Reregistration Eligibility
Decision (RED) for
| Sethoxydim
September 30, 2005
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
OFFICE OF
PREVENTION, PESTICIDES
AND TOXIC SUBSTANCES
CERTIFIED MAIL
Dear Registrant:
This is to inform you that the Environmental Protection Agency (hereafter
referred to as EPA or the Agency) has completed its review of the available data related
to the risk assessments for the herbicide sethoxydim. The enclosed Reregistration
Eligibility Decision (RED), which was signed on September 30, 2005, summarizes the
Agency's risk assessments for sethoxydim and its conclusions concerning the potential
human health and environmental risks of the current product uses, and conditions under
which these uses and products will be eligible for reregi strati on.
In this RED, the Agency has determined that all uses of sethoxydim will be
eligible for reregi strati on.
This RED also contains a generic and/or a product-specific Data Call-In(s) (DCI)
that outline(s) further data requirements for this chemical. Note, registrants of
sethoxydim must respond to DCIs issued by the Agency within 90 days of receipt of
this letter. For Product Reregistration, the second set of required responses is due 8
months from receipt of this letter. Registrants may avoid Agency enforcement action,
specifically suspension of their sethoxydim products registration(s), by submitting
complete and timely responses.
A Notice of Availability for the Reregistration Eligibility Decision for sethoxydim
is being published in the Federal Register. Electronic copies of the RED and all
supporting documents are available on the Internet. See
www.epa.gov/pesticides/reregistration/status.htm. To obtain a copy of the RED
document, please contact the OPP Public Regulatory Docket (7502C), US EPA, Ariel
Rios Building, 1200 Pennsylvania Avenue NW, Washington, DC 20460, telephone (703)
305-5805.
Please note that the sethoxydim risk assessments and the attached RED concern
only this particular pesticide. Unlike other pesticides for which EPA has followed a
cumulative risk approach based on a common mechanism of toxicity, EPA has not made
a common mechanism of toxicity finding as to sethoxydim and any other substances, and
sethoxydim does not appear to produce a toxic metabolite produced by other substances.
For the purposes of this tolerance action, therefore, EPA has not assumed that
sethoxydim shares a common mechanism of toxicity with other substances. For
information regarding EPA's efforts to determine which chemicals have a common
mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the
policy statements released by EPA's Office of Pesticide Programs concerning common
mechanism determinations and procedures for cumulating effects from substances found
-------
to have a common mechanism of EPA's website at
http://www.epa.gov/pesticides/cumulative/.
If you have questions on this document, please contact the Special Review and
Reregi strati on Division representative, Patrick Dobak, at (703) 308-8180. For questions
about product reregistration and/or the Product DCI that accompanies this document,
please contact the Product Reregistration Chemical Review Manager, Venus Eagle, at
(703) 308-8045.
Sincerely,
Debra Edwards, Ph.D.
Director
Special Review and Reregistration Division
Attachment
-------
Reregistration Eligibility Decision
for
Sethoxydim
List [B]
Case No. 2600
-------
Reregistration Eligibility Decision (RED) Document
for Sethoxydim
Approved by:
Debra Edwards, Ph. D.
Director
Special Review and Reregistration Division
Date: September 30, 2005
-------
Sethoxydim Reregistration Eligibility Decision Team
Office of Pesticide Programs:
Environmental Fate and Effects Risk Assessment
Michael Davy
William Eckel
Dana Spatz
Health Effects Risk Assessment
Wade Britton
William Donovan
Kimyata Morgan
Economic and Biological Analysis
Alan Halvorson
Bill Phillips
Rafael Prieto
Elisa Rim
Registration Support
Jim Tompkins
Risk Management
Patrick Dobak
Amaris Johnson
James Parker
Thomas Brennan
-------
Glossary of Terms and Abbreviations
AGDCI
ai
aPAD
AR
BCF
CFR
cPAD
CSF
CSFII
DCI
DEEM
DFR
DWLOC
EC
EEC
EPA
EUP
FDA
FIFRA
FFDCA
FQPA
FOB
G
GENEEC
GLN
HAFT
IR
LD
50
LOC
LOD
LOAEL
MATC
mg/kg/day
mg/L
Agricultural Data Call-In
Active Ingredient
Acute Population Adjusted Dose
Anticipated Residue
Bioconcentration Factor
Code of Federal Regulations
Chronic Population Adjusted Dose
Confidential Statement of Formula
USDA Continuing Surveys for Food Intake by Individuals
Data Call-In
Dietary Exposure Evaluation Model
Dislodgeable Foliar Residue
Drinking Water Level of Comparison.
Emulsifiable Concentrate Formulation
Estimated Environmental Concentration
Environmental Protection Agency
End-Use Product
Food and Drug Administration
Federal Insecticide, Fungicide, and Rodenticide Act
Federal Food, Drug, and Cosmetic Act
Food Quality Protection Act
Functional Observation Battery
Granular Formulation
Tier I Surface Water Computer Model
Guideline Number
Highest Average Field Trial
Index Reservoir
Median Lethal Concentration. A statistically derived concentration
of a substance that can be expected to cause death in 50% of test
animals. It is usually expressed as the weight of substance per
weight or volume of water, air or feed, e.g., mg/1, mg/kg or ppm.
Median Lethal Dose. A statistically derived single dose that can be
expected to cause death in 50% of the test animals when
administered by the route indicated (oral, dermal, inhalation). It is
expressed as a weight of substance per unit weight of animal, e.g.,
mg/kg.
Level of Concern
Limit of Detection
Lowest Observed Adverse Effect Level
Maximum Acceptable Toxicant Concentration
Micrograms Per Gram
Micrograms Per Liter
Milligram Per Kilogram Per Day
Milligrams Per Liter
11
-------
MOE
MRID
MUP
NA
NAWQA
NPDES
NR
NOAEL
OP
OPP
OPPTS
PAD
PCA
PDF
PHED
PHI
ppb
PPE
ppm
PRZM/EXAMS
Qi*
RAC
RED
REI
RfD
RQ
SCI-GROW
SAP
SF
SLC
SLN
TGAI
TRR
USDA
USGS
UF
UV
WPS
Margin of Exposure
Master Record Identification (number). EPA's system of recording
and tracking studies submitted.
