Introduction:

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

for the registration review of dichlorvos (DDVP). The Final Work Plan includes the expected 

registration review timeline. The FWP also addresses public comments received concerning the 

Preliminary Work Plan (PWP) in the Summary Document which was posted in the DDVP 

registration review docket (EPA-HQ-OPP-2009-0209) and any other comments concerning the 

initial docket postings. The Summary Document 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 is implementing the registration review program and will review 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/. 

DDVP (Case #0310) is an organophosphate (OP) insecticide registered for livestock, 

commercial, and residential uses. These uses include cattle, poultry, swine, agricultural 

equipment, feedlots, animal kennels, warehouses, mushroom houses, greenhouses, picnic areas, 

manure piles, refuse and solid waste sites, and residential dwellings. 

Naled and trichlorfon are pesticide active ingredients, which degrade to DDVP in food water, 

and the environment. Naled and trichlorfon are each being assessed individually under 

registration review. The registration review of these active ingredients will consider all residues 

of concern, including DDVP. The registration review of DDVP will consider DDVP exposure 

resulting from the use of naled, trichlorfon, and DDVP, itself. 

Comments Received on the Preliminary Work Plan:

On June 24, 2009, EPA opened a 60-day public comment period for the registration review of 

DDVP. However, during this public comment period, the DDVP registration review docket was 

missing some supporting documents. After placing the supporting documents in the docket, the 

Agency reopened the comment period for an additional 30-day period on October 14, 2009. The 

Agency received comments from three parties. After reviewing the comments, in addition to the 

anticipated data needs listed in the DDVP PWP, the Agency now anticipates requesting aquatic 

toxicity studies performed with DDVP’s degradates of concern and the DDVP typical end-use 

product. The Agency anticipates requiring degradate data because there is no available toxicity 

information for the two DDVP environmental degradates of concern: desmethyl DDVP, and 2, 

2-dichloroacetic acid. The Agency also anticipates requiring aquatic studies using the DDVP 

typical end-use product (TEP) because it is unknown whether an ingredient in the current TEP 

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other than the active ingredient could enhance toxicity to non-target aquatic organisms. The 

Agency has not altered the timeline detailed in the DDVP PWP. 

In the PWP, EPA also solicited comments on three specific topics: environmental justice, water 

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

public comment period concerning these issues.

An overview of comments is presented in the “Summary of Comments Received during Docket 

Opening” section of this document. A more detailed description of the comments received, the 

Agency’s response to these comments, and rationales for additional data the Agency anticipates 

requiring in registration review is available in the separate response memoranda from the 

Agency’s Environmental Fate and Effects Division (EFED) and Health Effects Division (HED) 

located in the DDVP registration review docket (EPA-HQ-OPP-2009-0209).

Summary of Comments Received During Docket Opening:

During the public comment period, the Agency received comments from the American 

Mushroom Institute, the Natural Resource Defense Council (NRDC), and AMVAC Chemical 

Corporation. The American Mushroom Institute requested that the mushroom use patterns and 

labeling changes required in the RED be maintained at the conclusion of Registration Review. 

NRDC and the technical registrant, AMVAC Chemical Corporation, each provided comments 

regarding the Environmental Fate and Effects Division’s Problem Formulation, the Health 

Effects Division’s Scoping Document, and the PWP. 

Some comments and responses have been described below. Comments relevant to human health 

have been addressed by the Health Effects Division’s document, Dichlorvos Response to 

comments on Preliminary Work Plan (S. Hummel, D35466112/22/2009). Comments regarding 

the ecological fate or effects of DDVP have been addressed by

the Environmental Fate and Effects Division’s document, EFED Response to Public Comments 

for Dichlorvos (DDVP PF: Docket ID# EPA-HQ-OPP-2009-0209 (T. Mason and C. Wendel, 

D354655,12/21/2009). Both documents are available in the docket (EPA-HQ-OPP-2009-0209), 

available at regulations.gov. 

Natural Resource Defense Council (NRDC) 

Comment: NRDC is not familiar with an additional study that measures DDVP air 

concentrations in houses from use of pest strips and requests that this study be placed in the 

DDVP registration review docket. 

Response: EPA required a special indoor air study in the DDVP reregistration eligibility 

decision (RED) data call-in (DCI). This study is a non-guideline study that will measure indoor 

air DDVP concentrations from the use of pest strips in closets and cupboards in homes. The 

study was required in order to confirm the residential pest-strip exposure estimates that EPA 

made in the DDVP RED. The study is due in July 2010, and EPA will, consistent with FIFRA 

section 10, make the completed study available for review. 

