Docket Number EPA-HQ-OPP-2010-0028 

www.regulations.gov 

Oxamyl Summary Document 

Registration Review: Initial Docket 

September 2010 

TABLE OF CONTENTS 

I. Preliminary Work Plan (PWP) 4 

II. Fact Sheet 12 

III. Summary of Data Gaps 20 

__________________________________________________________________ 

Please Note 

This Preliminary Work Plan and Fact Sheet summarize the Environmental Protection Agency's 

current position based on the following documents: 

1. Registration Review: Preliminary Problem Formulation for Environmental Fate, 

Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments for 

Oxamyl. Dated July 28, 2010. 

2. Oxamyl: Registration Review Scoping Document for Human Health Assessments. Dated 

August 18, 2010. 

3. Appendix A: Label, Use, and Usage Table. Dated June 5, 2009.

4. Updated Review of Oxamyl Incident Reports. Dated November 24, 2009. 

These and other supporting documents for the oxamyl registration review case may be found in 

the docket EPA-HQ-OPP-2010-0028 at http://www.regulations.gov. 

Notices, documents, and public comments associated with the N-Methyl Carbamate Cumulative 

Risk Assessment are located in the docket EPA-HQ-OPP-2007-0935. 

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I. Preliminary Work Plan – Oxamyl 

Introduction: 

The Food Quality Protection Act (FQPA) of 1996 mandated a registration review program. All 

pesticides distributed or sold in the United States (U.S.) generally must be registered by the 

Environmental Protection Agency (EPA or the Agency), based on scientific data showing that 

they will not cause unreasonable risks to human health or the environment when used as directed 

on product labeling. 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 the statutory standard of no unreasonable adverse effects to human health or the 

environment. Changes in science, public policy, and pesticide use practices will occur over time. 

Through the registration review program, the Agency periodically reevaluates pesticides to make 

sure that as change occurs, products in the marketplace can be used safely. Information on this 

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

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. The Agency will consider benefits information and data as required by FIFRA. The 

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

docket is the Agency’s opportunity to state what it knows about the pesticide and what additional 

risk analyses and data or information it believes are needed to make a registration review 

decision. After reviewing and responding to comments and data received in the docket during 

this initial comment period, the Agency will develop and commit to a final work plan and 

schedule for the registration review of oxamyl. 

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, the 

technical registrant of oxamyl. Risk assessments were conducted in 2009 and 2010 to evaluate 

these amendment requests and to incorporate updated toxicological data into assessments for the 

currently labeled uses of oxamyl. The new risk assessments identified risks of concern for some 

existing uses of oxamyl. EPA is currently working with the registrant to mitigate these concerns. 

All of the new and expanded use amendment requests were withdrawn by DuPont in December 

2009. 

Anticipated Risk Assessment and Data Needs:

The Agency anticipates the need to require data and conduct an ecological risk assessment for 

oxamyl, including an endangered species assessment. For human health, revised dietary and 

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occupational risk assessments may be needed during registration review to incorporate updated 

toxicological endpoints, exposure estimates, and data may need to be 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, which were later withdrawn. 

• The Agency completed an endangered species assessment evaluating the potential effects 

of oxamyl on one species consistent with a court order and settlement: Center for 

BiologicalDiversity v. Johnson, et al., No. 02-1580 (N.D. Cal., October 20, 2006) 

[addressing the California red-legged frog (CRLF)]. On February 20, 2009, the Agency 

transmitted the assessment to the U.S. Fish and Wildlife Service (USFWS) and initiated 

formal consultation under Section 7 of the Endangered Species Act. The Agency will 

consider any reasonable and prudent measures or risk assessment considerations that may 

be included in the future responses to the Agency’s requests for consultation on the 

CRLF. 

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 U.S. Fish and Wildlife Service and/or National Marine Fisheries Service (the 

Services), as appropriate. 

• 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 

anticipated registration review data call-in. 

