associated with ancymidol and its degradates. It also describes the preliminary ecological risk 

hypothesis and analysis plan for evaluating and characterizing risk to non-target species in 

support of the registration review of ancymidol. This document also recommends studies that 

should be included in a generic data call-in (DCI) to address uncertainties surrounding the 

environmental fate and potential ecological effects of ancymidol. 

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Problem Formulation for the Environmental Fate, 

Ecological Risk, Endangered Species, and Drinking Water 

Exposure Assessments in Support of the Registration Review 

of Ancymidol 

alpha-Cyclopropyl-alpha-(4-methoxyphenyl)-5-pyrimidylmethanol 

CAS Registry Number: 12771-68-5 

PC Code: 108601 

Prepared by:

Alicia Korol, Biologist

Faruque Khan, Ph.D., Senior Fate Scientist

U.S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by:

Michael Lowit, Ph.D., Ecologist 

Christopher M. Koper, M.S., Chemist 

March 28, 2011 

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Table of Contents 

1. Purpose ....................................................................................................................................... 5

2. Problem Formulation ................................................................................................................. 5

2.1. Nature of Regulatory Action ............................................................................................... 5

2.2. Previous Assessments ......................................................................................................... 6

2.2.1. Ecological Risk Assessments ....................................................................................... 6

2.2.2. Drinking Water Exposure Assessments ....................................................................... 6

3. Stressor Source and Distribution ............................................................................................... 6

3.1. Mechanism of Action .......................................................................................................... 6

3.2. Overview of Pesticide Use and Usage ................................................................................ 7

3.3. Environmental Fate and Transport...................................................................................... 8

3.5. Water Quality .................................................................................................................... 10

4. Receptors.................................................................................................................................. 10

4.1. Effects to Aquatic Organisms ........................................................................................... 11

4.2. Effects to Terrestrial Organisms ....................................................................................... 12

4.3. Incident Databases Review ............................................................................................... 14

4.4. Ecosystems Potentially at Risk .......................................................................................... 14

5. Assessment Endpoints ............................................................................................................. 15

6. Conceptual Model .................................................................................................................... 15

6.1. Risk Hypothesis ................................................................................................................ 16

6.2. Conceptual Diagram ......................................................................................................... 16

7. Analysis Plan ........................................................................................................................... 18

7.1. Stressors of Concern ......................................................................................................... 18

7.2. Measures of Exposure ....................................................................................................... 19

7.3. Measures of Effect ............................................................................................................ 21

7.4. Integration of Exposure and Effects ................................................................................. 22

7.5. Deterministic and Probabilistic Assessment Methods ...................................................... 22

7.6. Endangered Species Assessments ..................................................................................... 23

7.7. Drinking Water Assessment ............................................................................................. 23

7.8. Preliminary Identification of Data Gaps ........................................................................... 23

7.8.1. Environmental Fate .................................................................................................... 24

7.8.2. Effects Data ................................................................................................................ 25

8. References ................................................................................................................................ 31

APPENDIX A: SIP v.1.0 Description, Assumptions, Inputs and Outputs .................................. 35

APPENDIX B: Data Call-In Tables ............................................................................................ 37

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1. Purpose 

The purpose of this problem formulation is to provide an understanding of what is known about 

the environmental fate and ecological effects of ancymidol, considering its currently registered 

uses. Ancymidol (alpha-cyclopropyl-alpha-(4-methoxyphenyl)-5-pyrimidinemethanol; CAS No. 

12771-68-5; PC Code 108601) is in the pyrimidine class of pesticides which inhibit giberellin 

biosynthesis. When used as directed, ancymidol serves as a plant growth regulator that limits 

internode elongation. Ancymidol is currently registered for use on container-grown ornamentals, 

foliage, and bedding plants in nurseries, greenhouses, shadehouses, and interiorscapes. There are 

no residential uses for ancymidol nor are there ancymidol formulations classified as “restricted 

use.” This document provides a plan for analyzing data relevant to ancymidol and for 

conducting environmental fate, ecological risk, endangered species, and drinking water exposure 

assessments for its registered uses. Additionally, this problem formulation identifies data gaps, 

uncertainties, and potential assumptions used to address those uncertainties relative to 

characterizing the potential ecological risk associated with the registered used of ancymidol on 

container-grown plants in nurseries, greenhouses, shadehouses, and interiorscapes. 

