Interim Reregistration
Eligibility Decision for
Dimethoate
June 12, 2006
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3:
33
\
UJ
C3
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON D.C., 20460
OFFICE OF
PREVENTION, PESTICIDES AND TOXIC
SUBSTANCES
MEMORANDUM
DATE: July 31,2006
SUBJECT: Finalization of Interim Reregi strati on Eligibility Decisions (IREDs) and Interim
Tolerance Reassessment and Risk Management Decisions (TREDs) for the
Organophosphate Pesticides, and Completion of the Tolerance Reassessment and
Reregi strati on Eligibility Process for the Organophosphate Pesticides
FROM: Debra Edwards, Director
Special Review and Reregi strati on Division
Office of Pesticide Programs
TO: Jim Jones, Director
Office of Pesticide Programs
As you know, EPA has completed its assessment of the cumulative risks from the
Organophosphate (OP) class of pesticides as required by the Food Quality Protection Act of
1996. In addition, the individual OPs have also been subject to review through the individual-
chemical review process. The Agency's review of individual OPs has resulted in the issuance of
Interim Reregi strati on Eligibility Decisions (IREDs) for 22 OPs, interim Tolerance
Reassessment and Risk Management Decisions (TREDs) for 8 OPs, and a Reregi strati on
Eligibility Decision (RED) for one OP, malathion.l These 31 OPs are listed in Appendix A.
EPA has concluded, after completing its assessment of the cumulative risks associated
with exposures to all of the OPs, that:
(1) the pesticides covered by the IREDs that were pending the results of the OP
cumulative assessment (listed in Attachment A) are indeed eligible for reregistration; and
Malathion is included in the OP cumulative assessment. However, the Agency has issued a RED for malathion,
rather than an IRED, because the decision was signed on the same day as the completion of the OP cumulative
assessment.
Page 1 of 3
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(2) the pesticide tolerances covered by the IREDs and TREDs that were pending the
results of the OP cumulative assessment (listed in Attachment A) meet the safety standard under
Section 408(b)(2) of the FFDCA.
Thus, with regard to the OPs, EPA has fulfilled its obligations as to FFDCA tolerance
reassessment and FIFRA reregi strati on, other than product-specific reregi strati on.
The Special Review and Reregi strati on Division will be issuing data call-in notices for
confirmatory data on two OPs, methidathion and phorate, for the reasons described in detail in
the OP cumulative assessment. The specific studies that will be required are:
- 28-day repeated-dose toxicity study with methidathion oxon; and
- Drinking water monitoring study for phorate, phorate sulfoxide, and phorate sulfone
in both source water (at the intake) and treated water for five community water
systems in Palm Beach County, Florida and two near Lake Okechobee, Florida.
The cumulative risk assessment and supporting documents are available on the Agency's website
at www.epa.gov/pesticides/cumulative and in the docket (EPA-HQ-OPP-2006-0618).
Page 2 of 3
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Attachment A:
Organophosphates included in the OP Cumulative Assessment
Chemical
Acephate
Azinphos-methyl (AZM)
Bensulide
Cadusafos
Chlorethoxyphos
Chlorpyrifos
Coumaphos
DDVP (Dichlorvos)
Diazinon
Dicrotophos
Dimethoate
Disulfoton
Ethoprop
Fenitrothion
Malathion
Methamidophos
Methidathion
Methyl Parathion
Naled
Oxydemeton-methyl
Phorate
Phosalone
Phosmet
Phostebupirim
Pirimiphos-methyl
Profenofos
Propetamphos
Terbufos
Tetrachlorvinphos
Tribufos
Trichlorfon
Decision Document
IRED
IRED
IRED
TRED
TRED
IRED
TRED
IRED
IRED
IRED
IRED
IRED
IRED
TRED
RED
IRED
IRED
IRED
IRED
IRED
IRED
TRED
IRED
TRED
IRED
IRED
IRED
IRED
TRED
IRED
TRED
Status
IRED completed 9/2001
IRED completed 10/2001
IRED completed 9/2000
TRED completed 9/2000
TRED completed 9/2000
IRED completed 9/2001
TRED completed 2/2000
IRED completed 6/2006
IRED completed 7/2002
IRED completed 4/2002
IRED completed 6/2006
IRED completed 3/2002
IRED completed 9/2001
IRED addendum completed 2/2006
TRED completed 10/2000
RED completed 8/2006
IRED completed 4/2002
IRED completed 4/2002
IRED completed 5/2003
IRED completed 1/2002
IRED completed 8/2002
IRED completed 3/2001
TRED completed 1/2001
IRED completed 10/2001
TRED completed 12/2000
IRED completed 6/2001
IRED completed 9/2000
IRED completed 12/2000
IRED completed 9/2001
TRED completed 12/2002
IRED completed 12/2000
TRED completed 9/2001
Page 3 of 3
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Interim Reregistration Eligibility Decision
for
Dimethoate
List [B]
Case No. 0088
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Interim Reregistration Eligibility Decision (IRED)
Document for Dimethoate
Approved by:
Debra Edwards, Ph. D.
Director
Special Review and Reregistration Division
Date:
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Table of Contents
Dimethoate Interim Reregistration Eligibility Decision Team i
Glossary of Terms and Abbreviations ii
II. Chemical Overview 2
A. Regulatory History 2
B. Chemical Identification 3
C. Use Profile 3
III. Summary of Dimethoate Risk Assessments 5
A. Human Health Risk Assessment 5
1. Toxicity of Dimethoate 6
2. Dietary Exposure and Risk from Food and Water 9
3. Residential and Other Non-occupational Risk 12
4. Aggregate Exposure and Risk 13
5. Occupational Exposure and Risk 13
6. Human Incident Data 18
B. Environmental Risk Assessment 18
1. Environmental Exposure 18
2. Environmental Effects (Hazard) 20
3. Ecological Risk Estimation 23
4. Ecological Incidents 28
5. Risk Characterization 28
6. Endangered Species Considerations 30
IV. Interim Risk Management, Reregistration, and Tolerance Reassessment
Decision 30
A. Determination of Reregistration Eligibility 30
B. Public Comments and Responses 31
C. Regulatory Position 31
1. Food Quality Protection Act Findings 31
2. Interim Tolerance Summary 33
D. Regulatory Rationale 37
1. Significance of Use 43
2. Spray Drift 44
3. Endangered Species Considerations 44
V. What Registrants Need to Do 45
A. Manufacturing Use Products 47
1. Additional Generic Data Requirements 47
B. End-Use Products 48
1. Additional Product-Specific Data Requirements 48
2. Labeling for End-Use Products 48
Labeling Changes Summary Table 49
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Dimethoate Interim Reregistration Eligibility Decision Team
Office of Pesticide Programs:
Biological and Economic Analysis Assessment
Nikhil Mallampalli
Elisa Rim
Environmental Fate and Effects Risk Assessment
R. David Jones
Thomas Steeger
Health Effects Risk Assessment
Byong-Han (Paul) Chin
David Hrdy
Christina Jarvis
Diana Locke
Anna Lowit
Alan Nielsen
Registration Support
Dan Kenny
Anne Hanger
Risk Management
Stephanie Plummer
Laura Parsons
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Glossary of Terms and Abbreviations
AGDCI
ai
aPAD
AR
BCF
CFR
cPAD
CSF
CSFII
DCI
DEEM
EC
EDWC
EEC
EPA
EUP
FCID
FDA
FIFRA
FFDCA
FQPA
FOB
G
GENEEC
GLN
HAFT
IR
LD
50
LOC
LOD
LOAEL
MATC
Og/L
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
Emulsifiable Concentrate Formulation
Estimated Drinking Water Concentration
Estimated Environmental Concentration
Environmental Protection Agency
End-Use Product
Food Commodity Intake Database
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
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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
TAP
TCPSA
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)
Toxicity Adjustment Factor
2,3,3-trichloroprop-2-ene sulfonic acid (nitrapyrin Metabolite)
Technical Grade Active Ingredient
Total Radioactive Residue
United States Department of Agriculture
United States Geological Survey
Uncertainty Factor
Ultraviolet
Worker Protection Standard
in
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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 by the U.S. Environmental Protection Agency (hereafter referred to as
EPA or the Agency). 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 the pesticide, 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.
On August 3, 1996, the Food Quality Protection Act of 1996 (FQPA) was signed
into law. This Act amends FIFRA to require reassessment of all tolerances in effect on
the day before it was enacted by August 2006. EPA decided that, for those chemicals
that have tolerances and are undergoing reregi strati on, tolerance reassessment will be
accomplished through the reregi strati on process. FQPA also amended the Federal Food,
Drug, and Cosmetic Act (FFDCA) to require a safety finding in tolerance reassessment
based on factors that include an assessment of cumulative effects of chemicals with a
common mechanism of toxicity. The reason for consideration of other substances is that
the possibility exists that low-level exposures to multiple chemicals that cause a common
toxic effect lead to the same adverse health effect as would a high level of exposure to
any one of the other substances individually.
As mentioned above, FQPA requires EPA to consider "available information"
concerning the cumulative effects of a particular pesticide's residues and "other
substances that have a common mechanism of toxicity" when considering whether to
establish, modify, or revoke a tolerance. Dimethoate is a member of the organophosphate
(OP) class of pesticides. The OPs, as a group, have been determined to share a common
mechanism of toxicity. The Agency has completed a revised cumulative risk assessment
for OPs (USEPA, 2002), which can be found on the Agency's website
http://www.epa.gov/pesticides/cumulative/rra-op/. The Agency intends to issue the final
tolerance reassessment reregi strati on decisions for dimethoate and the OPs in August
2006. The Agency may need to pursue further risk mitigation for dimethoate to address
any risks identified in the cumulative assessment for the OPs.
This document presents EPA's revised human health and ecological risk assessments
and its progress toward tolerance reassessment, and the interim reregi strati on eligibility
decision for dimethoate. The document consists of six sections: section I contains the
regulatory framework for reregi strati on/tolerance reassessment; section II provides a
profile of the use and usage of the chemical; section III gives an overview of the revised
human health and environmental effects risk assessments based on data, public
comments, and other information received in response to the preliminary risk
assessments, section IV presents the Agency's reregi strati on eligibility, tolerance
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reassessment, and risk management decisions; section V summarizes label changes
necessary to implement the risk mitigation measures outlined in Section IV; and section
VI provides information on how to access related documents. Finally, the Appendices
list related and supporting documents and Data Call-In (DCI) information. The revised
risk assessment documents and related addenda are not included in this document, but are
available on the Agency's web page http://www.epa.gov/pesticides, and in the Public
Docket under docket number EPA-HQ-OPP-2005-0084.
II. Chemical Overview
A. Regulatory History
Dimethoate is a systemic organophosphate insecticide used on a large variety of
field grown agricultural crops, tree crops, and ornamentals. It was first registered in the
United States in 1962. All non-agricultural uses, including residential uses, were
cancelled in 2000. In addition, seven crops that were identified as significant dietary risk
contributors (apples, broccoli raab, cabbage, collards, grapes, head lettuce, and spinach),
along with four crops for which there were no field trial data to support tolerances
(fennel, lespedeza, tomatillo, and trefoil) were cancelled in 2005 (Federal Register
Notice/Vol. 70, No. 138/Wednesday, July 20, 2005/Notices/41714). None of these crops
were considered in the current risk assessments. Dimethoate is classified as a general use
pesticide, and is applied using ground and aerial equipment. About 1.8 million pounds of
active ingredient are used annually, with the largest use occurring on alfalfa. Use on four
major crops - alfalfa, wheat, cotton, and corn - account for more than 64% of total
dimethoate use.
There are currently 40 products containing dimethoate registered under Section 3
of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). There are also 39
active Special Local Need registrations registered under Section 24(c) of FIFRA. This
Interim Reregi strati on Eligibility Decision document evaluates risks from all currently
registered uses.
EPA released the revised human health and ecological risk assessments for a third
round of public comments on September 6, 2005. Prior to this, the last public comment
period had occurred in 1999, at which time the registrant submitted a developmental
neurotoxicity study. The results of that study necessitated major revisions to the risk
assessments.
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B.
Chemical Identification
Chemical Structure:
H \
S N - --—--~ _' P
H,C ' >r s - \
Common Name:
Chemical Name:
Chemical Family:
Empirical Formula:
CAS Registry Number:
Case Number:
OPP Chemical Code:
Molecular weight:
Trade Names:
Basic Manufacturers:
Dimethoate
O, O-dimethyl ^-(jV-methylcarbamoylmethyl)
phosphorodithioate
Organophosphate
C5Hi2NO3PS2
60-51-5
0088
035001
229.3
Digon, Duragon, Rebelate, Dimate
Cheminova, BASF Corporation, Drexel Chemical Co.
Dimethoate is a white crystalline solid with a mercaptan odor and a melting point
of 45-48° C. It is soluble in water at 25 g/L at 21° C, is highly soluble in chloroform,
methylene chloride, benzene, toluene, alcohols, esters, and ketones, and is only slightly
soluble in xylenes, carbon tetrachloride, and aliphatic hydrocarbons. Dimethoate is also
stable in aqueous solutions at pH 2-7, but hydrolyzes in alkaline media.
The major toxic degradate of dimethoate is omethoate (0,0-dimethyl S-(N-
methylcarbamoylmethyl) phosphorothioate). Omethoate is registered as an active
ingredient internationally, but not in the United States.
C.
Use Profile
The following is information on the currently registered uses of dimethoate,
including an overview of use sites and application methods. A detailed table on the uses
of dimethoate eligible for reregi strati on is contained in Appendix A.
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Type of Pesticide: General use systemic insect!cide/acaricide
Summary of Use: Used for control of a variety of insect pests on a number of
fruit, vegetable, grain, and field crops, as well as ornamentals
and non-cropland adjacent to agricultural fields
Food uses: Registered for use on the following crops/sites:
Alfalfa, asparagus, beans (excluding cowpeas), broccoli, Brussels sprouts, cauliflower,
celery, cherries, Chinese cabbage, cotton, endive, field corn, grapefruit, leaf lettuce,
lemons, lentils, kale, melons, mustard greens, oranges, pears, peas, pecans, peppers,
popcorn, potatoes, safflower, sorghum, soybeans, Swiss chard, tangerines, tangelos,
tomatoes, turnips, watermelons, wheat
Non-food uses:
Alfalfa for seed, forestry applications, grass for seed, non-crop land adjacent to
vineyards, nursery stock (including conifer seed farm uses), ornamentals (various)
Uses not supported for reregi strati on:
Food crops: kohlrabi, lupine, sainfoin, triticale
Non-agricultural uses - cottonwoods grown for pulp, outdoor household domestic
dwelling (ornamentals and shrubs), recreational areas, outdoor
commercial/institutional/industrial premises, outdoor refuse/solid waste, phragmites reed
beds, and sewage treatment systems
Target Pests: Aphids, citrus thrips, grasshoppers, leafminers, mites,
whiteflies, beetles, weevils, midges, scale, fruitworms,
moths, leafrollers, rootworms, mealybugs, leafhoppers,
lygus bugs, and maggots
Formulation Types: Emulsifiable concentrate and wettable powder end-use
products
Method and Rates of Application:
Application Methods: Applied primarily as a foliar spray, although soil
and bark drench uses are registered
Application Equipment: Aircraft, groundboom, airblast, chemigation,
backpack sprayer, low pressure handwand, and soil
drench equipment, sprinkler can and paint brush
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Application Rates: Currently labeled use rates vary from a minimum of
0.16 Ibs a.i./acre to a maximum of 33.2 Ibs. a.i./acre
per application. Many labels do not specify
numbers of applications, but typically 1 to 6
applications per year are made. For most crops, the
maximum application rate is 0.5 Ibs a.i./acre with
typically 3 applications made per year. Note that
Douglas fir seed orchards in Oregon and
Washington, pinyon pine, and cottonwood
application rates range from 8.0 Ibs a.i./acre to 33.2
Ib a.i./acre with one application per year.
Application Timing: Bearing, early spring, foliar, non-bearing
nurserystock, nurserystock, petal fall, petal fall
through foliar, postharvest, postplant, preharvest,
seed, seed crop, when needed
Use Classification: General
D. Estimated Usage of Pesticide
The estimate for total domestic use (annual average) of dimethoate is
approximately 1.8 million pounds of active ingredient, with the majority of use occurring
on the following crops: wheat, alfalfa, cotton, and corn.