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Comment: NRDC urges EPA not to grant the registrant’s request to waive the swine dermal 

study in the absence of reliable data showing that the metabolism in cattle is the same as in 

swine. We also request that EPA place the waiver petition into the registration review docket for 

public review and comment. 

Response: On May 21, 2009, EPA denied AMVAC Chemical Corporation’s request to waive 

the swine dermal study. The waiver petition and EPA’s response denying the request has been 

placed in the DDVP registration review docket. 

Comment: NRDC refers to a previous petition where it noted that in an oyster toxicity study, the 

end-use product was almost ten times more toxic than the technical product. NRDC is concerned 

that there are inert ingredients in the end use product that might be more toxic than the DDVP 

active ingredient. NRDC recommends that EPA determine the exact identity of the inerts in each 

of the products used in the oyster and mysid shrimp studies and examine the toxicity database for 

the inerts and call-in any needed toxicity data for these inerts. In addition, NRDC urges EPA to 

make public the identity of inerts and toxicity data relied upon by EPA to approve the inerts so 

the public in general and the world scientific community can examine the information. 

Response: EPA has updated the DDVP registration review workplan to specify that it anticipates 

calling-in aquatic ecotoxicity data for the typical DDVP end-use product. 

EPA also notes that it is currently moving forward on rulemaking to require the identities of 

potentially hazardous inert ingredients to appear on pesticide labels. This increased transparency 

will assist consumers and users of pesticides in making informed decisions and will better protect 

public health and the environment. 

 

The Agency anticipates publishing an advance notice of proposed rulemaking in the Federal 

Register within the next few weeks. In it, EPA will discuss ideas for greater disclosure of 

hazardous inert ingredient identities as well as of inert ingredients in general. EPA believes one 

way of discouraging the use of the more hazardous inert ingredients in pesticide formulations is 

by making their identities public. 

Comment: NRDC requests that EPA include in the registration review docket all of the 

documents upon which it intends to rely in making its decision. As a matter of convenience to the 

public, we recommend that all of the materials that were or are currently in all of the existing 

DDVP dockets (including EPA-HQ-OPP-2009-0629) be placed into the DDVP registration 

review docket. 

Response: Currently, there are three DDVP dockets available on regulations.gov: 

1. EPA-HQ-OPP-2002-0302 – Dichlorvos (DDVP); Reregistration Eligibility Decision (RED). 

2. EPA-HQ-OPP-2006-0629 – DDVP Special Review. 

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3. EPA-HQ-OPP-2009-0209—DDVP Registration Review; Dichlorvos Docket opened for 

Review and Comment. 

Each of these dockets was set up for an independent purpose, and contains different documents 

according to that purpose; therefore, the Agency does not anticipate combining these materials 

into one docket. All documents generated during registration review will be posted in the 

DDVP registration review docket. 

AMVAC Chemical Corporation

Comment: AMVAC continues to believe that some of the data that EPA has decided to require 

as part of the implementation of the Reregistration Eligibility Decision for DDVP are not needed 

for a proper and defensible risk assessment. AMVAC has previously requested that EPA waive 

certain data requirements, including studies of dermal sensitization, a dermal residue study in 

swine, and an indoor air exposure study. EPA has denied these waiver requests, but AMVAC 

intends to ask that each such denial be reconsidered. AMVAC will be basing these requests for 

reconsideration on the current availability of other data that are sufficient for risk assessment. 

Response: In May 2008, EPA issued a Generic Data Call-In (GDCI) for the active ingredient, 

DDVP in connection with EPA’s RED. Among other things, that DCI required that a dermal 

magnitude of the residue study on swine and an indoor air study be submitted to the Agency. 

However, the GDCI did not require the dermal sensitization study referenced in AMVAC’s 

comment. The GDCI established deadlines for submitting the residue study and the indoor air 

study of 24 months and 12 months, respectively. On August 29, 2008, AMVAC responded to 

the GDCI and requested waivers for the data requirements for a dermal magnitude of the residue 

study on swine and an indoor air study. On June 20, 2009, EPA sent a letter to AMVAC in 

which the Agency denied the waiver requests for these two studies. On September 30, 2009, 

EPA informed AMVAC that it would extend the time period required in the May 2008 GDCI for 

submitting the studies. The Agency stated that the time periods of 24 and 12 months, 

respectively, that the Agency allows to conduct these studies would start from the date of the 

waiver denial, and therefore, the indoor air study is due on July 20, 2010, and the dermal 

magnitude of the residue study on swine is due on July 20, 2011. 

