US Environmental Protection Agency 

Office of Pesticide Programs 

Revised Interim Reregistration 

Eligibility Decisions for Dimethoate 

This document contains the following: 

Revised LABEL TABLE for Dimethoate IRED to include:

 Memorandum - Revised LABEL TABLE for Dimethoate IRED - October 30, 2008 

Labeling Changes Summary Table (revised October 6, 2008) 

Revised Dimethoate IRED to include:

 Memorandum - Revised Dimethoate IRED - August 20, 2007

 Memorandum - Response to Public Comments on the Dimethoate RED - February 2, 2007

 Revised Dimethoate Label Table - (for DCI 2008) which replaces the previous 

version of the label table dated August 17, 2007. The August 17 version had errors on 

pages 10 - 11 (see below) which are correct in this April 23, 2008 version.* 

Memorandum - Finalization of IRED/TRED for Organophosphate Pesticides - July 31, 2006 

Dimethoate IRED - June 12, 2006 

* This label table corrects page 10, the entry for Succulent peas, by adding a sentence: “Not for use on field peas.” 

The label table also corrects page 11, the entry for Cottonwood (grown for pulp), by correcting the maximum 

application rate at 2 lbs a.i./A, and the maximum total rate per year at 6 lbs a.i./A. The date on the first page of 

this label table has been revised to read: (for DCI 2008), to avoid confusion with the previous label table, dated 

August 17, 2007. 
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

 PREVENTION, PESTICIDES 

 AND TOXIC SUBSTANCES 

October 30, 2008 

MEMORANDUM 

SUBJECT: Revised LABEL TABLE for Dimethoate IRED 

TO: Dimethoate Docket (EPA-HQ-OPP-2005-0084) 

This memorandum makes two changes on page 8 and two clarifications to the dimethoate 

label table. All dimethoate labels have been revised to reflect these changes and 

clarifications. This October 6 version of the label table removes the prohibition on use on 

citrus in Florida and also removes the prohibition on aerial application for citrus crops. 

These prohibitions were required in the RED and reflected in all previous label tables. 

Prior to the issuance of the RED, the risk assessment indicated drinking water risks from 

use of dimethoate on citrus and there was no reported use or need. Following the 

issuance of the RED, infestations of an exotic pest, the Asian citrus psyllid, which is a 

vector of citrus greening disease, became established in Florida citrus groves. Growers 

requested the use of dimethoate for this pest. EPA conducted a revised risk assessment 

for aerial and ground use at the requested rate and determined that the risk for potential 

drinking water contamination is below the level of concern. For more information on the 

need for this use and the risk assessment associated with the use on citrus, please refer to 

the dimethoate docket. 

Two clarifications were needed to the previous label table. 

 The first clarification is that the term “Succulent peas” has been replaced by 

“Peas”, a general term that covers all peas. The only peas that are not covered are 

field peas, and all the labels already have the disclaimer "Not for use on field 

peas". 

 The second clarification is that the phrase "Beans (including fresh, snap, lima, 

and dry beans)" has been revised to read "Beans (including fresh, snap, lima, 

and dry beans and excluding cowpeas)." Cowpeas are actually a bean variety, 

and are not a supported use. 

To avoid confusion with previous versions, the first page of this label table states 

“Revised October 6, 2008”. 

The complete dimethoate IRED, original and revised versions, with the Response to 

Public Comments and associated documents, can be found at: 

http://www.epa.gov/pesticides/reregistration/dimethoate/ 
Labeling Changes Summary Table (revised October 6, 2008)

In order to be eligible for reregistration, amend all product labels to incorporate the risk mitigation measures outlThe following table describes how language on the labels should be amended. 

Description Amended Labeling Language Placem

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, Christmas tree farms, conifer seed farms, cotton, endive, field corn, grass grown for seed, herbaceous ornamentals in commercial nurseries or greenhouses, grapefruit, leaf lettuce (except head 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, cottonwood grown for pulp, 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 byhomeowners 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 usessupported by a formulator or user 

“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 formulator, user group, or grower has complied with U.S. EPA 

Directions for Use

1
group 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 Stat

End Use Products Intended for Occupational Use 

PPE Requirements Established by the RED1For 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, flaggers, and other handlers must wear: > Long-sleeved shirt and long pants, > Shoes plus socks, > Chemical-resistant gloves,> a NIOSH-approved dust mist filtering respirator with MSHA/NIOSH approval number prefix TC-21C or a NIOSH-approved respirator with any N, R, P, or HE filter, and > Chemical-resistant apron when mixing, loading, cleaning up spills, or equipment.” “See Engineering Controls for additional requirements and exceptions.” Instruction to Registrant: Drop the “N” type filter from the respirator 

Immediately followPrecautionary StatHumans and Dom

2
statement, if the pesticide product contains, or is used with, oil. 

PPE Requirements Established by the RED1For 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 insertsA,B,C,D,E,F,G,or H] on an EPA chemical-resistance category selection chart." 

 “Mixers, loaders, applicators, flaggers, and other handlers must wear: > Long-sleeved shirt and long pants, > Shoes plus socks, > Chemical-resistant gloves,> a NIOSH-approved dust mist filtering respirator with MSHA/NIOSH approval number prefix TC-21C or a NIOSH-approved respirator with any N, R, P, or HE filter, and > Chemical-resistant apron when mixing, loading, cleaning up spills, or equipment.”  “See Engineering Controls for additional requirements and exceptions.” Instruction to Registrant: Drop the “N” type filter from the respirator statement, if the pesticide product contains, or is used with, oil. 

Immediately followPrecautionary StatHumans and Dom

User SafetyRequirements 

“Follow manufacturer's instructions for cleaning/maintaining PPE. If 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 StatHumans and Domimmediately followrequirements

Engineering Controls: (Water-Soluble “Engineering controls” Precautionary Stat

Humans and Dom

3
Packaging for Wettable 

Powder Formulations) 

“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)]. Pilots need not wear the PPE required in this labeling for applicators, but must wear at least a long-sleeve shirt, long pants, shoes, and socks.” “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.”

(Immediately folloSafety Requiremen

“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, except no respirator is required; and -- be provided and have immediately available for use in an emergency,such as a broken package, spill, or equipment breakdown: chemicalresistant footwear, and the type of respirator specified in the PPE section of this label.” 

Engineering Controls: For Liquid Formulations 

“Engineering controls” “Mixers and loaders supporting aerial application to alfalfa, cotton, soybeans, corn, safflower, sorghum, and wheat must use a closed systemthat meets the requirements listed in the Worker Protection Standard(WPS) for agricultural pesticides [40 CFR 170.240(d)(4)]. The systemmust be capable of removing the pesticide from the shipping container and transferring it into mixing tanks and/or application 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: 

Precautionary StatHumans and Dom(Immediately folloSafety Requiremen

4
-- wear the personal protective equipment required on this labeling for 

mixers/loaders, except 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, chemicalresistant 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)]. Pilots need not wear the PPE required in this labeling for applicators, but must wear at least a long-sleeve shirt, long pants, shoes, and socks.” “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 SafetyRecommendations 

“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 StatHazards to HumanAnimals immediatEngineering Contr(Must be placed in 

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.” 

Precautionary Statfollowing the User Recommendations

5
“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.” “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 fromrainfall-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 

box 

“PPE required for early entry to treated areas that is permitted under the 

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Worker Protection Standard and that involves contact with anything that 

has been treated, such as plants, soil, or water, is: > 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 R

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 R

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 Directabove the Agricult

Application Restriction “This product is for use in commercial setting only. Use in residential 

settings is prohibited.” 

Near the beginning Use 

Early Entry PersonalProtective Equipment for products with directions for use within the scope of the Worker Protection Standard (WPS) for Agricultural Pesticides 

> coveralls worn over long-sleeve shirt and long pants, 

Crop-SpecificApplication 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 seasonal treatment rates: 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), Safflower, and Wheat: 

Maximum single application rate: 0.5 lb a.i./A. Maximum total rate per crop cycle or cutting: 0.5 lb a.i./A. “The REI is 48 hours.” 

Directions for Use use directions for twhich the restricti

7
Cherries: Maximum application rate: 1.33 lbs a.i./A. Maximum total 

rate per year: 1.33 lbs a.i./A. “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.” Citrus: Maximum application rate: 1 lb a.i./A. Maximum total rate per year: 1 lb a.i./A. “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 

Asparagus, Beans (including fresh, snap, lima, and dry beans and excluding cowpeas) and Cotton: Maximum single application rate: 0.5 lb a.i./A., 14 day retreatment interval. Maximum total rate per season: 1 lb a.i./A. “The REI is 48 hours.” Field Corn and Popcorn: Maximum application rate: 0.5 lb a.i./A. Maximum total rate per year: 0.5 lb a.i./A. “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 lb a.i./A., 7 day retreatment interval. Maximum total rate per year: 1.5 lbs a.i./A. “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 lb a.i./A., 7 day retreatment interval. Maximum total rate per year: 1.5 lbs a.i./A. “The REI is 48 hours.” 

8
inches per year.” 

