,
very conservative assumptions--100% of soybeans and cereal grains will
contain sulfentrazone residues and those residues would be at the level
of the tolerances have been used which results in an overestimate of
Other potential sources of general population exposure to residues
of pesticides are residues in drinking water and exposure from non-
occupational sources. While the majority of field studies with
sulfentrazone indicate that movement into groundwater will not occur, a
single study in very vulnerable
soil has shown that a small percentage of material could reach shallow
groundwater under extreme conditions. Based on this worst case
situation, the maximum exposure to residues of sulfentrazone in
drinking water resulting from product use at extremely vulnerable sites
would be less than 50 ppb. There is no established Maximum Contaminant
Level(MCL) for residues of sulfentrazone in drinking water under the
Safe Drinking Water Act. However, a reasonable estimate of the
sulfentrazone MCL using the appropriate methodology would be 350 ppb.
The dietary contribution from these residues is included in the safety
determination for both the U.S. population and infants (shown below).
Non-occupational exposure for sulfentrazone has not been estimated
since the current registration for sulfentrazone is limited to
commercial soybean production. The potential for nonoccupational
exposure to the general population is, thus, insignificant.
EPA consideration of a common mechanism of toxicity is not
appropriate at this time since EPA does not have information to
indicate that toxic effects produced by sulfentrazone would be
cumulative with those of any other chemical compounds.
6. Determination of safety for U.S. population-- Reference Dose.
Using the conservative exposure assumptions described above, based on
the completeness and reliability of the toxicity data, the aggregate
exposure to sulfentrazone will utilize 4.5 percent of the RfD for the
U.S. population. EPA generally has no concern for exposures below 100
percent of the Reference Dose (RFD). Therefore, based on the
completeness and reliability of the toxicity data and the conservative
exposure assessment, FMC, concludes that there is a reasonable
certainty that no harm will result from aggregate exposure to residues
of sulfentrazone, including all anticipated dietary exposure and all
other non-occupational exposures.
7. Determination of safety for infants and children. Developmental
toxicity was observed in developmental toxicity studies using rats and
rabbits. The NOELs for developmental effect were established at 10 mg/
kg/day in the rat study and 100 mg/kg/day in the rabbit study. The
developmental effect observed in these studies is believed to be a
secondary effect resulting from decreased oxygen transport to the
Reference Dose. Using the conservative exposure assumptions
described above, FMC has concluded that the percent of the RfD utilized
by aggregate exposure to residues of sulfentrazone ranges from 4.3
percent for children 1 to 6 years old, up to 13.5 percent for non-
nursing infants. EPA generally has no concern for exposure below 100
percent of the Reference Dose. Therefore, based on the completeness and
reliability of the toxicity data and the conservative exposure
assessment, FMC concludes that there is a reasonable certainty that no
harm will result to infants and children from aggregate exposure to the
residues of sulfentrazone, including all anticipated dietary exposure
and all other non-occupational exposures.
8. Estrogenic effects. No specific tests have been conducted with
sulfentrazone to determine whether the pesticide may have an effect in
humans that is similar to an effect produced by a naturally occurring
estrogen or other endocrine effects.
9. Chemical residue. The qualitative nature of the residues in
plants and animals is adequately understood for the purposes of
registration. Residues of sulfentrazone do not concentrate in the
processed commodities. There are no Codex maximum residue levels
established for residues of sulfentrazone on soybeans. FMC has
submitted a practical analytical method for detecting and measuring
levels of sulfentrazone in or on food with a limit of detection that
allows monitoring of food with residues at or above the levels set in
these tolerances. EPA will information on this method to the Food and
Drug Administration. The method is available to anyone who is
interested in pesticide residue enforcement from the Field operations
Division, Office of Pesticide Programs.