• Data gaps exist in the environmental fate and toxicity databases for oxamyl. EPA 

anticipates requiring 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 

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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, freshwater 

850.2100 – Avian oral toxicity (passerine species) 

850.3040 – Field testing for pollinators 

850.4100 – Terrestrial plant toxicity, seedling emergence, Tier II 

850.4150 – Terrestrial plant toxicity, vegetative vigor, Tier II 

850.4400 – Aquatic plant growth, vascular plants, Tier II 

• The Agency seeks additional information, particularly use and usage information, in 

order to conduct a refined, complete ecological risk assessment, including an endangered 

species assessment for oxamyl. See the “Guidance for Commenters” section below. 

• 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) for a detailed discussion of the risk assessment and 

anticipated data needs. 

Human Health Risk:

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

of oxamyl was conducted in July 2010 to incorporate updated toxicological data 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 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 and 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 drinking water, percent crop treated information, points 

of departure, or uncertainty factors. 

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• EPA does not anticipate conducting 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 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. 

• As 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 by-product to livestock should be 

deleted from oxamyl labels as recommended per the September 2000 human health 

assessment. To date, this label restriction has not been removed, but the labeling revision 

will be incorporated into future product label amendments. 

 

• The toxicity database for oxamyl is nearly complete. However, EPA anticipates the need 

to 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 

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 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 incorporate any changes to the use patterns for oxamyl, as appropriate, into 

the 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) for a detailed discussion of the risk assessment and anticipated data 

needs. 

Endocrine Disruptor Screening Program: 

As required under FFDCA section 408(p), EPA has developed the Endocrine Disruptor 

Screening Program (EDSP) to determine whether certain substances (including pesticide active 

7
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, and 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 quantitative relationship between the dose and the E, A, or T effect. 

 

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. 

This list of chemicals was selected based on the potential for human exposure through pathways 

such as food and water, residential activity, and certain post-application agricultural scenarios. 

This list should not be construed as a list of known or likely endocrine disruptors. 

Oxamyl is among the group of 58 pesticide active ingredients on the initial list to be screened 

under the EDSP. For information on the status of the orders issued under the EDSP for each 

chemical, please visit our website at http://www.epa.gov/endo/ and click on the “Status of EDSP 

Orders/DCIs” in the Highlights Box. Additional information on the EDSP, including the policies 

and procedures, the list of 67 chemicals, the test guidelines and the Tier 1 screening battery, can 

also be found at this website. 

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Timeline:

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

review. 

Registration Review for Oxamyl – Projected Registration Review Timeline

Activities Estimated Date 

Opening the Docket 

Open Docket and Public Comment Period 2010 – September 

Close Public Comment 2010 – November 

Case Development 

Final Work Plan 2011 – February 

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) 1 6 

Guidance for Commenters: 

The public is invited to comment on EPA’s preliminary registration review work plan and 

rationale. The Agency will carefully consider all comments as well as any additional 

information or data provided in a timely manner prior to issuing a final work plan for the oxamyl 

case. 

Trade Irritants: 

Through the registration review process, the Agency intends to solicit information on trade 

irritants and, to the extent feasible, take steps toward facilitating irritant resolution. Growers and 

other stakeholders are asked to comment on any trade irritant issues resulting from lack of 

Maximum Residue Limits (MRLs) or disparities between U.S. tolerances and MRLs in key 

export markets, providing as much specificity as possible regarding the nature of the concern. 

Water Quality: 

Oxamyl is not identified as a cause of impairment for any water bodies listed as impaired under 

section 303(d) of the Clean Water Act, based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=88

5. In addition, no Total Maximum Daily Loads (TMDL) have been developed for oxamyl, based 

on information provided at http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_ 

 

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

9
detail?p_pollutant_group_id=885&p_pollutant_group_name=PESTICIDES. More information 

on impaired water bodies and TMDLs can be found at http://www.epa.gov/owow/tmdl/. The 

Agency invites submission of water quality data for this pesticide. To the extent possible, data 

should conform to the quality standards in Appendix A of the OPP Standard Operating 

Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process (see http://www.epa.gov/ 

oppsrrd1/registration_review/water_quality_sop.htm) in order to ensure they can be used 

quantitatively or qualitatively in pesticide risk assessments. 