2. Problem Formulation 

2.1. Nature of Regulatory Action 

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides distributed 

or sold in the United States generally must be registered by the Environmental Protection 

Agency (Agency). In determining whether a pesticide can be registered in the U.S., the Agency 

evaluates its safety to non-target species based on a wide range of environmental and health 

effects studies. In 1996, FIFRA was amended by the Food Quality Protection Act, and the 

Agency was mandated to implement a new program for the periodic review of pesticides, i.e., 

Registration Review (http://www.epa.gov/oppsrrd1/registration_review/). The Registration 

Review program is intended to ensure that, as the ability to assess risk evolves and as policies 

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

unreasonable adverse effects to human health and the environment. Changes in science, public 

policy, and pesticide use practices will occur over time. Through the new Registration Review 

program, the Agency periodically reevaluates pesticides to make sure that as change occurs, 

products in the marketplace can be used safely. 

As part of the implementation of the new Registration Review program pursuant to Section 3(g) 

of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is beginning its 

evaluation of ancymidol to determine whether it continues to meet the FIFRA standard for 

registration. This problem formulation for the environmental fate, ecological risk, endangered 

species, and drinking water assessment chapter in support of the registration review of ancymidol 

will be posted in the initial docket which will open the public phase of the review process. 

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2.2. Previous Assessments 

2.2.1. Ecological Risk Assessments 

Ancymidol was first registered by the Agency in 1973 by Elanco Products Co., division of Elli 

Lilly and Co. In 1993, the Agency issued a Data Call-In (DCI) to the registrant for submission 

of additional data. In 1995, ancymidol was granted reregistration. According the chemical’s 

Registration Eligibility Determination (RED), ancymidol use was determined to cause minimal 

adverse effects to Federally listed and nonlisted fish, aquatic invertebrates, aquatic plants, birds, 

mammals, and beneficial insects; Additionally, because very limited exposure was anticipated to 

terrestrial plants, minimal adverse effects were expected to this taxa (USEPA, 1995). 

After reviewing the previous risk assessment on ancymidol (i.e., RED), modifications to the 

previous risk analyses are expected. These changes are due to an evolution of Agency policy 

since ancymidol was re-registered (e.g., evaluating drinking water exposure to birds and 

mammals). While taxa-specific risk assessments were conducted, these assessments were based 

on data sets now considered incomplete by current EPA policy, on coarse exposure estimates, 

and on qualitative risk determinations in some cases (e.g. terrestrial plants). Further, label 

clarification of application rates is necessary for use in the final registration-review risk 

assessment. 

2.2.2. Drinking Water Exposure Assessments 

Since no food or feed uses were registered, no dietary exposure was considered from the 

pesticide uses of ancymidol during the reregistration evaluation phase. Therefore, a screening 

drinking water assessment has not been conducted for ancymidol. If a drinking water assessment 

is warranted by the Health Effects Division (HED), a drinking water exposure assessment using 

up-to-date models and data will be completed during the registration review process. At that 

time, the HED will be consulted in order to determine which, if any, of ancymidol degradates are 

residues of toxicological concern and should be included in the drinking water exposure 

assessment in support of the human health dietary risk assessment. 

3. Stressor Source and Distribution

3.1. Mechanism of Action 

Ancymidol is a plant growth regulator in the pyrimidine chemical class of pesticides that inhibits 

gibberellin biosynthesis. When used as directed, ancymidol reduces internode elongation for 

plant height control. Hofmannova, et. al., 2008, also demonstrated that ancymidol inhibits 

cellulose synthesis, which is independent of the interference with giberellin biosynthesis, and 

which in turn inhibits cell elongation and cell wall deposition. Plants absorb ancymidol through 

the foliage, stems, roots, seed coats, and at the stage of seed germination; as such, ancymidol can 

be applied a multiple stages throughout a plant’s life cycle. Ancymidol is a systemic growth 

regulator and is translocated from point of uptake to the terminal where it reduces internode 

elongation. 

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3.2. Overview of Pesticide Use and Usage 

Ancymidol is currently registered for use as a plant growth regulator in container-grown 

ornamental, foliage, and bedding plants in nurseries, greenhouses, shadehouses, and 

interiorscapes. Usages of ancymidol in nurseries and shadehouses are considered as outdoor 

uses. Five labels are currently registered for use in the United States: two (2) manufacturing-use 

only products, and three (3) formulated end-use products (Table 1). All three end-use products 

contain the active ingredient, ancymidol, only, and are formulated as water based solutions for 

application to foliage (ABIDETM and A-Rest* Solution®) and seed (A-REST* Seed Treatment®). 

