Docket Number EPA-HQ-OPP-2010-0028 

www.regulations.gov 

Oxamyl Final Work Plan for 

Registration Review 

February 2011 

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Introduction:

This is the Environmental Protection Agency’s (EPA or the Agency) Final Work Plan (FWP) 

for the registration review of oxamyl. The Final Work Plan includes the expected registration 

review timeline. The FWP also addresses public comments received on the Preliminary Work 

Plan (PWP) in the Summary Document which was posted in the oxamyl registration review 

docket (EPA-HQ-OPP-2010-0028). The Summary Document, dated September 17, 2010, 

provided information on what EPA knows about the pesticide and what additional risk analyses 

and data or information the Agency believes are needed to make a registration review decision. 

The Agency’s implementation of the registration review program requires review of each 

registered pesticide every 15 years to determine whether it continues to meet the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) standard for registration. Changes in 

science, public policy, and pesticide use practices occur over time. The registration review 

program is intended to make sure that, as the ability to assess risk evolves and as policies and 

practices change, all registered pesticides continue to meet that statutory standard. The public 

phase of registration review begins when the initial docket is opened for each case. Information 

on this program is provided at http://www.epa.gov/oppsrrd1/registration_review/ . 

Oxamyl is a restricted use N-methyl carbamate insecticide, acaricide, miticide, nematicide, and 

plant growth regulator registered for use on a variety of fruits, vegetables, and field crops. There 

are currently no residential uses for oxamyl. It is a member of the N-methyl carbamate (NMC) 

class of chemicals that share a common mechanism of toxicity and inhibit acetylcholinesterase. 

The Interim Reregistration Eligibility Decision (IRED) for Oxamyl was completed in October 

2000, and the Reregistration Eligibility Decision (RED) for Oxamyl was finalized in September 

2007 upon completion of the Revised N-Methyl Carbamate Cumulative Risk Assessment. 

In 2007 and 2008, EPA received several new and expanded use requests from DuPont Crop 

Protection (DuPont), the technical registrant of oxamyl. Risk assessments were conducted in 

2009 and 2010 to evaluate these amendment requests and to incorporate updated toxicological 

data and modeling methodologies into assessments for the currently labeled uses of oxamyl. 

Due to the recent improvements in EPA’s risk modeling methodologies, the new risk 

assessments identified risks of concern for some existing uses of oxamyl. All of the new and 

expanded use amendment requests were withdrawn by DuPont in December 2009. 

Updates Since the Summary Document:

EPA is continuing to work with DuPont to mitigate dietary and occupational risks of concern 

identified in the 2010 dietary and occupational risk assessments. Mitigation may result in a 

number of crop-specific regional labeling changes (e.g., lowering individual and annual 

application rates, reducing number of applications), longer restricted entry intervals for some 

crops, or other measures. EPA is working to refine the risk assessment and will mitigate where 

necessary to resolve risk concerns in advance of the draft risk assessments for registration 

review. 
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Comments Received on the Preliminary Work Plan:

The Agency received four submissions during the 60-day public comment period on the PWP, 

which began on September 22, 2010 and ended on November 22, 2010 (EPA-HQ-OPP-2010-

0028). Comments were submitted by the Physicians Committee for Responsible Medicine, the 

American Bird Conservancy, DuPont, and a member of the public. The comments do not 

address the timeline described in the PWP, but they do address the planned ecological data 

requirements and risk assessments. The submitted comments and EPA’s responses are presented 

in the “Summary of Comments and Agency Responses” section of this document. 

In the PWP, EPA also solicited comment on the specific topics of environmental justice, water 

body impairment, and trade irritants. No comments or information were received during the 

public comment period concerning these issues.

Risk Assessment and Data Needs:

The Agency will require data and conduct an ecological risk assessment for oxamyl, including an 

endangered species assessment. For human health, revised dietary and occupational risk 

assessments may be needed during registration review to incorporate updated toxicological 

endpoints, exposure estimates, and data required through a registration review data call-in. 

Below is a summary of the issues relevant to the registration review of oxamyl. 

Ecological Risk: 

• The most recent comprehensive (i.e., all use patterns) ecological risk assessment was 

completed in November 1999 and amended in March 2000 in support of the 2000 

Oxamyl IRED. 

