PMEP Home Page --> Pesticide Active Ingredient Information --> Herbicides, Growth Regulators and Desiccant --> sesone to vernolate (Vernam) --> sulfentrazone --> sulfentrazone (Authority) Pesticide Tolerance Petition 11/96

sulfentrazone (Authority) Pesticide Tolerance Petition 11/96

ENVIRONMENTAL PROTECTION AGENCY
[PF-670; FRL-5571-4]
 
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 
soybeans.
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: opp-docket@epamail.epa.gov. 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 
document.
    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: 
miller.joanne@epamail.epa.gov.
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 
sulfentrazone (N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-
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
[[Page 57421]]
workers and the population in general far exceed the EPA required level 
of 100.
    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 
irritation.
    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 
hematology effects.
    A 90-day feeding study in the rat with a NOEL of 1,000 ppm based on 
hematology findings.
    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 
hematology parameters.
    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 
liver histopathology.
    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 
doses.
    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
Infants........................................                      760
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 
human exposure.
    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
[[Page 57422]]
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 
fetus.
    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 
commodities.
    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
[[Page 57423]]
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:
    opp=Docket@epamail.epa.gov
    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 
recordkeeping requirements.
    Dated: October 21, 1996.
Peter Caulkins,
Acting Director, Registration Division, Office of Pesticide Programs.
[FR Doc. 96-28422 Filed 11-5-96; 8:45 am]
BILLING CODE 6560-50-F