III. Summary of Dimethoate Risk Assessments
The purpose of this summary is to assist the reader by identifying the key features
and findings of these risk assessments, and to help the reader better understand the
conclusions reached in the assessments. The human health and ecological risk
assessments form the basis of interim regulatory decisions for dimethoate. While the
risk assessments and related addenda are not included in this document, they are available
from the OPP Public Docket EPA-HQ-OPP-2005-0084 and may be accessed on the
internet at http://www.regulations.gov.
EPA released the revised risk assessments for dimethoate for a third public
comment phase on September 6, 2005. In response to comments received, the risk
assessments were further updated and refined.
A. Human Health Risk Assessment
The Agency prepared a revised human health risk assessment, "Dimethoate: The
Post-SAP HED Chapter of the Reregi strati on Eligibility Decision Document (RED)"
written by Diana Locke, et al (January 31, 2006), which addresses toxicology data and
comments submitted during the most recent public comment period for dimethoate. In
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addition, the drinking water assessment was revised to include all the uses that are
supported by the technical registrant with fully defined use patterns.
1. Toxicity of Dimethoate
(For a complete discussion, see section 3.0 of the human health risk assessment.)
Table 1. Acute Toxicity of Dimethoate
Guideline No.
870.1100
870.1200
870.2500
870.2600
870.6100
Study Type
Acute Oral - Rat
Acute Dermal - Rabbit
Acute Dermal Irritation -
Rabbit
Skin Sensitization - Guinea
Pig
Acute Delayed Neurotoxicity
-Hen
MRID No.
00164219
00164220
00164221
254924
42884401
Results
LD50 = 358 mg/kg
males), 414 mg/kg
(females)
LD50 = > 2.0 g/kg
Not a dermal irritant
Not a skin sensitizer
No clinical signs of acute
delayed neurotoxicity
and no compound-
related histological
changes in nerve tissue.
Toxicity
Category
II
III
IV
N/A
N/A
* Acceptable acute and primary eye irritation studies have not been submitted, and are therefore considered
data gaps at this time.
As with other organophosphate (OP) pesticides, the critical effect of dimethoate
for various exposure durations is inhibition of cholinesterase (ChE) in the brain or blood
compartment. ChE inhibition is the most sensitive endpoint in numerous studies with
adult and juvenile animals following oral, dermal, or inhalation exposures of dimethoate
or omethoate (the primary metabolite). ChE inhibition was the most sensitive endpoint in
an inhalation study with omethoate.
Oral studies evaluating the subchronic, chronic, developmental, and reproductive
toxicity in laboratory animals are available for both dimethoate and omethoate.
Developmental neurotoxicity (DNT), comparative cholinesterase, and special cross
fostering studies are available for dimethoate. These studies show that brain ChE
inhibition occurs at doses similar to or lower than those causing ChE inhibition in blood.
Furthermore, these studies show that brain ChE inhibition occurs at doses similar to those
associated with increases in pup mortality observed in the DNT study. The FIFRA
Scientific Advisory Panel met on November 30 and December 1, 2004 to deliberate on
the interpretation of the data from these studies and concluded that brain ChE inhibition
is an appropriate endpoint to use for risk assessment.
The risk assessment for dimethoate is based on benchmark dose values, rather
than No Observed Adverse Effect Level (NOAEL) and Lowest Observed Adverse Effect
Level (LOAEL) values. The Agency used this method because NOAELs and LOAELs
do not necessarily reflect the relationship between dose and response for a given
chemical, but instead are reflective of dose selection. In order to evaluate the appropriate
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point of departure (PoD) for ChE inhibition and pup mortality, EPA performed a
benchmark dose (BMD) analysis. ChE inhibition data from the following dimethoate
studies in rats were analyzed: the comparative ChE study, the reproductive toxicity
studies, and the 28-day subchronic toxicity study.
The dose at which 10% ChE inhibition would be expected to occur (BMDio) and
the lower 95% confidence intervals (BMDLio) were estimated by fitting the ChE data to
an exponential dose-response model, using generalized nonlinear least squares. The
BMDio was selected because it is generally at or near the limit of sensitivity for
discerning a statistically significant decrease in ChE activity across the blood and brain
compartments and is a response level close to the background ChE level.
The dose and endpoint for establishing the acute reference dose (aRfD) for all
population subgroups is the BMDLio =1.3 mg/kg for postnatal day 11 (PND 11) in
female pups. The endpoint of concern (ChE inhibition) was seen after a single oral dose,
and thus is appropriate for the general population and duration of concern. An
uncertainty factor (UF) of 100 was applied to account for inter-species extrapolation
(10X) and intra-species variability (10X), resulting in an aRfD of 0.013 mg/kg. The dose
and endpoint (ChE inhibition) for establishing the chronic reference dose (cRfD) for all
population subgroups is the BMDLio of 0.22 mg/kg/day from a chronic feeding study on
rats, which is the endpoint that was used in the dietary risk assessment for the OP
cumulative assessment. Again, an UF of 100 was applied, resulting in a cRfD of 0.0022
mg/kg/day. The BMDLio and other toxicity endpoints are outlined in Table 2 below.
FOP A Safety Factor
The FQPA Safely Factor (as mandated by the Food Quality Protection Act of
1996) is intended to provide up to an additional 10-fold safety factor (10X), to protect for
special sensitivity in infants and children to pesticide residues in food and drinking water
or from residential exposures, or to compensate for an incomplete database. In the case
of dimethoate, the Agency has concluded that the FQPA Safety Factor should be
removed based on the lack of pre- and/or postnatal susceptibility resulting following
exposure to dimethoate/omethoate, the lack of residual uncertainties for pre- and/or
postnatal toxicity, and the fact that the dimethoate food and drinking water assessments
are not expected to underestimate exposure.
Cancer Classification
The Agency's Cancer Peer Review Committee (CARC) classified dimethoate as a
Group C carcinogen (possible human carcinogen; final document dated 8/29/91) based on
equivocal hemolymphoreticular tumors in male B6C3F1 mice, the compound-related (no
dose response) weak effect of combined spleen (hemangioma and hemangiosarcoma),
skin (hemangiosarcoma), and lymph (angioma and angiosarcoma) tumors in male Wistar
rats, and positive mutagenic activity associated with dimethoate. For the purposes of risk
assessment and characterization for dimethoate, the PAD approach, and not a Qi*
approach, was considered more appropriate for quantification of potential human risk for
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the following reasons: as stated above, the mouse carcinogen!city study showed
equivocal hemolymphoreticular tumors, and the rat carcinogenicity study showed a
compound-related, weak effect of combined spleen (hemangioma and
hemangiosarcoma), skin (hemangiosarcoma), and lymph (angioma and angiosarcoma)
tumors, but there was no dose response. In addition, the chronic Reference Dose (RfD) is
considered protective enough of any potential cancer risk since the NOAEL from which
it is derived (0.05 mg/kg/d) is at least an order of magnitude lower than the NOAELs or
LOAELs derived from the systemic effects seen in the rat and mouse carcinogenicity
studies. On June 25, 1992, the FIFRA Scientific Advisory Panel (SAP) concurred with
the Agency's classification of dimethoate as Group C carcinogen.
Table 2. Toxicity Endpoints for Human Health Risk Assessment for Dimethoate
Exposure Scenario
Acute Dietary (all
populations)
Chronic Dietary (all
populations)
Short- (1-30 days)
and Intermediate-
term (1-6 months)
Occupational
Dermal
Short- (1-30 days)
and Intermediate-
term (1-6 months)
Occupational
Inhalation
Cancer
Dose,
Uncertainty
Factor, and
Safety Factor
BMDL10=1.3
mg/kg
UF = 100
FQPA SF = 1
Effect
Brain ChE inhibition in
PND11 females (BMD10 = 1.5
mg/kg)
Study
Comparative ChEI study in rats.
MRID 45529702
Acute RfD = Acute PAD = 0.013 mg/kg
BMDL10 =
0.22 mg/kg/d
UF = 100
FQPA SF = 1
Brain ChE inhibition in
females (BMD10 = 0.25
mg/kg/d).
2-Year chronic feeding study in
rats.
MRID 00164177
Chronic RfD = Chronic PAD = 0.0022 mg/kg/d
BMDL10 =
18.67 mg/kg/d
UF = 100
Brain ChE inhibition in males
at 28 days (BMD10 = 28.70
mg/kg/d).
28-Day repeated dose dermal
toxicity in rats.
MRID 44999101
Short- and Intermediate-term Occupational Dermal LOG = 100
BMCL10 =
0.38 mg/m3
(approxO.10
mg/kg/d)
UF = 100
Brain ChE inhibition in males
at 15 days (BMC10 = 0.51
mg/m3 ).
Omethoate 21 -day repeated
dose inhalation study in rats.
MRID 46358601.
(See discussion of relative
toxicity of omethoate in Sect.
III.A.2 below.)
Short- and Intermediate-term Occupational Inhalation LOG = 100
Classification: Group C or Possible Human Carcinogen
UF = Uncertainty Factor (10X for inter-species extrapolation and 10X for intra-species variation)
FQPA SF = Food Quality Protection Act Safety Factor
RfD = Reference Dose
PAD = Population Adjusted Dose (RfD - FQPA SF)
LOG = Level of Concern
-------
2. Dietary Exposure and Risk from Food and Water
Acute and chronic probabilistic dietary risk assessments were conducted using
DEEM-FCID™, Version 2.02, which incorporates consumption data from USDA's
CSFII, 1994-1996 and 1998, as well as monitoring data from PDF and the FDA
Surveillance Monitoring Program, estimated percent crop treated information, and
processing/cooking factors, where applicable. Since the tolerance expression includes
both dimethoate and omethoate, the residues of parent and its metabolite were summed
for use in the dietary risk assessment. Furthermore, since it was determined that
omethoate is twelve times more toxic than dimethoate in acute dietary exposure and three
times more toxic in chronic dietary exposure, residues of omethoate [including limit of
detection (LOD) values] in/on the same sample were multiplied by a toxicity adjustment
factor (TAP) of 12 in the acute and by a factor of 3 in the chronic dietary risk assessment
before addition to dimethoate residues. Exposure estimates are reported in milligrams
per kilogram of body weight per day, and risk is expressed as a percent of the aPAD or
cPAD. Exposure estimates that are less than 100% of the PAD are below the EPA's level
of concern. For a more detailed discussion on the relative toxicity of omethoate, see
Section 4.3.8 of the human health risk assessment.
The estimated drinking water concentrations (EDWCs) were calculated for
multiple crops, including those that are the major use sites for dimethoate, and other
representative sites. If appropriate, regional percent cropped area factors (PCA) were
considered. EPA assumed that dimethoate would convert completely (100%) to
omethoate during drinking water treatment, and therefore the TAFs were applied to the
acute and chronic exposure assessments, respectively. Please see "A Re-assessment of
the Drinking Water Exposure Due to Dimethoate Residues in Drinking Water,
Considering New Recommended Maximum Label Patterns from the Technical
Registrant" (Jones, R., 12/21/05) for detailed information. Table 3 shows the highest
EDWCs, resulting from use on broccoli in California (which is also representative of
cauliflower and celery) and the lowest EDWCs, resulting from use on pecans in Georgia.
Table 3. EDWCs for Dimethoate on Selected Agricultural Crops.
Source
Acute ED WC
Chronic EDWC
Surface Water
Broccoli/Cauliflower/Celery
Pecans
558
19.6
23.5
0.28
Ground Water
SCI-GROW
0.044
0.044
-------
Surface water monitoring data are available from a number of sources; however,
they are limited in scope, are not nationally representative, and did not include analysis of
omethoate. The California Department of Pesticide Regulation (CDPR) conducted a
monitoring study in which sampling was done over several years. The highest
concentration of dimethoate found was 2.4 ug/L, in the San Joaquin River basin. Given
the sampling pattern and frequency within the study, it is uncertain whether higher
concentrations would be observed at other times. The CDPR study did not monitor for
omethoate.
Ready to drink, treated drinking water data are not available for dimethoate.
Dimethoate converts to omethoate to some extent as a result of oxidation that occurs
when drinking water is treated via chlorination. One study has been conducted to test
conversion to omethoate during chlorination; however, the resulting data are limited in
scope. Due to the serious limitations of these data, 100% conversion of dimethoate to
omethoate during drinking water treatment of surface waters has been assumed as a
protective measure for this assessment. For more details on the conversion of dimethoate
to omethoate during drinking water treatment, see "A Re-assessment of the Drinking
Water Exposure Due to Dimethoate Residues in Drinking Water, Considering New
Recommended Maximum Label Patterns from the Technical Registrant" (Jones, R.,
12/21/05).
The ground water EDWCs were estimated using the SCI-GROW model, version
2.3. Since modeled EDWCs for ground water were much lower than surface water
concentrations, only surface water EDWCs were used in the dietary risk assessment.
Acute Dietary Risk Assessment for Food + Water
Estimated residues in drinking water were incorporated directly into the acute
dietary assessment. A refined, Tier 3 assessment was conducted using the full
distribution of estimated residues in surface water, generated by the PRZM-EXAMS
model for dimethoate use on California broccoli, the crop scenario resulting in the highest
estimated peak surface water concentration, and for Georgia pecans, the crop scenario
resulting in the lowest estimated peak surface water concentration.
Dietary risk from food alone occupies 32% of the aPAD. When food and water
are considered together, the resulting acute dietary exposure and risk estimates for the
California broccoli scenario exceed EPA's level of concern for all population subgroups.
Risk from aggregate dietary exposure on an acute basis occupies 460% of the aPAD for
the most highly exposed subgroup, infants less than one year of age.
10
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Table 4. Summary of Acute Dietary Exposure and Risk for Dimethoate at 99.9
Percentile
,th
Population
Subgroup
General US
Population
Infants < 1 year
Children 1-2
years old
Food Only
Dietary
Exposure
(mg/kg/day)
0.002134
0.001958
0.004160
%aPAD
16
15
32
Food + Drinking Water
(CA Broccoli)
Dietary
Exposure
(mg/kg/day)
0.017872
0.060155
0.026520
%
aPAD
140
460
200
Food + Drinking Water
(GA Pecans)
Dietary
Exposure
(mg/kg/da
y)
0.002160
0.002419
0.004373
%aPAD
17
19
34
Chronic Dietary Risk Assessment for Food + Water
A refined, Tier 3 chronic dietary exposure assessment was also conducted for the
supported food uses of dimethoate and for drinking water. Anticipated residues were
derived using field trial data, percent crop treated data, and, where available, processing
factors.
For the chronic assessment, a single point estimate (23.5 ppb) of dimethoate
residues in surface water was used to assess exposure from drinking water. The
estimated surface water concentration represents the 90th percentile annual mean
concentration generated by the PRZM-EXAMS model for California broccoli, the crop
scenario resulting in the highest estimated annual mean concentration.
Chronic dietary risks based on this analysis are below the Agency's level of
concern for all population subgroups. Risk from aggregate dietary exposure on a chronic
basis occupies 33% of the cPAD for the most highly exposed subgroup, infants less than
one year of age.
Table 5. Summary of Chronic Dietary Exposure and Risk for Dimethoate at 99.9
Percentile
,th
Population
Subgroup
General US
Population
Infants <1 year
Children 1-2
years old
Food Only
Dietary
Exposure
(mg/kg/day)
0.000028
0.000042
0.000111
% cPAD
1.3
1.9
5.1
Food + Drinking Water
(CA Broccoli)
Dietary
Exposure
(mg/kg/day)
0.000233
0.000715
0.000416
%
cPAD
11
33
19
Food + Drinking Water
(GA Pecans)
Dietary
Exposure
(mg/kg/day)
0.000031
0.000051
0.000115
% cPAD
1.4
2.3
5.2
Dietary Risk Characterization
For regulatory purposes, the Agency has assumed that 100% of the modeled water
concentrations of dimethoate will convert to omethoate during drinking water treatment.
11
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Therefore, the 12X toxicity factor for acute assessments and the 3X toxicity factor for the
chronic assessments were applied directly to the distribution of water residue values.
Data exist which indicate that in some instances, conversion could be as low as 20%, but
these data have serious limitations. The Agency is requiring the registrant to investigate
the rate and amount of dimethoate conversion to omethoate during water chlorination
under various water quality regimes.
