Docket Number EPA-HQ-OPP-2011-0907 

www.regulations.gov 

Tetramethrin Final Work Plan 

Registration Review 

May 2012 

 

3

FINAL WORK PLAN – TETRAMETHRIN

Introduction: 

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

the registration review of tetramethrin. The FWP includes the expected registration review 

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

(PWP) in the Summary Document, which was posted in the tetramethrin registration review 

docket (EPA-HQ-OPP-2011-0907). The Summary Document, dated December 15, 2011, 

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 on the Agency’s website1

. 

Tetramethrin is a broad-spectrum, first-generation synthetic pyrethroid insecticide. It is a rapid 

knockdown agent registered for use against flying and crawling insects, such as wasps, hornets, 

roaches, ants, fleas, and mosquitoes. There are no registered food or agricultural uses of 

tetramethrin. It is used primarily in residential, commercial, institutional, and industrial areas 

and can be used both indoors, including applications to pets, and outdoors. Although 

tetramethrin products are not classified as restricted use pesticides, some tetramethrin end-use 

products are labeled for use by pest control operators only. Products containing tetramethrin 

were first registered in 1968. The Reregistration Eligibility Decision (RED) for Tetramethrin

was completed in June 2008 and revised in April 2010. The cumulative risk assessment for the 

pyrethroids and pyrethrins was published on November 9, 2011 and is available in public docket 

EPA-HQ-OPP-2011-0746. 

Updates Since the Summary Document was Issued: 

There are no updates for tetramethrin since the Summary Document was issued and the initial 

registration review docket opened. 

Summary of Comments and Agency Responses: 

The Agency did not receive any comments on the tetramethrin PWP during the 60-day public 

comment period, which began on December 21, 2011 and ended on February 21, 2012. EPA 

also solicited comments on the specific topics of environmental justice, water body impairment, 

and trade irritants, but no comments or information were received on those issues. 

 

1

 http://www.epa.gov/oppsrrd1/registration_review/ 
4

Risk Assessment and Data Needs:

The Agency will require data to conduct a comprehensive ecological risk assessment, including 

an endangered species assessment, for all uses of tetramethrin. For human health, EPA will 

conduct revised residential and occupational risk assessments during registration review. If 

toxicological endpoints or points of departure are revised, they will be considered in the new 

assessment, as well as any changes to the standard operating procedures or default exposure 

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

tetramethrin. 

Ecological Risk: 

 The most recent comprehensive ecological risk assessment for tetramethrin was 

completed in February 2008 in support of the tetramethrin RED. 

 An updated comprehensive ecological risk assessment of all registered uses of 

tetramethrin 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. 

 Tetramethrin uses relevant to the ecological risk assessment are limited to spot treatments 

(e.g., spraying a wasp hive), space treatments (e.g., spraying of an aerosol can in a 

storage room or other enclosed space), and ornamental applications against crawling and 

flying insects (e.g., spraying hedges). EPA’s standard risk assessment methodology is 

not applicable for these kinds of uses because standard expected environmental 

concentrations (EECs) cannot be directly calculated (without major assumptions) using 

the Agency’s typical tools due to a number of factors, including non-standard use rates 

(e.g., 1-2 second burst, lbs a.i./ft3

) and estimations of the magnitude of use in a given area 

(e.g., a neighborhood or campsite) at a given time. For the tetramethrin risk assessment, 

the Agency will use the required ecological data and an estimate of exposure, taking into 

consideration the specific uses of tetramethrin, to assess the potential for ecological risk 

associated with its use. 

 Certain tetramethrin labels are unclear with respect to application parameters like the size 

of the treated area, the extent of a treated “spot,” retreatment intervals, or maximum 

annual application rates. In the absence of clear label information, EPA must 

approximate these parameters in order to conduct a quantitative assessment for 

tetramethrin. The Agency encourages clear and consistent label language for the sake of 

all stakeholders and encourages registrants to review tetramethrin product labels for 

clarity. 

 A risk assessment that supports a complete endangered species determination has not 

been conducted for tetramethrin. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether tetramethrin’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 
5

will consult with the U.S. Fish and Wildlife Service and/or National Marine Fisheries 

Service (the Services), as appropriate. 

 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 tetramethrin, 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.). 

