Docket Number EPA-HQ-OPP-2011-0482 

www.regulations.gov 

Ancymidol 

Interim Registration Review Decision 

Case Number 3017 

Approved by: 

Date: 

August 2014 

p~ ~ Richard P. Keigwin, Jr. 

Director 

Pesticide Re-evaluation Division 
2

Contents

I. INTRODUCTION...................................................................................................................... 3

II. SCIENTIFIC ASSESSMENTS................................................................................................... 4

A. Human Health Assessment............................................................................................................4

B. Environmental Assessment ............................................................................................................4

1. Environmental Exposure ............................................................................................................4

2. Environmental Risk Characterization........................................................................................5

3. Endangered Species Assessment ...............................................................................................5

C. Endocrine Disruptor Screening Program......................................................................................5

III. INTERIM REGISTRATION REVIEW DECISION............................................................... 6

IV. NEXT STEPS ........................................................................................................................... 6
3

I. INTRODUCTION

This document is the Environmental Protection Agency’s (EPA or the Agency) Interim Registration 

Review Decision for ancymidol, pursuant to 40 CFR § 155.56 and § 155.58. A registration review 

decision is the Agency’s determination that a pesticide meets, or does not meet, the standard for 

registration in the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The Agency may 

issue, when it deems appropriate, an interim registration review decision before completing a 

registration review. Among other things, the interim registration review decision may (1) require 

new risk mitigation measures; (2) impose interim risk mitigation measures; (3) identify data or 

information required to complete the review; and (4) include schedules for submitting the required 

data, conducting the new risk assessment, and completing the registration review.

FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandated the continuous 

review of existing pesticides. All pesticides distributed or sold in the United States generally must be 

registered by EPA, 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 and reduce risk evolves and as 

policies and practices change, all registered pesticides continue to meet the statutory standard of no 

unreasonable adverse effect to human health or the environment. Through the registration review 

program, the Agency periodically reevaluates pesticides to make sure that as these changes occur, 

products in the marketplace can be safely used. Information on this program is provided at: 

http://www.epa.gov/oppsrrd1/registration_review/. In 2006, the Agency implemented the 

Registration Review program pursuant to FIFRA Section 3(g) and will review each registered 

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

registration. 

Ancymidol is a pyrimidine plant growth regulator registered for treating container-grown herbaceous 

plants, ornamental woody shrubs, and bedding plants grown in greenhouses and in outdoor plant 

bedding areas for commercial production. It is also registered for use as a seed treatment for 

ornamental plants, and treated seeds are used to start plants. Treatment with ancymidol is intended 

to induce a more compact growth form by suppressing growth between nodes, resulting in bushier 

plants and shrubs. Use of ancymidol is limited to nursery grown ornamentals; no food, feed, or 

residential uses are registered for ancymidol. EPA completed a Reregistration Eligibility Decision 

(RED) for ancymidol in June 1995. 

Pursuant to 40 CFR § 155.50, the Agency formally initiated registration review for ancymidol (case 

3017) in June 2011. The following timeline highlights significant events that have occurred during 

the registration review of ancymidol:

 June 2011 - Publication of the Ancymidol Preliminary Work Plan (PWP) for a 60-day 

comment period. The PWP was accompanied by the scoping document and the problem 

formulation. 

 December 2011 - Publication of the Final Work Plan (FWP) and EPA’s response to the

single public comment received. The FWP did not modify the anticipated risk assessment, 

data needs, or registration review timeline described in the PWP. However, the FWP noted 

that a recent evaluation of environmental exposures might alter the Agency’s planned 
4

ecological risk assessment and anticipated data requirements for ancymidol by eliminating 

the need for a data call-in. 

 January 2013 - EPA revisited the planned registration review risk assessments and

supporting data requirements and determined that sufficient information was available to 

conduct qualitative risk assessments to support an interim registration review decision, 

pursuant to 40 CFR § 155.53(b). This decision shortened the registration review timeline 

described in the FWP. 

 March 2013 - EPA published qualitative human health and environmental fate and effects 

risk assessments for ancymidol in the ancymidol registration review docket for a 60-day 

comment period. No comments were received on the documents: Ancymidol. Registration 

Review Preliminary Risk Assessment (Human Health) or EFED Preliminary Risk Assessment to 

Classify Registered Ancymidol Uses as De Minimus Risk to Listed/Non-listed Species and “No Effects” 

Determinations. 

 June 4, 2014 – EPA published the Ancymidol Proposed Interim Registration Review Decision in the 

Federal Register (79 FR 32284; FRL-9911-16) for a 60-day comment period. EPA received 

comments from the Center for Biological Diversity; these comments supported the Agency’s 

Interim Registration Review Decision. 

For further information on the registration review of ancymidol, see EPA’s public docket (EPAHQ-OPP-2011-0482) at www.regulations.gov. 

II. SCIENTIFIC ASSESSMENTS

A summary of the Agency’s preliminary human health and environmental risk assessments,

published on March 12, 2013, is presented below. The preliminary risk assessments and additional 

supporting documents are located in the registration review docket, EPA-HQ-OPP-2011-0482. 