• In 2007 and 2009, crop-specific ecological risk assessments were conducted for oxamyl 

to evaluate FIFRA Section 3 proposed new uses on sugar beets and on dry bulb onions, 

shallots, and garlic. The requests for new uses were later withdrawn by the technical 

registrant. 

• The Agency completed an endangered species risk assessment for the California redlegged frog (CRLF) in February 2009, and is currently in consultation with the U.S. Fish 

and Wildlife Service (USFWS). 

• Although the Agency has completed a species-specific determination for the CRLF 

relative to oxamyl use, a risk assessment that supports a complete endangered species 

determination has not been conducted. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether oxamyl’s use has “no 

effect” or “may affect” federally listed threatened or endangered species (listed species) 

or their designated critical habitats. When an assessment concludes that a pesticide’s use 

“may affect” a listed species or its designated critical habitat, the Agency will consult 

with the USFWS and/or National Marine Fisheries Service (the Services), as appropriate. 
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• On January 19, 2011, the Center for Biological Diversity and the Pesticide Action 

Network North America filed a lawsuit in the United States District Court for the 

Northern District of California, against EPA for allegedly failing to undergo consultation 

with the Services regarding the effects of over 350 pesticides, including oxamyl, on over 

200 endangered and threatened species throughout the United States (Center for 

Biological Diversity, et al. v. EPA, et al., No. C 11-00293 (N.D.Cal.). 

• An updated ecological risk assessment of all registered uses of oxamyl will be conducted 

during registration review. The new assessment will incorporate the most up-to-date 

modeling methodologies, updated toxicological endpoints, and data submitted under the 

registration review data call-in. 

• Data gaps exist in the environmental fate and ecological effects databases for oxamyl. 

EPA will require the following guideline studies in order to conduct a complete 

ecological risk assessment, including an endangered species assessment, for the 

registration review of oxamyl. 

835.4400 – Anaerobic aquatic metabolism 

850.1025 – Acute toxicity estuarine and marine organisms (oyster shell 

deposition) 

850.1035 – Acute toxicity estuarine and marine organisms (mysid) 

850.1350 – Aquatic invertebrate life cycle, saltwater (mysid) 

850.1400 – Fish early life stage, saltwater fish1

850.2100 – Avian oral toxicity (passerine species) 

850.3040 – Field testing for pollinators 

850.4100 – Seedling emergence, terrestrial plant toxicity (Tier II) 

850.4150 – Vegetative vigor, terrestrial plant toxicity (Tier II) 

850.4400 – Aquatic plant growth, vascular plants (Tier II) 

• Please refer to the July 28, 2010 document Registration Review: Preliminary Problem 

Formulation for Environmental Fate, Ecological Risk, Endangered Species, and 

Drinking Water Exposure Assessments for Oxamyl in the registration review docket 

(EPA-HQ-OPP-2010-0028-0005) for a detailed discussion of the risk assessment and 

data needs. 

Human Health Risk:

• A refined acute dietary (food plus drinking water) risk assessment for all registered uses 

of oxamyl was conducted in July 2010 to incorporate updated toxicological data and 

modeling methodologies into assessments for the currently labeled uses of oxamyl. In 

addition, the Agency further refined the acute aggregate dietary assessment by 

incorporating the time and amounts consumed for each eating occasion from the United 

States Department of Agriculture’s (USDA’s) Continuing Surveys of Food Intakes by 

Individuals food diaries to estimate exposures and risks on each eating occasion 

 

1

 The Oxamyl Summary Document for Registration Review incorrectly stated that Guideline 850.4100 was required 

for freshwater fish. That was in error, and EPA is requiring the fish early life stage study for the saltwater species. 
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throughout the day and factoring in the cholinesterase (ChE) inhibition half-life related to 

oxamyl exposure. 

• The drinking water assessment may be updated as a result of mitigation implemented to 

address risks of concern identified in the most recent oxamyl dietary assessment. 

Additionally, the Agency may update the drinking water assessment during registration 

review if new environmental fate data are submitted, labeled use patterns are altered, 

residues of concern in drinking water are redefined, or the Agency’s drinking water 

assessment methodology is refined. 