Conifer Seed Orchards: Maximum application rate: 1 lb a.i./A. Maximum total rate per year: 1 lb a.i./A. “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 lbs a.i./A. Maximum total rate per year: 4.15 lbs a.i./A. “If airblast applications are applied at a rate greater than 1 lb a.i/ A., 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 lb a.i./A., 90 day retreatment interval. Maximum total rate per year: 1 lb a.i./A. “The REI is 48 hours.” Herbaceous Ornamentals Maximum application rate: 0.25 lb a.i./A. Maximum total rate per year: 0.25 lb a.i./A. “The REI is 48 hours.”Kale Maximum application rate: 0.25 lb a.i./A., 15 day reapplication interval. Maximum total rate per year: 0.5 lb a.i./A. “The REI is 48 hours.” Leaf lettuce, Swiss Chard, Endive and Escarole Maximum application rate: 0.25 lb a.i./A., 7 day reapplication interval. Maximum total rate per year: 0.75 lb a.i./A. “The REI is 48 hours.” 

9
Lentils, Melon, Honeydew, and Potatoes 

Maximum application rate: 0.5 lb a.i./A., 7 day reapplication interval. Maximum total rate per year: 1 lb a.i./A. “The REI is 48 hours.” Sorghum, and Soybeans Maximum application rate: 0.5 lb a.i./A., 7 day reapplication interval. Maximum total application rate per year: 1 lb a.i./A. “The REI is 48 hours.” Mustard Greens Maximum application rate: 0.25 lb a.i./A., 9 day reapplication interval. Maximum total rate per year: 0.5 lb a.i./A. “The REI is 48 hours.” Pears: Maximum application rate: 1 lb a.i./A. Maximum total application rate per year: 1 lb a.i./A. “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 lb a.i./A. Maximum total rate per year: 0.33 lb a.i./A. “The REI is 48 hours.” Peppers Maximum application rate: 0.33 lb a.i./A., 7 day reapplication interval. Maximum total rate per year: 1.65 lbs a.i./A. “The REI is 48 hours.” Peas Maximum application rate: 0.16 lb a.i./A. Maximum total rate per year: 0.16 lb a.i./A. “The REI is 48 hours.” “Not for use on field peas.” 

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Note: There are SLN registrations for succulent peas for which the total 

seasonal rate is not to exceed 0.5 lbs. a.i./acre. Tomatoes Maximum application rate: 0.5 lb a.i./A., 6 day reapplication interval. Maximum total rate per year: 1.0 lb a.i./A. “The REI is 48 hours.” Turnips Maximum application rate: 0.25 lb a.i./A., 3 day reapplication interval. Maximum total rate per year: 1.75 lbs a.i./A. “The REI is 48 hours.” Cottonwood (grown for pulp) Maximum application rate: 2 lbs a.i./A. Maximum total rate per year: 6 lbs a.i./A. “The REI is 14 days; however, the REI is increased to 24 daysin outdoor areas where the average annual rainfall is less than 25 inches per year.” Woody Ornamentals and Christmas Tree Nurseries “Maximum application rate: 1.0 lb a.i./A., 14 day reapplication interval. Maximum total rate per year: 3.0 lbs a.i./A. “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.” “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.” 

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 spraynozzles 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 ontarget 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, immediatelyprior 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 mayindicate 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 theground 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 hightemperatures.5. All aerial and ground application equipment must be properlymaintained 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 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. 9. 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 PP

The more protective PPE must be placed in the product labeling. For guidance on which PPE is considered more protectiv

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

PREVENTION, PESTICIDES 

AND TOXIC SUBSTANCES 

August 20, 2007 

MEMORANDUM 

SUBJECT: Revised Dimethoate IRED 

TO: Dimethoate Docket (EPA-HQ-OPP-2005-0084) 

This memorandum constitutes the revised Dimethoate IRED. 

This memorandum is in two parts. The first part is a February 2, 2007 memorandum entitled 

Response to Public Comments on the Dimethoate Reregistration Eligibility Decision. The 

Response to Comments memorandum provides the rationale for the changes from the 2005 

Dimethoate IRED which was posted for public comment. The Dimethoate IRED required 

several risk mitigation measures, including reductions in application rates and maximum 

numbers of applications, an increase in retreatment intervals for most crops, and the addition of 

best management practices (BMPs) to the labels to reduce spray drift. 

Cheminova provided additional comments on the mitigation required for handlers on March 30, 

2007. We agreed with those comments and have revised the types of respirators required and 

added chemical resistant gloves for all mixers, loader, applicators, flaggers and other handlers, 

with certain exceptions. These changes achieve label simplification and provide clear and 

protective instructions. The rationale for the changes is included in a 5-page addendum to the 

Response to Comment memorandum. 

The second part of this memorandum is an updated label table which includes the mitigation 

revisions discussed in the Response to Comments memorandum, as well as the modifications 

EPA proposed (72 FR 8986, February 28, 2007) in certain risk mitigation measures based on 

comments and requests received from users. These modifications included specifying a 

maximum seasonal application rate rather than a maximum number of applications per season, 

and increased seasonal rates for peppers and cherries. The label table has also been revised to 

correct several errors in the section with requirements for reducing spray drift. Specifically, we 

have deleted the erroneous requirements on buffer zones for ground boom, chemigation, orchard 

and airblast applications to potatoes. 

The label table has also been revised to include cottonwood for pulp as a use site. The RED 

stated that cottonwood for pulp would be cancelled, based on low perceived benefit in the 
risk/benefit balance required by FIFRA. The Agency and the technical registrants have since 

learned that use of dimethoate on cottonwood is considered a highly important use by the paper 

industry and the U.S. Department of Agriculture. The technical registrants, Cheminova and 

Drexel, have revised their labels to include this use in registration amendments submitted July 13 

and July 23, respectively. The Agency notes that dimethoate is scheduled for registration review 

in 2009, when the occupation risk assessment, along with the human health and ecological risk 

assessments, will be reviewed. 

For ease of reference, the June 2006 version of the Dimethoate IRED document is included here 

as Attachment 1. 




Addendum to February 2, 2007 Memorandum: 

Response to Public Comments on the Dimethoate IRED 

Dimethoate: HED’s Recommendations for Risk Mitigation for Handlers 

Prepared by: Alan Nielsen on 6/21 
Dimethoate: HED’s Recommendations for Risk Mitigation for Handlers 

In HED’s Response to Cheminova’s comments, dated September 11, 2006, regarding EPA’s 

interim reregistration eligibility decision document for dimethoate 

HED stated: “HED has no data to establish a short- or intermediate-term inhalation endpoint for 

dimethoate. Instead, it selected an endpoint based on an omethoate inhalation study. HED 

agrees that dimethoate is likely to be less toxic than omethoate via the inhalation route, although 

it has no means of quantifying the differential in toxicity. The risk assessment acknowledges 

that using the inhalation endpoint for omethoate to assess inhalation risks to dimethoate is 

conservative. In those occupational handler scenarios where inhalation risks are of concern even 

with the use of a quarter-face dust/mist respirator (protection factor of 5), then EPA will take 

into consideration the conservative nature of the assessment in determining whether more risk 

mitigation (i.e., half-face respirator or engineering controls) is justified.” 

Subsequent comments from Cheminova, dated March 30, 2007, indicated concerns about the 

risks mitigation to handlers, particularly regarding the requirement for a half- or full-face 

cartridge or canister respirator. HED agrees with Cheminova that given the conservative nature 

of the handler inhalation risk assessment, a quarter-face dust/mist filtering respirator would be 

adequate in many dimethoate handler scenarios. 

HED notes that it believes that residues of omethoate – the more highly toxic degradate of 

dimethoate – likely remain on mixing/loading and application equipment. HED has no data to 

assess potential handler exposures to omethoate residues, but believes the concern justifies a 

requirement for chemical-resistant gloves and a dust/mist respirator for dimethoate handlers who 

are not using engineering controls. 

HED has reviewed the handler risks to dimethoate and is proposing the following risk 

mitigation: 

• Water-soluble packaging plus baseline attire, chemical-resistant gloves, and a chemicalresistant apron for all wettable powder formulations, 

• Closed mixing/loading systems plus baseline attire, chemical-resistant gloves, and a 

chemical-resistant apron for handlers supporting aerial applications to alfalfa, cotton, 

soybeans, corn, safflower, sorghum, and wheat, 

• Enclosed cockpits plus baseline attire for pilots, and 

• Baseline attire plus chemical-resistant gloves and a quarter-face dust/mist filtering 

respirator for all other mixers, loaders, applicators, flaggers, and mixer/loader/ 

applicators. 
DIMTHETOATE LABELING FOR KEY SCENARIOS 

Mixing/Loading Liquids 

Equipment Crop IRED Mitigation Risks HED Proposed M

Aerial & Chemigation 

High Acreage Crops (0.5 lb ai/A) 

Closed Systems Aerial: 

G + 80% R = 32 Closed System = 90 Chemigation: G + 80% R = 110 Closed System = 310 

Aerial: Closed SyChemigation: G + (adequate mitigati

Woody Ornamentals & Conifer Seed Orchards at 1 lb ai/A) 

Closed Systems G + 80% R = 55 

G, DL, + 80% R = 60 Closed System = 150 

G + 80% R (label simplicity & endpoint uncertain

Pears,a Cherries (SLN) at 1.0 lb ai/A 

G + 90% R G + 80% R = 55 

G, DL, + 80% R = 60 Closed System = 150 

G + 80% R (label simplicity & endpoint uncertain

Typical acreage crops < 1.0 lb ai/A 

G + 90% R G + 80% R = 

≥ 110 G + 80% R 

(adequate mitigati

Groundboom High Acreage Crops 

(0.5 lb ai/A) 

G G = 53 

G + 80% R = 190 

G + 80% R (adequate mitigati

Woody Ornamentals & Conifer Seed Orchards (1 lb ai/A) 

G G = 66 

G + 80% R = 240 

G + 80% R (adequate mitigati

Typical acreage crops < 1.0 lb ai/A 

G G = >100 

G + 80% R = 

≥ 480 

G + 80% R (label simplicity) 