A. Human Health Assessment 

The Agency conducted a qualitative human health risk assessment for ancymidol. Ancymidol has no 

registered food/feed or residential uses and existing use patterns are not expected to contaminate 

surface or ground water; thus, dietary and residential exposure assessments were not conducted. 

EPA evaluated occupational handler risk only.

EPA conducted a qualitative occupational handler assessment for ancymidol based on its limited 

use, minimal potential for inhalation and dermal exposure, and general lack of evidence of 

significant toxicity to humans. The Agency believes, based on available information, that use of 

ancymidol should not pose a dermal or inhalation risk to workers. For details, see the March 5, 2013 

memo, Ancymidol. Registration Review Preliminary Risk Assessment.

B. Environmental Assessment 

1. Environmental Exposure 

Available data on the use of ancymidol in nurseries and greenhouses show that less than 20 pounds of 

active ingredient were used per year nationwide for the years 1999, 2002, 2004, and 2006. Most of the 
5

use of ancymidol occurs indoors, but a small amount may be used to treat plants in containers placed 

outdoors on nursery plant beds, or as a greenhouse seed treatment for ornamentals later planted 

outdoors. As a plant growth regulator, ancymidol acts systemically and is taken up by the plant when 

applied. Ancymidol is assumed to be absorbed very rapidly by the plant because the plants may be 

watered as soon as one hour after application, according to label directions, without an apparent

reduction in efficacy. Ancymidol is extremely dilute when applied, and the use is spread across 

thousands of facilities throughout the United States. As a result, environmental exposure is negligible. 

For details, see the November 28, 2011 memo, Equivalent outdoor per-acre application rates for ancymidol used 

on container-grown greenhouse transplants.

2. Environmental Risk Characterization

EPA conducted a qualitative environmental fate and effects assessment for ancymidol. EPA 

considered potential ancymidol exposure to non-target organisms, available information on the 

toxicity of ancymidol, and the registered uses of ancymidol in the qualitative assessment. 

The available toxicity data for ancymidol show low toxicity to freshwater and terrestrial organisms.

While the Agency does not currently have terrestrial plant toxicity data, effects to terrestrial plants 

are not reasonably expected to occur given the currently registered uses of ancymidol. When EPA 

compared conservative assumptions of environmental exposure from application of ancymidol 

products at the maximum use rates with available toxicity data, the resulting values were below the 

Agency’s level of concern. Therefore, given the types and extent of the registered uses of 

ancymidol, the low toxicity shown by existing studies, the small quantity used and the diffuse nature 

of use, the Agency believes that registered uses of ancymidol should not adversely affect non-target 

organisms. For details of the environmental risk assessment, see the February 25, 2013 memo, 

EFED Preliminary Risk Assessment to Classify Registered Ancymidol Uses as De Minimus Risk to Listed/Nonlisted Species and “No Effects” Determination. 

3. Endangered Species Assessment

There is no reasonable expectation for any registered use of ancymidol to cause direct or indirect 

adverse effects to threatened and endangered species. No adverse modification of critical habitat is 

expected to occur from use of ancymidol. This is because of the types and extent of use, the low 

toxicity shown by existing studies, the highly diffuse nature of the use site, and the extremely low 

annual usage. EPA has made a “no effect” determination under the Endangered Species Act (ESA) 

for all listed species and designated critical habitat for such species and has therefore concluded that 

consultation with the Fish and Wildlife Service and the National Marine Fisheries Service under 

ESA section 7(a)(2) is not required. For details, see the February 25, 2013 Preliminary Risk 

Assessment cited above. 

C. Endocrine Disruptor Screening Program 

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.” Under FFDCA section 408(p), the Agency must screen 

all pesticide chemicals. Between October 2009 and November 2010, EPA issued test orders/data 
6

call-ins for the first group of 67 chemicals and published a second list of chemicals proposed for

order issuance in the future. Ancymidol was not among the group of 58 pesticide active ingredients 

on the initial list nor is it proposed on the second list of chemicals to be screened under the 

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

for registration review chemicals, including ancymidol. For further information on the status of the 

EDSP, the policies and procedures, the list of 67 chemicals, future chemical lists proposed for 

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

website: http://www.epa.gov/endo/. In the interim, EPA is making no human health or 

environmental safety findings associated with the EDSP screening of ancymidol. Before completing 

this Registration Review, the Agency will make an EDSP FFDCA section 408(p) determination.

III. INTERIM REGISTRATION REVIEW DECISION

In accordance with 40 CFR Sections 155.56 and 155.58, the Agency is issuing this Interim 

Registration Review Decision. Except for the EDSP component of the ancymidol registration 

review case, the Agency has determined the following: (1) no additional data are required at this 

time; and (2) no changes to the affected registrations or their labeling are needed at this time. In 

addition, EPA does not expect ancymidol to have direct or indirect adverse effects to non-listed and 

listed species or to designated critical habitat. As such, EPA has made a “no effect” determination 

under the Endangered Species Act (ESA) for all listed species and designated critical habitat for such 

species.

IV. NEXT STEPS 

EPA will make a final registration review decision for ancymidol after an EDSP FFDCA section 

408(p) determination has been made.