• The oxamyl dietary risk assessment may be updated as a result of mitigation 

implemented to address risks of concern identified in the July 2010 oxamyl aggregate 

(food plus drinking water) acute dietary risk assessment. Additionally, an updated 

oxamyl acute dietary risk assessment may be required during registration review if there 

are changes to residues in food or concentrations in drinking water, points of departure, 

or uncertainty factors. 

• EPA will not conduct an oxamyl chronic dietary assessment during registration review. 

Acute exposure from oxamyl is the only duration of concern because of the rapid 

recovery of ChE activity. 

• A revised occupational and residential exposure (ORE) assessment for oxamyl was 

completed in July 2010 to incorporate updated toxicological data. 

• The ORE risk assessment may be updated as a result of mitigation implemented to 

address occupational risks of concern identified in the most recent assessment. 

Additionally, the Agency may update the assessments of oxamyl occupational handler 

and post-application activities during registration review if toxicological endpoints 

change, revisions to current policies and procedures for conducting these assessments are 

accepted, or new poisoning incident data are received. 

• Because there are no currently registered uses of oxamyl at residential sites, residential 

handler and post-application assessments will not be conducted during registration 

review. 

• The current label restriction against feeding cotton gin byproduct to livestock can be 

deleted from oxamyl labels once a tolerance of 120 ppm is established for residues of 

oxamyl on cotton gin byproduct. 

• The toxicity database for oxamyl is nearly complete. However, EPA will require 

Guideline 870.7800, Immunotoxicity study, in order to conduct a complete human health 

risk assessment for the registration review of oxamyl. 

• Oxamyl shares a common mode of action with other NMCs and was included in the 

Revised N-methyl Carbamate Cumulative Risk Assessment completed in 2007. Over time 

as new use requests, new data, or other information are submitted to the Agency for 
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individual chemicals within the cumulative group, single chemical risk assessments are 

updated. In the case of oxamyl, recent requests for new uses required updated risk 

assessments that indicated potential risks of concern for a number of existing uses. The 

Agency is working to address risk concerns for the individual chemical first. 

Subsequently, the Agency will consider any changes to the use patterns for oxamyl, as 

appropriate, for the NMC cumulative assessment in order to reach a determination for the 

cumulative group as a whole. 

• Please refer to the August 18, 2010 document Oxamyl: Registration Review Scoping 

Document for Human Health Assessments in the registration review docket (EPA-HQOPP-2010-0028-0004) for a detailed discussion of the risk assessment and data needs. 

Endocrine Disruptor Screening Program:

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its oxamyl reregistration decision, EPA reviewed these data and 

selected the most sensitive endpoints for relevant risk assessment scenarios from the existing 

hazard database. However, as required by FFDCA section 408(p), oxamyl is subject to the 

endocrine screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. Oxamyl was 

included on that list and has been issued an order to conduct the Tier 1 testing. Once all required 

Tier 1 and Tier 2 data have been received and reviewed, the endpoints and safety factors used for 

risk assessment purposes will be examined and a new risk assessment performed if necessary. 

For further information on the status of the EDSP, the policies and procedures, the list of 67 
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chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our 

website: http://www.epa.gov/endo/. 

Timeline:

EPA has created the following estimated timeline for the completion of the registration review 

for oxamyl. 

Registration Review for Oxamyl – Projected Registration Review Timeline

Activities Estimated Date 

Opening the Docket 

Open Docket and Public Comment Period Completed – Sept. 22, 2010

Close Public Comment Completed – Nov. 22, 2010

Case Development 

Final Work Plan Completed – February 2011

Issue DCI 2011 – Oct – Dec 

Data Submission 2013 – Oct – Dec 

Open Public Comment Period for Draft Risk Assessments 2015 – April – June 

Close Public Comment Period 2015 – July – Sept 

Registration Review Decision 

Open Public Comment Period for Proposed Registration Review 

Decision 

2015 – Oct – Dec. 

Close Public Comment Period 2016 – Jan. – March 

Registration Review Decision and Begin Post-Decision Follow-up 2016 

Total (years) 2 6 

Summary of Comments and Agency Responses:

During the public comment period on the Oxamyl Summary Document, the Agency received 

comments from the Physicians Committee for Responsible Medicine, the American Bird 

Conservancy, DuPont, and a member of the public. The following is a summary of the 

comments and the Agency’s responses. 

