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INTRODUCTION

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

the registration review of hydramethylnon. This work plan addresses public comments received 

concerning the Preliminary Work Plan (PWP), which was posted in the hydramethylnon

registration review docket (EPA-HQ-OPP-2012-0869). Hydramethylnon is a slow-acting 

stomach toxicant insecticide registered for use against ants, cockroaches, crickets, earwigs, 

silverfish, and termites. Hydramethylnon products are primarily used to control ants in non-crop 

lands such as lawns, turf, and non-bearing nursery stock. Hydramethylnon is also registered for 

the control of household ant species and cockroaches in nonfood use areas in and around 

domestic dwellings and commercial establishments. In addition to those uses, hydramethylnon is 

registered for use on grasses, rangelands, and in pineapple orchards.

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. 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 the 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 website.

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The FWP begins with any updates since the PWP was issued. Next is a summary of substantive 

comments received during the public comment period for the PWP concerning anticipated data 

needs, expected risk assessments, or the estimated timeline identified in the PWP, and a 

summary of the Agency’s responses to those comments. This section is followed by registration 

review planned data needs, risk assessments expected to be conducted, and the projected

registration review timeline for hydramethylnon. Lastly, there is a discussion of next steps.

UPDATES SINCE THE PWP WAS ISSUED

The Agency has updated the planned data needs and ecological risk assessments since the PWP 

as a result of comments received during the public comment period. After reviewing the 

comments, the Ecological Fate and Effects Division has decided to incorporate an urban runoff 

scenario into the ecological risk assessment as requested. These comments resulted in the 

addition of a Whole sediment: acute freshwater invertebrate (Hyalella azteca) study (GDLN 

850.1735) to, and the deletion of a Terrestrial Plant Toxicity, vegetative vigor study (GDLN 

850.4150) from the list of anticipated data needs. Available information indicates that a

freshwater amphipod (Hyalella azteca) may be substantially more sensitive to hydramethylnon 

than the commonly tested midge larvae and that hydramethylnon may partition into the sediment.

Therefore, the Agency feels the need to include GDLN 850.1735 to capture the more sensitive 

taxa. The Agency also determined that a vegetative vigor study is no longer needed for

hydramethylnon, as foliar exposure to terrestrial plants from the currently registered formulations 

(i.e., gel baits, bait stations and granular applications) is expected to be limited. For more 

 1 http://www.epa.gov/oppsrrd1/registration_review/
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information on this change please see Response to Public Comments on Hydramethylnon 

Registration Review Problem Formulation.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the Hydramethylnon Preliminary Work Plan, 

which opened on December 14, 2012 and closed on February 14, 2013, the Agency received 7

public comments. Comments were submitted by the technical registrant BASF Corporation, the 

California Stormwater Quality Association (CASQA), San Francisco Bay Regional Water 

Quality Control Board (SFB RWQCB), Dole Food Company, Glenn Taniguchi (a private 

pineapple grower), the Pineapple Growers’ Association of Hawaii, and FIFRA Endangered 

Species Task Force (FESTF). The comments address the timeline described in the PWP, as well 

as the planned ecological assessments and data requirements. In the PWP, EPA also solicited 

comments on the specific topics of environmental justice, water quality concerns, and trade 

irritants; comments were received regarding water quality concerns only.

This section does not capture every comment made about the PWP nor all of the Agency’s 

responses. Summarized below are public comments that resulted in changes to the anticipated

registration review data needs, risk assessments, or timeline, or are of a broader regulatory 

nature. Public comments and EPA responses in their entirety are located in the docket, EPAHQ-OPP-2012-0869. Summarized public comments and Agency responses related to the 

anticipated ecological risk assessment or data needs are in Response to Public Comments on 

Hydramethylnon Registration Review Problem Formulation. There were no comments received

regarding the anticipated human health risk assessment or data needs.

Comments submitted by CASQA and SFB RWQCB in EPA-HQ-OPP-2012-0869-(0014 

and 0015).

1. Comment: Hydramethylnon can be applied via broadcast application as a loose granular 

formulation. Impervious surfaces runoff through urban transport pathways should be 

included in the conceptual model and risk analysis.