If AMVAC fails to submit either of these studies on their respective due dates, EPA may issue a 

Notice of Intent to Suspend AMVAC’s DDVP registrations or an order revoking or modifying 

associated DDVP tolerances, pursuant to FIFRA section 3(c)(2)(B) or FFDCA section 408(f). 

AMVAC indicated in its comments that it intends to ask for reconsideration of EPA’s decision 

on its waiver request. Under the terms of the DDVP GDCI, a request for a waiver does not 

automatically extend the deadline for submission of required studies. In its discretion, EPA did 

extend the deadlines for submission of the dermal magnitude of the residue study on swine and 

the indoor air study, as indicated above. However, should AMVAC file a request for 

reconsideration, such a request will not automatically extend the study submission deadlines. 

The deadlines may be extended by the Agency only if EPA determines that such extension is 

appropriate and states that in writing. To date, EPA has seen nothing in AMVAC’s prior waiver 

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request that would justify any further extension of the deadlines for the submission of these two 

studies. The deadlines for submission of the studies to the Agency remain as stated in the 

Agency’s September 30, 2009 correspondence: July 20, 2010 for the indoor air study; and July 

20, 2011 for the dermal magnitude of the residue study on swine. 

Comment: AMVAC notes that EPA’s summary document includes a proposed requirement for a 

Foliar Dislodgeable Residue Dissipation study under Guideline 875.2100 to be utilized in 

assessing DDVP exposure from hand-held foggers. AMVAC believes that this is not necessary 

or appropriate. DDVP is not registered for outdoor use on any crop, and the lawn, turf, and 

ornamental uses have all been cancelled. Moreover, although DDVP technical products still 

permit use of liquid DDVP formulations in greenhouses, the use of hand-held foggers in 

greenhouses has been strictly prohibited. 

Response: Currently the AMVAC technical label states, “[H]and-held foggers are prohibited in 

warehouses, greenhouses, and mushroom houses.” This current label language allows hand-held 

fogger use in other commercial locations and there are no data to evaluate this applicator 

exposure scenario. However, if AMVAC amends its label to prohibit all hand-held fogger use, 

EPA will no longer have to assess this use scenario, and would no longer need to require the 

Foliar Dislodgeable Residue Dissipation study. 

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 

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

Between October 2009 and February 2010, EPA is issuing 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. 

DDVP is not among the group of 58 pesticide active ingredients on the initial list to be screened 

under the EDSP. Under FFDCA sec. 408(p) the Agency must screen all pesticide chemicals. 

Accordingly, EPA anticipates issuing future EDSP orders/data call-ins for all Registration 

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Review cases, including those for which EPA has already opened a Registration Review docket 

for a pesticide active ingredient. 

For further information on the status of the EDSP, the policies and procedures, the list of 67 

chemicals, the test guidelines and the Tier 1 screening battery, please visit our website: 

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

Risk Assessment and Data Needs:

The Agency anticipates updating and revising the ecological risk assessment for DDVP 

(including an endangered species risk assessment) and updating and revising the human health 

risk assessment. Additional data that the Agency anticipates needing to complete these 

assessments are identified below. 

 

Ecological Risk: 

• A national-level ecological risk assessment was completed in support of the 2006 DDVP 

RED. However, the Agency has not conducted a risk assessment that supports a 

complete endangered species determination. The ecological risk assessment planned 

during registration review will allow the Agency to determine whether DDVP’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. 

• In order to complete a new comprehensive ecological assessment that includes an 

endangered species risk assessment, the Agency is anticipating requiring studies to 

reduce remaining uncertainties regarding DDVP volatilization, avian inhalation toxicity, 

potential acute oral toxicity to passerine birds, terrestrial plant toxicity, and aquatic 

toxicity to freshwater, estuarine, and marine organisms. 

• The Agency anticipates requiring volatility studies for DDVP because volatilization is 

potentially a major route of dissipation. 

• The Agency is requesting an acute avian inhalation study to determine toxicological 

responses associated with the volatilization of DDVP. Submitted avian acute toxicity 

data also suggest that DDVP is very highly toxic to several species of birds on an acute 

oral basis; however, the results may not reflect risks to passerine birds which have been 

identified to be more sensitive to pesticides in some cases. 