Airblast Douglas fir in W

A & 

OR (4.15 lb ai/A) 

G G = 64 

G + 80% R = 230 

G + 80% R (adequate mitigati

≤ 1.0 lb ai/A G G = >100 

G + 80% R = 

≥ 480 

G + 80% R (label simplicity) 
Applicators 

Aerial All Enclosed cockpits Eng Controls = ≥120 Enclosed cockpits Groundboom High Acreage Baseline Baseline = 86 G + 80% R 

Crops G + 80% R = 310 (adequate mitigatiAll other crops Baseline Baseline = ≥110 G + 80% R 

G + 80% R ≥390 (label simplicity) 

Airblast Douglas fir in G + 90% R G + 80% R = 39 (PHED) G + 80% R 

WA & OR (4.3 lb ai/A) 

G + HG + 80% R = 85 (carbaryl) 

(label simplicity & endpoint uncertainspecialty use patte

Citrus, Pears,a G + 90% R G + 80% R = 80 G + 80% R Cherries (SLN) (label simplicity & 

endpoint uncertain

Cherries, G + 90% R G + 80% R = 240 G + 80% R Pecans (0.33 lb (label simplicity) ai/A) 

Flaggers 

Aerial Pears, Cherries Enclosed cab with Baseline = ≥ 49 G + 80% R 

(SLN), Woody Ornamentals, 

respirator G + 80% R > 100 (adequate mitigati

Conifer Seed Farms, Christmas Tree Farms (1.0 lb ai/A) All other crops Enclosed cab with Baseline = ≥98 G + 80% R (> 1.0 lb ai/A respirator G + 80% R > 100 (label simplicity) 
Mixer/Loader/Applicators 

High Pressure Handwand 

Woody ornamentals , Christmas tree farms, conifer seed orchards herbaceous ornamentals at 0.0025 lb ai/gal 

G = 90% R G = 21 

G + 80% R = 75 

G + 80% R (label simplicity & endpoint uncertain

Low Pressure Handwand 

Woody ornamentals , Christmas tree farms, and conifer seed orchards at 0.08 to 0.01 lb ai/gal 

Baseline PHED: 

Baseline = 3.9 – 31 G = 68 – 540 G + 80% R = 260 – 2100 ORETF: Baseline = 26 – 210 G = 490 – 3900 G + 80% R = 950 - 7600 

G + 80% R (label simplicity) 

Herbaceous ornamentals at 0.0025 lb ai/gal 

Baseline PHED: 

Baseline = 120 G = 2200 G + 80% R = 8400 ORETF: Baseline = 840 G = 16,000 G + 80% R = 30,000 

G + 80% R (label simplicity) 

a Pears are listed in the label table at 1.0 lb ai/A, but the proposed mitigation indicates that they will be 0.5 
Revised Dimethoate Label Table 
Labeling Changes Summary Table (for DCI 2008)

In order to be eligible for reregistration, amend all product labels to incorporate the risk mitigation measures outlThe following table describes how language on the labels should be amended. 

Description Amended Labeling Language Placem

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, Christmas tree farms, conifer seed farms, cotton, endive, field corn, grass grown for seed, herbaceous ornamentals in commercial nurseries or greenhouses, grapefruit, leaf lettuce (except head 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, cottonwood grown for pulp, 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 byhomeowners 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 usessupported by a formulator or user 

“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 formulator, user group, or grower has complied with U.S. EPA 

Directions for Use

1
group 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 Stat

End Use Products Intended for Occupational Use 

PPE Requirements Established by the RED1For 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, flaggers, and other handlers must wear: > Long-sleeved shirt and long pants, > Shoes plus socks, > Chemical-resistant gloves,> a NIOSH-approved dust mist filtering respirator with MSHA/NIOSH approval number prefix TC-21C or a NIOSH-approved respirator with any N, R, P, or HE filter, and > Chemical-resistant apron when mixing, loading, cleaning up spills, or equipment.” “See Engineering Controls for additional requirements and exceptions.” Instruction to Registrant: Drop the “N” type filter from the respirator 

Immediately followPrecautionary StatHumans and Dom

2
statement, if the pesticide product contains, or is used with, oil. 

PPE Requirements Established by the RED1For 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 insertsA,B,C,D,E,F,G,or H] on an EPA chemical-resistance category selection chart." 

 “Mixers, loaders, applicators, flaggers, and other handlers must wear: > Long-sleeved shirt and long pants, > Shoes plus socks, > Chemical-resistant gloves,> a NIOSH-approved dust mist filtering respirator with MSHA/NIOSH approval number prefix TC-21C or a NIOSH-approved respirator with any N, R, P, or HE filter, and > Chemical-resistant apron when mixing, loading, cleaning up spills, or equipment.”  “See Engineering Controls for additional requirements and exceptions.” Instruction to Registrant: Drop the “N” type filter from the respirator statement, if the pesticide product contains, or is used with, oil. 

Immediately followPrecautionary StatHumans and Dom

User SafetyRequirements 

“Follow manufacturer's instructions for cleaning/maintaining PPE. If 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 StatHumans and Domimmediately followrequirements

Engineering Controls: (Water-Soluble “Engineering controls” Precautionary Stat

Humans and Dom

3
Packaging for Wettable 

Powder Formulations) 

“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)]. Pilots need not wear the PPE required in this labeling for applicators, but must wear at least a long-sleeve shirt, long pants, shoes, and socks.” “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.”

(Immediately folloSafety Requiremen

“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, except no respirator is required; and -- be provided and have immediately available for use in an emergency,such as a broken package, spill, or equipment breakdown: chemicalresistant footwear, and the type of respirator specified in the PPE section of this label.” 

Engineering Controls: For Liquid Formulations 

“Engineering controls” “Mixers and loaders supporting aerial application to alfalfa, cotton, soybeans, corn, safflower, sorghum, and wheat must use a closed systemthat meets the requirements listed in the Worker Protection Standard(WPS) for agricultural pesticides [40 CFR 170.240(d)(4)]. The systemmust be capable of removing the pesticide from the shipping container and transferring it into mixing tanks and/or application 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: 

Precautionary StatHumans and Dom(Immediately folloSafety Requiremen

4
-- wear the personal protective equipment required on this labeling for 

mixers/loaders, except 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, chemicalresistant 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)]. Pilots need not wear the PPE required in this labeling for applicators, but must wear at least a long-sleeve shirt, long pants, shoes, and socks.” “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 SafetyRecommendations 

“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 StatHazards to HumanAnimals immediatEngineering Contr(Must be placed in 

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.” 

Precautionary Statfollowing the User Recommendations

5
“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.” “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 fromrainfall-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 

box 

“PPE required for early entry to treated areas that is permitted under the 

6
Worker Protection Standard and that involves contact with anything that 

has been treated, such as plants, soil, or water, is: > 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 R

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 R

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 Directabove the Agricult

Application Restriction “This product is for use in commercial setting only. Use in residential 

settings is prohibited.” 

Near the beginning Use 

Early Entry PersonalProtective Equipment for products with directions for use within the scope of the Worker Protection Standard (WPS) for Agricultural Pesticides 

> coveralls worn over long-sleeve shirt and long pants, 

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 seasonal treatment rates: 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), Safflower, and Wheat: 

Maximum single application rate: 0.5 lb a.i./A. Maximum total rate per crop cycle or cutting: 0.5 lb a.i./A. “The REI is 48 hours.” 

Directions for Use use directions for twhich the restricti

7
Asparagus, Beans (including fresh, snap, lima, and dry beans) and 

Cotton: Maximum single application rate: 0.5 lb a.i./A., 14 dayretreatment interval. Maximum total rate per season: 1 lb a.i./A. “The REI is 48 hours.” Field Corn and Popcorn: Maximum application rate: 0.5 lb a.i./A. Maximum total rate per year: 0.5 lb a.i./A. “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 lb a.i./A., 7 day retreatment interval. Maximum total rate per year: 1.5 lbs a.i./A. “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 lb a.i./A., 7 day retreatment interval. Maximum total rate per year: 1.5 lbs a.i./A. “The REI is 48 hours.” Cherries: Maximum application rate: 1.33 lbs a.i./A. Maximum total rate per year: 1.33 lbs a.i./A. “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.” Citrus: Maximum application rate: 1 lb a.i./A. Maximum total rate per year: 1 lb a.i./A. “Do not apply to citrus in Florida” “Aerial application to citrus is prohibited” “The REI is 10 days; however, the REI is 

8
increased to 14 days in outdoor areas where the average annual rainfall is 

less than 25 inches per year.” Conifer Seed Orchards: Maximum application rate: 1 lb a.i./A. Maximum total rate per year: 1 lb a.i./A. “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 lbs a.i./A. Maximum total rate per year: 4.15 lbs a.i./A. “If airblast applications are applied at a rate greater than 1 lb a.i/ A., 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 lb a.i./A., 90 day retreatment interval. Maximum total rate per year: 1 lb a.i./A. “The REI is 48 hours.” Herbaceous Ornamentals Maximum application rate: 0.25 lb a.i./A. Maximum total rate per year: 0.25 lb a.i./A. “The REI is 48 hours.”Kale Maximum application rate: 0.25 lb a.i./A., 15 day reapplication interval. Maximum total rate per year: 0.5 lb a.i./A. “The REI is 48 hours.” Leaf lettuce, Swiss Chard, Endive and Escarole Maximum application rate: 0.25 lb a.i./A., 7 day reapplication interval. Maximum total rate per year: 0.75 lb a.i./A. “The REI is 48 hours.” 