Environmental Justice: 

EPA seeks to achieve environmental justice, the fair treatment and meaningful involvement of all 

people, regardless of race, color, national origin, or income, in the development, implementation, 

and enforcement of environmental laws, regulations, and policies. To help address potential 

environmental justice issues, the Agency seeks information on any groups or segments of the 

population who, as a result of their location, cultural practices, or other factors, may have 

atypical, unusually high exposure to oxamyl compared to the general population. Please 

comment if you are aware of any sub-populations that may have atypical, unusually high 

exposure compared to the general population. 

Other Information: 

Stakeholders are also specifically asked to provide information and data that will assist the 

Agency in refining the risk assessments, including any species-specific ecological 

determinations. The Agency is interested in obtaining the following information: 

1. Additional information regarding the potential mode of action of this chemical as it 

relates to plants. The specific mode of action of oxamyl as it relates to growth regulation 

of plants (i.e. the apple blossom thinning use) is unknown. 

2. confirmation on the following label information 

a. sites of application 

b. formulations 

c. application methods and equipment 

d. maximum application rates 

e. frequency of application, application intervals, and maximum number of 

applications per season 

f. geographic limitations on use 

3. use or potential use distribution (e.g., acreage and geographical distribution of relevant 

crops) 

4. use history 

5. median and 90th percentile reported use rates (lbs ai/1000 sq ft) from usage data – 

national, state, and county 

6. application timing (date of first application and application intervals) by crop – national, 

state, and county 

7. sub-county crop location data 

8. usage/use information for non-agricultural uses 

9. directly acquired county-level usage data (not derived from state level data) 

a. maximum reported use rate (lbs ai/acre) from usage data – county 

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b. percent crop treated – county 

c. median and 90th percentile number of applications – county 

d. total pounds per year – county 

e. the year the pesticide was last used in the county/sub-county area 

f. the years in which the pesticide was applied in the county/sub-county area 

10. typical application interval (days) 

11. state or local use restrictions 

12. ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and 

mammalian mortalities) not already reported to the Agency 

13. monitoring data 

Next Steps: 

After the 60-day public comment period closes, the Agency will review and respond to any 

comments received in a timely manner and then issue a Final Work Plan for the registration 

review of oxamyl. 

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II. FACT SHEET 

 

Background Information: 

• Oxamyl registration review case number: 0253. 

• Oxamyl PC code: 103801. 

• Oxamyl CAS No.: 23135-22-0. 

• Oxamyl was first registered for use in the United States in 1974.

• The Oxamyl IRED was completed in October 2000, and the RED was finalized in 

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

Assessment.

• The technical registrant for oxamyl is E.I. du Pont de Nemours and Company, Inc. 

• There are currently two end-use products and one technical product registered for 

oxamyl. There are also 10 active state-specific Special Local Need registrations. 

• Product labels were amended in 2006 to incorporate labeling requirements from the 

Oxamyl RED. 

• Tolerances for oxamyl are established in 40 CFR Part 180.303. 

• Pesticide Re-evaluation Division, Chemical Review Manager: Monica Wait, 

wait.monica@epa.gov 

• Registration Division contact: Thomas Harris, harris.thomas@epa.gov

Use & Usage Information: (For additional details on label rates and use sites, refer to Appendix 

A: Label, Use, and Usage Table in the oxamyl docket EPA-HQ-OPP-2010-0028.) 

• Oxamyl is a restricted use pesticide for retail sale to and use only by certified applicators 

or persons under direct supervision of a certified applicator. 

• Oxamyl is registered for use on 30 agricultural crops including terrestrial food, feed, and 

non-food crops. These uses are organized into 23 use groups on the labels. 

• Both oxamyl end-use products are soluble liquid formulations. Vydate® C-LV contains 

directions for use only on cotton, peanuts, potatoes, and tobacco. Vydate® L contains 

directions for all registered uses. 

• Oxamyl can be applied by aircraft, ground spray equipment (broadcast, in-furrow, and 

band treatment), chemigation (gravity, drip, low pressure, and sprinkler), and a variety of 

soil incorporation and injection equipment. 