Comments submitted by the American Bird Conservancy (ABC) in EPA-HQ-OPP-2010-

0028-0015.1. 

For additional details regarding EPA’s response, please refer to the document “EFED Response 

to Comments on Preliminary Work Plan for Oxamyl,” dated January 20, 2011, included in the 

oxamyl registration review docket (EPA-OPP-2010-0028). 

1. Comment: ABC noted that although relatively few incidents involving oxamyl have been 

reported to ABC or EPA, the absence of incident reports cannot be construed as the absence 

of incidents. This is because poisoned birds may fly far from the site of pesticide application 

or be consumed by scavengers.

 

2

 An assessment of the potential cumulative risk from the NMC class of insecticides may impact this time estimate. 
9

Response: EPA agrees with this statement and includes a similar disclaimer in the discussion 

of incidents within our preliminary problem formulation document for oxamyl. Additionally, 

when EPA is ready to conduct the ecological risk assessment for oxamyl, we will review the 

Environmental Incident Information System, American Bird Conservancy database, and the 

aggregate incident reporting system for any additional incidents reported between the time of 

the EFED Problem Formulation and the risk assessment. 

2. Comment: “ABC suggests substitution of effective insecticides with much lower avian 

toxicity as alternatives to oxamyl, unless effective mitigation measures can be developed... 

Because the registration review process is so prolonged, we request that EPA mitigate uses 

of oxamyl that are found to pose high risks to migratory birds or threatened or endangered 

species.”

Response: In the 2000 Interim Reregistration Eligibility Decision for Oxamyl, the Agency 

concluded that potential risks to the environment, including to birds, from oxamyl would be 

mitigated with the incorporation of additional use restrictions on oxamyl product labels. All 

current product labels have been amended to reflect these measures. At this time, the 

Agency believes the current uses of oxamyl do not pose unreasonable adverse effects to 

birds, and therefore, no additional risk mitigation is required. Additionally, the Agency will 

perform an endangered species assessment for oxamyl as part of the registration review 

process, and will consult with the Services, as appropriate, if the assessment concludes that 

oxamyl’s use may affect a listed species or its designated critical habitat. 

3. Comment: “ABC requests an avian oral toxicity test using a passerine species.”

Response: The Oxamyl Summary Document for Registration Review and this Final Work 

Plan both list Guideline 850.2100, avian oral toxicity for passerine species as a data gap, for 

which EPA intends to issue a data call-in. 

4. Comment: “ABC strongly supports oxamyl to be tested under the EDSP, specifically the Tier 

II avian 2-generation tests.”

Response: Oxamyl is among the group of 58 pesticide active ingredients for which test 

orders were issued under Tier 1 of the Endocrine Disruptor Screening Program between 

October 2009 and February 2010. Oxamyl orders were issued on November 12, 2009. The 

Agency reviewed the “Other Scientifically Relevant Information” submitted by DuPont and 

determined that DuPont needs to conduct all Tier 1 assays. Once the Agency has received 

and reviewed all relevant data, including the Tier 1 results, the Agency will determine which, 

if any, of the Tier 2 tests are required. 

5. Comment: “ABC requests an avian reproductive and developmental study using a passerine 

species... Passerine species are altricial birds, and hatch at a very different developmental 

stage than precocial mallards and bobwhite quail... The differences in embryonic 

development between altricial and precocial birds could potentially lead to differences in 

sensitivity to pesticides...”
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Response: EPA is not aware of any data to show that oxamyl is more toxic to passerine 

species than it is to the bobwhite quail or mallard ducks on an acute or chronic exposure 

basis as it relates to reproductive endpoints. The Agency believes that the data from 

reproductive studies in the bobwhite quail and mallard duck studies will be adequate for 

assessing potential risks to birds from chronic oxamyl exposure. Further, EPA does not have 

a validated protocol for a chronic reproduction study in passerines. 

Comments submitted by the Physicians Committee for Responsible Medicine (PCRM) in 

EPA-HQ-OPP-2010-0028-0013.1. 