Response: The Agency concurs with the comments that the risk assessment should include 

impervious surface modeling for urban areas and appreciates the fact sheet submission of 

impervious surface coefficients. At the time of the Registration Review Risk Assessment, 

the Agency will revise the risk hypothesis and conceptual models to include relevant routes 

of exposure to hydramethylnon, including granular application on impervious surfaces. 

Detailed information on non-agricultural use and usage of hydramethylnon would be useful 

for refining the Registration Review Ecological Risk Assessment for hydramethylnon.

2. Comment: Additional sediment toxicity study using Hyalella azteca, is needed to quantify the 

environmental effects of hydramethylnon on aquatic invertebrates in sediments.

Response: The Agency has determined that submission of data on the sediment toxicity of 

hydramethylnon to Hyalella azteca is necessary, in addition to the existing Chironomus 

dilutus sediment toxicity data, as it is generally a more sensitive freshwater 

macroinvertebrate than Chironomus dilutus. The following study will be included in the 
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Registration Review DCI: Guideline 850.1735 – Whole sediment: acute freshwater 

invertebrates (Hyalella azteca). 

3. Comment: CASQA mentioned that an effective registration review process would prevent 

pesticide-related aquatic toxicity in waters and sediments of surface waters receiving urban 

runoff discharges. It is essential then that pesticide regulatory processes adequately

consider potential water quality impacts, so that such impacts are prevented before they 

result in Clean Water Act (CWA) Section 303(d) impaired waters listings.

Response: The Agency acknowledges the comments. At the time of the Registration Review 

Ecological Risk Assessment, all relevant CWA Section 303(d) impaired waters listings will 

be considered. The Agency’s goal is to ensure that its registration review decisions are 

protective of water resources and do not result in an additional burden for states under the 

CWA. 

4. Comment: CASQA and SFB RWQCB asks to modify the proposed registration review 

timeline to reflect a reasonable period for public review of the draft risk assessment, as the 

proposed 30-day public comment period is inadequate for review of these highly technical 

documents.

Response: As mentioned in the projected registration review timeline, regulations generally 

require the Agency to provide a public comment period of at least 30 calendar days for draft 

risk assessments. For conventional pesticides, the Agency plans to provide a 60 calendar day 

public comment period generally for draft risk assessments.

Comments submitted by BASF Corporation (BASF) in EPA-HQ-OPP-2012-0869-0012.

5. Comment: BASF states that the terrestrial plant toxicity vegetative vigor study (EPA 

Guideline 850.4150) is only conditionally required based on the use pattern (40 CFR 

158.660). Vegetative vigor studies are not required for contained pesticide treatment such as 

bait boxes and pheromone traps and are generally not required for granular formulations. 

Since there is no direct crop spray application use registered for hydramethylnon (registered 

only as gel baits, bait stations, and granular end use products), the risk for direct plant

exposure is limited. BASF believes the vegetative vigor study should be removed from the 

FWP.

Response: The Agency thanks BASF’s clarification that hydramethylnon is not labeled for 

direct crop spray application. The vegetative vigor study requirement (Guideline 850.4150)

is no longer included in the list of data needs based on the registered use pattern of gel baits, 

bait stations and granular applications that will result in limited exposure to terrestrial plants

through the foliar route. The Agency also thanks BASF for acknowledging EPA’s request in 

the PWP by providing additional use/usage information on hydramethylnon, this information 

will be considered in the registration review risk assessments.
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Comments submitted by The Pineapple Growers Association of Hawaii, Glenn Taniguchi,

and Dole Food Company in EPA-HQ-OPP-2012-0869-(0011, 0010, and 0009).

12. Comment: The Pineapple Growers Association of Hawaii, Glen Taniguchi, and Dole Food 

Company state that hydramethylnon has been used in pineapple cultivation for more than 30 

years, and stress the importance of the hydramethylnon (Amdro) product to the Hawaiian 

pineapple industry. Amdro is applied to their pineapple fields on an as-needed basis, up to 3 

times per year particularly where there is a known history of ant problems. Approximately 

750 acres are treated annually. They also provided the Agency with additional Hawaii use 

information and stress the safety of the product.