In light of the conservative assumptions regarding conversion to omethoate, the
Agency considered surface water modeling results from several crop and regional
scenarios. The resulting aggregated food plus drinking water values for dimethoate are
above 100% of the aPAD for some uses. Food alone represents 32% of the aPAD for the
most highly exposed population subgroup, and the addition of modeled water residues
results in estimates below the Agency's level of concern for several uses. Preliminary
DEEM modeling showed that a peak water residue estimate of 140 ppb is equivalent to
106% of the aPAD for food and water for the most exposed population. Of the 25
modeled scenarios, 17 resulted in peaks less than 140 ppb which is below the Agency's
level of concern prior to mitigation and 8 scenarios resulted in peak residues at 140 ppb
or greater. The mitigation the Agency is requiring is expected to reduce drinking water
estimates for all sites except broccoli, celery and cauliflower grown in coastal California.
For broccoli, celery and cauliflower, modeling was done for applications in the
winter season (November and December), and the predicted water concentrations were
high as a result of runoff from the high amount of rain received in coastal California in
the winter. Sensitivity analyses were conducted to explore different mitigation options,
and showed that reducing the number of applications or prohibiting aerial applications
did not result in drinking water risk estimates below 100% of the aPAD (when added to
food risks). USDA provided refined usage information indicating that while several
applications a year are needed for these vegetables, dimethoate is not used in November
and December in coastal areas of California. EPA then considered the effects of
changing the application timing to the fall or spring, or modeling applications in other
areas of the country, and these considerations did result in much lower values. The
Agency believes that when these facts are taken into account along with the conservative
assumption of 100% conversion to omethoate during drinking water treatment, the
drinking water residues resulting from dimethoate applications to these vegetables do not
pose dietary risks of concern.
3. Residential and Other Non-occupational Risk
All residential and other non-occupational uses of dimethoate were voluntarily
cancelled in 2002 (Federal Register Notice/Vol. 67, No. 84/Wednesday, May 1,
2002/Notices/21669). Therefore, EPA did not conduct a residential exposure and risk
assessment for dimethoate.
12
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4. Aggregate Exposure and Risk
(For a complete discussion, see Section 7 of the human health risk assessment.)
The Food Quality Protection Act (FQPA) amendments to the Federal Food, Drug
and Cosmetic Act (FFDCA, Section 408(b)(2)(A) (iii) require "that there is a reasonable
certainty that no harm will result from aggregate exposure to pesticide chemical residue,
including all anticipated dietary exposures for which there is reliable information."
Aggregate exposure will typically include dietary exposures (food plus drinking water),
residential uses of a pesticide, and other non-occupational sources of exposure.
There are no residential or other non-occupational uses of dimethoate. Therefore,
when addressing aggregate exposures, only the aggregate dietary pathways of food and
drinking water were considered. Since drinking water was incorporated directly into the
acute and chronic dietary assessments, the dietary risk estimates discussed above reflect
total estimated acute and chronic aggregate risks from dimethoate.
Acute aggregate risk estimates for food and drinking water exceed EPA's level of
concern for all population subgroups when estimated residues in drinking water from the
California broccoli scenario are assessed. When mitigation (i.e., reduced maximum
application rates, reduced numbers of applications per year, and increased retreatment
intervals) is considered, food and drinking water residues from all other uses do not
exceed the Agency's level of concern. Chronic aggregate risk estimates for food and
drinking water are below the Agency's level of concern for all population subgroups,
including the most highly exposed subgroup, infants less than one year of age.
5. Occupational Exposure and Risk
(For a complete discussion, see section 9 of the human health risk assessment.)
Workers can be exposed to a pesticide through mixing, loading, and/or applying a
pesticide, or re-entering treated sites. Occupational risk is measured by a Margin of
Exposure (MOE), which describes how close the occupational exposure comes to a No
Observed Adverse Effect Level (NOAEL). The target MOE for dimethoate is 100, which
includes the default uncertainty factors for interspecies extrapolation and intraspecies
variation. MOEs that fall below 100 indicate a possible need for mitigation.
Occupational handler scenarios were assessed using the short- and intermediate-
term endpoint for dermal and inhalation exposures. The short- and intermediate-term
dermal endpoint is a BMDLio of 18.67 mg/kg/day, based on a 28-day repeated dose
dermal toxicity study on rats. The short- and intermediate-term inhalation endpoint is 0.1
mg/kg/day, derived from an inhalation concentration level of 0.38 mg/m3 (BMDLio) from
a 28-day repeated dose inhalation study of omethoate using rats. Dermal and inhalation
exposures were combined to assess handler risk.
Occupational handler risk estimates have been assessed for short- and
intermediate-term exposures. Most occupational exposures are expected to occur in a
13
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short-term pattern (up to 30 days), but some intermediate-term (one to six month)
exposures are anticipated in some handler exposure scenarios, particularly those
involving applications by commercial applicators to large-acreage crops (e.g., field corn,
wheat, alfalfa, cotton). Long-term exposures are those that would result from use of a
pesticide for more than several months in a single year, and are not expected for
dimethoate.
No chemical-specific data for assessing worker exposures during pesticide
handling activities were submitted, so short- and intermediate-term dermal and inhalation
exposures for handlers were developed using the Pesticide Handlers Exposure Database
(PHED) Version 1.1.
The Agency has determined that there are potential exposures to individuals who
mix, load, apply, and otherwise handle dimethoate during the usual use patterns
associated with the pesticide. Several major occupational exposure scenarios were
identified based on the type of equipment that potentially can be used to make dimethoate
applications.
The calculations of short- and intermediate-term total risks to handlers indicate
that most occupational handler risks are below the Agency's level of concern (i.e., MOEs
are greater than 100) at some level of risk mitigation. Table 6 below shows only those
handler scenarios for which MOEs are less than 100.
Table 6. Summary of Handler Scenarios with MOEs Less Than 100 When Assessed with
Maximum Feasible Mitigation
Exposure Scenario
Mixing/loading liquids for
aerial and chemigation
applications
Mixing/loading liquids for
aerial applications
Mixing/loading wettable
Crop
Citrus
Woody ornamentals,
Christmas tree
plantations, and
conifer seed orchards
(other than Douglas
firs in OR and WA)
Cottonwood grown
for pulp
Wheat
Alfalfa, alfalfa grown
for seed, cotton, field
corn, pop corn, grass
grown for seed,
safflower, sorghum,
and soybeans
Pears
Maximum
Application
Rate (Ibs
a.i./A)
2.0
2.0
4.0
0.67
0.5
1.0
Daily
Treated
Area
(Acres)
350
350
350
1,200
1,200
350
MOEw/
Maximum
Feasible
Mitigation
Controls
77b
7?b
39b
67b
90b
68b
14
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Exposure Scenario
powders for aerial and
chemigation applications
Mixing/loading/applying
liquids with high pressure
handwand sprayers
Aerial spray applications of
liquids
Applying liquids with
airblast/mistblower sprayers
Crop
Woody ornamentals,
Christmas tree
plantations, and
conifer seed orchards
(other than Douglas
firs in OR and WA)
Wheat
Cottonwood grown
for pulp
Douglas fir seed
orchards in OR and
WA
Maximum
Application
Rate (Ibs
a.i./A)
0 75
0.01°
0.67
4.0
8.3
Daily
Treated
Area
(Acres)
350
1,000
gallons
1,200
350
20
MOEw/
Maximum
Feasible
Mitigation
Controls
91b
34a
92b
53b
76b
""Maximum feasible mitigation measure denotes additional PPE (double layer clothing plus gloves and a
half-face or full-face respirator).
bMaximum feasible mitigation measure denotes engineering controls (i.e., closed systems for mixers and
loaders or closed cabs for applicators).
Expressed in Ibs a.i./gal
Post-Application Occupational Risk
For workers entering a treated site, restricted entry intervals (REIs) are calculated
to determine the minimum length of time required before workers can safely reenter (i.e.,
MOEs > 100). The postapplication occupational risk assessment considered exposure to
dimethoate from entering treated fields and orchards. Given the nature of activities in
these locations, and the fact that dimethoate is applied at various times during plant
growth, contact with treated surfaces is likely. Potential exposure scenarios include key
tasks, such as harvesting, thinning, and pruning, as well as secondary tasks, such as
scouting, irrigating, and hand weeding. Other tasks of concern were also identified for
corn (detassling) and herbaceous ornamentals (tasks related to cutting carnations and
roses).
Postapplication exposures are influenced by geographic location and
environmental conditions near the time of application and the type of plant to which the
application is directed. For most crops, data show that following applications in arid
areas (i.e., outdoor areas where average annual rainfall is less than 25 inches), residues
persist longer than in non-arid areas. As a result, estimated REIs tend to be longer in arid
areas.
15
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Table 7. Summary of Posta
Crop Group
Endive,
escarole, kale,
leaf lettuce,
mustard
greens, Swiss
chard, turnips
Peas
Brussels
sprouts
Wheat
Beans, lentils,
celery
Melons,
watermelons
Tomatoes
Asparagus
Broccoli,
cauliflower
Alfalfa,
alfalfa grown
for seed,
soybeans,
safflower,
cotton,
potatoes
Field corn,
popcorn
Grain
sorghum
Max Single
App. Rate
(Ibs a.i./A)
0.25
0.16
1
0.67
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
pplication Risk Assessment for Dimethoate
Key Tasks
Transfer
Coefficient
2,500
harvest, thin
2,500
harvest
5,000
harvest,
irrigate,
prune, thin
&tie
1,000
scout,
irrigate
2,500
harvest
2,5000
harvest,
prune & thin
1,000
harvest,
prune, stake,
thin, tie &
train
500
scout
&irrigate
5,000
harvest,
irrigate,
prune, thin
&tie
1,500
scout &
irrigate
1,000
scout,
irrigate &
hand weed
1,000
scout,
REI (days)
Non-
Arid
12hrs
12hrs
3
1
1
1
12hrs
12hrs
2
1
12hrs
12hrs
Arid
1
12hrs
9
12hrs
2
2
12hrs
12hrs
5
12hrs
12hrs
12hrs
Secondary Tasks
Secondary
Transfer
Coefficient
1,500
scout &
irrigate
1,500
scout &
irrigate
REI (days)
Non-
Arid
12hrs
12hrs
Arid
12hrs
12hrs
NA
NA
1,500
scout &
irrigate
1,500
scout,
irrigate &
hand weed
700
scout &
irrigate
1
1
12hrs
12hrs
12hrs
12hrs
NA
NA
NA
NA
NA
16
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Crop Group
Herbaceous
ornamentals
Peppers
Douglas Fir
Seed
Orchards in
OR and WA
Cottonwoods
grown for
pulp
Conifer seed
orchards
(except
Douglas fir
seed orchards
in OR and
WA)
Woody
ornamentals
and Christmas
tree
plantations
Pecans
Pears
Citrus
Cherries
Max Single
App. Rate
(Ibs a.i./A)
0.5
0.33
8.3
4
2
2
0.33
1
0.75
0.5
2
1
0.5
1
0.33
Key Tasks
Transfer
Coefficient
irrigate
500
tasks related
to cut
flowers &
foliage,
except roses
& carnations
1,000
harvest,
stake & tie
1,000
scout,
irrigate &
weed
1,000
scout,
irrigate &
weed
1,000
scout,
irrigate &
weed
3,000
prune & thin
500
prune &
scout
3,000
harvest,
prune, train
&tie
3,000
prune
3,000
harvest &
prune
REI (days)
Non-
Arid
12hrs
12hrs
22
14
7
19
12hrs
10
8
5
24
13
6
10
2
Arid
12hrs
12hrs
39
24
11
36
12hrs
14
12
7
36
14
7
14
4
Secondary Tasks
Secondary
Transfer
Coefficient
REI (days)
Non-
Arid
Arid
400
tasks related
to nursery
crops,
except cut
flowers or
foliage
700
scout &
irrigate
12hrs
12hrs
12hrs
12hrs
NA
NA
NA
1,500
harvest
13
14
NA
1,000
scout,
irrigate &
hand weed
1,000
scout,
irrigate &
hand weed
1,000
scout,
irrigate &
hand weed
2
2
12hrs
7
2
12hrs
2
12hrs
4
2
12hrs
9
4
12hrs
4
12hrs
The risk assessment indicates that REIs of 12 hours are long enough for MOEs to
reach 100 for many crops; however, acute toxicity of omethoate was not taken into
consideration. If an active ingredient is categorized as a toxicity category I due to dermal
17
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toxicity, skin irritation, or eye irritation, the Agency requires a minimum of a 48-hour
REI. Data were not available on the acute toxicity of omethoate, but omethoate is known
to form on plants after application; therefore, EPA believes a minimum REI of 48-hours
is appropriate for dimethoate. This is consistent with current labels.
EPA will not be setting separate REIs for detassling corn, for which proposed
REIs are 4 and 15 days for non-arid and arid conditions, respectively, due to the fact that
this task is relevant only for seed corn, and dimethoate is not registered for use on seed
corn.
6. Human Incident Data
For a review of the pesticide poisoning incident data for dimethoate, EPA
consulted the following data bases: (1) OPP Incident Data System; (2) Poison Control
Centers; (3) California Department of Pesticide Regulation; and (4) National Pesticide
Telecommunications Network.
A review of the published incident data indicates that for outdoor agricultural
uses, the primary sources of occupational exposures associated with poisoning are
postapplication field residues and spray drift. Risks from agricultural uses appear to be
somewhat lower than with other insecticides. Dimethoate has the highest reported
incidence of poisonings (none life-threatening) among OPs used in residential settings,
but all residential uses for dimethoate were cancelled in 2002 (Federal Register
Notice/Vol. 67, No. 84/Wednesday, May 1, 2002/Notices/21669).
B. Environmental Risk Assessment
A summary of the Agency's environmental risk assessment for dimethoate is presented
below. The complete risk assessment is available in the public docket at
http://www.regulations.gov (docket # EPA-HQ-OPP-2005-0084).
1. Environmental Exposure
a. Environmental Fate and Transport
Dimethoate is a highly mobile, relatively non-persistent organophosphate
insecticide. The primary route of dissipation is microbially-mediated hydrolytic and
oxidative degradation in aerobic soil, particularly under moist conditions, with a half-life
of 2.2 days. Dimethoate does not photodegrade. It hydrolyzes very slowly in sterile
buffered solutions at pHs 5 and 7 (156 and 68 days, respectively), but hydrolyzes rapidly
to desmethyl dimethoate and dimethylthiophosphoric acid with a half-life of 4.4 days at
pH 9. The anaerobic half-life was found to be approximately 22 days, with the major
non-volatile degradate being desmethyl dimethoate.
In a soil column leaching study, 72-100% of the applied radioactivity was eluted
from the columns (loam, silt loam, sandy loam, and sand). A study measuring the
18
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volatility of dimethoate from the soil surface showed that volatility is not a significant
route of dissipation.
The primary toxic degradate, omethoate, was found under field conditions, though
it was not detected in the laboratory studies. The presence of omethoate has been
established through field studies in insects, plants, and mammals. Omethoate was the
only degradate analyzed in the dimethoate field dissipation study. The other degradates
identified in the laboratory studies were not included in the analysis because it is believed
that: 1) based on the aerobic soil metabolism study, they would not persist in the field;
and, 2) they are not lexicologically significant.
b. Aquatic Organism Exposure
For exposure to aquatic fish and invertebrates, EPA considers surface water only,
since most aquatic organisms are not found in groundwater. Surface water models are
used to estimate exposure to freshwater aquatic animals, since monitoring data are
generally not from studies targeted on small water bodies and primary streams, where
many aquatic animals are found. The modeling results used in risk calculations for
dimethoate are detailed in "A Supplement to the Environmental Fate and Ecological Risk
Assessment for the Re-registration of Dimethoate," dated January 13, 2006.
The Estimated Environmental Concentration (EEC) values used to assess
exposure to aquatic animals are not the same as the values used to assess human dietary
exposure from drinking water sources. Unlike the human drinking water assessment, the
assessment of aquatic environmental concentrations accounts for exposure to parent
dimethoate only. Omethoate is not expected to be a major degradate in water except as a
result of chlorination (i.e., drinking water treatment). Also, foliar dissipation data were
used in the modeling.
Several crop scenarios were assessed in the ecological risk assessment. The
California broccoli scenario represents the agricultural use with the maximum EEC, and
so was chosen for regulatory purposes. The highest and lowest EEC values used to
assess exposure to aquatic animals can be found in Table 8 below. For a complete listing
of EECs please refer to the ecological risk assessment.