• Depending on the specific use and application method, single maximum application rates 

of oxamyl range from 1 to 4 pounds of active ingredient per acre. Numerous geographic 

limitations are labeled by use group or, in other cases, by specific directions within use 

groups. 

• EPA conducted a Screening Level Usage Analysis (SLUA) for oxamyl using data from 

the USDA’s National Agricultural Statistics Service (2001-2007), California Department 

of Pesticide Regulation Pesticide Use Reporting database (2000-2005), private pesticide 

12
market research (2001-2007), and, in cases where data were not available from other 

sources, the National Pesticide Use Database of the CropLife Foundation (2002). The 

SLUA indicated that there is an estimated 700,000 pounds of oxamyl used per year. The 

majority of oxamyl usage per year was on potatoes (43% of total pounds oxamyl applied) 

and cotton (29%); other major uses included mint (8.6%), dry bulb onions (5.8%), and 

celery (2.9%), followed by lesser uses on nineteen other reported crops. 

Recent Actions:

• In May 2007, DuPont submitted a petition (PP6F7136) to EPA to establish a tolerance for 

the use of oxamyl on sugar beets, and in September 2007, they submitted a petition 

(PP7F7242) to establish a tolerance on wheat. Also, in 2008 EPA received a proposed 

label amendment to expand several existing uses of oxamyl. Assessments of these 

proposed amendments are summarized in the “Ecological Risk Assessment Status” and 

“Human Health Risk Assessment Status” sections of this Fact Sheet. The risk 

assessments are also posted in their entirety in the Oxamyl Registration Review docket 

(EPA-HQ-OPP-2010-0028). All requests for new and expanded uses of oxamyl were 

withdrawn by DuPont in December 2009. EPA is currently working with DuPont to 

mitigate risk concerns identified with existing uses.

Ecological Risk Assessment Status:

Please refer to the Registration Review: Preliminary Problem Formulation for Environmental 

Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments for 

Oxamyl, July 28, 2010 for a detailed discussion of the key findings of the most recent ecological 

risk assessments. A summary follows: 

 

Summary of Risks: 

• 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. This assessment identified acute and chronic risks to terrestrial animals 

and acute risk to freshwater invertebrates. Risks were also identified to federally-listed 

threatened / endangered species of terrestrial animals, amphibians, and freshwater and 

estuarine / marine invertebrates. However, mitigation measures specified in the Oxamyl 

RED, including voluntary cancellations/use terminations, reductions in rate and number 

of applications, soil incorporation, and a “restricted use” classification, were expected to 

reduce and adequately mitigate the potential risks. These mitigation measures have been 

incorporated into current oxamyl product labels. 

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

to evaluate several FIFRA Section 3 proposed new uses. The assessments identified 

potential risks of concern for adverse effects from acute and chronic exposures to nonlisted and listed terrestrial animals (i.e., mammals, birds, reptiles, terrestrial-phase 

amphibians, and terrestrial invertebrates), potential risk of adverse effects from acute 

exposure for non-listed estuarine / marine invertebrates and for listed freshwater and 

estuarine / marine invertebrates. Potential for risk of adverse effects was identified from 

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chronic exposures to non-listed and listed estuarine / marine invertebrates. Lastly, the 

assessment identified potential for risk of adverse effects to listed nonvascular aquatic 

plants and listed terrestrial dicots. All of the requests for new and expanded uses were 

subsequently withdrawn by the oxamyl registrant. 

• In 2009, the Agency completed an endangered species risk assessment of the potential 

effects of oxamyl on the threatened California red-legged frog (Rana aurora draytonii; 

CRLF) arising from current uses of oxamyl on uses that are registered in California. This 

endangered species risk assessment was part of the Center for Biological Diversity (CBD) 

vs. EPA et al. (Case No. 02-1580-JSW (JL)) settlement entered in the Federal District 

Court for the Northern District of California on October 20, 2006. The assessment 

resulted in a determination that the use of pesticide products containing oxamyl is likely 

to adversely affect the CRLF. This determination is based on the potential for oxamyl to 

both directly and indirectly affect the species and result in modification to designated 

critical habitat. 