Response: The Agency acknowledges the comments on the critical importance of this 

chemical to the pineapple industry and appreciates the clarification on the use pattern and 

techniques. EPA would also like to thank The Pineapple Growers Association of Hawaii for 

its suggested risk mitigation measures; these will be taken into consideration during 

registration review.

PLANNED DATA NEEDS

Table 1 below summarizes the planned data needs for hydramethylnon based on the Registration 

Review: Preliminary Problem Formulation for Environmental Fate, Ecological Risk, 

Endangered Species, and Drinking Water Exposure Assessments for Hydramethylnon,

Hydramethylnon. Human Health Assessment Scoping Document in Support of Registration 

Review, and Response to Public Comments on Hydramethylnon Registration Review Problem 

Formulation. The table has been updated since the PWP to reflect public comments which 

resulted in changes to the data needs.

Table 1: Planned Data Needs for the Hydramethylnon Registration Review

Guideline 

Number2 Study Title2

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

835.2240 Aquatic photodegradation TGAI 12

835.4300 Aerobic Aquatic Metabolism TGAI 24

835.4400 Anaerobic Aquatic Metabolism TGAI 24

850.1025 Acute toxicity estuarine and marine organisms 

(oyster shell growth) TGAI 12

850.1300 Freshwater invertebrate life cycle3 TGAI 12

 2 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850 – Ecological Effects Tests 

– including renumbering and other designations or changes for some guideline studies. See “Final Test Guidelines; 

OCSPP 850 Series; Notice of Availability” 77 FR 38282, June 27, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0154-0028 3 The planned DCI will specify that testing with either a freshwater invertebrate or an estuarine/marine invertebrate 

(for a species with a valid acute toxicity test) is to be performed. The resulting acute to chronic ratio (ACR) will 

then be applied to the other invertebrates.
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Table 1: Planned Data Needs for the Hydramethylnon Registration Review

Guideline 

Number2 Study Title2

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

850.1350 Saltwater invertebrate life cycle3 TGAI 12

850.1400 Fish early-life stage toxicity test (freshwater and 

estuarine/marine)4 TGAI 12

850.1735 Whole sediment: acute freshwater invertebrates 

(Hyalella azteca) TGAI 12

850.2100 Avian oral toxicity (passerine species) TGAI 12

850.4100 Seedling emergence and seedling growth TEP 12

850.4400 Aquatic plant toxicity test using Lemna spp TGAI 12

850.4500 Algal toxicity TGAI 12

850.4550 Cyanobacteria toxicity TGAI 12

850.6100

Environmental Chemistry Methods and Associated 

Independent Laboratory Validation for soil and 

water

TGAI 12

870.7800 Immunotoxicity5 TGAI 12

TGAI = technical grade active ingredient; TEP = typical end-use product; Degr. = degradate

RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of hydramethylnon. For human health,

EPA will not conduct a revised dietary, residential, and occupational risk assessments during

registration review though a drinking water assessment from surface water sources only will be 

conducted. If toxicological endpoints or points of departure are revised based on the data that 

are required for registration review, they will be considered in the new assessments, as well as 

any changes to the standard operating procedures or default exposure assumptions.

Table 2 below summarizes the planned registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document and has been updated since the PWP to 

reflect public comments which resulted in changes to the planned risk assessments. These 

changes to the planned risk assessments included the addition of an urban runoff scenario to 

 4 The planned DCI will specify that testing with either a freshwater fish or an estuarine/marine fish (for a species 

with a valid acute toxicity test) is to be performed. The resulting acute to chronic ratio (ACR) will then be applied 

to the other fish.

5 Recently, OPP published the findings of its retrospective analysis of immunotoxicity studies submitted to the 

Agency, concluding that none of the studies included in the analysis resulted in a Point of Departure (POD) that is 

lower than the PODs selected from other available guideline toxicology studies 

(http://www.epa.gov/pesticides/regulating/immunotoxicity-retro-analysis.pdf). EPA will consider requests for 

waivers for this study, particularly in light of the retrospective analysis. A weight-of-evidence rationale will be 

considered relative to the chemical’s toxicological profile, primary target organ system(s) and mode of toxic action, 

and any immuno-related data available from structurally-related compounds.
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reflect the Agency’s concurrence with CASQA and SFB RWQCB’s comments as seen on page 3 

(comment 1).