Table 1. Currently Registered Ancymidol End-Use Products. 

FORMULATION EPA REG. 

NO. 

% ACTIVE METHODS OF 

APPLICATION 

USE RESTRICTIONS 

ABIDETM 62097-22 0.026 Foliar spray, 

drench 

-Spray application must only be performed in 

enclosed areas, such as greenhouses, where spray 

drift outside the treated area cannot occur. 

-Drench applications can be applied indoor or 

outdoor 

 

A-Rest* Solution® 67690-2 0.026 Foliar spray, 

drench, 

chemigation 

-Chemigation is restricted in CA 

ANCYMIDOL 

Technical®

62097-23 99.72 n/a -For the formulation of plant growth regulator 

solutions for manufacturing use only 

A-REST* Seed 

Treatment®

67690-41 99.6 Seed treatment -Greenhouse use only for ornamental plant seeds 

to be sown in containers 

A-Rest* 

Technical® 

67690-5 99.6 n/a -For the formulation of plant growth regulator 

products for manufacturing use only 

The current formulations with labeled outdoor uses for spray, drench, and chemigation 

applications (ABIDETM and A-REST* Solution®) do not specify maximum application rates per 

plant type (e.g. bedding plants) on the basis of chemical weight (e.g. lbs/pot). Instead, general 

guidelines are provided that recommend concentrations of ancymidol in solution that will be 

used for treatment (i.e. 50 ppm). The labels explicitly state that the optimum rates will vary 

depending on the grower, desired plant height, growing conditions, application technique, 

species, and variety or cultivar, and that the labeled use rates should act as a baseline for further 

rate refinement. Maximum annual application rates per pot size, or application rates per 

growing season where appropriate, on a chemical weight basis must be specified for the 

Environmental Fate and Effects Division (EFED) to conduct an ecological risk assessment 

for all outdoor uses; maximum number of sequential applications per plant type must also 

be defined. The risk assessment for outdoor spray, drench, and chemigation applications of 

ancymidol cannot be completed without this information. 

For risk assessment purposes, rate specifications as described above (i.e. maximum annual 

application rates per pot size, or application rates per growing season where appropriate, on a 

chemical weight basis) are not necessary for labeled indoor (i.e. greenhouse or interiorscape) 

uses, as these would not result in sufficient environmental exposure to necessitate an ecological 

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risk assessment. The ancymidol seed treatment is labeled for greenhouse (indoor) use only and 

will not be assessed for outdoor exposures. 

No national level usage data is available for ancymidol use. However, information on ancymidol 

is available for the state of California from the California Department of Pesticide Regulation for 

the years 2006 to 2008. From this data, ancymidol usage was reported for nursery and/or 

greenhouse use only (as of 07/20/10), at a total maximum quantity of 1.5, 1.8, and 0.8 pounds 

applied/entire state for the years 2006, -07, and -08, respectively. This information can be found 

publically at: http://www.cdpr.ca.gov/docs/pur/purmain.htm. 

3.3. Environmental Fate and Transport 

Ancymidol is a pyrimidine class of pesticides and moderately soluble (650 mg/L) compound. 

The vapor pressure (2.0 x 10-7 mm Hg) and the estimated Henry's Law Constant of 1.09 x 10-10

atm m3

/mol indicate that the compound is relatively non-volatile under field conditions. The noctanol water partition coefficient (Log Kow =1.91) for ancymidol indicates a low potential for 

bioaccumulation. 

Based on limited environmental fate data, the major route of dissipation of ancymidol in the soil 

is by microbial metabolism (aerobic half-life = 14.9 days). In the aerobic soil metabolism study, 

ancymidol mineralized to carbon dioxide, which increased to a maximum of 44.89 percent of the 

applied ancymidol by 61 days post treatment and unextracted residues increased to 

approximately 43 percent at 61 days post treatment. Six unidentified degradates were detected at 

≤ 0.01 ppm. Ancymidol is hydrolytically stable in pH 5, pH 7, and pH 9 buffered solutions. 

However, there is uncertainty about the fate of ancymidol in anaerobic soils as well as aerobic 

and anaerobic aquatic environments since no studies were submitted related to these conditions. 

No photolytic degradation in aquatic and soil environments are available at his time. In addition, 

the fate behavior of ancymidol under field conditions cannot be determined for lack of a field 

dissipation study. The chemical formula, structure, and the physical, chemical, environmental 

fate and transport characteristics associated with ancymidol are summarized in Table 2. 