9
Lentils, Melon, Honeydew, and Potatoes 

Maximum application rate: 0.5 lb a.i./A., 7 day reapplication interval. Maximum total rate per year: 1 lb a.i./A. “The REI is 48 hours.” Sorghum, and Soybeans Maximum application rate: 0.5 lb a.i./A., 7 day reapplication interval. Maximum total application rate per year: 1 lb a.i./A. “The REI is 48 hours.” Mustard Greens Maximum application rate: 0.25 lb a.i./A., 9 day reapplication interval. Maximum total rate per year: 0.5 lb a.i./A. “The REI is 48 hours.” Pears: Maximum application rate: 1 lb a.i./A. Maximum total application rate per year: 1 lb a.i./A. “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 lb a.i./A. Maximum total rate per year: 0.33 lb a.i./A. “The REI is 48 hours.” Peppers Maximum application rate: 0.33 lb a.i./A., 7 day reapplication interval. Maximum total rate per year: 1.65 lbs a.i./A. “The REI is 48 hours.” Succulent peas Maximum application rate: 0.16 lb a.i./A. Maximum total rate per year: 0.16 lb a.i./A. “The REI is 48 hours.” “Not for use on field peas.” 

10
Note: There are SLN registrations for succulent peas for which the total 

seasonal rate is not to exceed 0.5 lbs. a.i./acre. Tomatoes Maximum application rate: 0.5 lb a.i./A., 6 day reapplication interval. Maximum total rate per year: 1.0 lb a.i./A. “The REI is 48 hours.” Turnips Maximum application rate: 0.25 lb a.i./A., 3 day reapplication interval. Maximum total rate per year: 1.75 lbs a.i./A. “The REI is 48 hours.” Cottonwood (grown for pulp) Maximum application rate: 2 lbs a.i./A. Maximum total rate per year: 6 lbs a.i./A. “The REI is 14 days; however, the REI is increased to 24 daysin outdoor areas where the average annual rainfall is less than 25 inches per year.” Woody Ornamentals and Christmas Tree Nurseries “Maximum application rate: 1.0 lb a.i./A., 14 day reapplication interval. Maximum total rate per year: 3.0 lbs a.i./A. “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.” “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.” 

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 

Directions for Use

11
crops thereof rendered unfit for sale, use, or consumption can occur.

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 spraynozzles 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 ontarget 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, immediatelyprior 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 mayindicate 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 theground 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 hightemperatures.5. All aerial and ground application equipment must be properlymaintained 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 

12
the top in orchard applications, spray must be directed into the canopy.

8. 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. 9. 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 PP

The more protective PPE must be placed in the product labeling. For guidance on which PPE is considered more protectiv

13
Attachment 1 

Signed Dimethoate IRED 

June 2006 
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 Reregistration Eligibility Decisions (IREDs) and Interim 

Tolerance Reassessment and Risk Management Decisions (TREDs) for the 

Organophosphate Pesticides, and Completion of the Tolerance Reassessment and 

Reregistration Eligibility Process for the Organophosphate Pesticides 

FROM: Debra Edwards, Director 

Special Review and Reregistration 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 individualchemical review process. The Agency’s review of individual OPs has resulted in the issuance of 

Interim Reregistration Eligibility Decisions (IREDs) for 22 OPs, interim Tolerance 

Reassessment and Risk Management Decisions (TREDs) for 8 OPs, and a Reregistration 

Eligibility Decision (RED) for one OP, malathion.1 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 

1 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 
(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 reregistration, other than product-specific reregistration. 

The Special Review and Reregistration 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 
Attachment A: 

Organophosphates included in the OP Cumulative Assessment 

Chemical Decision Document Status 

Acephate IRED IRED completed 9/2001 

Azinphos-methyl (AZM) IRED IRED completed 10/2001 

Bensulide IRED IRED completed 9/2000 

Cadusafos TRED TRED completed 9/2000 

Chlorethoxyphos TRED TRED completed 9/2000 

Chlorpyrifos IRED IRED completed 9/2001 

Coumaphos TRED TRED completed 2/2000 

DDVP (Dichlorvos) IRED IRED completed 6/2006 

Diazinon IRED IRED completed 7/2002 

Dicrotophos IRED IRED completed 4/2002 

Dimethoate IRED IRED completed 6/2006 

Disulfoton IRED IRED completed 3/2002 

Ethoprop IRED IRED completed 9/2001 

IRED addendum completed 2/2006 

Fenitrothion TRED TRED completed 10/2000 

Malathion RED RED completed 8/2006 

Methamidophos IRED IRED completed 4/2002 

Methidathion IRED IRED completed 4/2002 

Methyl Parathion IRED IRED completed 5/2003 

Naled IRED IRED completed 1/2002 

Oxydemeton-methyl IRED IRED completed 8/2002 

Phorate IRED IRED completed 3/2001 

Phosalone TRED TRED completed 1/2001 

Phosmet IRED IRED completed 10/2001 

Phostebupirim TRED TRED completed 12/2000 

Pirimiphos-methyl IRED IRED completed 6/2001 

Profenofos IRED IRED completed 9/2000 

Propetamphos IRED IRED completed 12/2000 

Terbufos IRED IRED completed 9/2001 

Tetrachlorvinphos TRED TRED completed 12/2002 

Tribufos IRED IRED completed 12/2000 

Trichlorfon TRED TRED completed 9/2001 

Page 3 of 3 
Interim Reregistration 

Eligibility Decision for 

Dimethoate 

June 12, 2006 
Interim Reregistration Eligibility Decision 
 

for 
 

Dimethoate
 

List [B] 
 

Case No. 0088 
 

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 
 
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 

i 
Glossary of Terms and Abbreviations 

AGDCI 	 Agricultural Data Call-In 

ai Active Ingredient 

aPAD 	 Acute Population Adjusted Dose 

AR Anticipated Residue 

BCF Bioconcentration Factor 

CFR 	 Code of Federal Regulations 

cPAD 	 Chronic Population Adjusted Dose 

CSF 	 Confidential Statement of Formula 

CSFII USDA Continuing Surveys for Food Intake by Individuals 

DCI Data Call-In 

DEEM	 Dietary Exposure Evaluation Model 

EC Emulsifiable Concentrate Formulation 

EDWC 	 Estimated Drinking Water Concentration 

EEC Estimated Environmental Concentration 

EPA Environmental Protection Agency 

EUP End-Use Product 

FCID Food Commodity Intake Database 

FDA 	 Food and Drug Administration 

FIFRA 	 Federal Insecticide, Fungicide, and Rodenticide Act 

FFDCA 	 Federal Food, Drug, and Cosmetic Act 

FQPA Food Quality Protection Act 

FOB Functional Observation Battery 

G Granular Formulation 

GENEEC 	 Tier I Surface Water Computer Model 

GLN Guideline Number 

HAFT	 Highest Average Field Trial 

IR Index Reservoir 

LC50	 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/l, mg/kg or ppm. 

LD50	 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. 

LOC Level of Concern 

LOD 	 Limit of Detection 

LOAEL	 Lowest Observed Adverse Effect Level 

MATC Maximum Acceptable Toxicant Concentration 

Φg/g Micrograms Per Gram 

Φg/L Micrograms Per Liter 

mg/kg/day 	 Milligram Per Kilogram Per Day 

mg/L Milligrams Per Liter 

ii 
MOE 	 Margin of Exposure 

MRID Master Record Identification (number). EPA's system of recording 

and tracking studies submitted. 

MUP Manufacturing-Use Product 

NA Not Applicable 

NAWQA 	 USGS National Water Quality Assessment 

NPDES 	 National Pollutant Discharge Elimination System 

NR Not Required 

NOAEL	 No Observed Adverse Effect Level 

OP 	 Organophosphate 

OPP EPA Office of Pesticide Programs 

OPPTS 	 EPA Office of Prevention, Pesticides and Toxic Substances 

PAD Population Adjusted Dose 

PCA Percent Crop Area 

PDP 	 USDA Pesticide Data Program 

PHED 	 Pesticide Handler's Exposure Data 

PHI Preharvest Interval 

ppb Parts Per Billion 

PPE Personal Protective Equipment 

ppm Parts Per Million 

PRZM/EXAMS 	 Tier II Surface Water Computer Model 

Q1* 	 The Carcinogenic Potential of a Compound, Quantified by the 

EPA's Cancer Risk Model 

RAC Raw Agriculture Commodity 

RED Reregistration Eligibility Decision 

REI Restricted Entry Interval 

RfD Reference Dose 

RQ Risk Quotient 

SCI-GROW 	 Tier I Ground Water Computer Model 

SAP Science Advisory Panel 

SF Safety Factor 

SLC Single Layer Clothing 

SLN 	 Special Local Need (Registrations Under Section 24(c) of FIFRA) 

TAF Toxicity Adjustment Factor 

TCPSA 	 2,3,3-trichloroprop-2-ene sulfonic acid (nitrapyrin Metabolite) 

TGAI Technical Grade Active Ingredient 

TRR Total Radioactive Residue 

USDA 	 United States Department of Agriculture 

USGS 	 United States Geological Survey 

UF Uncertainty Factor 

UV Ultraviolet 

WPS Worker Protection Standard 

iii 
I. Introduction 

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was amended 

in 1988 to accelerate the reregistration 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 reregistration 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). Reregistration 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 reregistration, tolerance reassessment will be 

accomplished through the reregistration 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 reregistration 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 reregistration eligibility 

decision for dimethoate. The document consists of six sections: section I contains the 

regulatory framework for reregistration/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 reregistration eligibility, tolerance 

1
 
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 Reregistration 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. 