Manufacturing-Use Product
Not Applicable
USGS National Water Quality Assessment
National Pollutant Discharge Elimination System
Not Required
No Observed Adverse Effect Level
Organophosphate
EPA Office of Pesticide Programs
EPA Office of Prevention, Pesticides and Toxic Substances
Population Adjusted Dose
Percent Crop Area
USDA Pesticide Data Program
Pesticide Handler's Exposure Data
Preharvest Interval
Parts Per Billion
Personal Protective Equipment
Parts Per Million
Tier II Surface Water Computer Model
The Carcinogenic Potential of a Compound, Quantified by the
EPA's Cancer Risk Model
Raw Agriculture Commodity
Reregi strati on Eligibility Decision
Restricted Entry Interval
Reference Dose
Risk Quotient
Tier I Ground Water Computer Model
Science Advisory Panel
Safety Factor
Single Layer Clothing
Special Local Need (Registrations Under Section 24(c) of FIFRA)
Technical Grade Active Ingredient
Total Radioactive Residue
United States Department of Agriculture
United States Geological Survey
Uncertainty Factor
Ultraviolet
Worker Protection Standard
in
-------
I. Introduction
The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was amended
in 1988 to accelerate the reregi strati on of products with active ingredients registered prior
to November 1, 1984. The amended Act calls for the development and submission of
data to support the reregi strati on of an active ingredient, as well as a review of all
submitted data to the EPA. Reregi strati on involves a thorough review of the scientific
database underlying a pesticide's registration. The purpose of the Agency's review is to
reassess the potential risks arising from the currently registered uses of sethoxydim, to
determine the need for additional data on health and environmental effects, and to
determine whether or not the pesticide meets the "no unreasonable adverse effects"
criteria of FIFRA. As a result of this review, EPA has determined that all products solely
containing the active ingredient sethoxydim are eligible for reregi strati on. The
completion of the sethoxydim RED does not result in any additional tolerances being
reassessed since all existing tolerances (85) were reassessed at the time a new food use
was established for sethoxydim [63FR54066 (10/8/1998)].
Risks summarized in this document are those that result only from the use of
sethoxydim. The Food Quality Protection Act (FQPA) requires that, when considering
whether to establish, modify, or revoke a tolerance, the Agency should consider "available
information" concerning the cumulative effects of a particular pesticide's residues and
"other substances that have a common mechanism of toxicity." Unlike other pesticides for
which EPA has followed a cumulative risk approach based on a common mechanism of
toxicity, EPA has not made a common mechanism of toxicity finding as to sethoxydim and
any other substances, and sethoxydim does not appear to produce a toxic metabolite
produced by other substances. Therefore, EPA has not assumed that sethoxydim shares a
common mechanism of toxicity with other substances. For information regarding EPA's
efforts to determine which chemicals have a common mechanism of toxicity and to
evaluate the cumulative effects of such chemicals, see the policy statements released by
EPA's Office of Pesticide Programs concerning common mechanism determinations and
procedures for cumulating effects from substances found to have a common mechanism of
toxicity on EPA's website at http://www.epa.gov/pesticides/cumulative/.
II. Use Profile
Sethoxydim [2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]3-hydroxy-2-
cyclohexen-1-one] is a member of the cyclohexanedione or cyclohexenone class of
herbicides. The mode of action for this herbicide is lipid biosynthesis inhibition.
Sensitivity has been demonstrated to be due to a greater susceptibility at the acetyl-CoA
carboxylase (ACCase) enzyme of grass species. These grass species are killed by the
inhibition of the ACCase enzyme., which is a key enzyme in the lipid biosynthetic
pathway.
Sethoxydim is used post-emergence for selective control of annual and perennial
grass weeds in broadleaf crops. Sethoxydim is currently registered for use in or on at
least 86 different agricultural crops such as various grains, fruits, tree nuts, vegetables
-------
and herbs, as well as non-agricultural sites, including ornamentals and flowering plants,
recreational areas, right-of-way, along fences, hedgerows, and public and commercial
buildings/structures. The principal sethoxydim uses are on soybeans, sunflowers, alfalfa,
dry peas/beans, sugar beets, peanuts and corn.
Sethoxydim is formulated as a liquid. Sethoxydim application methods include
high and low pressure handwand, backpack, garden hose-end, handgun (lawn) sprayers,
groundboom sprayers and aerial equipment. It is applied between 0.09 - 0.47 Ibs a.i./A in
or on actively growing crops ranging from a min. interval of 10-21 days on annual and
perennial grasses (based on the emergence of grass weeds).
Close to a million pounds of the active ingredient sethoxydim are applied each
year, with the vast majority being used in the agricultural setting. The principal
sethoxydim uses are on soybeans, sunflowers, alfalfa, dry peas/beans, sugar beets,
peanuts and corn.
III. Human Health Risk Assessment
A. Toxicology
For more detailed information, see "Sethoxydim: HED Chapter of the
Reregistration Eligibility Decision (RED) Document"; W. Donovan; 9/27/05.
The toxicity database for sethoxydim is complete and there are no data gaps. The
acute toxicity data indicate that sethoxydim is moderately toxic (Category III) via oral,
dermal, and inhalation routes of exposure. It is neither irritating to the eye nor the skin
(Category IV).
Table 1: Acute Toxicity Profile for Sethoxydim
Guideline No.
870.1100
870.1200
870.1300
870.2400
870.2500
870.2600
Study Type
Acute Oral- Rats
Acute Dermal- Rats
Acute Inhalation- Rats
Primary Eye Irritation-
Rabbits
Primary Skin Irritation-
Rabbits
Dermal Sensitization-
Guinea pigs
MRIDs #
00045847
00045848
00045849
00045850
00045851
00045852
Results
LD50 = M: 3125 mg/kg, F: 2676 mg/kg
LD50 = > 5000 mg/kg
LC50 = M: 603 m/L, F: 6.28 m/L
Aerosol composed of
NP-55 (25%), DMSO (75%).
No Irritation
No Irritation
Toxicity
Category
HI
HI
HI
IV
IV
Study waived based on lack of sensitization in guinea
pigs treated with an end-use product. Therefore, the
EPA does not consider sethoxydim to be a sensitizer.
-------
The liver appears to be the most significant target organ for sethoxydim exposure
in laboratory animals. In a chronic oral dog feeding study, increased absolute and
relative liver weights were observed at the higher dose levels, and clinical chemistry and
histopathology results also indicate liver effects. In addition, adverse liver effects were
observed via the oral route in another species (mice) and via another route of exposure
(inhalation) in rats.
The Agency considers the sethoxydim database to be adequate to assess
developmental toxicity without the need to require a developmental neurotoxicity (DNT)
study. Although the clinical signs following exposure in the rat prenatal developmental
toxicity study (MRTD 43092902) include irregular gait, decreased activity, excessive
salivation, and anogenital staining, which suggest neurotoxicity, the high dose at which
these effects occurred suggest a non-specific response and do not justify the need for a
DNT study.
Sethoxydim is not likely to be a carcinogenic in humans based on lack of
evidence of carcinogenicity in rats and mice; therefore, a dietary cancer exposure analysis
was not conducted.
The Agency reduced the default 10X FQPA safety factor for potential special
sensitivity in infants and children to IX because the sethoxydim database includes an
acceptable developmental study in rats (MRID 43092902) which showed no concerns for
pre- or post-natal toxicity. Further, the study showed a well characterized dose response,
and a clear NOAEL/LOAEL. Additionally, no evidence of sensitivity either in dose
response or in severity of the effects was observed.
