Docket Number: EPA-HQ-OPP-2011-0482 

www.regulations.gov

Ancymidol Final Work Plan 

Registration Review 

December 2011 

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ANCYMIDOL FINAL WORK PLAN 

Introduction: 

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

registration review of ancymidol. This work plan includes the expected registration 

review timeline. The work plan also addresses public comments received concerning the 

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

ancymidol registration review docket (EPA-HQ-OPP-2011-0482), 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 will 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 at: 

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

Ancymidol (Case 3017) is a plant growth regulator registered for treating containergrown herbaceous plants, ornamental woody shrubs, and bedding plants grown in 

greenhouses and other plant bedding areas for commercial production. There are no 

food/feed or residential uses of products containing this active ingredient. Growth 

regulator effects produced by ancymidol are the result of inhibition of gibberellin 

biosynthesis. Since gibberellin promotes growth, treatment with ancymidol induces a 

more compact growth form by suppressing growth between nodes. Ancymidol was the 

subject of a Reregistration Eligibility Decision (RED), which was completed in June 

1995. 

Available data suggest use of ancymidol is minimal. For the primary use, inside 

nurseries/greenhouses, less than 20 pounds were used per year in 1999, 2002, 2004, and 

2006. To better understand the exposure potential for ancymidol, given the current uses 

and application rates, the Agency has developed an estimate of environmental exposure 

(see “Equivalent outdoor” per-acre application rates for ancymidol used on containergrown greenhouse transplants, dated November 28, 2011). The Agency is in the process 

of determining how these estimates may change the current ecological risk assessment 

approach and the associated data requirements. If the Agency alters its risk assessment 

approach or data needs for the ancymidol registration review, it will document these 

changes in an amended final work plan that will be announced through a Federal 

Register notice. 
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Comments Received on Preliminary Work Plan: 

The ancymidol registration review docket was open for a 60-day comment period 

beginning on June 29, 2011. The Agency received one comment during the public 

comment period. There are no changes to the risk assessment, data needs or the timeline 

detailed in the ancymidol PWP. EPA also solicited comments, through the PWP, on 

three specific topics: environmental justice, water body impairment, and trade irritants. 

No comments or information were received during the comment period concerning these 

issues. Further, this document makes final the work plan for the ancymidol registration 

review process. 

Physicians Committee for Responsible Medicine (PCRM) Comments: 

PCRM supports three measures which they suggest may reduce the number of test 

animals needed for two separate studies which the Agency will require for ancymidol. 

 PCRM supports a revised OECD test guideline (TG223) for avian acute oral 

toxicity testing for passerine and waterfowl or upland game species. 

 PCRM supports use of a “limit test” approach for the acute toxicity study for both 

freshwater and estuarine/marine species. 

 PCRM encourages the use of quantitative structure–activity relationship

((Q)SAR) data either in place of, or in addition to, the fish experimental data. 

EPA Response: 

OECD test guideline: 

The Agency recently completed its review of the OECD validation report to determine if 

the TG223 effects endpoints and dose/response information adequately address the 

purposes of the avian acute oral data requirement as described in 40 CFR Part 158 and 40 

CFR Part 161. The Agency determined that a study conducted using TG223 may be 

classified as ‘acceptable’ if it is scientifically valid; is conducted using the ‘LD50- slope 

test’ or ‘limit dose test' guidelines (the LD50 - only test is not adequate for fulfilling data 

requirements); and meets all of the following criteria: 

 The study is conducted using bobwhite quail (other test species may be acceptable 

if they have low background mortality in the laboratory and do not regurgitate 

during the study). The background mortality data for the species in question 

should be available from the submitting laboratory at the time of the Agency 

review. 
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 The chemical being tested does not cause delayed effects. 

 For a ‘limit dose test,’ the study is to be conducted at 2,000 mg a.i./kg-bw or the 

environmentally-relevant concentration (whichever is greater). 

 For the ‘LD50 - slope test,’ the raw data and results are to be submitted 

electronically using the SEquential DEsign Calculator (SEDEC) (the Excel 

calculator that determines the placement of doses during testing and is used to 

estimate the LD50, slope and confidence limits for TG223 studies). 

 The study meets the same validity requirements as Guideline 850.2100 (e.g., a 

study should be invalidated if > 10% of the controls die). 

 Control birds are not added during the course of the study.

Studies that deviate from the above criteria may be classified as ‘acceptable’ or 

‘supplemental’ if they are considered adequate for use in risk assessment or ‘invalid’ if 

they are not scientifically sound; however, any TG223 study that deviates from the above 

criteria will need additional evaluation by the Agency to confirm the study’s 

classification. 

Agency use of ‘limit tests’: 

 

Limit tests may be acceptable if no mortality occurs at test concentrations that are 20-fold 

higher than peak estimated environmental concentrations. A factor of 20 is used because 

the endangered species level of concern is 0.05, which represents a value that is 20-fold 

lower than the LC50. 