2
 
B. Chemical Identification 

Chemical Structure: 

Common Name: Dimethoate 

Chemical Name: O,O-dimethyl S-(N-methylcarbamoylmethyl) 

phosphorodithioate 

Chemical Family: Organophosphate 

Empirical Formula: C5H12NO3PS2 

CAS Registry Number: 60-51-5 

Case Number: 0088 

OPP Chemical Code: 035001 

Molecular weight: 229.3 

Trade Names: Digon, Duragon, Rebelate, Dimate 

Basic Manufacturers: Cheminova, BASF Corporation, Drexel Chemical Co. 

Dimethoate is a white crystalline solid with a mercaptan odor and a melting point 

of 45-48o

 C. It is soluble in water at 25 g/L at 21o 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 (O,O-dimethyl S-(Nmethylcarbamoylmethyl) 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 reregistration is contained in Appendix A. 

3
 
Type of Pesticide:	 General use systemic insecticide/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 reregistration: 

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 

4
 
Application Rates: Currently labeled use rates vary from a minimum of 

0.16 lbs a.i./acre to a maximum of 33.2 lbs. 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 lbs 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 lbs a.i./acre to 33.2 

lb 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 Reregistration 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 

5
 
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. Study Type MRID No. Results 

Toxicity 

Category 

870.1100 Acute Oral - Rat 00164219 

LD50 = 358 mg/kg 

males), 414 mg/kg 

(females) 

II 

870.1200 Acute Dermal - Rabbit 00164220 LD50 = > 2.0 g/kg III 

870.2500 Acute Dermal Irritation ­

Rabbit 00164221 Not a dermal irritant IV 

870.2600 Skin Sensitization - Guinea 

Pig 254924 Not a skin sensitizer N/A 

870.6100 Acute Delayed Neurotoxicity 

- Hen 42884401 

No clinical signs of acute 

delayed neurotoxicity 

and no compoundrelated histological 

changes in nerve tissue. 

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 

6
 
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 (BMD10) and 

the lower 95% confidence intervals (BMDL10) were estimated by fitting the ChE data to 

an exponential dose-response model, using generalized nonlinear least squares. The 

BMD10 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 BMDL10 = 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 BMDL10 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 BMDL10 and other toxicity endpoints are outlined in Table 2 below. 

FQPA Safety Factor 

The FQPA Safety 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 Q1* 

approach, was considered more appropriate for quantification of potential human risk for 

7
 
the following reasons: as stated above, the mouse carcinogenicity 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 

Dose, 

Uncertainty 

Factor, and 

Safety Factor 

Effect Study 

Acute Dietary (all 

populations) 

BMDL10 = 1.3 

mg/kg 

UF = 100 

FQPA SF = 1 

Brain ChE inhibition in 

PND11 females (BMD10 = 1.5 

mg/kg) 

Comparative ChEI study in rats. 

MRID 45529702 

Acute RfD = Acute PAD = 0.013 mg/kg 

Chronic Dietary (all 

populations) 

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 

Short- (1-30 days) 

and Intermediateterm (1-6 months) 

Occupational 

Dermal 

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 LOC = 100 

Short- (1-30 days) 

and Intermediateterm (1-6 months) 

Occupational 

Inhalation 

BMCL10 = 

0.38 mg/m3 

(approx 0.10 

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 LOC = 100 

Cancer 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) 

LOC = Level of Concern 

8
 
2. Dietary Exposure and Risk from Food and Water 

Acute and chronic probabilistic dietary risk assessments were conducted using 

DEEM-FCIDTM, Version 2.02, which incorporates consumption data from USDA’s 

CSFII, 1994-1996 and 1998, as well as monitoring data from PDP 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 (TAF) 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 EDWC Chronic EDWC 

--------------------- μg L-1 dimethoate equivalents ----------­­

Surface Water 

Broccoli/Cauliflower/Celery 558 23.5 

Pecans 19.6 0.28 

Ground Water 

SCI-GROW 0.044 0.044 

9
 
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 μg/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
 
Table 4. Summary of Acute Dietary Exposure and Risk for Dimethoate at 99.9th 

Percentile 

Population 

Subgroup 

Food Only Food + Drinking Water 

(CA Broccoli) 

Food + Drinking Water 

(GA Pecans) 

Dietary 

Exposure 

(mg/kg/day) 

% aPAD 

Dietary 

Exposure 

(mg/kg/day) 

% 

aPAD 

Dietary 

Exposure 

(mg/kg/da 

y) 

% aPAD 

General US 

Population 

0.002134 16 0.017872 140 0.002160 17 

Infants < 1 year 0.001958 15 0.060155 460 0.002419 19 

Children 1-2 

years old 0.004160 32 0.026520 200 0.004373 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 99.9th 

Percentile 

Population 

Subgroup 

Food Only Food + Drinking Water 

(CA Broccoli) 

Food + Drinking Water 

(GA Pecans) 

Dietary 

Exposure 

(mg/kg/day) 

% cPAD 

Dietary 

Exposure 

(mg/kg/day) 

% 

cPAD 

Dietary 

Exposure 

(mg/kg/day) 

% cPAD 

General US 

Population 

0.000028 1.3 0.000233 11 0.000031 1.4 

Infants <1 year 0.000042 1.9 0.000715 33 0.000051 2.3 

Children 1-2 

years old 

0.000111 5.1 0.000416 19 0.000115 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 
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
 
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 intermediateterm endpoint for dermal and inhalation exposures. The short- and intermediate-term 

dermal endpoint is a BMDL10 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

 (BMDL10) 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
 
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 Crop 

Maximum 

Application 

Rate (lbs 

a.i./A) 

Daily 

Treated 

Area 

(Acres) 

MOE w/ 

Maximum 

Feasible 

Mitigation 

Controls 

Citrus 2.0 350 77b 

Mixing/loading liquids for 

aerial and chemigation 

applications 

Woody ornamentals, 

Christmas tree 

plantations, and 

conifer seed orchards 

(other than Douglas 

firs in OR and WA) 

2.0 350 77b 

Cottonwood grown 

for pulp 

4.0 350 39b 

Wheat 0.67 1,200 67b 

Mixing/loading liquids for 

aerial applications 

Alfalfa, alfalfa grown 

for seed, cotton, field 

corn, pop corn, grass 

grown for seed, 

safflower, sorghum, 

and soybeans 

0.5 1,200 90b 

Mixing/loading wettable Pears 1.0 350 68b 

14
 
Exposure Scenario Crop 

Maximum 

Application 

Rate (lbs 

a.i./A) 

Daily 

Treated 

Area 

(Acres) 

MOE w/ 

Maximum 

Feasible 

Mitigation 

Controls 

powders for aerial and 

chemigation applications 0.75 350 91b 

Mixing/loading/applying 

liquids with high pressure 

handwand sprayers 

Woody ornamentals, 

Christmas tree 

plantations, and 

conifer seed orchards 

(other than Douglas 

firs in OR and WA) 

0.01c 1,000 

gallons 

34a 

Aerial spray applications of 

liquids 

Wheat 0.67 1,200 92b 

Cottonwood grown 

for pulp 

4.0 350 53b 

Applying liquids with 

airblast/mistblower sprayers 

Douglas fir seed 

orchards in OR and 

WA 

8.3 20 76b 

a

Maximum feasible mitigation measure denotes additional PPE (double layer clothing plus gloves and a 

half-face or full-face respirator). 

b

Maximum feasible mitigation measure denotes engineering controls (i.e., closed systems for mixers and 

loaders or closed cabs for applicators). c

Expressed in lbs 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
 
Table 7. Summary of Postapplication Risk Assessment for Dimethoate 

Crop Group 

Max Single 

App. Rate 

(lbs a.i./A) 

Key Tasks Secondary Tasks 

Transfer 

Coefficient 

REI (days) Secondary 

Transfer 

Coefficient 

REI (days) 

NonArid Arid NonArid Arid 

Endive, 

escarole, kale, 

leaf lettuce, 

mustard 

greens, Swiss 

chard, turnips 

0.25 2,500 

harvest, thin 12 hrs 1 

1,500 

scout & 

irrigate 

12 hrs 12 hrs 

Peas 0.16 2,500 

harvest 12 hrs 12 hrs 

1,500 

scout & 

irrigate 

12 hrs 12 hrs 

Brussels 

sprouts 1 

5,000 

harvest, 

irrigate, 

prune, thin 

& tie 

3 9 NA 

Wheat 0.67 

1,000 

scout, 

irrigate 

1 12 hrs NA 

Beans, lentils, 

celery 0.5 2,500 harvest 1 2 

1,500 

scout & 

irrigate 

1 12 hrs 

Melons, 

watermelons 

0.5 

2,5000 

harvest, 

prune & thin 

1 2 

1,500 

scout, 

irrigate & 

hand weed 

1 12 hrs 

Tomatoes 0.5 

1,000 

harvest, 

prune, stake, 

thin, tie & 

train 

12 hrs 12 hrs 

700 

scout & 

irrigate 

12 hrs 12 hrs 

Asparagus 0.5 

500 

scout 

&irrigate 

12 hrs 12 hrs NA 

Broccoli, 

cauliflower 0.5 

5,000 

harvest, 

irrigate, 

prune, thin 

& tie 

2 5 NA 

Alfalfa, 

alfalfa grown 

for seed, 

soybeans, 

safflower, 

cotton, 

potatoes 

0.5 

1,500 

scout & 

irrigate 

1 12 hrs NA 

Field corn, 

popcorn 

0.5 

1,000 

scout, 

irrigate & 

hand weed 

12 hrs 12 hrs NA 

Grain 

sorghum 0.5 1,000 

scout, 12 hrs 12 hrs NA 

16
 
Crop Group 

Max Single 

App. Rate 

(lbs a.i./A) 