Table 8. Estimated Environmental Concentrations (ug ai/L) of Dimethoate in Surface
Water for Selected Use Patterns
Crop
Broccoli, CA
Peas
Maximum
Hg/L
33.4
1.28
4-Day
Hg/L
32.0
1.20
21-Day
Hg/L
28.2
0.96
60-Day
Hg/L
21.6
0.60
90-Day
Hg/L
17.7
0.44
19
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c. Terrestrial Organism Exposure
The Agency assessed exposure to terrestrial organisms by first predicting the
amount of dimethoate residues found on animal food items and then using information on
typical food consumption by various species of birds and mammals to determine the
amount of pesticide consumed. The amount of residues on animal feed items is based on
the Fletcher nomogram and the current maximum application rates and minimum
application intervals proposed by the technical registrant for dimethoate. The Fletcher
nomogram is a model developed by Hoerger and Kenaga (1972) and modified by
Fletcher (1994). For non-food uses, the Agency used a conservative estimate of 25
applications with a 3-day re-application interval, since no maximum numbers of
applications or minimum retreatment intervals appear on current product labels or were
proposed by the registrant.
Terrestrial exposure estimates for avian and mammalian risk assessments were
derived using the TREX model (Version 1.1), which calculates the decay of a chemical
applied to surfaces of food items as single or multiple applications. A complete list of the
EEC values used to assess exposure to terrestrial animals can be found in the ecological
risk assessment.
2. Environmental Effects (Hazard)
a. Toxicity to Aquatic Organisms
Freshwater and Estuarine/Marine Fish
Dimethoate is practically non-toxic to estuarine/marine fish and moderately toxic
to freshwater fish on an acute basis. Chronic toxicity testing with aquatic animals
revealed reduced growth for freshwater fish (NOAEC = 0.43 mg/L). No data were
available on the chronic effects of dimethoate on estuarine/marine fish. Table 9
summarizes the data that support the toxicity endpoints used in assessing the risks to fish.
Table 9. Summary of Acute and Chronic Toxicity Estimates for Fish Using Technical
Grade Dimethoate
Species
Rainbow Trout
Oncorhynchus mykiss
Acute Toxicity
96-hr LC50
(mg/L)
6.2
Acute Toxicity
(MRID)
Moderately
toxic
(400940-02)
Chronic Toxicity
NOAEC/LOAEC
(mg/L)
0.43/0.84
Affected
Endpoints
(MRID)
Reduced
growth
(431063-03)
Freshwater and Estuarine/Marine Invertebrates
Dimethoate is considered to be slightly toxic to estuarine/marine invertebrates and
very highly toxic to freshwater invertebrates on an acute basis. Chronic toxicity testing
with aquatic animals revealed reduced growth, survival, and reproductive effects
(NOAEC = 0.04 mg/L) for freshwater invertebrates. No studies are available on the
chronic toxicity of dimethoate to estuarine/marine invertebrates. Table 10 provides a
20
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summary of the data that support the toxicity endpoints used in assessing the risks to
aquatic invertebrates.
Table 10. Summary of Acute and Chronic Toxicity Estimates for Aquatic Invertebrates
Using Technical Grade Dimethoate
Species
Stonefly
Pteronarcys
californica
Water flea
Daphnia magna
Mysid shrimp
Mysidopsis bahia
Acute Toxicity
96-hr LC50
(mg/L)
0.043 (48-hr)
3.32
15
Acute Toxicity
(MRID)
Very highly toxic
(00003503)
ND
Slightly toxic
(427600-03)
Chronic Toxicity
NOAEC/LOAEC
(mg/L)
ND*
0.04/0.1
ND
96-hr LC50
(mg/L)
ND
Reproductive,
survival, growth
(428647-01)
ND
*ND = Not determined
Aquatic Plants
No toxicity data have been submitted to the Agency for either terrestrial or
aquatic plants; however, information from the open literature indicates that dimethoate is
highly toxic to blue-green algae.
b. Toxicity to Terrestrial Organisms
Birds
Dimethoate is considered very highly toxic to birds on an acute basis. Chronic
toxicity testing resulted in reproductive effects (reduced egg production and number of
viable embryos), growth effects (reduced 14-day survivor weight), and survival effects
(reduced number of 14-day survivors) in birds. The chronic NOAEC was 4 mg/kg diet.
Table 11. Summary of Avian Toxicity Data
Species
Red-winged blackbird
Agelaius phoeniceus
Ring-necked pheasant
Phasianus colchicus
LD50
(mg/kg)
5.4
ND
Acute Oral
Toxicity
(MRID)
Very highly
toxic
(00020560)
ND
5-day LC50
(ppm)
ND*
332
Subacute
Dietary
Toxicity
(MRID)
ND
Highly toxic
(00022923)
*ND = Not determined
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Table 12. Summary of Avian Chronic Toxicity Data
Species
NOAEC/
LOAEC (ppm)
(MRID)
Affected Endpoints
Northern bobwhite quail
Colinus virginianus
4.0/10.1
(440490-01)
Reduced egg production, viable embryos, 3-
week old embryos, normal hatchlings, 14-day
old survivors, 14-day old survivor weight, adult
male and female body weight, and egg shell
thickness
No registrant-submitted data are available with which to evaluate the toxicity of
omethoate to birds and no data on avian species are available through ECOTOX.
Although the open literature suggests that birds can be particularly sensitive to the O-
analog (oxon) of phosphorodithioate insecticides, there are no data currently available to
determine whether this is true for omethoate. Thus, the sensitivity of birds to omethoate
is an uncertainty in the Agency's risk assessment.
Mammals
Dimethoate is moderately toxic to mammals on an acute exposure basis. Data
from a developmental neurotoxicity study (NOAEC=0.1 mg/kg bw) were used to assess
the risk of chronic toxicity of dimethoate to mammals. This endpoint is considerably
more sensitive than that used in the previous (1999) risk assessment for dimethoate. The
NOAEL from the developmental neurotoxicity study of rats is based on reproductive
impairment as measured by decreased pup survival and increased percentage of rat litters
lost. After treating maternal rats during gestation and nursing, there was a dose-
dependent increase in pup death and litter loss.
Table 13. Summary of Acute and Chronic Toxicity Data for Mammals Exposed to
Dimethoate
Species
Laboratory
mouse
Mus
musculus
Laboratory
rat
Rattus
norvegicus
Acute Toxicity
LD50
(mg/kg)
120
420
Acute Oral
Toxicity
(MRID)
Moderately
toxic
(00055371)
Moderately
toxic
(247669)
5-day
LC50
(ppm)
ND
ND
Subacute
Dietary
Toxicity
(MRID)
ND
ND
Chronic Toxicity
NOAEC/
LOAEC (ppm)
(MRID)
ND
32/400
mg/kg/day
(00051675)
0.1/1.0
mg/kg/day
(455297-03)
Affected Endpoints
ND
CHel and decreased
weight
Pup mortality
Non-target Insects
Dimethoate is characterized as highly toxic to bees on an acute exposure basis,
based on a honey bee acute contact study (LD50 = 0.05 ug/bee). Contact toxicity data on
parasitic wasps (Bathyplectus curculionus) indicate that some beneficial insects may be
22
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considerably more sensitive than honeybees (LD50=0.00043 ug/wasp) on an acute contact
basis.
3. Ecological Risk Estimation
The Agency's ecological risk assessment compares toxicity endpoints from
ecological toxicity studies to estimated environmental concentrations (EECs) based on
environmental fate characteristics and pesticide use data. To evaluate the potential risk to
non-target organisms from the use of dimethoate products, the Agency calculates a Risk
Quotient (RQ), which is the ratio of the EEC to the most sensitive toxicity endpoint
values, such as the median lethal dose (LDso) or the median lethal concentration (LCso).
These RQ values are then compared to the Agency's levels of concern (LOCs), given in
Table 14, which indicate whether a pesticide, when used as directed, has the potential to
cause adverse effects on non-target organisms. When the RQ exceeds the LOG for a
particular category, (e.g., endangered species), the Agency presumes a risk of concern to
that category. These risks of concern may be addressed by further refinements of the risk
assessment or mitigation. Use, toxicity, fate, and exposure are considered when
characterizing the risk, as well as the relative degree of uncertainty in the assessment.
EPA further characterizes ecological risk based on any reported incidents to non-target
terrestrial or aquatic organisms in the field (e.g., fish or bird kills).
Table 14. EPA's Levels of Concern and Associated Risk Presumptions
Risk Presumption
Acute Risk - there is potential for acute risk
Acute Endangered Species - endangered species may be
adversely affected
Chronic Risk - there is potential for chronic risk
LOC
terrestrial
animals
0.5
0.1
1
LOC
aquatic animals
0.5
0.05
1
For a more detailed explanation of the ecological risks posed by the use of
dimethoate, refer to "A Supplement to the Environmental Fate and Ecological Risk
Assessment for the Re-registration of Dimethoate," dated January 13, 2006.
a. Risk to Aquatic Organisms
Freshwater Fish and Invertebrates
No acute RQs exceed the acute risk LOC for freshwater fish or invertebrates (RQs
range from <0.01 to 0.03).
No chronic RQs exceed the chronic risk LOC for freshwater fish (RQs range from
<0.01 to 0.14). For freshwater invertebrates, the only exceedance of the LOC is
associated with use on Christmas trees (RQ = 1.96). Risks to aquatic animals from use of
dimethoate on Christmas trees was estimated assuming 25 applications at the maximum
labeled rate, with 3 day application intervals. This number of applications is likely
23
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greater than the actual value, but was assessed because current labels do not specify
limits. As a result of this reregi strati on decision, labels will be revised to limit the
number of applications per season. For all other use scenarios, chronic RQs were below
the LOG.
Estuarine/Marine Fish and Invertebrates
RQs were not calculated for estuarine/marine animals; however, since the acute
toxicity endpoints for estuarine/marine fish and invertebrates are considerably higher than
for their freshwater counterparts (LCso > 111,000 ug/L for sheepshead minnow, and LCso
= 15,000 ug/L for mysid shrimp), the Agency believes that none of the acute RQs would
exceed the acute risk LOG. No chronic toxicity data are currently available for
estuarine/marine fish or invertebrates, and therefore chronic risks could not be assessed.
b. Risk to Non-target Terrestrial Organisms
Birds
Avian RQs were calculated based on maximum residues of dimethoate on forage
items following a single application and an LCso of 332 ppm from a subacute dietary
toxicity study on ring-necked pheasants. At rates of 1 Ibs a.i./A or less, the highest acute
RQ is for birds feeding on short grass (RQ = 0.72). At rates greater than or equal to 0.75
Ibs a.i./A, the acute risk and endangered species LOCs are exceeded for birds foraging on
short grass. The acute endangered species LOG is not exceeded for birds feeding on tall
grass and broadleaf plants/insects. In order to reduce RQs to below the endangered
species LOG for the most vulnerable avian species, rates would have to be reduced to a
single application of 0.13 Ibs a.i./A. This low rate would not be efficacious.
Following multiple applications of dimethoate, the acute risk LOG is exceeded for
all applications equal to or greater than 1 Ibs a.i./A (RQ = 0.72). Multiple applications at
rates greater than 0.16 Ibs a.i./A exceed the endangered species LOG for herbivores
across all uses (Table 15). Mean avian acute RQs were not calculated for multiple
applications, but would be expected to result in no acute risk exceedances, except with
application rates greater than 1 Ibs a.i./A, but endangered species exceedances would still
occur.
Table 15. Summary of Estimated Acute Avian RQs from Multiple Application of
Dimethoate at Maximum Foliar Residues
Use Site
Application Rate
(#/year / interval)
Citrus
1.0 Ib a.i./A
(2/31)
Broccoli, Cauliflower, Celery
Food Items
Short grass
Tall grass
Broadleaf plants/small insects
Fruits, pods, seeds, and large insects
Short grass
Maximum
RQ
0.72
0.33
0.41
0.05
0.44
24
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Use Site
Application Rate
(#/year / interval)
0.5 Ib a.i./A
(6/7)
Cotton, Safflower
0.5 Ib a.i./A
(2/14)
Alfalfa
0.5 Ib a.i./A
(1/na)
Food Items
Tall grass
Broadleaf plants/small insects
Fruits, pods, seeds, and large insects
Short grass
Tall grass
Broadleaf plants/small insects
Fruits, pods, seeds, and large insects
Short grass
Tall grass
Broadleaf plants/small insects
Fruits, pods, seeds, and large insects
Maximum
RQ
0.20
0.25
0.03
0.37
0.17
0.21
0.02
0.36
0.17
0.20
0.02
LOG = 0.5 for acute risk and 0.01 for endangered species
Chronic avian RQs exceed the LOG (RQ>1.0) by factors of one to 178 for nearly
all use scenarios at maximum residues. At mean residue levels, RQs decrease by roughly
60%. Chronic RQ values based on mean residues range from 0.28 to 63. At application
rates below 0.5 Ibs a.i./A, the chronic risk LOG is not exceeded for birds feeding on
fruits, pods, seeds and large insects, however, if the retreatment interval is reduced to 7
days, the LOG is exceeded. In order to reach maximum residues that do not result in RQs
exceeding the chronic risk LOG, the maximum single application rate would have to be
reduced to 0.016 Ibs a.i./A, a rate that is not efficacious.
Table 16. Summary of Estimated Chronic Avian RQs from Use of Dimethoate at Mean
Foliar Residues
Use
Application Rate (#/year /
interval)
Citrus
1.0 Ibs a.i./A
(2/3)
Broccoli, Cauliflower, Celery
0.5 Ibs a.i./A
(6/7)
Cotton, Safflower
Food Items
Short grass
Tall grass
Broadleaf plants/small insects
Fruits, pods, and large insects
Short grass
Tall grass
Broadleaf plants/small insects
Fruits, pods, and large insects
Short grass
Tall grass
MeanRQ
63a
27a
33a
5.2a
13a
5.5a
6.9a
i.r
ir
4.7a
25
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Use
Application Rate (#/year /
interval)
0.5 Ibs a.i./A
(2/14)
Alfalfa
Food Items
Broadleaf plants/small insects
Fruits, pods, and large insects
Short grass
Tall grass
Broadleaf plants/small insects
Fruits, pods, and large insects
MeanRQ
5.8a
0.91
11"
4.5a
5.6a
0.88
aExceeds chronic risk level of concern (RQ>1.0)
Mammals
The acute mammalian risk assessment is based on a mouse acute oral LD50 of 120
mg/kg and RQ values are expressed as dose-based values. The dose-based RQs are
calculated using a body weight-adjusted and consumption-weight equivalent dose. By
expressing the Kenaga nomogram estimated residues in terms of daily equivalent dose,
estimated environmental concentrations can then be compared to the dose-based LD50.
After a single application rate of 1 Ib a.i./A, the acute risk LOG is exceeded for mammals
weighing less than 35 grams and feeding on short grass, tall grass, and broadleaf
plants/insects, with RQs up to 3.5.
Following multiple applications of dimethoate at rates greater than 0.25 Ibs a.i./A,
the acute risk LOG is exceeded for small and intermediate-sized mammals feeding on
short grass (RQs range from 0.76 to 5.3). The acute endangered species LOG is exceeded
across small and intermediate-sized herbivorous mammals at application rates greater
than 0.16 Ibs a.i./A.
Table 17. Summary of Estimated Acute Mammalian RQs from Multiple Applications of
Dimethoate at Maximum Foliar Residues
Use
Application
Rate
(#/year/
interval)
Citrus
1.0 Ibs a.i./A
(2/31)
Broccoli,
Cauliflower,
Celery
.5 Ibs a.i./A
(6/7)
Cotton,
Safflower
Body Weight (g)
15
35
1,000
15
35
1,000
15
35
Mammalian Acute Risk Quotients
Short Grass
1.8
1.5
0.81
1.10
0.93
0.50
0.92
0.78
Tall Grass
0.81
0.7
0.37
0.50
0.43
0.23
0.42
0.36
Broadleaf
Plants/Small
Insects
1.0
0.85
0.46
0.61
0.52
0.28
0.52
0.44
Fruits/Pods/
Large Insects
0.11
0.09
0.05
0.06
0.07
0.03
0.06
0.05
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Use
Application
Rate
(#/year/
interval)
.5 Ibs a.i./A
(2/14)
Alfalfa
0.5 Ib a.i./A
(1 appper
year)
Body Weight (g)
1,000
15
35
1,000
Mammalian Acute Risk Quotients
Short Grass
0.42
0.89
0.76
0.41
Tall Grass
0.19
0.41
0.35
0.19
Broadleaf
Plants/Small
Insects
0.24
0.50
0.43
0.23
Fruits/Pods/
Large Insects
0.03
0.06
0.05
0.03
As seen in Table 18 below, all uses of dimethoate result in RQs which exceed the
chronic mammalian level of concern based on a NOAEL of 0.1 mg/kg/day. For a
complete listing of mammalian RQs for both maximum and mean foliar residues, please
see Tables 28 and 29 of the environmental risk assessment. For further information on
the chronic risks to mammals, please see Section 5 "Risk Characterization" below.