A rat developmental study (MRID 43092902) was used to select the dose and
endpoint for establishing the acute reference dose (RfD) of 1.8 mg/kg/day. The acute
RfD was calculated by dividing the No-Observed-Adverse-Effect-Level (NOAEL) of 180
mg/kg/day from this study by an uncertainty factor (UF) of 100 [10X for interspecies
extrapolation and 10X for intraspecies variation]. Both Maternal effects (gait
impairment) and offspring effects (filamentous tail and lack of tail due to the absence of
sacral and/or caudal vertebrae, and delayed ossification in the hyoids, vertebral centrum
and/or transverse processes, sternebrae and/or metatarsals, and pubes in pups) were
observed at the LOAEL of 650 mg/kg/day. Since the developmental effects and maternal
effects were observed at the same dose level, this RfD is applicable to the general U.S.
population as well as females ages 13-50 and all other population subgroups. The acute
Population-Adjusted-Dose (aPAD) (the dose at which an individual could be exposed on
any given day and no adverse health effects would be expected) is equal to the acute RfD
divided by the FQPA SF (IX), and therefore the aPAD is equal to the acute RfD (1.8
mg/kg/day).
The mouse combined chronic toxicity/carcinogenicity study was used to select the
dose and endpoint for establishing the chronic RfD of 0.14 mg/kg/day. The FQPA SF is
IX, and therefore the chronic Population-Adjusted-Dose (cPAD) is 0.14 mg/kg/day. The
NOAEL of 14 mg/kg/day and the LOAEL of 41.2 mg/kg were based on early onset of
-------
liver effects including hepatocellular hypertrophy and fatty degeneration. A 100-fold
uncertainty factor (10X interspecies and 10X intraspecies) was applied.
No dermal toxicity endpoints have been established because no dermal or systemic
toxicity was seen following repeated dermal applications of sethoxydim at the limit-dose to
rabbits. The 21-day dermal study showed no effects at the highest dose tested.
A rat developmental study (the same as was used for assessing acute dietary
exposure) was used to select the dose and endpoint for short-term incidental oral
exposure. The maternal NOAEL was 180 mg/kg/day and maternal LOAEL was 650
mg/kg/day based on irregular gait observed in dams on the first day of dosing.
Intermediate-term incidental oral exposure is not anticipated; therefore, no endpoint was
selected.
A rat 28-day inhalation study (MRID 44021202) was used to select the dose and
endpoint for inhalation exposure. The NOAEL was 0.3 mg/L (81 mg/kg/day) and LOAEL
was 2.4 mg/L (651 mg/kg/day) based on liver weight, clinical chemistry (bilirubin) and
histology. This endpoint was used for all inhalation exposure durations.
Table 2 provides a summary of the toxicological endpoints selected for sethoxydim.
Table 2: Sethoxydim Endpoint Selection Summary
Exposure
Scenario
Acute Dietary
(general
population)
Acute Dietary
(females 13-50
years old)
Chronic
Dietary (all
populations
Occupational
and
Residential
Inhalation
(short -term)
Residential
Incidental Oral
(short -term)
Dose & Uncertainty
Factor
NOAEL 180 mg/kg/day
UF = 100X
FQPA SF = Ix
Acute PAD = 1.8 mg/kg/day
NOAEL 180 mg/kg/day
UF = 100X
FQPA SF = Ix
Acute PAD = 1.8 mg/kg/day
NOAEL = 13.8 mg/kg/day
UF = 100X
FQPA SF = Ix
Acute PAD = 0.1 4
mg/kg/day
NOAEL = 81 mg/kg/day
UF = 100X
NOAEL = 180 mg/kg/day
UF = 100X
FQPA SF = Ix
Endpoint
Irregular gait that was
observed in 12/34 dams
on the first day of
dosing.
Decreased fetal body
weight, tail
abnormalities, delayed
ossification.
Early onset of liver
effects including
Hepatocellualr
hypertrophy and fatty
degeneration in male
mice.
Based on increased
liver weight, clinical
chemistry (increased
total serum bilirubin)
and liver
histopathology.
Based on irregular gait
observed in 12/34 dams
on the first day of
dosing
Study/MRID
Rat Developmental Toxicity
LOAEL = 650 mg/kg/day.
MRID No. 43092902
Rat Developmental Toxicity
developmental LOAEL = 650
mg/kg/day.
MRID No. 43092902
Chronic
toxicity /carcinogenicity study
in mice.
MRID No. 00100527
28-day Rat Inhalation
LOAEL = 651 mg/kg/day
MRID No. 44021202
Rat Developmental Toxicity
LOAEL = 650 mg/kg/day.
MRID No. 43092902
Sethoxydim is not a likely human carcinogen based on lack of evidence of carcinogenicity in rats and mice
-------
B. Dietary Risk from Food
For more detailed information, see "Sethoxydim: HED Chapter of the
Reregistration Eligibility Decision (RED) Document"; W. Donovan; 9/27/05
The acute dietary exposure was estimated using DEEM-FCID™, Version 1.30,
which incorporates food consumption data from USDA's Continuing Survey of Food
Intake by Individuals (CSFII), 1994-1996, 1998. The acute assessment used tolerance
level residues for most of the crops. Limited refinement, however, was obtained through
the incorporation of field trial data and processing factors for some of the crops expected
to be more highly associated with dietary exposure to sethoxydim. Specifically, field
trial data were used for pome fruit, grapes, oranges, potatoes, strawberries, peaches,
succulent green peas, succulent green beans, and succulent lima beans. Empirical
processing factors were used for apples, grapes, tomatoes, potatoes, and oranges. The
processing factor for orange juice was translated to other citrus juices. Percent crop
treated information was available for most crops and was used wherever possible to
refine the assessment. Tolerance level residues were used for meat, poultry, milk, and
eggs.
Acute dietary risk is calculated based on the toxicity as well as the type and
quantity of food eaten in one day and the maximum, or high-end, residue values in the
food. A risk estimate that is less than 100% of the aPAD does not exceed the Agency's
level of concern.
Exposure at the 99.9th percentile showed an estimated 5.3% of the aPAD for the
general US population, and an estimated 9.2% of the aPAD for children 1-2 years old and
children 3-5 years old (the two most highly exposed population subgroups). Thus, the
acute dietary analysis for sethoxydim shows that the estimated risks from acute dietary
exposure to sethoxydim are well below the Agency's level of concern (<100% of the
aPAD) for the general US population and all other population subgroups. Table 3,
below, summarizes the acute dietary risks.