Agency use of (Q)SAR data: 

EPA considers SAR/QSAR (Structure Activity Relationship/Quantitative SAR) predicted 

estimates to address data requirements on a case-by-case basis. Uncertainty in those 

predicted estimates may be higher than those from empirical data. Although (Q)SAR 

estimates may be considered in a weight-of-evidence analysis, confirmatory tests are 

generally required when risks cannot be confidently dismissed based solely on the 

(Q)SAR estimates.

Risk Assessment and Data Needs: 

The Agency will conduct a comprehensive ecological risk assessment, including an 

endangered species assessment for all uses of ancymidol. The Agency will require data 

in order to conduct the planned ecological risk assessment. Below is a summary of the 

ecological and human health issues relevant to the registration review of ancymidol: 
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Ecological Risk: 

 The most recent ecological risk assessment for ancymidol was completed in 1995 

in support of the RED. 

 As noted earlier, available data suggest use of ancymidol is minimal. The Agency 

is in the process of evaluating the environmental exposure potential for 

ancymidol, given the current uses and application rates. Depending on the results 

of this evaluation, the current risk assessment approach and the associated data 

requirements may change. 

 EPA may conduct an ecological risk assessment for the indoor and outdoor uses 

of ancymidol during registration review. The Agency is evaluating whether 

indoor uses (i.e., greenhouse plants transplanted into ornamental beds) may result 

in sufficient environmental exposure to necessitate an ecological risk assessment. 

 The planned assessment will incorporate the most up-to-date modeling 

methodologies, updated assessment endpoints, and data submitted under the 

registration review data call-in. 

 The Agency has not conducted an ecological risk assessment that supports a 

complete endangered species determination for ancymidol. The ecological risk 

assessment planned during registration review will allow the Agency to determine 

whether ancymidol’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 (FWS) and/or National Marine Fisheries Service 

(NMFS) (the Services), as appropriate. 

 Data gaps exist in the environmental fate and toxicity databases for ancymidol. In 

the ecological risk assessment completed for the 1995 RED, the Agency 

concluded that, because of the limited treated acreage, minor use sites (e.g., 

ornamental flowers and shrubs), and low toxicity cited in the submitted studies, 

adverse effects to birds, mammals, aquatic organisms and non-target plants were 

expected to be minimal. Accordingly, no additional ecological data were required 

at that time. Based on current environmental fate and ecological risk assessment 

standards, data are needed for the registration review assessment of ancymidol. 

However, depending on the results of the Agency’s evaluation of the 

environmental exposure potential for ancymidol given the current uses and 

application rates, the data requirements may change. 

 Current formulations with labeled outdoor uses for spray, drench, and 

chemigation applications do not specify maximum application rates per plant 

type. Maximum annual application rates per pot size or application rates per 

growing season, where appropriate, on a chemical-weight basis need to be 
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specified; also a maximum number of sequential applications per plant type need 

to be defined. In the absence of this occurring, the Agency will employ 

conservative assumptions in the endangered species risk assessment. 

 The Agency will require the following environmental fate and environmental 

effects data during registration review for use in ecological assessment, including 

an endangered species assessment of ancymidol: 

o Guideline (GLN) No. 835. 2240 – Photodegradation in Water 

o GLN No. 835.2410 – Photodegradation in Soil 

o GLN No. 835.4100 – Aerobic Soil Metabolism 

o GLN No. 835.4200 – Anaerobic Soil Metabolism 

o GLN No. 835.4300 – Aerobic Aquatic Metabolism 

o GLN No. 835.4400 – Anaerobic Aquatic Metabolism 

o GLN No. 835.6100 – Terrestrial Field Dissipation 

o GLN No. 835.6200 – Environmental Chemistry Analytical Methods for 

Residues in Water and Sediment and Independent Laboratory Validation 

o GLN No. 850.2100 – Avian Oral Toxicity (passerine and waterfowl or 

upland game) 

o GLN No. 850.2200 – Avian Dietary Toxicity Test (waterfowl) 

o GLN No. 850.2300 – Avian Reproduction Test (waterfowl and upland 

game species) 

o GLN No. 850.1025 – Oyster Acute Toxicity Test 

o GLN No. 850.1035 – Mysid Acute Toxicity Test 

o GLN No. 850.1045 – Penaeid Acute Toxicity Test 

o GLN No. 850.1055 – Bivalve Acute Toxicity Test 

o GLN No. 850.1075 – Fish Acute Toxicity Test (Freshwater) 

o GLN No. 850.1075 – Fish Acute Toxicity Test (Estuarine/Marine) 

o GLN No. 850.1300 – Daphnid Chronic Toxicity Test 

o GLN No. 850.1400 – Fish Early-Life Stage Toxicity Test (Freshwater) 

o GLN No. 850.4100 – Nontarget Area Phytotoxicity Tier II, Seedling 

Emergence 

o GLN No. 850.4150 – Nontarget Area Phytotoxicity Tier II, Vegetative 

Vigor 

o GLN No. 850.5400 – Nontarget Area Phytotoxicity Tier II, Aquatic Plant 

Growth (Algal Plants) 

 Please refer to Registration Review – Preliminary Problem Formulation for the 

Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water 

Exposure Assessments for Ancymidol, dated March 28, 2011, located in the 

docket, for a detailed discussion of these anticipated risk assessment and data 

needs. 
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Human Health Risk: 

 The most recent human health risk assessment was completed in 1995 in support 

of the RED. This assessment evaluated occupational exposures only, as no 

food/feed or residential uses are registered for ancymidol. 