Table 18. Summary Estimated Chronic Mammalian RQs from Multiple Applications of
Dimethoate Based on Mean Foliar Residues
Use
Application Rate
Citrus
2.0 Ibs a.i./A
(2/31)
Broccoli,
Cauliflower,
Celery
0.5 Ibs a.i./A
(6/7)
Cotton, Safflower
0.5 Ibs a.i./A
(2/14)
Alfalfa
0.5 Ib a.i./A
(1 appper year)
Body
Weight (g)
15
35
1,000
15
35
1,000
15
35
1,000
15
35
1,000
Mammalian Risk Quotients
Short
Grass
1,042
890
477
639
546
293
538
460
247
521
445
238
Tall Grass
477
408
219
293
250
134
247
211
113
239
204
109
Broadleaf
Plants/Small
Insects
586
501
268
359
307
135
303
259
139
293
250
134
Fruits/Pods/
Large
Insects
65
56
30
40
34
18
34
29
15
33
28
15
Seeds
14
12
6.6
8.5
7.6
4.1
7.5
6.4
3.4
7.2
6.2
o o
5.5
LOC= 1.0
Non-target Plants
There are no available plant toxicity data on dimethoate, so EPA has not
calculated risks to non-target plants.
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4. Ecological Incidents
There are a total of 22 field incidents reported between 1972 and 2000. Most of
the reported incidents are not recent. Relative to other organophosphate pesticides,
dimethoate was ranked 13th out of 32 organophosphate pesticides evaluated in terms of
the number of incidents reported in the Ecological Incident Information System.
The majority (73%) of reported incidents involved terrestrial animals and were
split equally between birds (8) and bee-related (8) incidents. Canada geese and cedar
waxwings were the most frequently affected birds. The number of geese killed ranged
from 25 to "hundreds" while the number of waxwings killed ranged from 60 to 80. All
of the incidents involving Canada geese (4) were associated with the use of dimethoate
on alfalfa; of these, two were from the registered use of the pesticide (one of which was
for treated seed) and two were a result of accidental misuse. The three incidents
involving cedar waxwings were from the registered use of dimethoate in the garden or on
woody ornamentals. Of the eight incidents involving bees, seven occurred in Washington
State and were primarily associated with the use of dimethoate on beans and orchard
crops.
Of the five reported incidents that involved aquatic animals, one resulted from the
registered aerial use of dimethoate, and that was on soybeans. In this incident, 9,237 fish
were reported killed with the majority of affected fish being minnows (89%), sunfish
(6%), and shad (2%). Five turkeys were also reported killed in this same incident. There
are insufficient details reported for the incident to determine whether there were unusual
circumstances (e.g. a rain event) which may have resulted in increased aquatic exposure.
The remaining four incidents affecting aquatic animals were from intentional or
accidental misuse; two were associated with loading areas, one from use on tobacco and
one from use on a lake.
The one incident reported to have involved damage to grass resulted from the
misuse of dimethoate on spray applications to lentils in Washington; the extent of
damage to the grass is not reported. There have been no other reported incidents of
phytoxicity resulting from dimethoate use.
Consistent with risk estimates for birds, reports of non-target species mortality
have involved birds. Although risk quotients estimated for fish do not suggest that fish
will be subject to acute mortality, incident reports show that freshwater fish have been
affected.
5. Risk Characterization
Although RQs do not exceed levels of concern for aquatic species, dimethoate has
been shown to be moderately toxic to fish and highly toxic to aquatic invertebrates. This
is evidenced by reported fish kills associated with the use of dimethoate, signifying the
possibility of aquatic effects.
28
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Dimethoate was shown to be very highly toxic to some species of birds by the
acute oral route. There are acute LOG exceedances at the application rate of 1.0 Ib ai/A
for small birds eating short grass, with a maximum RQ of 0.7. Organophosphorus
compounds are known to be toxic to birds by dermal and inhalation routes. There have
been several incidents involving birds including large birds such as Canadian geese,
which may be the result of exposures by these non-dietary routes.
For chronic risks to birds, the avian assessment shows LOG exceedances with the
maximum RQs of 63 for two applications at 1 Ibs ai/A, based on mean foliar residues.
There are exceedances for acute risk LOG for small mammals with the maximum
RQ of 2.6 for small mammals eating short grass treated with two applications of 1.0 Ib
ai/A. There are no reported mammalian incidents resulting from acute toxicity exposures
to dimethoate.
The highest estimated ecological risks from use of dimethoate are chronic risks to
mammals, with RQs calculated using mean foliar residues ranging from <1 to 1,092. The
high values are from two applications of 1.0 Ib ai/A with a 3 day re-application interval.
Most applications are at a maximum of 0.5 Ib ai/A which results in RQs around 220.
The endpoint used for risk assessment comes from a developmental neurotoxicity
study, which was conducted for the human health risk assessment. The endpoint used for
the ecological risk assessment is rat pup mortality, observed at very low levels of
exposure (NOAEL of 0.1 mg/kg/day). A different endpoint (cholinesterase inhibition)
from the same study was used for the human health risk assessment because: 1) ChE
inhibition occurred at lower doses, and was therefore considered to be more protective for
human health risks; and 2) the mechanism of the pup mortality is not well understood.
The Science Advisory Panel noted that the pup mortality observed in the DNT study is
dose-related, and the Agency believes that although pup mortality is not a standard
endpoint, it is an appropriate endpoint to use for chronic mammalian risk assessment.
The previous ecological chronic mammalian risk assessment, dated January 23,
1998, was based on the standard two generation reproduction study. The endpoint for
this study was a NOAEL of 32 mg/kg/day based on maternal effects and decreased
reproduction. RQ calculated from this endpoint ranged from <1-10.
While there are differences in the magnitude of the RQs from both assessments,
both sets of RQs indicate that potential for chronic, reproductive risk to small mammals
is very high. Applications of dimethoate are made to large acreage crops such as alfalfa,
corn and cotton. It is expected that mammals whose forage range is small, will be
affected if they live in or near treated areas.
To reduce the chronic mammalian risk quotient below the Agency's level of
concern, the application rate would have to be lowered to 0.02 Ib ai/A, which would be
far below the efficacious level for pest control. The Agency is requiring lowered
29
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application rates and lowered numbers of applications to reduce exposure for non-target
mammals, and thereby provide some protection against population loss.
6. Endangered Species Considerations
The Agency's preliminary risk assessment for endangered species indicates that
RQs exceed the endangered species LOG for birds and mammals. Further, potential
indirect effects to any species dependent upon a species that experiences effects from use
of dimethoate, can not be precluded based on the screening level ecological risk
assessment. These findings are based solely on EPA's screening level assessment and do
not constitute "may affect" findings under the Endangered Species Act.
IV. Interim Risk Management, Reregistration, and Tolerance Reassessment
Decision
A. Determination of Reregistration Eligibility
Section 4(g)(2)(A) of FIFRA calls for the Agency to determine, after submission
of relevant data concerning an active ingredient, whether or not products containing the
active ingredient are eligible for reregi strati on. The Agency has previously identified and
required the submission of the generic (technical or manufacturing-use grade) data
required to support reregi strati on of products containing dimethoate as an active
ingredient.
The Agency has completed its review of submitted data and its assessment of the
dietary, occupational, and ecological risks associated with the use of pesticide products
containing the active ingredient dimethoate. Based on these data, the Agency has
sufficient information on the human health and ecological effects of dimethoate to make
its interim decisions as part of the tolerance reassessment process under FFDCA and the
reregi strati on process under FIFRA, as amended by FQPA, pending completion of the
cumulative assessment of the organophosphate class of pesticides, of which dimethoate is
a member. Additional mitigation may be necessary after this cumulative assessment is
completed. The Agency has determined that products containing dimethoate will be
eligible for reregi strati on provided that (i) required product-specific data are submitted;
(ii) the risk mitigation measures outlined in this document are adopted; (iii) label
amendments are made to reflect these measures; and (iv) any additional measures needed
to reduce cumulative risks are adopted. Needed label changes and language are listed in
Section V. Appendix A is a detailed table listing all dimethoate uses that are eligible for
reregi strati on, or uses which require tolerances or tolerance consideration. Appendix B
identifies generic data requirements that the Agency reviewed as part of its determination
of the interim reregi strati on eligibility of dimethoate, and lists the submitted studies the
Agency found acceptable. Data gaps are identified as either outstanding generic data
requirements that have not been satisfied with acceptable data, or additional data
necessary to confirm the decision presented here.
30
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Based on its evaluation of dimethoate, the Agency has determined that dimethoate
products, unless labeled and used as specified in Sections IV and V this document, would
present risks inconsistent with FIFRA and FFDCA. Accordingly, should a registrant fail
to implement any of the risk mitigation measures identified in this document, the Agency
may take regulatory action to address the risk concerns from the use of dimethoate. If all
changes outlined in this document are incorporated into the product labels, then all
current risks for dimethoate will be adequately mitigated for the purposes of this interim
determination under FIFRA. Additionally, once an endangered species assessment is
completed, further changes to these registrations may be necessary, as explained in
Section IV.D.3 of this document.
B. Public Comments and Responses
Through the Agency=s public participation process, EPA worked extensively with
stakeholders and the public to reach the regulatory decisions for dimethoate. During the
most recent public comment period on the risk assessments, which closed on November
7, 2005, the Agency received comments from five sources: Cheminova, the Natural
Resource Defense Council, The Rachel Carson Council, and two private citizens. The
comments included some urging the Agency to be more stringent in its regulation of
dimethoate, as well as some requesting that the Agency retain certain uses. These
comments, in their entirety, are available in the public docket (docket # OPP-2005-0084)
at http://www.regulations.gov. EPA has prepared responses to these comments and they
are posted in the docket, along with this IRED.
In addition, EPA worked with USDA to solicit input from the grower community
on the importance of dimethoate use for those crops with < 1% of cropped area treated
with dimethoate. EPA received many comments from growers through this process.
EPA has considered these comments, and will be responding to them through a formal
response to comments memo, which will be placed in the public docket, along with this
document.
The IRED and technical supporting documents for dimethoate are also available to
the public through EPA=s electronic public docket and comment system, the Federal
Docket Management System (FDMS), under [legacy] docket identification (ID) number
EPA-HQ-OPP-2005-0084. In addition, the dimethoate IRED may be downloaded or
viewed through the Agency=s website at
http://www.epa.gov/pesticides/reregistration/status.htm.
C. Regulatory Position
1. Food Quality Protection Act Findings
a. ARisk Cup@ Determination
As part of the FQPA tolerance reassessment process, EPA assessed the risks
associated with this organophosphate. The assessment is for this individual OP, and does
-------
not attempt to fully reassess these tolerances as required under FQPA. FQPA requires
the Agency to evaluate food tolerances on the basis of cumulative risk from substances
sharing a common mechanism of toxicity, such as the toxicity expressed by the OPs
through a common biochemical interaction with the cholinesterase enzyme. The Agency
has completed a revised cumulative risk assessment for OPs (USEPA, 2002), which can
be found on the Agency's website http://www.epa.gov/pesticides/cumulative/rra-op/.
The Agency intends to issue the final tolerance reassessment reregi strati on decisions for
dimethoate and the OPs in August 2006. The Agency may need to pursue further risk
mitigation for dimethoate to address any risks identified in the cumulative assessment for
the OPs.
EPA has determined that risk from food (dietary sources only) exposure to
dimethoate is within its own "risk cup." An aggregate assessment was conducted, and
considered exposures through food and drinking water. No residential uses or non-
occupational exposure scenarios exist. This assessment showed that risks from food
alone are below the EPA's level of concern, but that risks from food and drinking water
together are above the Agency's level of concern on an acute basis for all population
subgroups when surface water modeling for some of the vegetables is considered.
Exceedances of the level of concern result from estimated residues of dimethoate and
omethoate in drinking water, which were estimated using a conservative assumption that
100% percent of dimethoate converts to omethoate during drinking water treatment via
chlorination. Please refer to the dietary risk characterization section of this document for
more information on the conservative assumptions made in the drinking water
assessment.
The Agency is requiring mitigation that is expected to reduce the amount of
dimethoate that reaches surface water bodies, including reducing application rates and the
maximum numbers of applications per year, as well as increasing the number of days
between applications. For citrus, aerial application will be prohibited. All applications to
citrus will also be prohibited in Florida, since this use contributed to drinking water
concerns in previous assessments. In addition, the registrant will be required to conduct
studies evaluating the conversion of dimethoate to omethoate during drinking water
chlorination under a variety of conditions. Given these requirements, the Agency has
determined that the human health risks from these combined exposures will be within
acceptable levels. In other words, EPA has made an interim decision (pending
cumulative) that tolerances for dimethoate meet FQPA safety standards. In reaching this
determination, EPA has considered the available information on the special sensitivity of
infants and children, as well as aggregate exposure from food and water.
b. Endocrine Disrupter Effects
EPA is required under the FFDCA, as amended by FQPA, to develop a screening
program to determine whether certain substances (including all pesticide active and other
ingredients) "may have an effect in humans that is similar to an effect produced by a
naturally occurring estrogen, or other endocrine effects as the Administrator may
designate." Following recommendations of its Endocrine Disrupter Screening and
32
-------
Testing Advisory Committee (EDSTAC), EPA determined that there was a scientific
basis for including, as part of the program, the androgen and thyroid hormone systems, in
addition to the estrogen hormone system. EPA also adopted EDSTAC's recommendation
that EPA include evaluations of potential effects in wildlife. For pesticides, EPA will use
FIFRA and, to the extent that effects in wildlife may help determine whether a substance
may have an effect in humans, FFDCA authority to require the wildlife evaluations. As
the science develops and resources allow, screening of additional hormone systems may
be added to the Endocrine Disrupter Screening Program (EDSP).
c. Cumulative Risks
Dietary risks summarized in this document are those that result only from the use
of dimethoate. The Food Quality Protection Act (FQPA) requires that the Agency
consider "available information" concerning the cumulative effects of a particular
pesticide's residues and "other substances that have a common mechanism of toxicity."
The reason for consideration of other substances is due to the possibility that low-level
exposures to multiple chemical substances that cause a common toxic effect by a
common toxic mechanism could lead to the same adverse health effect as would a higher
level of exposure to any of the substances individually. Dimethoate and omethoate (not
registered in the U.S.) are members of the organophosphate (OP) class of pesticides. The
Agency has completed a revised cumulative risk assessment for OPs, (USEPA, 2002)
which can be found on the Agency's web site
http://www.epa.gov/pesticides/cumulative/rra-op/. It assesses the cumulative effects of
exposure to multiple OPs, including dimethoate. The Agency intends to issue final
tolerance reassessment reregi strati on decisions for dimethoate and the OPs in August
2006 and may need to pursue further risk mitigation for dimethoate to address any risks
identified in the cumulative assessment for the OPs.
2. Interim Tolerance Summary
Tolerances for residues of dimethoate in/on plant commodities [40 CFR
§180.241] are presently expressed in terms of the combined residues of dimethoate and
its principal metabolite, omethoate. Following evaluation of plant metabolism studies,
the Agency has determined that the appropriate dimethoate residues are those which are
currently regulated.
Additional residue data are needed to confirm the appropriateness of existing
tolerance levels. At such time as the additional field trial data are received and deemed
adequate, these certain tolerances may be revised; however, based on existing data,
dietary risks are below EPA's level of concern and EPA considers the tolerances to be
reassessed at their current levels.