Table 3: Acute Dietary Risk from Sethoxydim*
Population Subgroup
General U.S. Population
Children 1-2 years old
Children 3-5 years old
999111 Percentile
Exposure (mg/kg/day)
0.096
0.165
0.165
% aPAD
5.3
9.2
9.2
* Assuming an aPAD of 1.8 mg/kg/day
DEEM™ was also used to calculate the chronic dietary exposure estimates based
on average consumption for the U.S. population and population subgroups including
infants and children. The chronic analysis (limited refined dietary risk assessment) used
tolerance level residues for all crops, percent crop treated for many crops, and anticipated
residues for meat and milk. The most highly exposed population subgroup is infants (<1
-------
year old), at an estimated 7.5% of the cPAD. The results of the analysis indicate that the
chronic dietary risk (food only) associated with existing uses of sethoxydim is well below
the Agency's level of concern (<100% of the cPAD) for the general U.S. population and
all population subgroups. Table 4, below, summarizes the chronic dietary risks.
Table 4: Chronic Dietary Risk for Sethoxydim*
Population Subgroup
General U.S. Population
All Infants (< 1 year old)
Exposure (mg/kg/day)
0.004
0.010
% cPAD
2.7
7.5
* Assuming a cPAD of 0.14 mg/kg/day
C. Dietary Risk from Drinking Water
For more detailed information, see "Sethoxydim: HED Chapter of the
Reregistration Eligibility Decision (RED) Document"; W. Donovan; 9/27/05
Exposure to pesticides through drinking water can occur as a result of
groundwater or surface water contamination. EPA considers both acute (one day) and
chronic (multiple year) drinking water risks and uses either modeling or actual
monitoring data, if available, to estimate those risks. Modeling is carried out in tiers of
increasing refinement, but is designed to provide high-end estimates of exposure. To
determine the maximum allowable contribution from water in the diet, EPA first looks at
how much of the overall risk is contributed by food and then determines a "drinking
water level of comparison" (DWLOC). The DWLOC represents the maximum allowable
contribution to the human diet that may be attributed to residues of a pesticide in drinking
water after dietary exposure is subtracted from the aPAD or cPAD.
For sethoxydim, the predominant degradates in soil are the sulfoxide and sulfone
derivatives of the parent (MSO and MSO2). These degradates are expected to be found
in water along with MIS and M2S. Toxicology data for the four degradates are not
available. In the absence of such data, the Agency has assumed that these degradates are
as toxic as the parent to ensure that risk will not be underestimated. Therefore, for risk
assessment purposes the "total sethoxydim residues" in water should be used instead of
the levels for only parent sethoxydim. Modeling estimates were used to quantify possible
drinking water exposure. The Estimated Drinking Water Concentrations (EDWCs) were
less than the DWLOCs for both acute and chronic exposure to sethoxydim in drinking
water, and therefore below the Agency's level of concern.
The surface water assessment used a Tier 1 model called FIRST (FQPA Index
Reservoir Screening Tool), which is a simulation model based on a high runoff scenario
(Mississippi cotton) with a storm two days after application. The modeling was performed
using the maximum number of applications (four) and maximum application rate of 0.47
pounds active ingredient per acre, assuming a 14-day retreatment interval. The default
percent cropped area (PCA) assumed that sethoxydim-treated crops were grown on 87% of
the acres of land in the modeled watershed, which is the highest PCA for any watershed in
the continental United States and is used as the default value for minor crops. Lower PCA
-------
values could have been applied for the major crops on which sethoxydim is used such as
soybeans, cotton and corn. However, because there is such a variety of uses, it is likely that
there is usage on major and minor crops in the same watershed, so the crop-specific PCA
may not be applicable.
The EDWC for ground water was estimated by the SCI-GROW model, version
2.3. The results of the model for acute and chronic scenarios are 1.5 ppb for parent
sethoxydim plus metabolites when assuming a maximum use rate of 1.875 Ib ai/A per
year.
DWLOCs are calculated by subtracting the contribution of food exposure from
the PAD. Because the EDWCs are much less than the DWLOCs, dietary (food plus
drinking water) risk is below the EPA's Level of Concern (LOG). See Table 5, below,
for a summary of these findings.
Table 5: Sethoxydim: Acute and Chronic DWLOC Values Compared to Modeled
EDWCs
Assessment
Type
Acute
Chronic
Most Sensitive Population
Subgroup
Children 1-2 yrs. & Children 3-5 yrs.
All infants (<1 year)
DWLOC
(ppb)
16,400
1,300
EDWC (Surface
Water) (ppb)
130
16
EDWC (Ground
Water) (ppb)
1.5
1.5
D.
Residential Risk
Sethoxydim is registered for residential (consumer) use on ornamentals and
flowering plants, lawns, recreational areas, and around buildings/structures (outdoor).
Homeowners who apply sethoxydim may be exposed for short-term durations through
the dermal and inhalation routes of exposure. Children who have contact with
sethoxydim-treated turf in recreational or residential settings after a sethoxydim
application has occurred (post-application) may be exposed for short-term durations
through the dermal and incidental oral routes of exposure. For sethoxydim, however, the
dermal route of exposure was not assessed because no toxic effects were seen in the
dermal toxicity study. See Table 2 for a summary of the sethoxydim endpoints selected
for this RED.
Residential risk is measured by a Margin of Exposure (MOE) which measures
how close the residential exposure comes to the NOAEL from animal studies. For
sethoxydim, exposure scenarios that yield MOEs that are greater than 100 do not exceed
the Agency's level of concern. This incorporates the standard uncertainty factors of lOx
for interspecies variability and lOx for intraspecies variability.
Residential Handler Risk:
Inhalation MOEs calculated for residential handler scenarios ranged from
1,400,000 to 1,600,000. These MOEs are greater than 100, and therefore these use
scenarios are not of concern to the agency.
-------
Residential Post-application Risk:
Post-application risk scenarios assessed for sethoxydim included the following
toddler scenarios: hand-to-mouth activity on turf; object-to-mouth activity on turf; and
incidental soil ingestion.
Estimated MOEs for short-term post-application incidental ingestion to toddlers
range from 26,000 for hand-to-mouth incidental exposures to 7,600,000 for soil
ingestion. These MOEs are above the target MOE of 100 and, therefore, are not of
concern to EPA.
E. Exposure from Use of Tobacco - Health Risk Assessment
Based on cigarette smoking exposure information, field trial data, a tobacco
pyrolysis study, and an assumption that 100% of the sethoxydim will be inhaled and
absorbed, EPA estimates that exposure to sethoxydim will not exceed 0.00016 mg/kg/day
for males and 0.00018 mg/kg/day for females. The inhalation NOAEL is 81 mg/kg/day
and is based on a 28-day inhalation study in the rat. The Agency did not examine the
intermediate or long-term exposure to sethoxydim via tobacco due to the severity and
quantity of health effects associated with the use of tobacco products. Based on the
inhalation NOAEL, the short-term MOE for sethoxydim exposure from the use of
tobacco is estimated to be greater than 100 (males = 500,000; females = 440,000). This
risk is below the Agency's level of concern for all adult populations.