Table 2. Physical, Chemical Properties and Environmental Fate Properties of Ancymidol. 

Parameter Value Reference Comments 

Chemical Name Ancymidol MRID 417235-01

Chemical Family Pyrimidine MRID 417235-01

Empirical Formula C15H16N2O2 MRID 417235-01

IUPAC (RS)-α-cyclopropyl-4-

methoxy-α-(pyrimidin-5-

yl)benzyl alcohol 

MRID 417235-01

CAS Name α-cyclopropyl-α-(4-

methoxyphenyl)-5-

pyrimidinemethanol

MRID 417235-01

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Parameter Value Reference Comments 

Structure MRID 417235-01

Selected Physical/Chemical Parameters

Molecular mass 236.30 g/mol MRID 418212-01 

Vapor pressure (25°C) 2.0 x 10-7 mm Hg MRID 418212-01 

Solubility (25°C) 650 mg/L (water) 

2.5g/L (Acetone) 

0.7g/L (Acetotrile) 

MRID 417235-01 

Henry’s law constant (20°C, pH 7) 1.09 x 10-10 Calculated HLC = (VAPR÷760) ÷ 

(SOL÷MWT) 

Octanol-water partition coefficient 

(LogKOW) (25°C) 

1.91 MRID 00162638 

Persistence

Hydrolysis 

pH 5: stable 

pH 7: stable 

pH 9: stable 

MRID 417235-03 

Aqueous Photolysis (t 1⁄2 ) 

No data -- 

Soil Photolysis (t 1⁄2 ) 

No data -- 

Aerobic Soil Metabolism 

(t 1⁄2 ) 14.9 days MRID 420530-01 Sandy loam soil 

Anaerobic Soil Metabolism 

No data -- 

Anaerobic Aquatic Metabolism (t 1⁄2 ) 

No data 

Aerobic Aquatic Metabolism 

No data -- 

Mobility

Soil Partition Coefficient Kf (mL/g)

0.11 (sand) 

0.73 (loam) 

0.55 (sandy loam)a

0.82 (clay loam soil) 

Kfoc (mL/g )

58 (sand) 

90(loam) 

77 (sandy loam) 

68 (clay loam soil) 

MRID 417235-02 There was correlation 

between Kf and % 

organic carbon. In 

general, adsorption 

appeared to increase 

with increasing organic 

carbon content of soils. 

Field Dissipation

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Parameter Value Reference Comments 

Terrestrial Field Dissipation (t 1⁄2 ) No data -- 

a

MRID 419137-01, a soil column leaching study supports reported Kf of 0.55 mL/g for sandy loam soil. 

3.4. Degradates of Concern 

Major degradates are compounds that form at greater than 10% of the applied in at least one fate 

study, or are known to be toxicologically significant. There were no major degradates except 

CO2 reported based on limited environmental fate studies. No toxicity data is available for any 

degradate of ancymidol. 

3.5. Water Quality 

Ancymidol is not identified as a cause of impairment for any water bodies under section 303(d) 

of the Clean Water Act1

. In addition, no Total Maximum Daily Loads (TMDL) have been 

developed for ancymidol2 and there are no aquatic life criteria for ancymidol3. More information 

on impaired water bodies and TMDLs can be found at http://www.epa.gov/owow/tmdl/. 

The Agency invites submission of water quality data for this pesticide. To the extent possible, 

data should conform to the quality standards in Appendix A of the OPP Standard Operating 

Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process (see: 

http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-sop.pdf), in order to ensure 

they can be used quantitatively or qualitatively in pesticide risk assessments. 

No monitoring data were available for ancymidol. Neither the USGS’s National Water Quality 

Assessment (NAWQA) program nor the California Department of Pesticide Regulation 

monitoring programs included ancymidol as an analyte. 

4. Receptors 

Consistent with the process described in the Overview Document (USEPA, 2004), the risk 

assessment for ancymidol relies on a surrogate species approach. Toxicological data generated 

from surrogate test species, which are intended to be representative of broad taxonomic groups, 

are used to extrapolate the potential effects on a variety of species (receptors) included under 

these taxonomic groupings. 