The Codex Alimentarius Commission has established separate maximum residue
limits (MRLs) for dimethoate per se and omethoate per se in/on various commodities
(see Guide to Codex Maximum Limits for Pesticide Residues, Part 2, FAO CX/PR, 4/93)
resulting from application of the insecticides dimethoate, formothion, and omethoate.
33
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Formothion and omethoate are presently not registered for use in the U.S. The Codex
and U.S. tolerances are not harmonized with respect to MRL/tolerance expression since
the U.S. tolerance expression is in terms of the combined residues of dimethoate and
omethoate, as a metabolite.
An interim summary of dimethoate tolerance reassessment and
recommended modifications in commodity definitions is presented in Table 19,
below.
Table 19. Interim Tolerance Summary for Dimethoate
Commodity
Current Tolerance
(ppm)
Tolerance
Reassessment (ppm)
Comment/
[Correct Commodity Definition]
Tolerances Listed Under 40 CFR §180.204(a):
Alfalfa
Apples
Pears
Beans, dry
Beans, lima
Beans, snap
Blueberries
Broccoli
Cabbage
Cauliflower
Collards
Kale
Mustard greens
Cattle, fat
Cattle, mbyp
Cattle, meat
Celery
Endive (escarole)
Lettuce
2
2
2
2
2
2
1
2
2
2
2
2
2
0.02(N)
0.02(N)
0.02(N)
2
2
2
2
Revoke
2
2
2
2
1
2
Revoke
2
Revoke
2
2
0.02
0.02
0.02
2
2
Revoke
Separate tolerances should be
established for Alfalfa, forage and
Alfalfa, hay, each at 2 ppm
Use cancelled 7/20/05. Existing
stocks may be sold until 7/20/06, and
use may continue until stocks are
depleted.
Change to Pear.
[Bean, dried and Bean, succulent}
Change to Blueberry.
Use cancelled 7/20/05. Existing
stocks may be sold until 7/20/06, and
use may continue until stocks are
depleted.
Use cancelled 7/20/05. Existing
stocks may be sold until 7/20/06, and
use may continue until stocks are
depleted.
Negligible residue designation is
inappropriate. Change cattle, mbyp
to Cattle, meat byproducts
Change to Endive.
Change to Leaf lettuce.
Use on head lettuce cancelled
7/20/05. Existing stocks may be sold
until 7/20/06, and use may continue
until stocks are depleted.
34
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Commodity
Spinach
Swiss chard
Corn, fodder
Corn, forage
Corn, grain
Cottonseed
Eggs
Goats, fat
Goats, mbyp
Goats, meat
Grapefruit
Lemons
Oranges
Tangerines
Grapes
Hogs, fat
Hogs, mbyp
Hogs, meat
Horses, fat
Horses, mbyp
Horses, meat
Lentils
Melons
Current Tolerance
(ppm)
2
2
1
1
O.l(N)
0.1
0.02(N)
0.02(N)
0.02(N)
0.02(N)
2
2
2
2
1
0.02(N)
0.02(N)
0.02(N)
0.02(N)
0.02(N)
0.02(N)
2.0
1
Tolerance
Reassessment (ppm)
Revoke
2
1
1
0.1
0.1
0.02
0.02
0.02
0.02
2
2
2
2
Revoke
0.02
0.02
0.02
0.02
0.02
0.02
Revoke
1
Comment/
[Correct Commodity Definition]
Use cancelled 7/20/05. Existing
stocks may be sold until 7/20/06, and
use may continue until stocks are
depleted.
Separate tolerances should be
established for Corn, field, stover
(fodder) and Corn, pop, stover
(fodder), each at 1 ppm. Change to
Corn, field, stover and Corn, pop,
stover
[Corn, field, forage] and Corn,
sweet, forage
Separate tolerances should be
established for Corn, field, grain and
Com, pop, grain, each at 0.1 ppm.
Negligible residue designation is
inappropriate.
[Cotton, undelinted seed]
Negligible residue designation is
inappropriate.
Negligible residue designation is
inappropriate. Change to Goat, fat
Goat, meat byproducts, Goat, meat
Change to Lemon.
Change to Orange.
Change to Tangerine.
Use cancelled 7/20/05. Existing
stocks may be sold until 7/20/06, and
use may continue until stocks are
depleted.
Negligible residue designation is
inappropriate. Change to Hog, fat;
Hog, meat byproducts; Hog, meat
Negligible residue designation is
inappropriate. Change to Horse, fat;
Horse, meat byproducts;
Horse, meat.
The established tolerance for peas
applies to lentils.
Change to Melon.
35
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Commodity
Milk
Peas
Pecans
Peppers
Tomatoes
Potatoes
Poultry, fat
Poultry, mbyp
Poultry, meat
Safflower seed
Sheep, fat
Sheep, mbyp
Sheep, meat
Sorghum, forage
Sorghum, grain
Soybeans
Soybeans, forage
Soybeans, hay
Turnips, roots
Turnips, tops
Wheat, grain
Wheat, green fodder
Wheat, straw
Current Tolerance
(ppm)
0.002(N)
2
0.1
2
2
0.2
0.02(N)
0.02(N)
0.02(N)
0.1
0.02(N)
0.02(N)
0.02(N)
0.2
0.1
0.05(N)
2
2
2
2
0.04(N)
2
2
Tolerance
Reassessment (ppm)
TBD
2
0.1
2
2
0.2
0.02
0.02
0.02
0.1
0.02
0.02
0.02
0.1
0.1
0.05
2
2
0.2
2
0.04
2
2
Comment/
[Correct Commodity Definition]
Once outstanding metabolism data
are submitted, the available
magnitude of the residue data for
milk will be reevaluated and
tolerance revisions may be required.
Negligible residue designation is
inappropriate.
[Peas, dried and succulent]
Change to Pea, dried and Pea,
succulent.
Change to Pecan.
Change to Pepper.
Change to Tomato.
Change to Potato.
Negligible residue designation is
inappropriate.
Poultry, mbyp should be Poultry,
meat byproducts.
[Safflower, seed]
Negligible residue designation is
inappropriate.inappropriate.
Sheep, mbyp should be Sheep, meat
byproducts.
Based on available field trial data,
HED recommends a lower tolerance.
Change to Sorghum, grain, grain.
Negligible residue designation is
inappropriate.
Change to Soybean, seed.
Change to Soybean, forage.
Change to Soybean, hay.
Based on available field trial data,
HED recommends a lower tolerance
for dimethoate residues of concern
in/on turnip roots.
Should be Turnip, roots.
Should be Turnip, tops.
Negligible residue designation is
inappropriate.
[Wheat, forage]
Tolerances That Need To Be Proposed/Established Under 40 CFR §180.204(a):
Cowpeas, forage
None
TBD
Tolerances for these commodities
will be required if the registrant
wishes to support use of dimethoate
on cowpeas grown for livestock
feeding.
36
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Commodity
Cowpeas, hay
Cotton, gin byproducts
Peas, field, vines
Peas, field, hay
Sorghum, stover (fodder)
Wheat hay
Current Tolerance
(ppm)
None
None
None
None
None
None
Tolerance
Reassessment (ppm)
TBD
TBD
TBD
TBD
0.1
2 ppm
Comment/
[Correct Commodity Definition]
Residue data are required.
Tolerances for these commodities
will be required if the registrant
wishes to support use of dimethoate
on field peas.
Change to Pea, field, vines and Pea,
field, hay
Change to Sorghum, grain, stover.
CBRS does not expect residues in/on
wheat hay to be higher than the
tolerance level established for wheat
straw. Therefore, a level of 2 ppm
may be proposed for wheat hay.
Tolerances Listed Under 40 CFR §180.204(b)
Asparagus
Brussels sprouts
Cherries
0.15
5
2
0.15
5
2
CBRS recommends that this
tolerance be listed under 40 CFR
§180.204(a).
Change to Cherry.
Tolerances Listed Under 40 CFR §186.2100
Dried citrus pulp
5
Revoke
Revoked concomitant with the
establishment of tolerance for
[Citrus, pulp, dried] - to be listed
under 40 CFR §180.204(a).
D. Regulatory Rationale
The following is a summary of the rationale for managing risks associated with
the use of dimethoate. Where labeling revisions are warranted, specific language is set
forth in the summary tables of Section V of this document. In general, the application
rates and maximum numbers of applications have been reduced, and retreatment intervals
have been increased, to reduce dietary, worker, and ecological risks. These actions will
result in reduced exposure to dimethoate. Table 20 lists all the use sites for which
application rates and label requirements have been revised.
In order to reduce drinking water risks of concern, application rates and the
number of applications are being lowered for a number of crops. Aerial applications are
prohibited for citrus and use is not allowed on citrus grown in Florida which contributed
to drinking water concerns in previous risk assessments. In addition, best management
practices (BMPs) will be added to labels, with the purpose of reducing the amount of
dimethoate that enters surface water bodies through spray drift. These BMPs include
requiring medium or coarser sprays for aerial applications and prohibiting aerial sprays in
winds greater than 10 miles per hour. To further reduce the amount of dimethoate
entering surface water bodies as runoff, the Agency recommends use of Vegetative Filter
Strips, if practical.
37
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In order to reduce occupational risks of concern, in addition to reduced
application rates and a reduction in numbers of applications permitted, handlers will be
required to use additional protective equipment, such as additional PPE or engineering
controls, depending on the handler scenario. All human flaggers supporting aerial
applications will be required to be in closed cabs. Also, high pressure handwand
applications will be prohibited for applications to woody ornamentals. Use on
cottonwoods grown for pulp will be cancelled. See Table 20 below for detailed
mitigation which is required in order for dimethoate to be eligible for reregistration. EPA
expects that these mitigation measures will result in MOEs of 100 or greater for most
handler scenarios.
Postapplication risks will be reduced by extending REIs for some crops, in
particular, orchard fruits and woody ornamentals. The occupational risk assessment for
dimethoate indicates that REIs of 12 hours are adequate to reach MOEs of 100 for a
number of scenarios. However, when the acute toxicity of omethoate is taken into
consideration, the Agency believes a 48 hour REI is more appropriate. Therefore, no
crop scenario has an REI shorter than 48 hours. This is consistent with current labels.
Regarding cole crops (broccoli, cauliflower, Brussels sprouts, and celery), the human
health risk assessment indicates that a five day REI is needed to reach an MOE of 100 for
applications in arid areas. Growers of these crops indicated an REI of greater than 3 days
is not feasible for them; EPA assessed the impacts of this longer REI, and concurred.
Therefore, EPA is allowing an REI of 3 days for applications made to cole crops in arid
areas which results in an MOE of 89.
Risks to endangered species identified in the Environmental Fate and Ecological
Risk Assessment for dimethoate are based solely on EPA's screening level assessment
and do not constitute "may effect" findings under the Endangered Species Act. Rather,
this assessment serves as a screen to determine the need for any species specific
assessments that will evaluate whether exposure may be at levels that could cause harm
to specific listed species and their critical habitat. That assessment refines the screening-
level assessment to take into account the geographic area of pesticide use in relation to
the listed species, the habits and habitat requirements of the listed species, etc. If the
Agency's specific assessments result in the need to modify use of the pesticide in specific
geogrpahic areas, those changes to the pesticide's registration will take through the
process described in the Agency's Federal Register Notice (54 FR 27984) regarding
implementation of the Endangered Species Protection Program.
The primary ecological risks of concern are to birds and mammals on a chronic
basis. The Agency is attempting to reduce those risks by reducing application rates and
numbers of applications, and increasing application intervals.
38
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Table 20. Revised Use Site Parameters and Requirements for Dimethoate
Crop
Cherries
Asparagus
Citrus
Pears
Alfalfa (seed
and hay)
Succulent
peas
Beans -
fresh, snap,
lima, dry
Broccoli
App method
Aerial
Aerial,
chemigation,
and airblast
Aerial
chemigation,
groundboom
Chemigation,
Aerial,
chemigation,
airblast (liquid
andWP)
Aerial
chemigation,
groundboom
A priol
-iiX/lldl^
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
Max
rate
per app
(Ibs
1 (SLN)
0.33
0.5
1
1
0.5
0.16
0.5
0.5
$ apps/
interval
1
2/14
1
1
l(per
cutting)
1
2/14
3/7
~J 1 1
REI (days)
Non-
arid
10
2
2
10
10
2
2
2
2
Arid
14
4
2
14
14
2
2
2
,,
Other
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Airblast: M/L must wear gloves and
apron, Applicators must wear gloves
and a respirator.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Prohibit aerial applications.
Prohibit all applications in Florida.
Chemigation: M/L must wear
gloves, apron, and respirator.
Airblast: M/L must wear gloves and
apron, Applicators must wear gloves
and a respirator.
For WPs: water-soluble packaging
plus gloves and apron for M/L
For liquids:
Aerial/Chemigation. gloves, apron,
respirator for M/L;
Airblast: M/L must wear gloves and
apron,
For both: Pilots in enclosed
cockpits, gloves and respirator for
airblast applicators
Aerial and Chemigation: closed
systems plus gloves and apron for
M/L; Pilots in enclosed cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
39
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Crop
Cauliflower
Celery
Cotton
Lentils
Melon
Potatoes
App method
groundboom
Aerial
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial
chemigation,
groundboom
(liquid and
'
Max
rate
per app
(Ibs
0.5
0.5
0.5
0.5
0.5
0.5
# apps/
interval
3/7
3/7
2/14
2/7
2/7
2/7
REI (days)
Non-
arid
2
2
2
2
2
2
Arid
3
2
2
2
2
2
Other
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Also: BMPs, vegetative filter strips
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for appl.
Also: BMPs, vegetative filter strips
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Also: BMPs, vegetative filter strips
Aerial/ Chemigation: closed
systems plus gloves and apron for
M/L; Pilots in enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Also: BMPs for aerial
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Also: BMPs
For WPs: water-soluble packaging
plus gloves and apron for M/L; Pilots
in enclosed cockpits; gloves for
groundboom apps
For liquids:
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Also: BMPs
40
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Crop
Soybeans
Tomatoes
Field corn;
popcorn
Safflower
Sorghum
Wheat
Pecans
Peppers
Grass for
seed
App method
A priol
.iiX/lldl^
chemigation,
groundboom
Aerial
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial
chemigation,
groundboom
Aerial
chemigation,
groundboom
A priol
.iiX/lldl^
chemigation,
groundboom
Aerial,
chemigation,
airblast
A priol
.iiX/lldl^
chemigation,
groundboom
Aerial,
chemigation,
Max
rate
per app
(Ibs
0.5
0.5
0.5
0.5
0.5
0.5
0.33
0.33
0.5
$ apps/
interval
2/7
2/6
1
1
2/7
1
1
3/7
2/90
REI (days)
Non-
arid
2
2
2
2
2
2
2
2
2
Arid
2
2
2
2
2
2
2
2
2
Other
Aerial/Chemigation: closed
systems plus gloves and apron for
M/L; Pilots in enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: closed
systems plus gloves and apron for
M/L; Pilots in enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators
Aerial/Chemigation: closed
systems plus gloves and apron for
M/L; Pilots in enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: closed
systems plus gloves and apron for
M/L; Pilots in enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: closed
systems plus gloves and apron for
M/L; Pilots in enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: gloves, apron,
and respirator for M/L; Pilots in
enclosed cockpits.
Airblast: gloves and apron for M/L;
gloves and respirator for apps.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: M/L must
wear gloves, apron, and respirators.
41
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Crop
Leaf lettuce
Swiss chard
Endive
(escarole)
Kale
Turnips
Mustard
greens
Brussels
sprouts
Herbaceous
ornamentals
App method
groundboom
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Aerial,
chemigation,
groundboom
Groundboom,
low pressure
handwand
Max
rate
per app
(Ibs
a.i./A)
0.25
0.25
0.25
0.25
0.25
0.25
0.5
0.25
# apps/
interval
3/7
3/7
3/7
2/15
3/7
2/9
3/7
1
REI (days)
Non-
arid
2
2
2
2
2
2
2
2
Arid
2
2
2
2
2
2
3
2
Other
Pilots in enclosed cockpits.
Groundboom: gloves and apron for
M/L; gloves for applicators.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators.
Aerial/Chemigation: gloves, apron,
respirator for M/L; Pilots in enclosed
cockpits.
Groundboom: : M/L must wear
gloves and apron, gloves for
applicators.
Also: BMPs, vegetative filter strips
Groundboom and Low Pressure
handwand: M/L must wear gloves
and apron, Gloves for applicators.