F. Aggregate Risk
In accordance with FQPA, the Agency must consider and aggregate pesticide
exposures and risks for varying durations of exposure from the following major sources
or pathways: food, drinking water, and residential exposure to homeowners.
In the case of sethoxydim, residential exposure was aggregated with dietary
exposures only for the short-term exposure duration. Acute residential exposure was not
aggregated with acute dietary exposures because it is extremely unlikely that acute turf
exposures would occur concurrently with high-end acute dietary exposures. Likewise,
there are no chronic residential scenarios for sethoxydim; therefore, chronic dietary risks
were not aggregated with residential risks. As a result, acute and chronic aggregate risks
are equal to acute and chronic dietary risks. Section IIIC above presents these results
which are below EPA level of concern for the U.S. population and all population
subgroups.
Short-Term Aggregate Risk:
Short-term aggregate risk assessments were not calculated for adult handlers
because oral and inhalation endpoints lack a common toxicity endpoint. Dermal risks
were not assessed because there is no dermal endpoint of concern for sethoxydim.
-------
Short-term aggregate risk assessments are required for children/toddlers because
there is a potential for incidental oral post-application exposure resulting from the
residential uses of sethoxydim. The children/toddlers 1-2 years of age scenario was
chosen because it was the highest estimated food exposure and thus, is also protective of
all other children. The MOEs are greater than 100, and therefore the short-term
residential risks are below the Agency's level of concern. For surface and ground water,
the estimated average concentrations of sethoxydim are less than the Agency's calculated
DWLOCs for sethoxydim in drinking water as a contribution to short-term aggregate
exposures. Therefore, EPA concludes with reasonable certainty that aggregate risks
resulting from exposure to sethoxydim in food, drinking water, and in residential settings
do not result in risks of concern. See Table 6 below for a summary of these results.
Table 6: Short-Term Aggregate DWLOCs for Sethoxydim
Population
Subgroup
Short-term:
Children
(1-2 years old)
NOAEL
(ing/kg/
day)
180
Target
MOE1
100
Target
Maximum
Exposure
(mg/kg/
day)
1.8
Estimated
Food
Exposure
(mg/kg/
day)
0.0095
Estimated
Residential
Exposure
(mg/kg/
day)
0.0088
Allowable
Water
Exposure
(mg/kg/
day)
1.7817
Groundwater
EDWC
0"g/L)4
1.5
water
EDWC
\t*&L')
16
DWLOC 5
(Hg/L)
17,800
1 The short-term target MOE for sethoxydim includes the standard intra- and inter-species uncertainty factors of 10X, as well as the
FQPA uncertainty safety factor of IX.
2 Target Max Exposure = NOAEL / Target MOE
3 Maximum Water Exposure (mg/kg/day) = Target Maximum Exposure (mg/kg/day) - Aggregate Food and Residential Exposure
(mg/kg/day).
4 Estimate for the highest use rate was chosen.
5 DWLOC (ug/L) = Max. water exposure (mg/kg/day) x body wt (kg) -^ [(10-3 mg/ug) * water consumed daily (L/day)]. HED
standard body weight: All Infants/Children, 10 kg. HED standard daily drinking rate: 1 L/day for children.
G. Cumulative Risk
Unlike other pesticides for which EPA has followed a cumulative risk approach
based on a common mechanism of toxicity, EPA has not made a common mechanism of
toxicity finding as to sethoxydim and any other substances and sethoxydim does not
appear to produce a toxic metabolite produced by other substances. For the purpose of
this assessment, EPA has not assumed that sethoxydim shares a common mechanism of
toxicity with other substances. For information regarding EPA's efforts to determine
which chemicals have a common mechanism of toxicity and to evaluate the cumulative
effects of such chemicals, see the policy statements released by EPA's Office of Pesticide
Programs at http://www.epa.gov/pesticides/cumulative/.
H. Occupational Risk
For more detailed information, see "Sethoxydim: Occupational and Residential
Exposure Assessment and Recommendations for the Reregistration Eligibility Decision
Document"; W. Britton; 6/22/05.
Pesticide handlers are likely to be exposed during the occupational use of
sethoxydim in a variety of occupational environments. Since no chemical-specific
-------
handler exposure data are available for sethoxydim, short- and intermediate-term
inhalation exposures were assessed using data from the Pesticide Handlers Exposure
Database (PHED) Version 1.1. PHED data were used with other Agency standard values
for areas treated per day, body weight and the level of personal protective equipment
(PPE) and engineering controls to assess handler exposures to sethoxydim. Using these
assumptions, the calculated occupational handler inhalation risks do not exceed EPA's
level of concern (i.e., MOEs > 100) for all exposure scenarios. Short- and intermediate-
term inhalation MOEs range from 3,100 (right-of-way sprayer application) to more than
1,900,000 (mixing/loading/applying liquids for low pressure handwand application) at
baseline, i.e., no respirator. Dermal exposure was not assessed because a dermal
endpoint of concern has not been identified for sethoxydim.
Post-application exposure was not assessed because there is no dermal endpoint
of concern and post-application inhalation exposure is expected to be negligible.
IV. Ecological Risk Assessment
For more detailed information, see "EFED 's Reregistration Eligibility Decision
Chapter for Sethoxydim Screening"; Michael Davy, et al; 6/22/2005.
A. Environmental Fate and Transport
Sethoxydim has a high solubility and mobility with a low octanol/water partition
coefficient. Sethoxydim is unlikely to contaminate ground or surface waters because it is
not persistent under most conditions. Under aerobic conditions, half-lives were <1 day.
However, the sethoxydim transformation products may be persistent and mobile enough
to cause a potential threat to water resources. The transformation mechanisms of parent
sethoxydim and residues include: photodegradation; aerobic metabolism in water and
soil; and acid-catalyzed hydrolysis in water.
B. Aquatic Organism Risk
The technical sethoxydim acute LOCs for fish and aquatic invertebrates are not
exceeded (at application rate of 0.47 Ib/A).
Chronic aquatic data submitted for estuarine fish and invertebrates indicate that
chronic risks to estuarine animals are below the Agency's level of concern. Chronic data
for freshwater fish and invertebrates are not available to the Agency. Therefore, a risk
assessment for freshwater fish and invertebrates can not be conducted at this time.
Sethoxydim is known to be phytotoxic to terrestrial grasses, but aquatic grasses
(monocots) were not tested for their response to sethoxydim; thus we cannot make a
definitive assessment of the risk to vascular aquatic plants. The tested species (duckweed)
is a dicot, and is not expected to be sensitive to sethoxydim (at the maximum exposure rate
of 0.47 Ib ai/A). However, adverse effects to aquatic monocots cannot be precluded.