Key Tasks Secondary Tasks 

Transfer 

Coefficient 

REI (days) Secondary 

Transfer 

Coefficient 

REI (days) 

NonArid Arid NonArid Arid 

irrigate 

Herbaceous 

ornamentals 

0.5 

500 

tasks related 

to cut 

flowers & 

foliage, 

except roses 

& carnations 

12 hrs 12 hrs 

400 

tasks related 

to nursery 

crops, 

except cut 

flowers or 

foliage 

12 hrs 12 hrs 

Peppers 0.33 

1,000 

harvest, 

stake & tie 

12 hrs 12 hrs 

700 

scout & 

irrigate 

12 hrs 12 hrs 

Douglas Fir 

Seed 

Orchards in 

OR and WA 

8.3 

1,000 

scout, 

irrigate & 

weed 

22 39 NA 

Cottonwoods 

grown for 

pulp 

4 

1,000 

scout, 

irrigate & 

weed 

14 24 NA 

Conifer seed 

orchards 

(except 

Douglas fir 

seed orchards 

in OR and 

WA) 

2 

1,000 

scout, 

irrigate & 

weed 

7 11 NA 

Woody 

ornamentals 

and Christmas 

tree 

plantations 

2 3,000 

prune & thin 19 36 1,500 harvest 13 14 

Pecans 0.33 

500 

prune & 

scout 

12 hrs 12 hrs NA 

1 3,000 10 14 1,000 2 4 

Pears 0.75 harvest, 

prune, train 

& tie 

8 12 scout, 

irrigate & 

hand weed 

2 2 

0.5 5 7 12 hrs 12 hrs 

2 24 36 1,000 7 9 

Citrus 

1 3,000 

prune 

13 14 scout, 

irrigate & 

hand weed 

2 4 

0.5 6 7 12 hrs 12 hrs 

Cherries 

1 3,000 

harvest & 

prune 

10 14 1,000 

scout, 

irrigate & 

hand weed 

2 4 

0.33 2 4 12 hrs 12 hrs 

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 
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
 
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 toxicologically 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 (μg ai/L) of Dimethoate in Surface 

Water for Selected Use Patterns 

Crop Maximum 

μg/L 

4-Day 

μg/L 

21-Day 

μg/L 

60-Day

 μg/L 

90-Day 

μg/L 

Broccoli, CA 33.4 32.0 28.2 21.6 17.7 

Peas 1.28 1.20 0.96 0.60 0.44 

19
 
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 

Acute Toxicity Chronic Toxicity 

96-hr LC50 

(mg/L) 

Acute Toxicity 

(MRID) 

NOAEC/LOAEC 

(mg/L) 

Affected 

Endpoints 

(MRID) 

Rainbow Trout 

Oncorhynchus mykiss 6.2 

Moderately 

toxic 

(400940-02) 

0.43/0.84 

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 
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 

Acute Toxicity Chronic Toxicity 

96-hr LC50 

(mg/L) 

Acute Toxicity 

(MRID) 

NOAEC/LOAEC 

(mg/L) 

96-hr LC50 

(mg/L) 

Stonefly 

Pteronarcys 

californica 

0.043 (48-hr) Very highly toxic 

(00003503) ND* ND 

Water flea 

Daphnia magna 3.32 ND 0.04/0.1 

Reproductive, 

survival, growth 

(428647-01) 

Mysid shrimp 

Mysidopsis bahia 15 Slightly toxic (427600-03) ND 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 LD50 

(mg/kg) 

Acute Oral 

Toxicity 

(MRID) 

5-day LC50 

(ppm) 

Subacute 

Dietary 

Toxicity 

(MRID) 

Red-winged blackbird 

Agelaius phoeniceus 5.4 

Very highly 

toxic 

(00020560) 

ND* ND 

Ring-necked pheasant 

Phasianus colchicus 

ND ND 332 Highly toxic 

(00022923) 

*ND = Not determined 

21
 
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 Oanalog (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 dosedependent increase in pup death and litter loss. 

Table 13. Summary of Acute and Chronic Toxicity Data for Mammals Exposed to 

Dimethoate 

Species 

Acute Toxicity Chronic Toxicity 

LD50 

(mg/kg) 

Acute Oral 

Toxicity 

(MRID) 

5-day 

LC50 

(ppm) 

Subacute 

Dietary 

Toxicity 

(MRID) 

NOAEC/ 

LOAEC (ppm) 

(MRID) 

Affected Endpoints 

Laboratory 

mouse 

Mus 

musculus 

120 

Moderately 

toxic 

(00055371) 

ND ND ND ND 

Laboratory 

rat 420 

Moderately 

toxic ND ND 

32/400 

mg/kg/day 

(00051675) 

CHeI and decreased 

weight 

Rattus 

norvegicus (247669) 0.1/1.0 

mg/kg/day 

(455297-03) 

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 μg/bee). Contact toxicity data on 

parasitic wasps (Bathyplectus curculionus) indicate that some beneficial insects may be 

22 
considerably more sensitive than honeybees (LD50=0.00043 μg/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 (LD50) or the median lethal concentration (LC50). 

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 LOC 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 LOC 

terrestrial 

animals 

LOC 

aquatic animals 

Acute Risk - there is potential for acute risk 0.5 0.5 

Acute Endangered Species - endangered species may be 

adversely affected 

0.1 0.05 

Chronic Risk - there is potential for chronic risk 1 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
 
greater than the actual value, but was assessed because current labels do not specify 

limits. As a result of this reregistration decision, labels will be revised to limit the 

number of applications per season. For all other use scenarios, chronic RQs were below 

the LOC. 

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 (LC50 > 111,000 μg/L for sheepshead minnow, and LC50 

= 15,000 μg/L for mysid shrimp), the Agency believes that none of the acute RQs would 

exceed the acute risk LOC. 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 LC50 of 332 ppm from a subacute dietary 

toxicity study on ring-necked pheasants. At rates of 1 lbs 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 

lbs a.i./A, the acute risk and endangered species LOCs are exceeded for birds foraging on 

short grass. The acute endangered species LOC is not exceeded for birds feeding on tall 

grass and broadleaf plants/insects. In order to reduce RQs to below the endangered 

species LOC for the most vulnerable avian species, rates would have to be reduced to a 

single application of 0.13 lbs a.i./A. This low rate would not be efficacious. 

Following multiple applications of dimethoate, the acute risk LOC is exceeded for 

all applications equal to or greater than 1 lbs a.i./A (RQ = 0.72). Multiple applications at 

rates greater than 0.16 lbs a.i./A exceed the endangered species LOC 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 lbs 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) 

Food Items 

Maximum 

RQ 

Short grass 0.72 

Citrus 

Tall grass 0.33 

1.0 lb a.i./A 

(2/31) 

Broadleaf plants/small insects 0.41 

Fruits, pods, seeds, and large insects 0.05 

Broccoli, Cauliflower, Celery Short grass 0.44 

24
 
Use Site 

Application Rate 

(#/year / interval) 

Food Items 

Maximum 

RQ 

0.5 lb a.i./A 

(6/7) 

Tall grass 0.20 

Broadleaf plants/small insects 0.25 

Fruits, pods, seeds, and large insects 0.03 

Short grass 0.37 

Cotton, Safflower Tall grass 0.17 

0.5 lb a.i./A 

(2/14) 

Broadleaf plants/small insects 0.21 

Fruits, pods, seeds, and large insects 0.02 

Short grass 0.36 

Alfalfa Tall grass 0.17 

0.5 lb a.i./A 

(1/na) Broadleaf plants/small insects 0.20 

Fruits, pods, seeds, and large insects 0.02 

LOC = 0.5 for acute risk and 0.01 for endangered species 

Chronic avian RQs exceed the LOC (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 lbs a.i./A, the chronic risk LOC is not exceeded for birds feeding on 

fruits, pods, seeds and large insects, however, if the retreatment interval is reduced to 7 

days, the LOC is exceeded. In order to reach maximum residues that do not result in RQs 

exceeding the chronic risk LOC, the maximum single application rate would have to be 

reduced to 0.016 lbs 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) 

Food Items Mean RQ 

Citrus Short grass 63a 

Tall grass 27a 

1.0 lbs a.i./A Broadleaf plants/small insects 33a 

(2/3) Fruits, pods, and large insects 5.2a 

Broccoli, Cauliflower, Celery Short grass 13a 

Tall grass 5.5a 

0.5 lbs a.i./A 

(6/7) 

Broadleaf plants/small insects 6.9a 

Fruits, pods, and large insects 1.1a 

Cotton, Safflower Short grass 11a 

Tall grass 4.7a 

25
 
Use 

Application Rate (#/year / 

interval) 

Food Items Mean RQ 

0.5 lbs a.i./A Broadleaf plants/small insects 5.8a 

(2/14) Fruits, pods, and large insects 0.91 

Alfalfa Short grass 11a 

Tall grass 4.5a 

Broadleaf plants/small insects 5.6a 

Fruits, pods, and large insects 0.88 a

Exceeds 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 lb a.i./A, the acute risk LOC 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 lbs a.i./A, 

the acute risk LOC is exceeded for small and intermediate-sized mammals feeding on 

short grass (RQs range from 0.76 to 5.3). The acute endangered species LOC is exceeded 

across small and intermediate-sized herbivorous mammals at application rates greater 

than 0.16 lbs a.i./A. 