• Terrestrial and aquatic plant studies are needed to assess direct and indirect 

environmental risks that DDVP may pose to endangered species. 

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• There are no available toxicity information available for the DDVP degradates of concern 

and there is the potential of DDVP to drift to water bodies near application areas. 

Therefore, EPA will be submitting data call-in requests for all aquatic organisms (acute 

and chronic studies) for the degradates of concern, desmethyl DDVP and 2,2-

dichloroacetic acid 

• There is uncertainty regarding the toxicity of the DDVP TEP. Therefore, EPA 

anticipates requesting acute ecotoxicity studies for all aquatic organisms for the current 

DDVP TEP. The registrant may fulfill many of these data requirements with previous 

studies submitted to the Agency, if the end-use product used in these studies is still 

“typical.” 

• The Agency anticipates needing the following data in order to conduct a complete 

ecological risk assessment for DDVP, including an endangered species assessment: 

Ecological Toxicity Studies: 

DDVP 

o GDLN 850.1010 – Acute Toxicity Freshwater Invertebrates (Typical End-Use 

Product) 

o GDLN 850.1025 – Acute Toxicity Estuarine and Marine Organisms (Typical 

End-Use Product) 

o GDLN 850.1035 – Acute Toxicity Estuarine and Marine Organisms (Mysid) 

(Typical End-Use Product) 

o GDLN 850.1075 – Freshwater Fish Toxicity (Typical End-Use Product) 

o GDLN 850.2100 – Acute Avian Oral Toxicity – Passerine (Technical Grade 

Active Ingredient) 

o GDLNs 850.4100, 850.4150 – Terrestrial Plant Toxicity Test, Tier I, Seedling 

Emergence and Vegetative Vigor (Technical Grade Active Ingredient) 

o GDLNs 850.4400 and 850.5400 – Aquatic Plant Growth (Tier I Aquatic Plant 

Growth) (Typical End-Use Product and Technical Grade Active Ingredient) 

o Special Study – Acute Avian Inhalation Study (Technical Grade Active 

Ingredient) 

Desmethyl DDVP 

o GDLN 850.1010 – Acute Toxicity Freshwater Invertebrates 

o GDLN 850.1025 – Acute Toxicity Estuarine and Marine Organisms (Oyster) 

o GDLN 850.1035 – Acute Toxicity Estuarine and Marine Organisms (Mysid) 

o GDLN 850.1075 – Freshwater Fish Toxicity 

o GLDN 850.1300 – Aquatic Invertebrate Life-Cycle (Freshwater) 

o GLDN 850.1350 – Aquatic Invertebrate Life-Cycle (Saltwater) 

o GDLN 850.1400 – Fish Early-Life Stage (Freshwater) 

o GDLNs 850.4400 and 850.5400 - Aquatic Plant Growth (Tier I Aquatic Plant 

Growth) 

2,2-dichloroacetic acid 

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o GDLN 850.1010 – Acute Toxicity Freshwater Invertebrates 

o GDLN 850.1025 – Acute Toxicity Estuarine and Marine Organisms (Oyster) 

o GDLN 850.1035 – Acute Toxicity Estuarine and Marine Organisms (Mysid) 

o GDLN 850.1075 – Freshwater Fish Toxicity 

o GLDN 850.1300 – Aquatic Invertebrate Life-cycle (freshwater) 

o GLDN 850.1350 – Aquatic Invertebrate Life-Cycle (Saltwater) 

o GDLN 850.1400 – Fish Early-Life Stage (Freshwater) 

o GDLNs 850.4400 and 850.5400 – Aquatic Plant Growth (Tier I Aquatic Plant 

Growth) 

Environmental Fate Studies: 

o GDLN 835.1410 – Volatility – Laboratory 

o GLDN 835.8100 – Volatility – Field 

 

Please refer to the document, Registration Review – Preliminary Problem Formulation for the 

Ecological Risk Assessment of Dichlorvos (DDVP), May 14, 2009 and EFED Response to Public 

Comments for Dichlorvos (DDVP PF: Docket ID# EPA-HQ-OPP-2009-0209 (T. Mason and C. 

Wendel, D354655,12/21/2009)for a detailed discussion of the Agency’s anticipated ecological 

risk and environmental fate assessment needs.

Human Health Risk: 

• No effects on the immune system have been seen in the DDVP toxicity studies submitted 

to date; however, based on a new immunotoxicity data requirement for DDVP (GDLN 

870.7800), the Agency expects to reevaluate the toxicity endpoints used for human health 

risk assessment purposes in the registration review of DDVP. Updated dietary, 

residential, aggregate, and occupational risk assessments may be required during 

registration review to reflect any toxicology endpoint modifications. 