Forty separate residue trials have been conducted with
sulfentrazone on soybeans. Analysis of these trials shows that the
maximum total combined residue for sulfentrazone and its major
metabolite will be below 0.05 ppm. Virtually no detectable residues of
sulfentrazone were found in soybean meal, soapstock and oil treated at
an exaggerated rate. Because of the very low level of these residues,
no food additive tolerances are being proposed for these processed
Tolerances have been requested for residues of sulfentrazone and
its major metabolite on soybean seed at the low level of 0.05 ppm. In
addition, tolerances for residues of sulfentrazone and its major
metabolites have been requested to cover inadvertent residues found in
rotational crops of the cereal grain crop grouping (excluding sweet
corn). For these rotational crop tolerances, the requested levels are
as follows: 0.1 ppm in or on grain; 0.2 ppm in or on hay; 0.6 ppm in or
on straw; 0.2 ppm in or on forage; 0.1 ppm in or on stover and 0.2 ppm
in or on bran.
The proposed tolerance levels are adequate to cover residues likely
to be present from the proposed use of sulfentrazone. Therefore, no
special processing to reduce the residues will be necessary. There is
no need for tolerances in animal meat, milk, poultry or eggs since
there is no reasonable expectation of residues in these materials. This
is based on the results of goat and poultry metabolism studies, as well
as the soybean metabolism and crop rotation studies. Calculated
transfer factors are extremely low and maximum expected residues in
meat, milk, poultry and eggs would be in the part per trillion range.
Since the level of detection of the available methods would be higher
than the maximum expected level in each of the matrixes, no detectable
residues would be found.
10. Environmental fate. Laboratory studies indicate that
sulfentrazone has the potential to persist in soil and be mobile.
However, the results of field dissipation studies run in the three
largest soybean producing states (Iowa, Illinois, Arkansas) indicate
that downward movement of sulfentrazone is limited, with no
quantifiable residues being found below 18. In a single field study
conducted under highly vulnerable conditions (very high sand content
and low organic matter), small amounts of sulfentrazone were detected
in shallow groundwater when sulfentrazone was applied at exaggerated
rates. The site for this study received excessive record rainfall early
during the study which contributed to the movement observed.
Sulfentrazone has been found to be stable to chemical hydrolysis in
the pH range of environmental concern. However, the compound is subject
to rapid extensive degradation in water in the presence of natural
sunlight. Under these conditions, sulfentrazone residues rapidly break
down, with more than 50% of the residue disappearing in 1 hour at
environmental pH. Under aerobic conditions in soil, the major metabolic
pathway for sulfentrazone is oxidation of the methyl group on the
triazolinone ring. A minor metabolic pathway under aerobic conditions
is the cleavage of the sulfonamide group on sulfentrazone.
Sulfentrazone residues do not bioaccumulate in fish.
II. Administrative Matters
Interested persons are invited to submit comments on this notice of
filing. Comments must bear a notation indicating the document control
number, [PF-670]. All written comments filed in response to this
petition will be available, in the Public Response and Program
Resources Branch, at the address given above from 8 a.m. to 4 p.m.,
Monday through Friday, except legal holidays.
A record has been established for this notice of filing under
docket number [PF-670] including comments and data submitted
electronically as described below). A public version of this record,
including printed, paper versions of electronic comments, which does
not include any information claimed as CBI, is available for inspection
from 8 a.m. to 4:30 p.m., Monday through Friday, excluding legal
holidays. The public record is located in Room 1132 of the Public
Response and Program resources Branch, Field Operations Division
(7506C), Office of Pesticide Programs, Environmental Protection Agency,
Crystal Mall #2, 1921 Jefferson Davis highway, Arlington, VA.
Electronic comments can be sent directly to EPA at:
Electronic comments must be submitted as ASCII file avoiding the
use of special characters and any form of encryption.
The official record for this notice of filing, as well as the
public version, as described above will be kept in paper form.
Accordingly, EPA will transfer all comments received electronically
into printed, paper form as they are received and will place the paper
copies in the official record which will also include all comments
submitted directly in writing. The official rulemaking record is the
paper record maintained at the address in ``ADDRESSES'' at the
beginning of this document.
List of Subjects
Environmental Protection, Administrative practice and procedure,
Agricultural commodities, Pesticides and pests, Reporting and
Dated: October 21, 1996.
Acting Director, Registration Division, Office of Pesticide Programs.
[FR Doc. 96-28422 Filed 11-5-96; 8:45 am]
BILLING CODE 6560-50-F