Table 17. Summary of Estimated Acute Mammalian RQs from Multiple Applications of 

Dimethoate at Maximum Foliar Residues 

Use Mammalian Acute Risk Quotients 

Application 

Rate 

(#/year / 

interval) 

Body Weight (g) Short Grass Tall Grass 

Broadleaf 

Plants/Small 

Insects 

Fruits/Pods/ 

Large Insects 

Citrus 15 1.8 0.81 1.0 0.11 

35 1.5 0.7 0.85 0.09 

1.0 lbs a.i./A 

(2/31) 1,000 0.81 0.37 0.46 0.05 

Broccoli, 15 1.10 0.50 0.61 0.06 

Cauliflower, 35 0.93 0.43 0.52 0.07 

Celery 

.5 lbs a.i./A 

(6/7) 

1,000 0.50 0.23 0.28 0.03 

Cotton, 15 0.92 0.42 0.52 0.06 

Safflower 35 0.78 0.36 0.44 0.05 

26
 
Use Mammalian Acute Risk Quotients 

Application 

Rate 

(#/year / 

interval) 

Body Weight (g) Short Grass Tall Grass 

Broadleaf 

Plants/Small 

Insects 

Fruits/Pods/ 

Large Insects 

.5 lbs a.i./A 

(2/14) 

1,000 0.42 0.19 0.24 0.03 

Alfalfa 15 0.89 0.41 0.50 0.06 

35 0.76 0.35 0.43 0.05 

0.5 lb a.i./A 

(1 app per 

year) 

1,000 0.41 0.19 0.23 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 

Body 

Weight (g) 

Mammalian Risk Quotients 

Short 

Grass Tall Grass 

Broadleaf 

Plants/Small 

Insects 

Fruits/Pods/ 

Large 

Insects 

Seeds 

Citrus 15 1,042 477 586 65 14 

35 890 408 501 56 12 

2.0 lbs a.i./A 

(2/31) 1,000 477 219 268 30 6.6 

Broccoli, 15 639 293 359 40 8.5 

Cauliflower, 35 546 250 307 34 7.6 

Celery 

0.5 lbs a.i./A 

(6/7) 

1,000 293 134 135 18 4.1 

Cotton, Safflower 15 538 247 303 34 7.5 

35 460 211 259 29 6.4 

0.5 lbs a.i./A 

(2/14) 1,000 247 113 139 15 3.4 

Alfalfa 15 521 239 293 33 7.2 

35 445 204 250 28 6.2 

0.5 lb a.i./A 

(1 app per year) 1,000 238 109 134 15 3.3 

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. 

27 
 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
 
Dimethoate was shown to be very highly toxic to some species of birds by the 

acute oral route. There are acute LOC exceedances at the application rate of 1.0 lb 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 LOC exceedances with the 

maximum RQs of 63 for two applications at 1 lbs ai/A, based on mean foliar residues. 

 There are exceedances for acute risk LOC for small mammals with the maximum 

RQ of 2.6 for small mammals eating short grass treated with two applications of 1.0 lb 

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 lb ai/A with a 3 day re-application interval. 

Most applications are at a maximum of 0.5 lb 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 lb ai/A, which would be 

far below the efficacious level for pest control. The Agency is requiring lowered 

29
 
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 LOC 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 reregistration. The Agency has previously identified and 

required the submission of the generic (technical or manufacturing-use grade) data 

required to support reregistration 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 

reregistration 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 reregistration 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 

reregistration, 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 reregistration 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
 
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 

31
 
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 reregistration 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 nonoccupational 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 Disruptor 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 Disruptor 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 Disruptor 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 reregistration 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
 
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 2 2 

Separate tolerances should be 

established for Alfalfa, forage and 

Alfalfa, hay, each at 2 ppm 

Apples 2 Revoke 

Use cancelled 7/20/05. Existing 

stocks may be sold until 7/20/06, and 

use may continue until stocks are 

depleted. 

Pears 2 2 Change to Pear. 

Beans, dry 2 2 [Bean, dried and Bean, succulent] 

Beans, lima 2 2 

Beans, snap 2 2 

Blueberries 1 1 Change to Blueberry. 

Broccoli 2 2 

Cabbage 2 Revoke 

Use cancelled 7/20/05. Existing 

stocks may be sold until 7/20/06, and 

use may continue until stocks are 

depleted. 

Cauliflower 2 2 

Collards 2 Revoke 

Use cancelled 7/20/05. Existing 

stocks may be sold until 7/20/06, and 

use may continue until stocks are 

depleted. 

Kale 2 2 

Mustard greens 2 2 

Cattle, fat 0.02(N) 0.02 Negligible residue designation is 

inappropriate. Change cattle, mbyp 

to Cattle, meat byproducts 

Cattle, mbyp 0.02(N) 0.02 

Cattle, meat 0.02(N) 0.02 

Celery 2 2 

Endive (escarole) 2 2 Change to Endive. 

Lettuce 2 Revoke 

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
 
Commodity Current Tolerance 

(ppm) 

Tolerance 

Reassessment (ppm) 

Comment/ 

[Correct Commodity Definition] 

Spinach 2 Revoke 

Use cancelled 7/20/05. Existing 

stocks may be sold until 7/20/06, and 

use may continue until stocks are 

depleted. 

Swiss chard 2 2 

Corn, fodder 1 1 

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, forage 1 1 [Corn, field, forage] and Corn, 

sweet, forage 

Corn, grain 0.1(N) 0.1 

Separate tolerances should be 

established for Corn, field, grain and 

Corn, pop, grain, each at 0.1 ppm. 

Negligible residue designation is 

inappropriate. 

Cottonseed 0.1 0.1 [Cotton, undelinted seed] 

Eggs 0.02(N) 0.02 Negligible residue designation is 

inappropriate. 

Goats, fat 0.02(N) 0.02 Negligible residue designation is 

inappropriate. Change to Goat, fat 

Goat, meat byproducts, Goat, meat 

Goats, mbyp 0.02(N) 0.02 

Goats, meat 0.02(N) 0.02 

Grapefruit 2 2 

Lemons 2 2 Change to Lemon. 

Oranges 2 2 Change to Orange. 

Tangerines 2 2 Change to Tangerine. 

Grapes 1 Revoke 

Use cancelled 7/20/05. Existing 

stocks may be sold until 7/20/06, and 

use may continue until stocks are 

depleted. 

Hogs, fat 0.02(N) 0.02 Negligible residue designation is 

inappropriate. Change to Hog, fat; 

Hog, meat byproducts; Hog, meat 

Hogs, mbyp 0.02(N) 0.02 

Hogs, meat 0.02(N) 0.02 

Horses, fat 0.02(N) 0.02 Negligible residue designation is 

inappropriate. Change to Horse, fat; 

Horse, meat byproducts; 

Horse, meat. 

Horses, mbyp 0.02(N) 0.02 

Horses, meat 0.02(N) 0.02 

Lentils 2.0 Revoke 

The established tolerance for peas 

applies to lentils. 

Melons 1 1 Change to Melon. 

35
 
Commodity Current Tolerance 

(ppm) 

Tolerance 

Reassessment (ppm) 

Comment/ 

[Correct Commodity Definition] 

Milk 0.002(N) TBD 

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 2 2 

[Peas, dried and succulent] 

Change to Pea, dried and Pea, 

succulent. 

Pecans 0.1 0.1 Change to Pecan. 

Peppers 2 2 Change to Pepper. 

Tomatoes 2 2 Change to Tomato. 

Potatoes 0.2 0.2 Change to Potato. 

Poultry, fat 0.02(N) 0.02 Negligible residue designation is 

inappropriate. 

Poultry, mbyp should be Poultry, 

meat byproducts. 

Poultry, mbyp 0.02(N) 0.02 

Poultry, meat 0.02(N) 0.02 

Safflower seed 0.1 0.1 [Safflower, seed] 

Sheep, fat 0.02(N) 0.02 Negligible residue designation is 

inappropriate.inappropriate. 

Sheep, mbyp should be Sheep, meat 

byproducts. 

Sheep, mbyp 0.02(N) 0.02 

Sheep, meat 0.02(N) 0.02 

Sorghum, forage 0.2 0.1 Based on available field trial data, 

HED recommends a lower tolerance. 

Sorghum, grain 0.1 0.1 Change to Sorghum, grain, grain. 

Soybeans 0.05(N) 0.05 

Negligible residue designation is 

inappropriate. 

Change to Soybean, seed. 

Soybeans, forage 2 2 Change to Soybean, forage. 

Soybeans, hay 2 2 Change to Soybean, hay. 

Turnips, roots 2 0.2 

Based on available field trial data, 

HED recommends a lower tolerance 

for dimethoate residues of concern 

in/on turnip roots. 

Should be Turnip, roots. 

Turnips, tops 2 2 Should be Turnip, tops. 

Wheat, grain 0.04(N) 0.04 Negligible residue designation is 

inappropriate. 

Wheat, green fodder 2 2 [Wheat, forage] 

Wheat, straw 2 2 

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
 
Commodity Current Tolerance 

(ppm) 

Tolerance 

Reassessment (ppm) 

Comment/ 

[Correct Commodity Definition] 

Cowpeas, hay None TBD 

Cotton, gin byproducts None TBD Residue data are required. 