High Pressure Handwand: M/L
42
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Crop
Douglas fir
orchards in
WA and OR
Conifer seed
orchards
Woody
ornamentals
and
Christmas
tree
nursenes
Cottonwood
grown for
pulp
App method
Airblast-
Aerial,
Groundboom
Aerial,
Groundboom
Max
rate
per app
(Ibs
4.15
1
1
# apps/
interval
1
1
3/14
REI (days)
Non-
arid
16
2
10
Arid
25
4
14
Other
must wear gloves and apron, Gloves
and respirator for applicators.
Airblast: M/L must wear gloves and
apron, Applicators must wear gloves
and a respirator.
Aerial: M/L must wear gloves,
apron, and respirator. Pilots in
enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, Gloves for
applicators.
Aerial: M/L must wear gloves,
apron, and respirator. Pilots in
enclosed cockpits.
Groundboom: M/L must wear
gloves and apron, Gloves for
applicators.
Canceling use
* Enclosed cockpits are required for all aerial applications.
1. Significance of Use
Dimethoate is a systemic insecticide which is widely used to control pests on
vegetable and row crops. It has a relatively short pre-harvest interval (PHI) and some
residual efficacy which often makes it a compound of choice for fresh market vegetable
production.
During the three public comment periods on the dimethoate risk assessments, the
Agency received many grower comments in support of retaining dimethoate use for
various crops.
EPA divided uses into two groups based on percent crop treated. If a low
percentage of a crop is treated, the Agency makes the preliminary assumption that the
significance of use on that crop is also low. For these crops, the Agency consulted with
the USD A Office of Pest Management Policy (OPMP) to determine whether there were
niche uses which should be considered in any mitigation plan. The twelve use sites in
this category are: alfalfa, cherries, citrus, cotton, corn (field and pop), grass grown for
seed, pears, pecans, peppers, safflower, and succulent peas. OPMP received comments
from their Regional offices on dimethoate use. While growers in some regions do not
apply any dimethoate on these crops, all twelve sites had some limited usage, primarily
for control of flare-ups of spider mites, thrips, aphids, or fleahoppers. There was also
some occasional use for grasshopper control which is not necessary every year, but for
43
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which dimethoate was cited as a very important tool. The alternatives to these uses were
generally other organophosphates, carbamates or pyrethroids. Several regional experts
stated that many of the alternatives are restricted-use products, and so dimethoate
products are more attractive because dimethoate is an efficacious general use compound.
For the use sites with greater than 5% crop treated with dimethoate, the Agency
assumed that the higher use frequency implied significance of use. For these sites, the
Agency examined dimethoate use patterns and available alternatives and generally
evaluated the feasibility of extending restricted entry intervals (but not the impacts of
cancellation). Please refer to the Biological and Economic Analysis Divisions
memorandum entitled "Dimethoate application information for specific crops (DP #
291616) " and dated March 8, 2006. Through this assessment, the Agency concluded
that the required worker mitigation will effectively reduce risk without major impacts on
the importance of dimethoate to users.
2. Spray Drift
The Agency has been working with the Spray Drift Task Force, EPA Regional
Offices and State Lead Agencies for pesticide regulation, and other parties to develop the
best spray drift management practices. The Agency has completed its evaluation of the
new data base submitted by the Spray Drift Task Force, a membership of U.S. pesticide
registrants, and is developing a policy on how to appropriately apply the data and the
AgDRTFT computer model to its risk assessments for pesticides applied by air, orchard
airblast and ground hydraulic methods. After the policy is in place, the Agency may
impose further refinements in spray drift management practices to reduce off-target drift
and risks associated with aerial, as well as other application types, where appropriate.
From its assessment of dimethoate as summarized in this document, the Agency
concluded that the major source of dimethoate entering surface water bodies is through
runoff. Therefore, the Agency will require that use of vegetative buffers be encouraged
on product labels. The Agency is requiring mitigation that will also reduce the amount
entering through spray drift. Namely, aerial applications are being cancelled for a few
crops and labels will be revised to include best management practices including lowered
boom height and largest effective droplet size.
3. Endangered Species Considerations
From the screening level assessment, RQs exceed the endangered species LOG
for some of the representative exposure scenarios considered. At the rates assessed, acute
and chronic RQs exceed the LOG for endangered birds and mammal across all use sites.
After a single application of 0.16 Ibs a.i./A, the endangered species acute and chronic risk
LOCs are exceeded for birds and mammals for some use sites. Further, potential indirect
effects to any species dependent upon a species that experiences effects from use of
dimethoate, can not be precluded based on the screening level ecological risk assessment.
44
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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/IREDs 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. When conducted, this
species-specific analysis will take into consideration any regulatory changes
recommended in this IRED that are being implemented at that time.
Following this future species-specific analysis, a determination that there is a
likelihood of potential impact to a listed species or its critical habitat may result in:
limitations on the use of dimethoate, 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 dimethoate "may affect" listed species or
their designated critical habitat, EPA will employ the provisions in the Services
regulations (50 CFR Part 402). Until that species-specific analysis is completed, the risk
mitigation measures being implemented through this IRED will reduce the likelihood that
endangered and threatened species may be exposed to dimethoate at levels of concern.
EPA is not requiring specific dimethoate 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.
V. What Registrants Need to Do
The Agency has determined that dimethoate will be eligible for reregi strati on
provided that: (i) the risk mitigation measures outlined in this document are adopted and
(ii) label amendments are made to reflect these measures. To implement the risk
mitigation measures, the registrants must amend their product labeling to incorporate the
label statements set forth in the Label Summary Table in Section D below. The
additional data requirements that the Agency intends to obtain will include, among other
things, submission of the following:
A. For dimethoate technical grade active ingredient products, the registrant needs
to submit the following items:
Within 90 days from receipt of the generic data call in (DCI):
1. completed response forms to the generic DCI (i.e., DCI response
form and requirements status and registrant's response form); and
45
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2. any time extension and/or waiver requests with a full written
justification.
Within the time limit specified in the generic DCI:
1. citation of any existing generic data which address data requirements
or submit new generic data responding to the DCI.
Please contact Stephanie Plummer at (703) 305-0076 with questions regarding
generic reregi strati on.
By US mail: By express or courier service:
Document Processing Desk (DCI/SRRD) Document Processing Desk (DCI/SRRD)
Stephanie Plummer Stephanie Plummer
US EPA (7508C) Office of Pesticide Programs (7508C)
1200 Pennsylvania Ave., NW Room 266A, Crystal Mall 2
Washington, DC 20460 1801 S. Bell Street
Arlington, VA 22202
B. For end-use products containing the active ingredient dimethoate, the
registrant needs to submit the following items for each product:
Within 90 days from the receipt of the product-specific data call-in (PDCI):
1. completed response forms to the PDCI (i.e., PDCI response form and
requirements status and registrant's response form); and
2. submit any time extension or waiver requests with a full written
justification.
Within eight months from the receipt of the PDCI:
1. two copies of the confidential statement of formula (EPA Form 8570-
4);
2. a completed original application for reregi strati on (EPA Form 8570-
1). Indicate on the form that it is an "application for reregi strati on";
3. five copies of the draft label incorporating all label amendments
outlined in Table 31 of this document;
4. a completed form certifying compliance with data compensation
requirements (EPA Form 8570-34); and
5. if applicable, a completed form certifying compliance with cost share
offer requirements (EPA Form 8570-32); and
6. the product-specific data responding to the PDCI.
Please contact Venus Eagle at (703) 308-8045 with questions regarding product
reregi strati on and/or the PDCI. All materials submitted in response to the PDCI should
be addressed as follows:
46
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By US mail: By express or courier service:
Document Processing Desk (PDCI/PRB) Document Processing Desk (PDCI/PRB)
Venus Eagle Venus Eagle
US EPA (7508C) Office of Pesticide Programs (7508C)
1200 Pennsylvania Ave., NW Room 266A, Crystal Mall 2
Washington, DC 20460 1801 South Bell Street
Arlington, VA 22202
A. Manufacturing Use Products
1. Additional Generic Data Requirements
The generic database supporting the interim of dimethoate for the uses specified in this
document has been reviewed and determined to be substantially complete. However, the
data listed below are necessary to confirm the Interim Reregi strati on Eligibility Decision
outlined in this document.
Studies required for dimethoate
850.1350 Mysid life cycle
850.1400 Estuarine/marine fish early life-stage
850.4225 Seedling emergence (Tier II)
850.4250 Vegetative vigor (Tier II)
850.4400 Aquatic Plant (Tier II)
860.1380 Storage stability data for meat, milk, poultry, and eggs
860.1500 Magnitude of residue on alfalfa grown for seed
860.1500 Magnitude of residue data for cotton gin byproducts
163-1 Batch equilibrium study
Non-guideline study Forestry field dissipation study (in support of poplar,
spruce seed orchard, and larch uses)
Non-guideline study Water treatment assay to determine percent conversion
with chlorination in a variety of water chemistries
The reregi strati on requirements for the magnitude of residue in plants have been
fulfilled for pea vines and pea hay. The registrant must either petition the Agency for the
establishment of tolerances for the total residues of dimethoate and omethoate in/on pea
vines and pea hay or amend product labels to restrict the use of dimethoate to peas (not
including field peas).
Studies required for metabolites
850.2100 Acute oral (bobwhite quail and mallard duck) - omethoate
850.2200 Subacute dietary (bobwhite quail and mallard duck) -
omethoate
850.2300 Reproduction (bobwhite quail and mallard duck) -
omethoate
47
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860.1500 Magnitude of residue data for metabolites of concern (O-
desmethyl omethoate, O-desmethyl omethoate carboxylic
acid, and O-desmethyl isodimethoate)
Non-guideline study Comparative cholinesterase study on rats for metabolites of
concern (O-desmethyl omethoate, O-desmethyl omethoate
carboxylic acid, and O-desmethyl isodimethoate)
B. End-Use Products
1. Additional Product-Specific Data Requirements
Section 4(g) (2) (B) of FIFRA calls for the Agency to obtain any needed product-
specific data regarding the pesticide after a determination of eligibility has been made.
The registrant must review previous data submissions to ensure they meet current EPA
acceptance criteria and if not, commit to conduct new studies. If a registrant believes that
previously submitted data meet current testing standards, then the study MRID numbers
should be cited according to the instructions in the Requirement Status and Registrations
Response Form provided for each product. The Agency intends to issue a separate
product-specific Data Call-In outlining specific data requirements
2. Labeling for End-Use Products
Labeling changes are necessary to implement measures outlined in Section IV
above. Specific language to incorporate these changes is specified in Table 22.
Existing stocks time frames will be established on a case-by-case basis, depending
on the number of products involved, the number of label changes, and other factors.
Please refer to "Existing Stocks of Pesticide Products; Statement of Policy," Federal
Register, Volume 56, No. 123, June 26, 1991.
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Labeling Changes Summary Table
In order to be eligible for reregi strati on, amend all product labels to incorporate the risk mitigation measures outlined in
Section IV. The following table describes how language on the labels should be amended.
Table 22. Label Changes Summary Table for Dimethoate
Description
Amended Labeling Language
Placement on Label
For all Manufacturing
Use Products
"Only for formulation into an insecticide for the following use(s) [alfalfa,
alfalfa for seed, asparagus, beans (excluding cowpeas), broccoli, Brussels
sprouts, cauliflower, celery, cherries, Chinese cabbage, Christmas tree
farms, conifer seed farms, cotton, endive, field corn, grass grown for
seed, herbaceous ornamentals in commercial nurseries or greenhouses,
grapefruit, leaf lettuce, lemons, lentils, kale melons, mustard greens,
oranges, pears, peas, pecans, peppers, popcorn, potatoes, safflower,
sorghum, soybeans, Swiss chard, tangerines, tangelos, tomatoes, turnips,
watermelons, wheat, and woody ornamentals in commercial nurseries or
greenhouses ]."
"Not for formulation into wettable powder end use products (EUP),
unless the EUP is packaged in water soluble bags."
Not for formulation into end-use products intended for use by
homeowners or that permit use at residential sites.
Directions for Use
One of these statements
may be added to a label
to allow reformulation
of the product for a
specific use or all
additional uses
supported by a
"This product may be used to formulate products for specific use(s) not
listed on the MP label if the formulator, user group, or grower has
complied with U.S. EPA submission requirements regarding support of
such use(s)."
"This product may be used to formulate products for any additional
use(s) not listed on the Manufacturing Use Product (MUP) label if the
Directions for Use
49
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formulator or user
group
formulator, user group, or grower has complied with U.S. EPA
submission requirements regarding support of such use(s)."
Environmental Hazards
Statements Required
by the RED and
Agency Label Policies
"Do not discharge effluent containing this product into lakes, streams,
ponds, estuaries, oceans, or other waters unless in accordance with the
requirements of a National Pollution Discharge Elimination System
(NPDES) permit and the permitting authority has been notified in writing
prior to discharge. Do not discharge effluent containing this product to
sewer systems without previously notifying the local sewage treatment
plant authority. For guidance contact your State Water Board or
Regional Office of the EPA."
Precautionary Statements
End Use Products Intended for Occupational Use
PPE Requirements
Established by the
RED1
For Wettable Powder
Formulations (wettable
powder products must
be packaged in water
soluble bags to be
eligible for
reregistration)
"Personal Protective Equipment (PPE)"
"Some materials that are chemical-resistant to this product are"
(registrant inserts correct chemical-resistant material). "If you want
more options, follow the instructions for category" [registrant inserts
A,B,C,D,E,F,G,or H] "on an EPA chemical-resistance category selection
chart."
"Mixers, loaders, applicators, and other handlers must wear:
>Long-sleeved shirt and long pants,
> Shoes plus socks,
> Chemical-resistant apron for mixers and loaders,
> Chemical-resistant gloves.
In addition, applicators using airblast or high pressure handwand
equipment, must wear:
> NIOSH-approved respirator with
~ an organic-vapor-removing cartridge with a prefilter approved for
pesticides (MSHA/NIOSH approval number prefix TC-23C), or
.. a canister approved for pesticides (MSHA/NIOSH approval number
Immediately following/below
Precautionary Statements: Hazards to
Humans and Domestic Animals
50
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prefix TC-14G), or
~ an organic-vapor-removing cartridge or canister with any N, R, P or
HE prefilter."
"See Engineering Controls for additional requirements."
Instruction to Registrant: Drop the "N" type prefilter from the respirator
statement, if the pesticide product contains, or is used with, oil.
PPE Requirements
Established by the
RED1
For Liquid
Formulations
"Personal Protective Equipment (PPE)"
"Some materials that are chemical-resistant to this product are"
(registrant inserts correct chemical-resistant material). "If you want
more options, follow the instructions for category" [registrant inserts
A,B,C,D,E,F,G,or H] "on an EPA chemical-resistance category selection
chart."
"Mixers, loaders, applicators, and other handlers; must wear:
Long-sleeved shirt and long pants, and
> Shoes plus socks,
> Chemical-resistant apron for mixers and loaders,
> In addition, all mixers and loaders, plus applicators using airblast or
high pressure handwand equipment must wear chemical-resistant gloves.
> In addition, mixers and loaders supporting aerial and chemigation
applications, and applicators using airblast or high pressure handwand
equipment must wear:
> NIOSH-approved respirator with
~ an organic-vapor-removing cartridge with a prefilter approved for
pesticides (MSHA/NIOSH approval number prefix TC-23C), or
.. a canister approved for pesticides (MSHA/NIOSH approval number
prefix TC-14G), or
.. an organic-vapor-removing cartridge or canister with any N, R, P or
HE prefilter."
Immediately following/below
Precautionary Statements: Hazards to
Humans and Domestic Animals
51
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"See Engineering Controls for additional requirements."
Instruction to Registrant: Drop the "N" type prefilter from the respirator
statement, if the pesticide product contains, or is used with, oil.
User Safety
Requirements
"Follow manufacturer's instructions for cleaning/maintaining PPE. jf no
such instructions for washables exist, use detergent and hot water. Keep
and wash PPE separately from other laundry."
"Discard clothing and other absorbent materials that have been drenched
or heavily contaminated with this product=s concentrate. Do not reuse
them."