 The Agency has evaluated the status of the human health assessments for 

ancymidol and determined that no additional human health exposure or hazard 

information are required to support the registration review of ancymidol. 

 Please refer to the Ancymidol. Human Health Assessment Scoping Document in 

Support of Registration Review, dated June 7, 2011, located in the docket, for a 

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

health. 

Endocrine Disruptor Screening Program: 

As required by FFDCA section 408(p), ancymidol 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. 

Ancymidol 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 

ancymidol. 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/.
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Timeline: 

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

ancymidol. 

Registration Review for Ancymidol – Registration Review Timeline

Activities Estimated Date 

Opening the Docket 

Open Docket and Public Comment Period 2011 – June 

Close Public Comment 2011 – August 

Case Development 

Final Work Plan 2011 – December 

Issue DCI 2012 – July – Sept. 

Data Submission 2014 – July – Sept. 

Open Public Comment Period for Draft Risk Assessments 2016 – Jan. – March 

Close Public Comment Period 2016 – April – June 

Registration Review Decision 

Open Public Comment Period for Proposed Registration Review 

Decision 

 2016 – July – Sept. 

Close Public Comment Period 2016 – Oct. – Dec. 

Registration Review Decision and Begin Post-Decision Follow-up 2017 

Total (years) 6 

Next Steps: 

The Agency plans to develop a Data Call-In Notice for this pesticide and plans to issue it 

in mid-2012. This new information will be used to conduct risk assessments for 

ancymidol uses. 
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Summary of Data Gaps – Ancymidol:

The table below summarizes the data requirements for ancymidol. The Agency 

will require the following environmental fate and environmental effects data during 

registration review to support an ecological assessment of ancymidol. Please refer to 

Registration Review – Preliminary Problem Formulation for the Environmental Fate, 

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

Ancymidol for a detailed discussion of these upcoming risk assessment and data needs. 

Guideline 

Number Study Title Test 

Material 

Estimated 

Timeframe 

835.2240 Photodegradation in Water TGAI1 12 

835.2410 Photodegradation in Soil TGAI 12 

835.4100 Aerobic Soil Metabolism TGAI 24 

835.4200 Anaerobic Soil Metabolism TGAI 24 

835.4300 Aerobic Aquatic Metabolism TGAI 24 

835.4400 Anaerobic Aquatic Metabolism TGAI 24 

835.6100 Terrestrial Field Dissipation TGAI 24 

835.6200 Aquatic Field Dissipation2 TGAI 12 

850.2100 Avian Oral Toxicity (passerine and waterfowl 

or upland game) TGAI 12 

850.2200 Avian Dietary Toxicity Test (waterfowl) TGAI 12 

850.2300 Avian Reproduction Test (waterfowl and 

upland game species) TGAI 24 

850.1025 Acute Toxicity Estuarine/Marine Organisms 

(Oyster) TGAI 12 

850.1035 Mysid Acute Toxicity Test TGAI 12 

850.1045 Penaeid Acute Toxicity Test TGAI 12 

850.1055 Bivalve Acute Toxicity Test TGAI 12 

850.1075 Fish Acute Toxicity Test (Estuarine/Marine) TGAI 12 

850.1075 Fish Acute Toxicity Test (Freshwater) TGAI 12 

850.1300 Daphnid Chronic Toxicity Test TGAI 12 

850.1400 Fish Early-Life Stage Toxicity Test 

(Freshwater) TGAI 12 

 

1

 Technical Grade Active Ingredient (TGAI). 

2

 Only the Environmental Chemistry Methods and Independent Laboratory Validation portions of the 

study are needed. 
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Guideline 

Number Study Title Test 

Material 

Estimated 

Timeframe 

850.4100 Nontarget Area Phytotoxicity Tier II, Seedling 

Emergence3 TEP4

 12 

850.4150 Nontarget Area Phytotoxicity Tier II, 

Vegetative Vigor 3 TEP 12 

850.5400 Nontarget Area Phytotoxicity Tier II, Aquatic 

Plant Growth (Algal Plants) 3 TEP 12 

 

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 A Tier II study is expected to be required. The DCI expected to be issued 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. 

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 Typical End-use Product (TEP).