 Data gaps exist in the ecological database for tetramethrin. EPA will require the 

following studies for use in conducting a complete ecological risk assessment, including 

an endangered species assessment, for the registration review of tetramethrin. 

835.6100 – Terrestrial field dissipation study 2

835.6200 – Aquatic field dissipation study 2

850.1025 – Acute toxicity estuarine and marine organisms (oyster shell growth) 

850.1035 – Acute toxicity estuarine and marine organisms (mysid) 

850.1075 – Acute toxicity estuarine and marine organisms (fish) 

850.1075 – Freshwater fish toxicity (using TEP) 

850.2100 – Avian oral toxicity (passerine species)

850.4100 – Terrestrial plant toxicity, seedling emergence, Tier II 

850.4150 – Terrestrial plant toxicity, vegetative vigor, Tier II 

Non-guideline – Aquatic invertebrate acute toxicity testing using Hyalella azteca

(using TGAI and TEP) 3

 Studies conducted with freshwater invertebrates and fish will be required using a typical 

end-use product (TEP) containing tetramethrin and the synergist piperonyl butoxide in 

addition to a TEP containing tetramethrin and the synergist MGK-264. Tetramethrin is 

co-formulated with either or both synergists in numerous products. Because available 

information indicates that greater toxicity enhancement can occur at higher synergist-toactive ingredient ratios, selection of the TEPs for these data requirements would include 

those with the highest synergist-to-active ingredient ratio that are registered for outdoor 

uses. 

 Please refer to the December 5, 2011 document Registration Review – Preliminary 

Problem Formulation for the Ecological Risk Assessment for Tetramethrin in the 

registration review docket (EPA-HQ-OPP-2011-0907-0003) for a detailed discussion of 

the upcoming risk assessment and data needs. 

 

2

 See footnote 7 of 40 CFR 150.1300. EPA will require only the environmental chemistry analytical methods and 

independent laboratory validation (ILV) portions of this guideline for soil and water, rather than the full field 

dissipation study. 

3

 The Summary Document erroneously listed this data requirement as Guideline 850.1020. 
6

Human Health Risk:

 The most recent comprehensive human health risk assessment for tetramethrin was 

conducted in June 2008 in support of the tetramethrin RED. The occupational and 

residential exposure assessments were revised in 2009 and 2010. 

 The Food Quality Protection Act (FQPA) requires the Agency to consider the cumulative 

risks of chemicals sharing a common mechanism of toxicity. Tetramethrin is a member 

of the pyrethroid/pyrethrins common mechanism group (http://www.regulations.gov; 

EPA-HQ-OPP-2008-0489). The members of this group share the ability to interact with 

voltage-gated sodium channels ultimately leading to neurotoxicity. The cumulative risk 

assessment for the pyrethroids/pyrethrins was published on November 9, 2011 and is 

available at http://www.regulations.gov; EPA-HQ-OPP-2011-0746. No cumulative risks 

of concern were identified, allowing the Agency to consider new uses for pyrethroid 

active ingredients. For information regarding EPA’s efforts to evaluate the risk of 

exposure to pyrethroids, refer to the Agency’s website4

.

 A dietary (food) exposure assessment is not needed during registration review because 

there are currently no registered food or feed uses for tetramethrin. Dietary exposure is 

not expected based on registered uses.

 A drinking water dietary assessment for tetramethrin will not be conducted during 

registration review given the limited extent of potential exposures based on currently 

registered use sites and the environmental fate properties of tetramethrin that limit its 

mobility.

 Revised residential and occupational exposure assessments will be conducted during 

registration review to reflect current standard operating procedures and revised 

toxicological endpoints. 

 During registration review, EPA will consider data submitted in response to the 2010 

RED data call-in (DCI) (GDCI-069003-28621) and will revise toxicological endpoints as 

needed. See the “Summary of Data Gaps” table for further details regarding the 

previously-issued DCI. No additional human health data will be required in the 

registration review DCI. 