Human Health Risk Assessment Status: 

Please refer to Oxamyl: Registration Review Scoping Document for Human Health Assessments,

August 18, 2010 for a detailed discussion of the key findings of the most recent human health 

risk assessment. A summary follows: 

• Past oxamyl risk assessments rely in part on data from studies in which adult human 

subjects were intentionally exposed to a pesticide to determine their dermal and 

inhalation exposure. Many such studies, involving exposure to many different pesticides, 

comprise generic pesticide exposure databases such as the Pesticide Handlers Exposure 

Database (PHED) and the Agricultural Reentry Task Force (ARTF) Database. EPA has 

reviewed all the studies supporting these multi-pesticide generic exposure databases, and 

has found no clear and convincing evidence that the conduct of any of them was either 

fundamentally unethical or significantly deficient relative to the ethical standards 

prevailing at the time the research was conducted. All applicable requirements of EPA’s 

Rule for the Protection of Human Subjects of Research (40 CFR Part 26) have been 

satisfied, and there is no regulatory barrier to continued reliance on these studies. 

Hazard Characterization:

• Oxamyl is a member of the N-methyl carbamate class of chemicals sharing a common 

mode of action [inhibition of the acetyl cholinesterase enzyme (AChE)] with other NMC 

pesticides. NMCs bind loosely with AChE, thus allowing reactivation of the enzyme. 

The acute inhibition of AChE in the brain and in red blood cells, therefore, is the 

exposure duration of concern for oxamyl. 

• An updated benchmark dose (BMD) analysis, performed in November 2009 for the new 

Section 3 registration requests, utilized all of the appropriate ChE data for the oxamyl 

hazard assessment. All of the requests for new and expanded uses were subsequently 

withdrawn by the oxamyl registrant. 

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• A comparative cholinesterase assay (CCA) was conducted for oxamyl to assess the 

relative sensitivity between adult and juvenile animals. The FQPA factor is based on a 

data-derived approach, as is consistent with other NMCs.

• Oxamyl is classified as “not likely” to be carcinogenic to humans. 

Dietary (Food and Drinking Water):

• Refined drinking water exposure assessments were completed for oxamyl in 2009 and 

2010 to evaluate FIFRA Section 3 proposed new uses on sugar beets and dry bulb onions, 

shallots, and garlic along with the existing uses of oxamyl. These drinking water 

assessments modeled all of the proposed and current oxamyl use groups. The 

assessments used maximum regional application rates identified on product labels, 

regional percent cropped area factors, data submitted after the 2000 IRED, and current 

aquatic exposure models. Usage data that reflected upper-end rates and mean 

applications per year were also used to characterize exposure resulting from lower than 

maximum application rates for some use sites. All of the requests for new and expanded 

uses were subsequently withdrawn by the oxamyl registrant. 

Refined surface water concentration estimates were up to 256 μg/L (acute), 9.1 μg/L 

(chronic), and 3.6 μg/L (cancer) for the maximum use patterns (peppers and eggplant) in 

the most vulnerable growing region for each crop. Screening-level surface water 

modeling techniques were applied to ginger, pineapple, and yams because oxamyl is only 

applied to those crops grown in Hawaii or Puerto Rico. EPA does not have appropriate 

refined modeling scenarios and data to represent Hawaii and Puerto Rico. Use on 

pineapple resulted in the highest screening-level surface water exposure estimate of 593 

μg/L (acute). 

Screening-level ground water exposure estimates were up to 1.3 μg/L for the maximum 

use pattern (ginger root, only labeled for use in Hawaii), whereas, the maximum 

concentration detected in prospective ground water studies was 3.9 μg/L (detected below 

a site cropped to cotton at application). 

• An updated dietary risk assessment was completed on existing oxamyl uses in July 2010 

to incorporate revised water residue estimates from the most recent drinking water risk 

assessment. This refined dietary assessment aggregated food and drinking water in one 

analysis, updated residue data, and incorporated percent crop treated data. As with other 

NMCs, an “eating occasion” analysis was conducted to account for cholinesterase 

inhibition and rapid reactivation of the enzyme (inhibition half-life of 150 minutes). 