10
-------
C. Terrestrial Organism Risk
The Agency assessed exposure to terrestrial organisms by first predicting the
amount of sethoxydim residues found on animal food items and then by determining the
amount of pesticide consumed by using information on typical food consumption by
various species of birds and mammals. The amount of residues estimated to be found on
animal feed items is based on the Fletcher nomogram (a model developed by Fletcher,
Hoerger, Kenaga, et al.) and the current maximum application rate for sethoxydim.
Terrestrial wildlife exposure estimates are typically calculated for birds and
mammals, emphasizing a dietary exposure route for uptake of pesticides. These
exposures are considered as surrogates for terrestrial-phase amphibians as well as
reptiles. For acute exposure to terrestrial organisms, such as birds and small mammals,
pesticide residues on food items are estimated, based on maximum application rate and
estimated residues at the time of application. Degradation is factored into chronic
exposure calculations.
Since sethoxydim is practically non-toxic to birds on an acute basis, we presume
that birds are not at acute risk. When maximum EECs are considered, all chronic RQ
values for birds exceed the LOG of 1.0 for most food items. However, when mean EECs
were considered, the chronic LOG was exceeded only for animals consuming short grass
from applications to citrus and tree nut sites. The highest modeled RQs were for citrus
and tree nut sites, where the RQ for the short grass scenario based on maximum EECs
was >3.12, assuming a default foliar half-life of 35 days. RQs calculated for maximum
and mean EECs for various crops and food items are given in Table 7
Table 7: Avian Organism Chronic Risk Quotient (Chronic Level of Concern = 1)
Site (not inclusive)
Citrus, tree nuts
Alfalfa, birdfoot trefoil, sainfoin,
clover, cotton,
Fruiting and leafy vegetable crop group
No. of
Apps.
4
3
3
App.Rate
(Ibs ai/A)
0.47
0.47
0.28
Food Items
Short grass
Tall grass
Broadleaf
plants/Insect
Seeds
Short grass
Tall grass
Broadleaf
plants/Insect
Seeds
Short grass
Tall grass
Broadleaf
plants/Insect
Seeds
Avian Chronic Risk Quotient
based on Max. EEC and
NOAEC < 100 ppm1
>3.12
>1.43
>1.76
>0.20
>2.63
>1.21
>1.48
>0.16
>1.57
>0.72
>0.88
>0.10
Avian Chronic Risk Quotient
based on Mean EEC and
NOAEC < 100 ppm
>1.11
>0.47
>0.59
>0.09
>0.93
>0.39
>0.49
>0.08
>0.56
>0.24
>0.29
>0.05
11
-------
Site (not inclusive)
Soybeans, grape, berries, peanut, Head
& petiole vegetable crop subgroup,
mint, pea, potato, safflower, sugar
beets, Christmas tree farms,
ornamentals, rights of way, roadsides,
turf
Orchard floor middles, strawberry,
sunflower
No. of
Apps.
2
1
App.Rate
(Ibs ai/A)
0.47
0.47
Food Items
Short grass
Tall grass
Broadleaf
plants/Insect
Seeds
Short grass
Avian Chronic Risk Quotient
based on Max. EEC and
NOAEC < 100 ppm1
>1.98
>0.91
>1.12
>0.12
>1.13
Avian Chronic Risk Quotient
based on Mean EEC and
NOAEC < 100 ppm
>0.70
>0.30
>0.37
>0.06
>0.40
* Assuming NO AEC<100ppm.
Technical sethoxydim is practically non-toxic to mammals on an acute basis and
no risks are expected for maximum label rates. The chronic RQs for mammals did not
exceed the LOG of 1.0 with a maximum RQ of 0.5 at the highest exposure level.
Sethoxydim is practically non-toxic to honey bees. Adverse effects to beneficial
insects are not expected at maximum label rates.
For terrestrial plants, sethoxydim is selectively toxic to grasses, which are
monocot plants, and is not particularly toxic to dicots. Based on the screening risk
assessment, there is a risk to non-target grasses.
Based on modeled EECs and the available toxicity data, RQ values for all uses of
sethoxydim application scenarios exceed the LOG for listed and non-listed non-target
terrestrial plants and terrestrial plants in semi-aquatic areas. RQs resulting from spray
drift are not of concern, but RQs resulting from run-off scenarios for non-listed plants
range from 1.3 to 3.1 and RQs for listed plants range from 1.7 to 4.1. These risks were
calculated from toxicity values from the technical product and not the formulated
product. Plant risks are generally calculated from formulated product and, therefore,
these RQs may underestimate the risks to terrestrial plants from use of sethoxydim due to
presence of solvents in end-use products.
D. Risk Characterization
The Agency usually assesses ecological risks for animals on the technical active
ingredient only. As described in the ecological risk assessment section, the parent
compound does not pose a risk to the aquatic environment. However, for sethoxydim,
the Agency had some additional aquatic organism toxicity studies conducted with the
formulated products which contained two chemical stressors: the first is the active
ingredient; sethoxydim and its degradates; and the second stressor is the petroleum
solvent used in some end-use formulations including POAST® and POAST® Plus. This
solvent is known to contain several percent by weight of naphthalene, which is also a
registered active ingredient (PC code 055801). Naphthalene will be considered in a
separate reregi strati on eligibility decision (RED scheduled for March, 2008). In these
studies, the Agency assumes that sethoxydim is the stressor responsible for most
12
-------
observed effects to plants and birds, and the petroleum solvent is the stressor responsible
for most observed effects risks to fish and aquatic invertebrates (fresh- and salt-water).
While technical sethoxydim is practically non-toxic to fish and invertebrates on
an acute basis, an 18% Typical End-Use product (TEP) is moderately toxic to these
organisms. The formulation of the TEP contains a petroleum solvent (CAS Registry. No.
64742-94-5) that is known to contain naphthalene. Acute toxicity data for naphthalene
indicate that it has toxicity similar to that of the TEP. Thus, any acute risk to aquatic
freshwater or estuarine animals from the use of sethoxydim formulated with this
petroleum solvent may be in fact attributable to the solvent. The estuarine chronic
studies which resulted in low toxicity were also conducted with formulated products, but
the solvent content in these formulations is unknown.
Since, the avian chronic reproduction study with the active ingredient did not
achieve a no effect level, chronic avian toxicity may be underestimated. However, RQs
were generally not of concern even though conservative exposure assumptions were used
for calculation purposes.
The estimated risk to non-target plants may be underestimated due to lack of valid
vegetative vigor studies conducted with a Typical End Use product (TEP). Using the TEP
in terrestrial plant studies is important because most herbicides use adjuvants to penetrate
the plant cuticle and other plant defenses in order to get the active ingredient into the
plant to adversely affect the plant. Another tier II vegetative vigor study conducted with
a TEP on at least three grass species including corn should be conducted to assess risk to
non-target grass species. Although there are currently no data which will allow
comparison of toxicity between technical sethoxydim and the TEP, both appear to be
phytotoxic to grass species only. There are no data available to the Agency which would
allow comparison of toxicity between the technical active ingredient and a TEP.