 Please refer to the December 13, 2011 document Tetramethrin: Human Health Risk 

Scoping Document in Support of Registration Review in the registration review docket 

(EPA-HQ-OPP-2011-0907-0005) for a detailed discussion of upcoming risk assessments 

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 

 

4 http://www.epa.gov/oppsrrd1/reevaluation/pyrethroids-pyrethrins.html
7

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 reregistration decision for tetramethrin, 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), tetramethrin 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. Tetramethrin 

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

the EDSP. Accordingly, as part of registration review, EPA will issue future EDSP orders/data 

call-ins, requiring the submission of EDSP screening assays for tetramethrin. For further 

information on the status of the EDSP, the policies and procedures, the list of 67 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 tetramethrin’s 

registration review. 

Registration Review for Tetramethrin – Projected Registration Review Timeline

Activities Estimated Date 

Opening the Docket 

Open Docket and Public Comment Period Dec. 2011 - Completed 

Close Public Comment Feb. 2012 - Completed 

Case Development 

Final Work Plan May 2012 - Completed 

Issue DCI 2013 – Jan. – March 
8

Registration Review for Tetramethrin – Projected Registration Review Timeline

Activities Estimated Date 

Data Submission 2014 – Jan. – March 

Open Public Comment Period for Draft Risk Assessments 2015 – July – Sept. 

Close Public Comment Period 2015 – Oct. – Dec. 

Registration Review Decision 

Open Public Comment Period for Proposed Registration Review 

Decision 

2016 – Jan. – March 

Close Public Comment Period 2016 – April – June 

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

Total (years)5 5 

Next Steps: 

As noted previously, the Agency plans to require several environmental fate and ecological 

effects studies through a DCI, expected to be issued in early 2013. In addition, the Agency will 

review toxicity data submitted as required by the 2010 DCI. This new information will be used 

to conduct complete risk assessments for all registered uses of tetramethrin. 

 

 

5

 Any changes in the cumulative risk from the pyrethroid class of insecticides may impact this time estimate. 
9

SUMMARY OF DATA GAPS – TETRAMETHRIN 

The table below summarizes the data needs for tetramethrin listed in Registration Review – 

Preliminary Problem Formulation for the Ecological Risk Assessment for Tetramethrin, dated 

December 5, 2011; Tetramethrin: Human Health Risk Scoping Document in Support of 

Registration Review, dated December 13, 2011; and outstanding data previously required 

through EPA’s DCI process. 

Guideline 

Number Data Needs 

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

835.6100 Terrestrial field dissipation study 6 TGAI 12 

835.6200 Aquatic field dissipation study 6 TGAI 12 

850.1025 Acute toxicity estuarine and marine organisms 

(oyster shell growth) TGAI 12 

850.1035 Acute toxicity estuarine and marine organisms 

(mysid) TGAI 12 

850.1075 Acute toxicity estuarine and marine organisms 

(fish) 

TGAI 12 

850.1075 Freshwater fish toxicity TEP 12 

850.2100 Avian oral toxicity (passerine species) TGAI 12 

850.4100 Terrestrial plant toxicity, seedling emergence, Tier 

II 7 TEP 12 

850.4150 Terrestrial plant toxicity, vegetative vigor, Tier II 7 TEP 12 

Nonguideline 

Aquatic invertebrate acute toxicity using Hyalella 

azteca 8 TGAI & TEP 12 

The studies below were previously required through a generic DCI (GDCI-069003-28621), issued in 

June 2010 and are still outstanding. The studies are listed for reference although they will NOT be 

included in the registration review DCI. 

870.3700 Prenatal developmental toxicity TGAI due 6/2012 

870.6200 Acute and subchronic neurotoxicity battery TGAI due 6/2012 

870.6300 Developmental neurotoxicity 9 TGAI due 6/2014 

 

6

 See footnote 7 of 40 CFR 150.1300. EPA will require only the environmental chemistry analytical methods and 

ILV portions of this guideline for soil and water, rather than the full field dissipation study. 7

 The registration review DCI will provide that a Tier I plant study may be conducted in lieu of a Tier II study with 

the understanding that any adverse effects observed by the Tier I study would necessitate conduct and submission 

of a Tier II study as well. 

8

 The Summary Document erroneously listed this data requirement as Guideline 850.1020. 9

 The June 2010 DCI included the statement, “EPA has determined that, as an alternative to the generation and 

submission of a new DNT study, pyrethroid registrants may instead choose to cite the six previously submitted 

DNT studies for pyrethroid pesticides.”