Acute and chronic toxicity data from studies submitted by pesticide registrants along with the 

available open literature are used to evaluate the potential direct and indirect effects of 

ancymidol to aquatic and terrestrial receptors. This includes toxicity on the technical grade 

 

1

 based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885, 

accessed January 26, 2011 

2

 based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_

group_name=PESTICIDES, accessed January. 26, 2011 3

 based on information provided at http://www.epa.gov/waterscience/criteria/aqlife/index.html

-10 of 46-
active ingredient, degradates, and when available, formulated products (e.g., “Six-Pack” studies). 

The open literature studies are identified through EPA’s ECOTOXicology (ECOTOX) database, 

which employs a literature search engine for locating chemical toxicity data for aquatic life, 

terrestrial plants, and wildlife. The evaluation of both sources of data may also provide insight 

into the direct and indirect effects of ancymidol on biotic communities from loss of species that 

are sensitive to the chemical and from changes in structure and functional characteristics of the 

affected communities. Data from an ECOTOX run for ancymidol will be evaluated for possible 

quantitative and/or qualitative inclusion in the risk assessment in support of Registration Review. 

At that time, endpoints more sensitive than available guideline studies will be reviewed from the 

open literature studies. 

A summary of the most sensitive data representing non-target organisms exposed to ancymidol 

in aquatic and terrestrial habitats is provided in Section 4.1. A summary of ecological incidents 

associated with ancymidol and a description of ecosystems potentially at risk are provided in 

Section 4.2. 

4.1. Effects to Aquatic Organisms 

Effects data are available on aquatic animals and plants for ancymidol; no data on aquatic 

organisms are available for the formulations or any degradate. Based on the available data, 

ancymidol is categorized as practically non-toxic on an acute exposure basis to freshwater fish 

and invertebrates. There are no data available for estuarine/marine animals or chronic toxicity 

data for freshwater animals. Data on aquatic vascular and nonvascular plants are available. A 

summary of all submitted aquatic animal toxicity studies are presented in Table 3.

Table 3. Summary of Submitted Aquatic Animal Toxicity Studies for Ancymidol. 

TAXON SPECIES ENDPOINT CHEMICAL/ 

FORMULATION MRID 

STUDY 

CLASSIFICATION 

Freshwater 

Fish (Acute) 

Rainbow Trout 

(Oncorhynchu

s mykiss) 

96-hr LC50 

 >99.2 mg 

a.i./L 

Ancymidol 

(99.9%) 41670603 Acceptable (“Core”) 

Freshwater 

Invertebrate 

(Acute) 

Daphnid 

(Daphnia 

magna) 

48-hr EC50 

>96.4 mg 

a.i./L 

Ancymidol 

(99.9%) 41670601 Acceptable (“Core”) 

Data from an acceptable 96-hour freshwater fish study is available for rainbow trout 

(Onchorhynchos mykiss) (MRID 41670603). The study was conducted as a limit test at 100 mg 

a.i./L (nominal) and no mortality was observed at a mean-measured concentration of 99.2 mg 

a.i./L for the duration of the study. Sublethal effects were observed in 5 of the 30 fish exposed to 

ancymidol and included labored respiration, prostration, and a distended ventral surface. Based 

on this study, ancymidol is classified practically non-toxic to rainbow trout on an acute exposure 

basis. 

One 48-hour freshwater invertebrate toxicity study was submitted for the daphnid, Daphnia 

magna (MRID 41670601). By test termination, no mortality or sublethal effects were noted. 

The reported EC50 and NOAEC for this limit test were >96.4 and 96.4 mg a.i./L, respectively. 

-11 of 46-
Based on these results, ancymidol is classified practically non-toxic to Daphnia magna on an 

acute exposure basis. 

The most sensitive species for both vascular and nonvascular aquatic plants for ancymidol from 

submitted toxicity studies are presented in Table 4. 

Table 4. Summary of Submitted Aquatic Plant Toxicity Studies for Ancymidol. 