E. Endangered Species Concerns
The risk profile for various taxa varies based upon whether assessments were
performed using data from studies conducted with the active ingredient or a formulated
product. Based on data obtained from studies using the active ingredient, the screening
level ecological risk assessment for endangered species resulted in a determination that
sethoxydim results in no direct effects, either chronic or acute, to: mammals; aquatic
phase amphibians; mollusks; and marine/estuarine fish and crustaceans. There also are
no direct acute effects to avian species, freshwater fish and crustaceans, and no direct
effects to terrestrial and semi-aquatic dicots. A bee toxicity study indicted that
sethoxydim technical is practically non-toxic to bees on an acute contact basis which
implies there is likely not a direct acute effect to insects.
The Agency's levels of concern is exceeded for direct chronic effects to birds, and
effects to terrestrial and semi-aquatic monocots. Testing on aquatic plants is only
required on Lemna gibba, a dicotyledonous species, which did not demonstrate effects.
However, effects to aquatic grasses can not be ruled out. Reptiles and terrestrial phase
13
-------
amphibians are not tested but are assumed to have potential effects similar to the effects
observed in birds. Based on the exceedence of the LOG for direct chronic effects to bird,
effects to reptiles and to terrestrial phase amphibians can not be ruled out based on the
screening level assessment. Additionally, there are no data to assess potential chronic
effects to freshwater fish and crustaceans and therefore, chronic risk to these species can
not be ruled out. Further, indirect effects can not be ruled out for any species that
depends upon a taxa that may experience direct effects.
Even given the determinations above, because there are uncertainties regarding
the potential toxicity of the TEPs, and the potential exposure from spray drift to shallow
bodies of water, direct acute effects can not be precluded at this time to freshwater fish
and crustaceans, aquatic phase amphibians, mollusks, marine/estuarine fish and
marine/estuarine crustaceans (see section C. Aquatic Organism Risk to Formulated
Product, above).
These findings are based solely on EPA's screening level assessments and do not
constitute "may affect" findings under the Endangered Species Act.
V. Risk Mitigation Summary
The Agency is not requiring any additional risk-based mitigation measures for
sethoxydim at this time. The sethoxydim database is sufficient to perform the necessary
risk assessments. The chemical's toxicity, when reviewed in conjunction with the current
use patterns, does not result in the need to impose additional label restrictions under
FIFRA at this time. However, additional data are required in order to confirm the risk
conclusions reached in this document. The tolerance revision actions outlined in Table 8
below are necessary based on the legal requirements of FIFRA, FFDCA and FQPA,
despite the absence of dietary risk. No additional tolerances are considered reassessed as
a result of this RED.
For worker risks, per the Worker Protection Standard, a 12-hour restricted entry
interval (REI) is required for chemicals classified as acute Toxicity Category III for
dermal toxicity and IV for skin and eye irritation. Sethoxydim is classified in Toxicity
Category III for acute oral, dermal and inhalation, and Toxicity Category IV for and
primary eye and skin irritation; therefore, the current REI of 12 hours is appropriate and
will remain on labels. This assessment also confirms that the baseline PPE currently on
sethoxydim labels is still adequate for this chemical, and no changes to the labeled PPE
statements are required.
A. Tolerance Reassessment
For more detailed information, see "Sethoxydim. HED Chemistry Chapter of the
Registration Eligibility Decision (RED)"; W. Donovan; 9/27/2005.
Tolerances have been established under 40 CFR §180.412 for the combined
residues of sethoxydim [2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-
cyclohexen-1-one] and its metabolites containing the 2-cyclohexene-l-one moiety
14
-------
(calculated as sethoxydim) in or on numerous plant and animal, food and feed
commodities. The completion of the sethoxydim RED does not result in any additional
tolerances being reassessed since all existing tolerances (85) were reassessed at the time a
new food use was established for sethoxydim [63FR54066 (10/8/1998)]. See Table 8,
below, for a summary of the sethoxydim tolerances.
Table 8. Tolerance Reassessment Summary for Sethoxydim
Commodity
Alfalfa forage
Alfalfa hay
Almond, hulls
Apple, dry pomace
Apple, wet pomace
Apricot
Artichoke, globe
Asparagus
Bean, dry, seed
Bean, forage
Bean, hay
Bean, succulent
Beet, garden
Beet, sugar, molasses
Beet, sugar, roots
Beet, sugar, tops
Blueberry
Caneberry subgroup
Canola/rapeseed
Canola/rapeseed, meal
Carrot
Cattle, fat
Cattle, meat
Cattle, meat byproducts
Cherry, sweet
Cherry, tart
Citrus, dried pulp
Citrus, molasses
Clover, forage
Clover, hay
Coriander
Corn, field, grain
Corn, forage
Corn, fodder
Corn, sweet, forage
Corn, sweet, kernel plus cob
Corn, sweet, stover
Cotton, seed, soapstock
Cotton, undelinted seed
Cranberry
Egg
Established
Tolerance
(ppm)
40
40
2
0.8
0.8
0.2
5
4
20
15
50
15
1
10
1
3
4
5
35
40
1
0.2
0.2
1
0.2
0.2
1.5
1.5
35
50
4
0.5
2
2.5
o
J
0.4
3.5
1.5
5
2
2
Tolerance
Reassessment
(ppm)
40
40
2
0.80
Revoke
0.2
5
4
Revoke
15
50
15
1
10
1
3
4
5
35
40
1
0.2
0.2
1
0.2
0.2
1.5
Revoke
35
55
4
0.5
2
2.5
3
0.4
3.5
Revoke
5
2.5
2
Comments (correct commodity
definition)
Apple, dried pomace
Revoke: not a significant feedstuff
Tolerance with Regional Registration
Included in subgroup 6C
Cowpea, forage
Cowpea, hay
Beet, garden, roots
Caneberry subgroup 13 A
Rapeseed, seed
Rapeseed, meal
Revoke: not a significant feedstuff
The maximum residue observed was 50.7
ppm
Coriander, leaves
Corn, field, forage
Corn, field, stover
Revoke: not a significant feedstuff
The maximum residue observed was 2.2
ppm
15
-------
Commodity
Flax, meal
Flax, seed
Flax, straw
Fruit, citrus
Fruit, pome
Goat, fat
Goat, meat
Goat, meat byproducts
Grape
Grape, raisin
Hog, fat
Hog, meat
Hog, meat byproducts
Horse, fat
Horse meat
Horse, meat byproducts
Horseradish
Juneberry
Lentil, seed
Lingonberry
Milk
Nectarine
Peach
Peanut
Peanut, soapstock
Pea and bean, dried shelled,
except soybean, subgroup 6C
Pea, dry, seed
Pea, field, hay
Pea, field, vines
Pea, succulent
Peppermint, tops (stems and
leaves
Pistachio
Potato, flakes
Potato, granules
Potato waste, processed (wet
and dry)
Poultry, fat
Poultry, meat
Poultry, meat byproducts
Rhubarb
Safflower
Salal
Sheep, fat
Sheep, meat
Sheep, meat byproducts
Soybean
Soybean, hay
Spearmint, tops (stems and
Established
Tolerance
(ppm)
7
5
2
0.5
0.2
0.2
0.2
1
1
2
0.2
0.2
1
0.2
0.2
1
4
5
30
5
0.5
0.2
0.2
25
75
—
40
40
20
10
30
0.2
8
8
8
0.2
0.2
2
0.3
15
5
0.2
0.2
1
16
10
30
Tolerance
Reassessment
(ppm)
Revoke
5
Revoke
0.5
0.2
0.2
0.2
1
1
2
0.2
0.2
1
0.2
0.2
1
4
5
Revoke
5
0.5
0.2
0.2
25
Revoke
25
Revoke
40
20
10
30
0.2
8
8
0.2
0.2
2
0.3
15
5
0.2
0.2
1
16
10
30
Comments (correct commodity
definition)
Revoke: Covered by flax, seed tolerance
Revoke: not a significant feedstuff
Fruit, citrus, group 10
Fruit, pome, group 1 1
Included in subgroup 6C
Revoke: not a significant feedstuff
Supported by dry pea and dry bean data
and tolerance spreadsheet results
Included in subgroup 6C
Pea, field, forage
Peppermint, tops
Combine these two tolerance expressions
into the following: Potato, granules/flakes
Potato, processed potato waste
Tolerance with Regional Registration
Safflower, seed: Two additional safflower
field trials are needed from Region 10.