• The results of the acute dietary analysis for food alone was below EPA’s level of concern 

[less than 100% of the acute Population Adjusted Dose (aPAD)] at the 99.9th percentile of 

the exposure distribution for the general U.S. population and all population subgroups. 

The eating occasion analysis results for the two population subgroups with the highest 

risk, children 1-2 years old and all infants, calculated food alone to be only 16% and 13% 

of the aPAD, respectively. 

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When residues in drinking water resulting from various crops treated at maximum and/or 

reported application rates were added to the estimated residues in food, the exposures 

exceeded 100% of the aPAD for most scenarios. Exposures remained below 100% aPAD 

for carrot, celery, and eggplant at reported use rates and peanut, pear, sweet potato, and 

tobacco at maximum rates for both population subgroups, children 1-2 years old and all 

infants. 

• Due to the rapid recovery of ChE activity after exposure to oxamyl, a chronic dietary 

assessment was not conducted during the most recent risk assessment. 

Residential (Non-occupational): 

 

• As there are no currently registered uses at residential sites, residential handler and postapplication assessments were not included in the most recent risk assessment. 

Aggregate: 

• An aggregate risk assessment typically evaluates the combined risk from dietary 

exposure (food plus drinking water) and any residential uses. However, there are 

currently no residential uses for oxamyl; therefore, the oxamyl aggregate risk assessment 

includes only dietary exposure. As noted above, a revised acute aggregate dietary 

exposure assessment, conducted to support Section 3 registration requests, resulted in 

risks concerns for several existing uses of oxamyl. 

Occupational:

• The most recent occupational and residential exposure (ORE) assessment was completed 

in July 2010. The new ORE assessment included existing uses of oxamyl and 

incorporated new dermal and inhalation endpoints based on an updated BMD analysis. 

• The 2010 ORE assessment indicated that both dermal and inhalation pathways were 

significant sources of exposure for occupational handlers. EPA has determined that there 

is potential for occupational handlers to be exposed to oxamyl during mixing, loading, or 

application activities / scenarios. The short- and intermediate-term dermal risks did not 

exceed the Agency’s level of concern at some level of risk mitigation (personal protective 

equipment requirements, closed loading systems, etc.) for all handler scenarios, except: 

 Mixing/loading liquid concentrates to support aerial applications to cotton in 

California and Arizona at 1.0 lb ai/A. 

 Mixing/loading liquid concentrates to support chemigation applications at 2.0 lb 

ai/A; 

 Applying sprays by aircraft to cotton in California and Arizona at 1.0 lb ai/A. 

The short- and intermediate-term inhalation risks did not exceed the Agency’s level of 

concern at the baseline level (no respirator) for all handler scenarios, except 

mixing/loading to support aerial applications to cotton in California and Arizona at the 

1.0 lb ai/day application rate. 

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The short- and intermediate-term combined dermal plus inhalation risks did not exceed 

the Agency’s level of concern at some level of risk mitigation for all handler scenarios, 

except: 

 Mixing/loading liquid concentrates to support aerial applications to cotton in 

California and Arizona at 1.0 lb ai/A. 

 Mixing/loading liquid concentrates to support chemigation applications at 2.0 lb 

ai/A; 

 Applying sprays by aircraft to cotton in California and Arizona at 1.0 lb ai/A. 

• The 2010 ORE assessment also determined that there is the potential for post-application 

exposures to individuals entering treated areas following oxamyl applications. As a 

result of the August 2000 ORE assessment, a restricted-entry interval (REI) of 48 hours 

was assessed for all crops except citrus, which has a 4-day REI. However, the 2010 ORE 

assessment indicated that in order for risks to be below the Agency’s level of concern, 

REIs for many field crops would need to be longer than 2 days, depending on the crop 

and the post-application task (estimated REIs range from 12 hours to 13 days). The 2010 

assessment also indicated that REIs for most tree crops would need to be longer than 2 

days, depending on the crop and the post-application task (estimated REIs range from 1 

day to 27 days), in order to not exceed the Agency’s level of concern. 