Table 2: Planned Risk Assessments for the Hydramethylnon Registration Review

Type of Risk Assessment Conduct? Notes

Ecological and Environmental Fate

Comprehensive ecological 

(species to be assessed 

include terrestrial and 

aquatic organisms), 

including endangered 

species 

Y Regarding degradates of concern: The Agency has 

concluded that the stressor of concern is the parent 

hydramethylnon. Two known major degradates6

will not be assessed further because of the low 

toxicity based on the ECOSAR analysis. 

However, several unidentified degradates from 

photolysis and anaerobic degradation studies will 

be assumed as the parent hydramethylnon unless 

they are properly identified.

Incidents Will check 

for updates

For a discussion of reported ecological incidents

for hydramethylnon, see page 16 of the Problem 

Formulation.

Human Health

Dietary

Food N It is unlikely that a new assessment will be 

needed, unless the planned drinking water 

assessment determines significant estimated 

residues in drinking water from surface water 

sources.

Drinking water Y The Agency plans to conduct an assessment of 

drinking water from surface water sources only, 

since hydramethylnon appears to have a low 

potential for groundwater contamination.

Occupational

Handlers (mixers, loaders, 

applicators)

N Absent any new toxicity or exposure data, 

changes to the standard operating procedures, or 

default exposure assumptions, the Agency plans 

to rely on previous assessments where there was

no risk estimates of concern associated with 

hydramethylnon handler or post-application 

occupational exposure.

Post-application N

Residential

Handlers N There is very low potential for dermal and 

inhalation exposures to residential handlers due to 

the properties of the gel formulation and baitstation packaging.

Post-application N

 6 1,5-bis(alpha, alpha, alpha-trifluoro-p-tolyl)-1,4-pentadien-3-one (CL98,724, 28%) and 4H-pyrimido [2-1-c]astriazio-4-one1,6,7,8-tetrahydro-7,7-dimethyl-3-[p-(trifluoromethyl)-styryl] (CL247,176, 25.2% and 30.5%)
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Other

Aggregate N Evaluates the combined risk from dietary and 

residential exposures. Based on current estimated 

risk levels, a new quantitative aggregate risk 

assessment is not likely to be necessary.

Cumulative N/A Hydramethylnon has not been identified as a 

member of a common mechanism group.

Tolerances Y The tolerance expression for hydramethylnon will 

be reviewed during registration review to ensure 

that it appropriately covers the metabolites and 

degradates of hydramethylnon and that it specifies 

the residues to be measured for each commodity.

Incidents Will check 

for updates

For a discussion of reported human incidents for 

hydramethylnon, see page 10 of the Scoping 

Document and Hydramethylnon: Review of 

Human Incidents.

TIMELINE

EPA has created the following estimated timeline for the completion of the hydramethylnon

registration review in Table 3 below. The projected timeline has been modified to indicate that 

the Agency plans to provide a 60 day public comment period generally for conventional 

pesticide draft risk assessments.

Table 3: Registration Review for Hydramethylnon – Projected Registration Review 

Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period Dec 2013– Completed

Close Public Comment Feb 2013 – Completed

Case Development

Final Work Plan May – Completed

Issue DCI Jan. – March – 2014

Data Submission Jan. – March – 2016

60-day Public Comment Period for Draft Risk Assessments7 July – Sept. – 2017

Registration Review Decision

60-day Public Comment Period for Proposed Registration Review 

Decision

Jan. – March – 2018

Registration Review Decision and Begin Post-Decision Follow-up 2018

Total (years) 6

 7 The regulations governing Registration Review generally require the Agency to provide a public comment period 

of at least 30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the 

Agency plans to provide a 60 calendar day public comment period generally for draft risk assessments.
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NEXT STEPS

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

and human health studies for hydramethylnon through a Data Call-In Notice, expected to be 

issued early 2014.