• The Agency does not expect to conduct a drinking water assessment (DWA) as part of 

registration review for DDVP because the current labeled uses of DDVP are unlikely to 

result in exposure to drinking water. However, DDVP will be assessed in drinking water 

as part of the naled and trichlorfon registration review cases. In the event that two or all 

three of these pesticides can be used in the same use area, then the contribution of DDVP 

from each chemical present will be incorporated in the DDVP human health risk 

assessment. 

• The dietary exposure database for DDVP is complete. In a 2007 DDVP dietary risk 

assessment (Morton, 2007), aggregate acute and chronic dietary exposure for food and 

drinking water did not exceed the Agency’s level of concern. The 2007 dietary risk 

assessment will be used in registration review if recent monitoring data and usage data 

for DDVP, naled, and trichlorfon show that dietary exposure to DDVP has not increased. 

• Residue chemistry data are adequate to support the current food uses, with the exception 

of a dermal magnitude of the residue study for swine, which was required in the DDVP 

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RED DCI and is due in July 2011. Adequate analytical methods are available to enforce 

the DDVP tolerances. 

• The registrant has voluntarily amended its technical registration to terminate the uses of 

hand held foggers in mushroom houses, greenhouses, and warehouses. However, handheld foggers are not prohibited in other indoor commercial locations (e.g., indoor 

agricultural farm structures and tobacco processing plants); therefore, data are expected 

to be needed to evaluate this applicator exposure scenario unless all applicable 

registrations are amended to prohibit this application method in all indoor locations. 

• Should the Agency determine that new information on DDVP is available which could 

potentially impact the OP cumulative risk assessment and result in a risk of concern, the 

Agency will revisit the cumulative risk assessment. 

• The Agency anticipates needing the following data in order to conduct a complete human 

health effects risk assessment for dietary (food and drinking water), residential, and 

occupational exposures to DDVP under registration review: 

o GDLN 870.7800 Immunotoxicity Study 

o GDLNs 875.1200, 875.1400, & 875.2100 – Indoor Dermal, Indoor Inhalation, 

and Post-Application Dermal and Inhalation Exposure from DDVP Indoor HandHeld Fogger Use. 

• Please refer to Dichlorvos (DDVP). Human Health Assessment Scoping Document in 

Support of Registration Review, May 6, 2009, available in the docket for a detailed 

discussion of the anticipated risk assessment and data needs for completing the human 

health risk assessment. 

Other Data Needs: 

• GLDN 830.750 UV/Visible Light Absorption – this study is a new data requirement 

under 40 CFR part 158 (Product Chemistry Data Requirements) for registration of a 

pesticide (food and non-food uses). The Agency anticipates requiring this study to obtain 

basic information about the compound’s identity/composition and the wavelengths at 

which the compound may be susceptible to photochemical degradation.

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11

Timeline:

 

The Agency has created the following estimated timeline for the completion of the DDVP 

registration review. 

Registration Review for DDVP – Projected Registration Review Timeline 

Activities Estimated 

Year/Month 

Opening the Docket 

Open Docket and Public Comment Period 2009 – June 

Close Public Comment 2009 – November1

Case Development 

Issue Final Work Plan (FWP) 2009 – December 

Issue Data Call-in (DCI) 2010 – July – 

September 

Data Submission 2012 – July - 

September 

Open Public Comment Period for Preliminary Risk Assessments 2014 – April – June 

Close Public Comment Period 2014 – July – 

September 

Registration Review Decision 

Open Public Comment Period for Proposed Registration Review 

Decision 

2014 – October –

December 

Close Public Comment Period 2015 – January – 

March 

Final Registration Review Decision & Begin Post-Decision 

Follow-up 2015 

Total (years) 6 

Next Steps:

As noted previously, the Agency anticipates requiring several ecological effects and human 

health studies through a Data Call-In Notice, expected to be issued in 2010. This new 

information will be used to conduct complete risk assessments for all DDVP uses. 

 

1

 On June 24, 2009, EPA opened an initial 60-day public comment period for the registration review of DDVP, 

which closed on August 24, 2009. However, during the initial public comment period, the DDVP registration 

review docket was missing some supporting documents. The Agency reopened the comment period for an 

additional 30-day period on October 14, 2009, which closed on November 13, 2009.