Based on these results, occupational post-application exposure scenarios for many 

existing uses indicate risks of concern to the Agency and must be mitigated. See the 

“Recent Actions” section for further information. 

Cumulative: 

• FQPA requires the Agency to consider the cumulative risks of chemicals sharing a 

common mechanism of toxicity. Oxamyl is a member of the N-methyl carbamate 

common mechanism group. The most recent cumulative risk assessment for the NMCs 

was issued on September 26, 2007. 

• The NMC cumulative risk assessment concluded that risks from food, drinking water, 

and residential exposure to N-methyl carbamate pesticides did not exceed the Agency’s 

level of concern, and that there was a reasonable certainty that no harm would result from 

exposure to the NMC pesticides covered by the assessment. 

Incidents: 

• A search of the Environmental Incident Information System (EIIS) database for 

ecological incidents identified three incidents involving exposures to oxamyl. The first 

incident involved the death of hundreds of fish and over 100 birds in Alamance County, 

North Carolina, in May of 1991. The certainty that the deaths of the animals were 

associated with exposure to oxamyl was considered “probable” but the legality of use 

was indicated as “intentional misuse.” The second incident, with a certainty index of 

“possible” and legality of use indicated as “undetermined,” involved the death of a redcockaded woodpecker in Sussex County, Virginia, in February of 2003. The third 

17
incident involved the deaths of 13 laughing gulls and 1 cattle egret in the British Virgin 

Islands in 2004. The cause of mortality was defined as “toxicosis caused by both 

methomyl and oxamyl.” The certainty that the deaths of the birds were associated with 

exposure to either pesticide was considered “possible,” and the legality of use was 

“undetermined.” 

• One source of uncertainty associated with the EIIS database is the nature of reporting of 

incidents. Many more incidents may have occurred due to oxamyl exposures but may not 

have been reported due to various factors. Therefore, the lack of an incident report does 

not necessarily indicate a lack of an incident. 

• A summary report listing human incidents for oxamyl has been provided in the docket 

item entitled Updated Review of Oxamyl Incident Reports, November 24, 2009. The 

Office of Pesticide Programs Incident Data System (IDS) was consulted for reports of 

oxamyl poisoning incidents occurring in the United States from 2002 to the present. The 

IDS includes reports of incidents from registrant reporting, from other government 

agencies, and from individual consumers. Of the five incidents reported, symptoms 

appear generic and not confirmed to be related to exposure, and there is no clear evidence 

of a trend or exposure pattern. Therefore, at this time, the Agency can not discern any 

suggestion of a trend or pattern regarding the health effects due to the alleged exposure to 

the pesticide oxamyl.

• The NIOSH SESNOR database was queried for acute occupational pesticide-related 

illnesses and identified five cases where exposure to oxamyl was determined to be 

definite, probable, or possible. The health effects most often reported include dermal 

(20%), cardiovascular (20%), respiratory (40%), ocular (40%), gastrointestinal (60%), 

and neurological (60%). Symptoms are not mutually exclusive, and a patient may have 

multiple symptoms. All cases were ranked low severity, and there were no fatalities.

Tolerances and International Harmonization: 

• The residue of concern in plant commodities for risk assessment purposes based on 

cholinesterase inhibition is oxamyl alone. The tolerance expression for plant 

commodities is based on oxamyl and its metabolite oxime, because the analytical method 

used for the field trials that established the tolerance converts oxamyl to oxime by 

employing a hydrolysis step. The tolerances established in 40 CFR § 180.303 for 

residues of the insecticide oxamyl include its metabolites and degradates in or on the 

commodities listed. Compliance with the tolerance levels is to be determined by 

measuring only the sum of oxamyl (methyl N,N -dimethyl- N -[(methylcarbamoyl)-oxy]-

1-thiooxamimidate) and its oxime metabolite (methyl N,N-dimethyl-N-hydroxy-1-

thiooxamimidate), calculated as the stoichiometric equivalent of oxamyl, in or on the 

commodity. No tolerances have been established or are currently required in the United 

States for any animal commodities. Adequate analytical methods exist for data collection 

and tolerance enforcement. 