Soybean, seed
Spearmint, tops
16
-------
Commodity
leaves
Strawberry
Sunflower, meal
Sunflower, seed
Tomato, concentrated products
Tomato, dry pomace
Tree nut
Vegetable, brassica, leafy,
group 5
Vegetable, bulb, group 3
Vegetable, cucurbit, group 9
Vegetable, fruiting, group 8
Vegetable, leafy, except
brassica, group 4
Tuberous and corn vegetable
crop subgroup
Established
Tolerance
(ppm)
10
20
7
24
12
0.2
5
1
4
4
4
4
Tolerance
Reassessment
(ppm)
10
20
7
Revoke
Revoke
0.2
5
1
4
4
4
4
Comments (correct commodity
definition)
Revoke: not a significant feedstuff
Revoke: not a significant feedstuff
Nut, tree, group 14
Vegetable, cucurbit, group 9
Vegetable, fruiting, group 8
Vegetable, leafy, except Brassica , group
4
Vegetable, tuberous and corm, subgroup
1C
In an attempt to improve sethoxydim tolerance harmonization between the US
and Canada, the Agency has reexamined the residue data and tolerance levels for pulse
crops. The residue data for dry peas and dry beans reflect identical use patterns and are
sufficient to support a tolerance for crop subgroup 6C, "Pea and bean, dried shelled,
except soybean, subgroup 6C". Inserting the field trial data for dry beans and dry peas
into the tolerance spreadsheet devised by the NAFTA Tolerance/MRL Harmonization
Workgroup results in a recommended tolerance level of 25 ppm for subgroup 6C.
Accordingly, the Agency recommends for the establishment of this tolerance level, while
the separate tolerance levels for dry pea, dry bean and lentil are revoked since these crops
are covered by the crop subgroup tolerance. Harmonization between the US tolerance
and the Canadian MRL is under consideration between EPA and Canada's Pest
Management Regulatory Agency (PMRA). The US use pattern specifies a 30-day PHI
while the Canadian use pattern specifies a 60-day PHI.
The limited field accumulation study indicated that residues were below the limit
of quantitation (0.1 or 0.2 ppm LOQ) of the enforcement method in all rotational crop
RACs at all plantback intervals. Since residues in rotational crops are expected to be
below the limit of quantitation of the method, tolerances are not required for rotational
crops planted greater than 30 days after the primary crop is treated with sethoxydim. The
associated label language for this restriction has been submitted by the registrant and
approved by the Agency since the revised risk assessments were completed.
B. Data Gaps
Ecological Data Requirements
850.4525 Seedling emergence (using TEP)
850.2300 Avian Reproductive
17
-------
850.1400 Early-life stage Estuarine Fish (using 40% TEP or the technical
sethoxydim)
850.1350 Life Cycle Aquatic Invertebrate
850.4225 Seedling Emergence
850.4250 Vegetative Vigor (Partial)
850. SS1 Vascular aquatic plant toxicity for grasses (using TEP)
Residue Chemistry
860.1500 Two safflower field trials from Region 10
C. Endangered Species
Potential risks to listed species from the use of sethoxydim are based on a
screening level ecological risk assessment and the findings do not constitute "may affect"
findings under the Endangered Species Act. Thus, EPA is not imposing any mitigation at
this time. However, should EPA's endangered species-specific assessment indicate that
use of sethoxydim "may affect" listed species, then changes to the registered uses of
sethoxydim may need to be made as noted below.
The Agency has developed the Endangered Species Protection Program to
identify pesticides whose use may cause adverse impacts on endangered and threatened
species, and to implement mitigation measures that address these impacts. The
Endangered Species Act (ESA) requires federal agencies to ensure that their actions are
not likely to jeopardize listed species or adversely modify designated critical habitat. To
analyze the potential of registered pesticide uses that may affect any particular species,
EPA uses basic toxicity and exposure data developed for the REDs and considers it in
relation to individual species and their locations by evaluating important ecological
parameters, pesticide use information, geographic relationship between specific pesticide
uses and species locations, and biological requirements and behavioral aspects of the
particular species, as part of a refined species-specific analysis.
Following this future species-specific analysis, a determination that sethoxydim
may affect a listed species or adversely modify its critical habitat may result in:
limitations on the use of sethoxydim, other measures to mitigate any potential impact, or
consultations with the Fish and Wildlife Service or the National Marine Fisheries Service
as necessary. If the Agency determines use of sethoxydim "may affect" listed species or
their designated critical habitat, EPA will employ the provisions in the Services
regulations (50 CFR Part 402). EPA is not requiring specific sethoxydim label language
at the present time relative to threatened and endangered species. If, in the future,
specific measures are necessary for the protection of listed species, the Agency will
implement them through the Endangered Species Protection Program.
18
-------
D. Conclusions
The Agency is issuing this Reregi strati on Eligibility Document (RED) for
sethoxydim, as announced in a Notice of Availability published in the Federal Register.
This RED does not include any requirements to amend sethoxydim product label
language. The Agency has determined that all currently registered uses of sethoxydim
are eligible for reregi strati on. The completion of the sethoxydim RED does not result in
any additional tolerances being reassessed since all existing tolerances (85) were
reassessed at the time a new food use was established for sethoxydim [63FR54066
(10/8/1998)].
19
------- |