Precautionary Statements: Hazards to
Humans and Domestic Animals
immediately following the PPE
requirements
Engineering Controls:
(Water-Soluble
Packaging for Wettable
Powder Formulations)
"Engineering controls"
"Water-soluble packets, when used correctly, qualify as a closed
mixing/loading system under the Worker Protection Standard for
Agricultural Pesticides [40 CFR 170.240(d)(4)]. Mixers and loaders
using water-soluble packets must:
~ wear the personal protective equipment required in the PPE section of
this labeling for mixers and loaders, and
~ be provided and have immediately available for use in an emergency,
such as a broken package, spill, or equipment breakdown: chemical-
resistant footwear, and the type of respirator specified in the PPE section
of this label."
"Pilots must use an enclosed cockpit that meets the requirements listed in
the Worker Protection Standard (WPS) for agricultural pesticides [40
CFR 170.240(d)(6)]."
Precautionary Statements: Hazards to
Humans and Domestic Animals
(Immediately following PPE and User
Safety Requirements.)
52
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Flaggers supporting aerial applications must use an enclosed cab that
meets the definition in the Worker Protection Standard for Agricultural
Pesticides [40 CFR 170.240(d)(5)] for dermal protection. In addition,
flaggers must:
~ wear long-sleeve shirt, long pants, shoes, socks and,
~ either wear the type of respirator specified in the PPE section of this
labeling or use an enclosed cab that is declared in writing by the
manufacturer or by a government agency to provide at least as much
respiratory protection as the respirator specified in this labeling,
~ be provided and have immediately available for use in an emergency
when they must exit the cab in the treated area: coveralls, chemical-
resistant gloves, chemical-resistant footwear, and chemical-resistant
headgear, if overhead exposure and, if using an enclosed cab that
provides respiratory protection, a respirator of the type specified in the
PPE section of this labeling,
~ take off any PPE that was worn in the treated area before reentering the
cab, and
~ store all such PPE in a chemical-resistant container, such as a plastic
bag, to prevent contamination of the inside of the cab."
"When applicators use enclosed cabs in a manner that meets the
requirements listed in the Worker Protection Standard (WPS) for
agricultural pesticides (40 CFR 170.240(d)(5), the handler PPE
requirements may be reduced or modified as specified in the WPS."
Engineering Controls:
For Liquid
Formulations
"Engineering controls"
'Mixers and loaders supporting aerial or chemigation applications to
alfalfa, cotton, soybeans, corn, safflower, sorghum, and wheat, must use a
closed system that meets the requirements listed in the Worker Protection
Standard (WPS) for agricultural pesticides [40 CFR 170.240(d)(4)]. The
system must be capable of removing the pesticide from the shipping
container and transferring it into mixing tanks and/or application
Precautionary Statements: Hazards to
Humans and Domestic Animals
(Immediately following PPE and User
Safety Requirements.)
53
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equipment. At any disconnect point, the system must be equipped with a
dry disconnect or dry couple shut-off device that is warranted by the
manufacturer to minimize drippage to no more than 2 ml per disconnect.
In addition, mixers and loaders must:
~ wear the personal protective equipment required on this labeling for
mixers/loaders, except that no respirator is required;
- wear protective eyewear, if the system operates under pressure; and
~ be provided and have immediately available for use in an emergency,
such as a broken package, spill, or equipment breakdown, chemical-
resistant footwear and a respirator of the type specified in the PPE section
of this labeling."
"Pilots must use an enclosed cockpit that meets the requirements listed in
the Worker Protection Standard (WPS) for agricultural pesticides [40
CFR 170.240(d)(6)]."
Flaggers supporting aerial applications must use an enclosed cab that
meets the definition in the Worker Protection Standard for Agricultural
Pesticides [40 CFR 170.240(d)(5)] for dermal protection. In addition,
flaggers must:
~ wear long-sleeve shirt, long pants, shoes, socks and,
~ either wear the type of respirator specified in the PPE section of this
labeling or use an enclosed cab that is declared in writing by the
manufacturer or by a government agency to provide at least as much
respiratory protection as the respirator specified in this labeling,
~ be provided and have immediately available for use in an emergency
when they must exit the cab in the treated area: coveralls, chemical-
resistant gloves, chemical-resistant footwear, and chemical-resistant
headgear, if overhead exposure, and, if using an enclosed cab that
provides respiratory protection, a respirator of the type specified in the
PPE section of this labeling,
~ take off any PPE that was worn in the treated area before reentering the
cab, and
— store all such PPE in a chemical-resistant container, such as a plastic
54
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bag, to prevent contamination of the inside of the cab."
"When handlers use closed systems, or enclosed cabs in a manner that
meets the requirements listed in the Worker Protection Standard (WPS)
for agricultural pesticides (40 CFR 170.240(d)(4-5), the handler PPE
requirements may be reduced or modified as specified in the WPS."
User Safety
Recommendations
"USER SAFETY RECOMMENDATIONS'
'Users should wash hands before eating, drinking, chewing gum, using
tobacco, or using the toilet."
"Users should remove clothing/PPE immediately if pesticide gets inside.
Then wash thoroughly and put on clean clothing."
"Users should remove PPE immediately after handling this product.
Wash the outside of gloves before removing. AS soon as possible, wash
thoroughly and change into clean clothing."
Precautionary Statements under:
Hazards to Humans and Domestic
Animals immediately following
Engineering Controls
(Must be placed in a box.)
Environmental Hazards
"Do not apply directly to water, or to areas where surface water is present
or to intertidal areas below the mean high water mark. DO not
contaminate water when disposing of equipment washwater or rinsate."
"Dimethoate is known to leach through soil into ground water under
certain conditions as a result of label use. Use of this chemical in areas
where soils are permeable, particularly where the water table is shallow,
may result in ground-water contamination."
"This product may contaminate water through drift of spray in wind.
This product has a high potential for runoff for several days after
application after application. Poorly draining soils and soils with shallow
water tables are more prone to produce runoff that contains this product."
Precautionary Statements immediately
following the User Safety
Recommendations
55
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"A level, well maintained vegetative buffer strip between areas to which
this product is applied and surface water features such as ponds, streams,
and springs will reduce the potential for contamination of water from
rainfall-runoff. Runoff of this product will be reduced by avoiding
applications when rainfall is forecasted to occur within 48 hours."
"A vegetative filter strip constructed and maintained in accordance with
the 2000 Natural Resources Conservation Service publication
"Conservation Buffers to Reduce Pesticide Losses"
(http://www.nrcs.usda.gov/feature/buffers/) will significantly reduce the
potential for contamination of water from rainfall-runoff."
Restricted-Entry
Intervals for products
with directions for use
within the scope of the
Worker Protection
Standard (WPS) for
Agricultural Pesticides
(WPS)
"Do not enter or allow worker entry into treated areas during the
restricted entry interval (REI)."
In the Agricultural Use Requirements
box
Early Entry Personal
Protective Equipment
for products with
directions for use
within the scope of the
Worker Protection
Standard (WPS) for
Agricultural Pesticides
"PPE required for early entry to treated areas that is permitted under the
Worker Protection Standard and that involves contact with anything that
has been treated, such as plants, soil, or water, is:
> coveralls worn over long-sleeve shirt and long pants,
> chemical-resistant gloves made of any waterproof material,
> chemical-resistant footwear plus socks, and
> chemical-resistant headgear (if overhead exposure)"
Direction for Use
Agricultural Use Requirements box
Double Notification
Statement
"Notify workers of the application by warning them orally and by posting
warning signs at entrances to treated area."
Direction for Use
Agricultural Use Requirements box
56
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General Application
Restrictions
"Do not apply this product in a way that will contact workers or other
persons, either directly or through drift. Only protected handlers may be
in the area during application."
Place in the Direction for Use directly
above the Agricultural Use Box.
Application Restriction
"This product is for use in commercial setting only. Use in residential
settings is prohibited."
Near the beginning of the Directions for
Use
Crop-Specific
Application
Restrictions and REIs
The maximum
application rate also
must be stated in terms
of the pounds or
gallons of formulation
Labels must be amended to reflect the following equipment restrictions,
maximum application rates, retreatment interval, and the maximum
number of treatments per year:
High Pressure Handwand Equipment: "When applications are made
by high pressure handwand equipment, the maximum application rate for
all crops and use-patterns is 0.0025 pounds active ingredient per gallon."
Alfalfa (grown for seed and for hay)
Maximum application rate: 0.5 Ib ai/acre and no more than one
application per crop cycle or cutting. Maximum 3 applications per year.
"The REI is 48 hours."
Asparagus, Beans (including fresh, snap, lima, and dry beans) and
Cotton
Maximum application rate: 0.5 Ib ai/acre , 14 day retreatment interval and
no more than 2 applications per year. "The REI is 48 hours."
Field Corn and Popcorn
Maximum application rate: 0.5 Ib ai/acre and no more than one
Directions for Use associated with the
use directions for the specific crop to
which the restriction pertains
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application per year. "The REI is 48 hours. PROHIBITION: Workers are
prohibited from entering the treated area to perform detasseling tasks for
4 days in nonarid areas and for 15 days in outdoor areas where the
average annual rainfall is less than 25 inches per year."
Broccoli, Brussels Sprouts, and Cauliflower
Maximum application rate: 0.5 Ib ai/acre, 7 day retreatment interval and
no more than 3 applications per year. "The REI is 48 hours; however, the
REI is increased to 72 hours in outdoor areas where the average annual
rainfall is less than 25 inches per year."
Celery
Maximum application rate: 0.5 Ib ai/acre, 7 day retreatment interval, and
no more than 3 applications per year. "The REI is 48 hours."
Cherries
Maximum application rate: 0.33 Ib ai/acre and no more than one
application per year. "The REI is 48 hours; however, the REI is
increased to 4 days in outdoor areas where the average annual rainfall is
less than 25 inches per year."
Note: There is an SLN for Cherries where the rate is 1 Ib. per acre and
no more than one application per year. "The REI is 10 days; however, the
REI is increased to 14 days in outdoor areas where the average annual
rainfall is less than 25 inches per year." This information must be placed
on the SLN label
Citrus
Maximum application rate: 1 Ib ai/acre and no more than one application
per year. "Do not apply to citrus in Florida" "Aerial application to citrus
is prohibited" "The REI is 10 days; however, the REI is increased to 14
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days in outdoor areas where the average annual rainfall is less than 25
inches per year."
Conifer Seed Orchards
Maximum application rate: 1 Ib ai/acre and no more than one application
per year. "The REI is 48 hours; however, the REI is increased to 4 days
in outdoor areas where the average annual rainfall is less than 25 inches
per year."
Special Exception for airblast applications to Douglas Fir Seed
Orchards in WA and OR only
Maximum application rate: 4.15 Ib ai/acre. The limit of one application
per year applies. "If airblast applications are applied at a rate greater than
1 Ib a.i/ acre, the REI is 16 days; however, the REI is increased to 25
days in outdoor areas where the average annual rainfall is less than 25
inches per year."
Grass Grown for Seed
Maximum application rate: 0.5 Ib ai/acre 90 day retreatment interval and
no more than 2 applications per year. "The REI is 48 hours."
Herbaceous Ornamentals
Maximum application rate: 0.25 Ib ai/acre and no more than 1 application
per year. "The REI is 48 hours."
Kale
Maximum application rate: 0.25 Ib ai/acre, 15 day reapplication interval,
and no more than 2 applications per year. "The REI is 48 hours."
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Leaf lettuce, Swiss Chard, Endive and Escarole
Maximum application rate: 0.25 Ib ai/acre, 7 day reapplication interval,
and no more than 3 applications per year. "The REI is 48 hours."
Lentils, Melon, Honeydew, and Potatoes
Maximum application rate: 0.5 Ib ai/acre, 7 day reapplication interval,
and no more than 2 applications per year. "The REI is 48 hours."
Safflower and Wheat
Maximum application rate: 0.5 Ib ai/acre and no more than 1 application
per year. "The REI is 48 hours."
Sorghum, and Soybeans
Maximum application rate: 0.5 Ib ai/acre, 7 day reapplication interval,
and no more than 2 applications per year. "The REI is 48 hours."
Mustard Greens
Maximum application rate: 0.25 Ib ai/acre, 9 day reapplication interval,
and no more than 2 applications per year. "The REI is 48 hours."
Pears
Maximum application rate: 1 Ib ai/acre and no more than one application
per year. "The REI 10 days; however, the REI is increased to 14 days in
outdoor areas where the average annual rainfall is less than 25 inches per
year."
Pecans
Maximum application rate 0.33 Ib ai/acre and no more than one
application per year. "The REI is 48 hours."
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Peppers
Maximum application rate 0.33 Ib ai/acre, 7 day reapplication interval,
and no more than three applications per year. "The REI is 48 hours."
Succulent peas
Maximum application rate 0.16 Ib ai/acre and no more than one
application per year. "The REI is 48 hours."
Note: There are SLN registrations for succulent peas for which the total
seasonal rate is not to exceed 0.5 Ibs. a.i./acre.
Tomatoes
Maximum application rate 0.5 Ib ai/acre, 6 day reapplication interval, and
no more than 2 applications per year. "The REI is 48 hours."
Turnips
Maximum application rate 0.25 Ib ai/acre, 3 day reapplication interval,
and no more than 7 applications per year. "The REI is 48 hours."
Woody Ornamentals and Christmas Tree Nurseries
Maximum application rate 1.0 Ib ai/acre, 14 day reapplication interval,
and no more than 3 applications per year. "Do not apply by high pressure
handwand to conifer and other ornamental tree crops" "The REI 10 is
days; however, the REI is increased to 14 days in outdoor areas where the
average annual rainfall is less than 25 inches per year."
Spray Drift
"Requirements for Reducing Spray Drift
Do not apply under circumstances where possible drift to unprotected
persons or to food, forage, or other plantings that might be damaged or
crops thereof rendered unfit for sale, use, or consumption can occur.
Directions for Use
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1. Use the largest droplet size consistent with acceptable efficacy.
Formation of very small droplets may be minimized by appropriate
nozzle selection, by orienting nozzles away from the air stream as much
as possible, and by avoiding excessive spray boom pressure. For
groundboom and aerial applications, use medium or coarser spray
nozzles according to ASAE 572 definition for standard nozzles or a
volume mean diameter (VMD) of 300 microns or greater for spinning
atomizer nozzles.
2. Make aerial or ground applications when the wind velocity favors on-
target product deposition. Apply only when the wind speed is less than
or equal to 10 mph. For all non-aerial applications, wind speed must be
measured adjacent to the application site on the upwind side, immediately
prior to application.
3. Do not make aerial or ground applications into areas of temperature
inversions. Inversions are characterized by stable air and increasing
temperatures with increasing distance above the ground. Mist or fog may
indicate the presence of an inversion in humid areas. Where permissible
by local regulations, the applicator may detect the presence of an
inversion by producing smoke and observing a smoke layer near the
ground surface.
4. Low humidity and high temperatures increase the evaporation rate of
spray droplets and therefore the likelihood of increased spray drift.
Avoid spraying during conditions of low humidity and/or high
temperatures.
5. All aerial and ground application equipment must be properly
maintained and calibrated using appropriate carriers.
6. For groundboom applications, apply with nozzle height no more than
4 feet above the ground or crop canopy.
7. For airblast applications, turn off outward pointing nozzles at row
ends and when spraying the outer two rows. To minimize spray loss over
the top in orchard applications, spray must be directed into the canopy.
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8. For ground-boom, chemigation, orchard, or other airblast applications,
do not apply within 25 feet of permanent water bodies (rivers, natural
ponds, lakes, streams, reservoirs, marshes, estuaries, or commercial fish
ponds).
9. For aerial application to potatoes, do not apply within 150 feet of
permanent water bodies (aquatic buffer zone).
10. For aerial application to crops other than potatoes, do not apply
within 50 feet of permanent water bodies (aquatic buffer zone).
11. For aerial applications, release spray at the lowest height consistent
with efficacy and flight safety. If the application includes an aquatic
buffer zone, do not release spray at a height greater than 10 feet above the
ground or crop canopy.
12. For aerial applications, the spray boom should be mounted on the
aircraft so as to minimize drift caused by wing tip vortices. The
minimum practical boom length should be used and must not exceed 75%
of the wingspan of 90% of rotor blade diameter. Use upwind swath
displacement.
1 PPE that is established on the basis of Acute Toxicity of the end-use product must be compared to the active ingredient PPE in this document.
The more protective PPE must be placed in the product labeling. For guidance on which PPE is considered more protective, see PR Notice 93-7.
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