Peas, field, vines None TBD 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 

Peas, field, hay None TBD 

Sorghum, stover (fodder) None 0.1 Change to Sorghum, grain, stover. 

Wheat hay None 2 ppm 

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 0.15 0.15 

Brussels sprouts 5 5 

CBRS recommends that this 

tolerance be listed under 40 CFR 

§180.204(a). 

Cherries 2 2 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
 
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 screeninglevel 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
 
Table 20. Revised Use Site Parameters and Requirements for Dimethoate 

Crop App method 

Max 

rate 

per app 

(lbs 

a.i./A) 

# apps/ 

interval 

REI (days) 

Non- Other

arid Arid 

Cherries 

Aerial 1 (SLN) 

1 

10 14 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, 

and airblast 

0.33 2 4 

Asparagus 

Aerial, 

chemigation, 

groundboom 

0.5 2/14 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: M/L must wear 

gloves and apron, gloves for 

applicators 

Citrus 

Chemigation, 

and airblast 1 1 10 14 

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. 

Pears 

Aerial, 

chemigation, 

airblast (liquid 

and WP) 

1 1 10 14 

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 

Alfalfa (seed 

and hay) 

Aerial, 

chemigation, 

groundboom 

0.5 1 (per 

cutting) 2 2 

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 

Succulent 

peas 

Aerial, 

chemigation, 

groundboom 

0.16 1 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: M/L must wear 

gloves and apron, gloves for 

applicators 

Beans – 

fresh, snap, 

lima, dry 

Aerial, 

chemigation, 

groundboom 

0.5 2/14 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: M/L must wear 

gloves and apron, gloves for 

applicators 

Broccoli Aerial, 

chemigation, 0.5 3/7 2 3 Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

39
 
Crop App method 

Max 

rate 

per app 

(lbs 

a.i./A) 

# apps/ 

interval 

REI (days) 

Non- Other

arid Arid 

groundboom cockpits. 

Groundboom: M/L must wear 

gloves and apron, gloves for 

applicators 

Also: BMPs, vegetative filter strips 

Cauliflower Aerial, 

chemigation, 

groundboom 

0.5 3/7 2 3 

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 

Celery Aerial, 

chemigation, 

groundboom 

0.5 3/7 2 2 

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 

Cotton Aerial 0.5 2/14 2 2 

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 

Lentils Aerial, 

chemigation, 

groundboom 

0.5 2/7 2 2 

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 

Melon 

Aerial, 

chemigation, 

groundboom 

0.5 2/7 2 2 

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 

Potatoes 

Aerial, 

chemigation, 

groundboom 

(liquid and 

WP) 

0.5 2/7 2 2 

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
 
Crop App method 

Max 

rate 

per app 

(lbs 

a.i./A) 

# apps/ 

interval 

REI (days) 

Non- Other

arid Arid 

Soybeans Aerial, 

chemigation, 

groundboom 

0.5 2/7 2 2 

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 

Tomatoes Aerial, 

chemigation, 

groundboom 

0.5 2/6 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: M/L must wear 

gloves and apron, gloves for 

applicators. 

Field corn; 

popcorn 

Aerial, 

chemigation, 

groundboom 

0.5 1 2 2 

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 

Safflower Aerial, 

chemigation, 

groundboom 

0.5 1 2 2 

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. 

Sorghum Aerial, 

chemigation, 

groundboom 

0.5 2/7 2 2 

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. 

Wheat Aerial, 

chemigation, 

groundboom 

0.5 1 2 2 

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. 

Pecans 

Aerial, 

chemigation, 

airblast 

0.33 1 2 2 

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. 

Peppers Aerial, 

chemigation, 

groundboom 

0.33 3/7 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: M/L must wear 

gloves and apron, gloves for 

applicators. 

Grass for 

seed 

Aerial, 

chemigation, 0.5 2/90 2 2 Aerial/Chemigation: M/L must 

wear gloves, apron, and respirators. 

41
 
Crop App method 

Max 

rate 

per app 

(lbs 

a.i./A) 

# apps/ 

interval 

REI (days) 

Non- Other

arid Arid 

groundboom Pilots in enclosed cockpits. 

Groundboom: gloves and apron for 

M/L; gloves for applicators. 

Leaf lettuce Aerial, 

chemigation, 

groundboom 

0.25 3/7 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: : M/L must wear 

gloves and apron, gloves for 

applicators 

Swiss chard Aerial, 

chemigation, 

groundboom 

0.25 3/7 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: : M/L must wear 

gloves and apron, gloves for 

applicators. 

Endive 

(escarole) 

Aerial, 

chemigation, 

groundboom 

0.25 3/7 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: : M/L must wear 

gloves and apron, gloves for 

applicators. 

Kale Aerial, 

chemigation, 

groundboom 

0.25 2/15 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: : M/L must wear 

gloves and apron, gloves for 

applicators. 

Turnips Aerial, 

chemigation, 

groundboom 

0.25 3/7 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: : M/L must wear 

gloves and apron, gloves for 

applicators. 

Mustard 

greens 

Aerial, 

chemigation, 

groundboom 

0.25 2/9 2 2 

Aerial/Chemigation: gloves, apron, 

respirator for M/L; Pilots in enclosed 

cockpits. 

Groundboom: : M/L must wear 

gloves and apron, gloves for 

applicators. 

Brussels 

sprouts 

Aerial, 

chemigation, 

groundboom 

0.5 3/7 2 3 

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 

Herbaceous 

ornamentals 

Groundboom, 

low pressure 

handwand 

0.25 1 2 2 

Groundboom and Low Pressure 

handwand: M/L must wear gloves 

and apron, Gloves for applicators. 

High Pressure Handwand: M/L 

42
 
Crop App method 

Max 

rate 

per app 

(lbs 

a.i./A) 

# apps/ 

interval 

REI (days) 

Non- Other

arid Arid 

must wear gloves and apron, Gloves 

and respirator for applicators. 

Douglas fir 

seed 

orchards in 

WA and OR 

Airblast- 4.15 1 16 25 

Airblast: M/L must wear gloves and 

apron, Applicators must wear gloves 

and a respirator. 

Conifer seed 

orchards 

Aerial, 

Groundboom 

1 1 2 4 

Aerial: M/L must wear gloves, 

apron, and respirator. Pilots in 

enclosed cockpits. 

Groundboom: M/L must wear 

gloves and apron, Gloves for 

applicators. 

Woody 

ornamentals 

and 

Christmas 

tree 

nurseries 

Aerial, 

Groundboom 

1 3/14 10 14 

Aerial: M/L must wear gloves, 

apron, and respirator. Pilots in 

enclosed cockpits. 

Groundboom: M/L must wear 

gloves and apron, Gloves for 

applicators. 

Cottonwood 

grown for 

pulp 

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 USDA 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
 
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 

AgDRIFT 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 LOC 

for some of the representative exposure scenarios considered. At the rates assessed, acute 

and chronic RQs exceed the LOC for endangered birds and mammal across all use sites. 

After a single application of 0.16 lbs 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
 
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 reregistration 

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
 
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 reregistration. 

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 reregistration (EPA Form 8570­

1). Indicate on the form that it is an “application for reregistration”; 

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 

reregistration and/or the PDCI. All materials submitted in response to the PDCI should 

be addressed as follows: 

46
 
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 Reregistration 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 reregistration 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 

Reproduction (bobwhite quail and mallard duck) – 

omethoate 

47
 

850.2300 
860.1500 Magnitude of residue data for metabolites of concern (Odesmethyl 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 productspecific 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. 

48
 
Labeling Changes Summary Table 

In order to be eligible for reregistration, amend all product labels to incorporate the risk mitigation measu

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 Placem

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
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 Stat

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 followPrecautionary StatHumans and Dom

50
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." 

Immediately followPrecautionary StatHumans and Dom

“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.” ------ 

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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. If 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 StatHumans and Domimmediately followrequirements 

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: chemicalresistant 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 StatHumans and Dom(Immediately folloSafety Requiremen

52
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, chemicalresistant 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 

Precautionary StatHumans and Dom(Immediately follo

alfalfa, cotton, soybeans, corn, safflower, sorghum, and wheat, must use a Safety Requiremenclosed 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 

53
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, chemicalresistant 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, chemicalresistant 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
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 StatHazards to HumanAnimals immediatEngineering Contr(Must be placed in 

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 Statfollowing the User Recommendations 

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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 

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 R

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 R

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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 Directabove the Agricult

Application Restriction “This product is for use in commercial setting only. Use in residential 

settings is prohibited.” 

Near the beginning 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 lb 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 lb 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 lb ai/acre and no more than one 

Directions for Use use directions for twhich the restricti

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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 lb 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 lb 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 lb 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 lb. 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 lb 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 lb 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 lb ai/acre. The limit of one application per year applies. “If airblast applications are applied at a rate greater than 1 lb 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 lb 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 lb ai/acre and no more than 1 application per year. “The REI is 48 hours.” Kale Maximum application rate: 0.25 lb 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 lb 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 lb 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 lb ai/acre and no more than 1 application per year. “The REI is 48 hours.” Sorghum, and Soybeans Maximum application rate: 0.5 lb 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 lb ai/acre, 9 day reapplication interval, and no more than 2 applications per year. “The REI is 48 hours.” Pears Maximum application rate: 1 lb 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 lb 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 lb 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 lb 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 lbs. a.i./acre. Tomatoes Maximum application rate 0.5 lb 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 lb 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 lb 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 ontarget 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 PP

The more protective PPE must be placed in the product labeling. For guidance on which PPE is considered more protectiv

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