• The Codex Alimentarius Commission and Mexico have established maximum residue 

limits (MRLs) for oxamyl, but they are not harmonized with all U.S. tolerances. Canada 

18
has not currently established any MRLs for oxamyl. Any oxamyl tolerances reassessed 

during registration review will be considered for possible harmonization with 

international MRLs. 

• A crop field trial study for cotton gin byproducts was recently reviewed by the Agency. 

The Agency’s review of the study indicated that a tolerance of 120 ppm should be 

established for residues of oxamyl on cotton gin byproducts. 

Data Call-In Status: 

• A generic data call-in (GDCI-103801-17865) was issued in November 2000 as a result of 

the data requirements listed in the 2000 Oxamyl IRED. All of the data requirements have 

been fulfilled from this data call-in with the exception of Guideline 830.7050: 

UV/Visible Absorption. The Agency has received a study intended to fulfill this 

guideline, which is currently in review. 

Labels: 

 

• A list of registration numbers for the oxamyl case is provided below, and the labels can 

be obtained from the Pesticide Product Label System (PPLS) website: 

http://oaspub.epa.gov/pestlabl/ppls.home. 

Registration 

# Registration Name Company Name % Active Ingredient 

352-372 Vydate L Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 24 

352-400 DuPont Oxamyl Technical 42 Insecticide / 

Nematicide 

E.I. DuPont de Nemours and Co., Inc. 42 

352-532 Vydate C-LV Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 42 

CA060028 DuPont Vydate C-LV Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 42 

CO010005 DuPont Vydate L Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 24 

MD080003 DuPont Vydate C-LV Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 42 

NV070002 DuPont Vydate L Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 24 

NY080001 DuPont Vydate C-LV Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 42 

NY990002 DuPont Vydate L Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 24 

PA070002 DuPont Vydate C-LV Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 42 

UT990004 DuPont Vydate L Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 24 

WA000018 DuPont Vydate L Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 24 

WI070005 DuPont Vydate L Insecticide / Nematicide E.I. DuPont de Nemours and Co., Inc. 24 

19
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III. Summary of Data Gaps – Oxamyl 

The table below summarizes all anticipated data needs for oxamyl in Section I, of this 

document (Preliminary Work Plan), 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 Anticipated Data Need Test 

Material 

Estimated 

Timeframe 

835.4400 Anaerobic aquatic metabolism TGAI 24 

850.1025 Acute toxicity estuarine and marine organisms1 TGAI 12 

850.1035 Acute toxicity estuarine and marine organisms2 TGAI 12 

850.1350 Aquatic invertebrate life cycle, saltwater TGAI 12 

850.1400 Fish early life stage, freshwater TGAI 12 

850.2100 Avian oral toxicity3 TGAI 12 

850.3040 Field testing for pollinators TGAI 24 

850.4100 Tier II terrestrial plant toxicity, seedling emergence4 TGAI 12 

850.4150 Tier II terrestrial plant toxicity, vegetative vigor4 TGAI 12 

850.4400 Aquatic plant growth, vascular plants, Tier II4 5 TGAI 12 

870.7800 Immunotoxicity Study TGAI 12 

 

1 Acute toxicity data should be submitted where mysid are exposed to TGAI oxamyl. 2 Acute toxicity data should be submitted where oysters are exposed to TGAI oxamyl.

3 A passerine study protocol must be submitted for review by the Agency prior to initiation of this study. 4 Registrants may opt to conduct a Tier I study, with the understanding that any adverse effects (even if <25%) will necessitate a 

Tier II study. A Tier II study will enable the Agency to conduct an endangered species assessment for nontarget plants. 5 A supplemental study is available to characterize the effects of oxamyl on vascular aquatic plants (specifically duckweed) 

(MRID 45546103). This toxicity study was considered scientifically sound, but was classified “supplemental” due to a lack of 

constant exposure of test organisms to the test material. Therefore, there is uncertainty associated with the results of this study in 

that the endpoint obtained from this study may underestimate the effects of oxamyl on aquatic vascular plants.