For additional details regarding EPA’s response, please refer to the document “EFED Response 

to Comments on Preliminary Work Plan for Oxamyl,” dated January 20, 2011, included in the 

oxamyl registration review docket (EPA-OPP-2010-0028). 

6. Comment: “We strongly support the use of the newly revised OECD Test Guideline 223 for 

the acute avian oral toxicity test, which has been adopted by the OECD.”

Response: At this time, EPA is actively evaluating the results of the OECD validation report 

to determine if the OECD TG 223 effects endpoints and dose/response information 

adequately address the purposes of the avian acute oral data requirement as described in 40 

CFR Part 158. Until EPA’s evaluation of that validation report is complete, EPA will not 

classify avian toxicity studies conducted using the TG 223 protocol, and the studies cannot 

be used to fulfill data requirements. 

Comments submitted by DuPont Crop Protection in EPA-HQ-OPP-2010-0028-0014.1. 

7. Comment: DuPont indicated that they intend to address the data requirements that EPA 

plans to call-in through the registration review process. DuPont also stated that they will 

provide the most current and relevant information to EPA on topics such as label 

information, mode of action, or use and usage data to allow the Agency to conduct human 

health and ecological risk assessments.

Response: EPA thanks DuPont for stating their intention with regard to the data call-in and 

additional useful information. 

8. Comment: “DuPont is working with the Agency to address the concerns raised in the 

occupational exposure assessment.”

Response: As was stated in the “Updates Since the Summary Document” section of this 

Final Work Plan, EPA is working with DuPont to mitigate dietary and occupational risks of 

concern identified in the 2010 dietary and occupational risk assessments.

9. Comment: “DuPont’s Guideline 830.7050 UV/Visible Absorption study (MRID 45510101) 

has been reviewed by the Agency (DP Barcode 382386), found to be acceptable, and fulfills 

this data requirement.”
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Response: EPA agrees with this statement and transmitted the Data Evaluation Record to 

DuPont on October 20, 2010.

Summary of Data Gaps – Oxamyl:

The table below summarizes all data needs for oxamyl as listed in the Registration Review: 

Preliminary Problem Formulation for Environmental Fate, Ecological Risk, Endangered 

Species, and Drinking Water Exposure Assessments for Oxamyl, dated July 28, 2010, and the 

Oxamyl: Registration Review Scoping Document for Human Health Assessments, dated August 

18, 2010. 

Guideline 

Number Data Requirement Test Material 

Estimated 

Timeframe 

(months) 

835.4400 Anaerobic aquatic metabolism TGAI 24 

850.1025 Acute toxicity estuarine and marine organisms3 TGAI 12 

850.1035 Acute toxicity estuarine and marine organisms4 TGAI 12 

850.1350 Aquatic invertebrate life cycle, saltwater5 TGAI 12 

850.1400 Fish early life stage, saltwater fish6 TGAI 12 

850.2100 Avian oral toxicity7 TGAI 12 

850.3040 Field testing for pollinators TEP 24 

850.4100 Seedling emergence, terrestrial plant toxicity (Tier 

II) TEP 12 

850.4150 Vegetative vigor, terrestrial plant toxicity (Tier II) TEP 12 

850.4400 Aquatic plant growth, vascular plants (Tier II) TEP 12 

870.7800 Immunotoxicity Study TGAI 12 

Next Steps:

As noted previously, the Agency plans to require several ecological effects and human health 

studies through a data call-in, expected to be issued in late 2011. This new information will be 

used to conduct complete risk assessments for all registered uses of oxamyl. 

Additionally, EPA will continue to work with DuPont to mitigate dietary and occupational risks 

of concern identified in the 2010 dietary and occupational risk assessments. 

 

3

 Acute toxicity data should be submitted where Eastern oysters are exposed to TGAI oxamyl. 

4

 Acute toxicity data should be submitted where mysid shrimp are exposed to TGAI oxamyl. 

5

 Life cycle toxicity data should be submitted for the mysid shrimp. 

6

 The Oxamyl Summary Document for Registration Review incorrectly stated that Guideline 850.4100 was required 

for freshwater fish. That was in error, and EPA is requiring the fish early life stage study for the saltwater species. 7

 A passerine study protocol must be submitted for review by the Agency prior to initiation of this study.