TAXON ENDPOINT

CHEMICAL/ 

FORMULATI

ON

MRID STUDY 

CLASSIFICATION

Aquatic Nonvascular Plants 

Freshwater 

Green Alga 

(Psuedo-kirchneriella 

subcapitata,formerly 

Selenastrum 

capricornutum)

96-hr EC50 = 26.9 mg 

a.i./L 

Slope: 2.91 

NOAEC = 13.6 mg a.i./L 

(algal cell density) 

Ancymidol 

(99.8%) 43140502 Acceptable (“Core”) 

Aquatic Vascular Plants 

Duckweed 

(Lemna gibba) 

14-day EC50 = 0.292 mg 

a.i./L (frond number) 

Slope: 1.67 

NOAEC = 0.0684 mg 

a.i./L (frond number) 

Ancymidol 

(99.8%) 43140501 Acceptable (“Core”) 

Tier II aquatic nonvascular plant data on the freshwater green alga, P. subcapitata, is available 

for the TGAI (MRID 43140502). Algae were exposed to the six treatment concentrations of 

8.14, 13.6, 23.2, 36.5, 58.4, and 98.6 mg a.i./L (mean-measured) plus a negative control for 120 

hours. The resulting EC50 and NOAEC based on cell density were 26.9 (7.42-81.64) and 13.6 

mg a.i./L, respectively. 

Data on the TGAI from an acceptable 14-day Tier II aquatic vascular plant study is available for 

duckweed (L. gibba) (MRID 43140501). Duckweed was exposed to seven treatment 

concentrations of 0.0154, 0.0312, 0.0684, 0.151, 0.263, 0.523, and 1.06 mg a.i./L (meanmeasured) plus a negative control. The resulting EC50 and NOAEC based on frond number 

were 0.292 (0.193-0.488) and 0.0684 mg a.i./L, respectively. 

4.2. Effects to Terrestrial Organisms 

Table 5 summarizes the all of the terrestrial animal ecological toxicity endpoints for ancymidol 

and its formulations based on an evaluation of submitted studies. Ancymidol is categorized as 

practically nontoxic to birds on a subacute dietary exposure basis and is slightly toxic to 

mammals on an acute oral exposure basis. Ancymidol is practically nontoxic to young adult 

honey bees on an acute contact exposure basis. No chronic data has been submitted for 

terrestrial animal exposure to ancymidol. Likewise, no data on exposures of ancymidol to 

terrestrial plants has been submitted. 

Table 5. Summary of the Submitted Terrestrial Toxicity Studies for Ancymidol. 

TAXON ENDPOINT CHEMICAL/ 

FORMULATION MRID STUDY CLASSIFICATION 

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TAXON ENDPOINT CHEMICAL/ 

FORMULATION 

STUDY MRID CLASSIFICATION 

BIRDS 

Sub-Acute Dietary

Bobwhite quail 

(Colinus 

virginianus) 

8-day LC50 > 5192 

mg a.i./kg-diet Ancymidol (99.9%) 41670602 Acceptable (“Core”) 

MAMMALS 

Acute 

Laboratory Rat 

(Rattus norvegicus) 

LD50 = 1016 mg/kgbw (females) Ancymidol (100%) 42480601 Acceptable 

Laboratory Rat 

(Rattus norvegicus) 

LD50 > 4965 mg/kg 

bw (males and 

females) 

A-Rest* Solution® 

(0.0264%) 00162642 Acceptable 

Laboratory Rat 

(Rattus norvegicus) 

LD50 > 2000 mg/kg 

bw (females) ABIDETM (0.0264%) 47331303 Acceptable 

TERRESTRIAL INVERTEBRATES 

Acute

Honey Bee (Apis 

melifera) 

48-hr LD50 >100 μg 

a.i./bee Ancymidol (99.8%) 43140504 Acceptable (“Core”) 

An acceptable avian dietary toxicity study with bobwhite quail (Colinus virginianus) is available 

for ancymidol (MRID 41670602); the resulting 8-day LD50 was > 5192 mg a.i./kg diet based on 

no mortality in the control and treatment groups. The corresponding NOAEC was 2638 mg 

a.i./kg-diet based on significant reduction in mean body weight in the 5192 mg a.i./kg diet 

treatment group. No reductions in feed consumption were observed in any treatment group. 

Necropsy of birds was conducted on the eyes, and while one bird revealed bilateral congenital 

cortical cataracts, this condition was not considered treatment related. All birds were normal in 

appearance and behavior throughout the study except for one bird (at 5192 mg a.i./kg diet) who 

was constantly pacing the cage with its head drooping. This effect was not considered treatmentrelated by the study author. Based on these results, ancymidol is categorized as practically nontoxic to bobwhite quail on a subacute dietary basis. 

An acute oral toxicity study with rats has been submitted for the TGAI, and the formulations ARest* Solution® (0.0264%) and ABIDETM (0.0264%). The test design of the study using the 

TGAI (MRID 42480601) included three treatments groups at 750, 1375, and 2500 mg a.i./kg bw 

and a vehicle control group. Deaths of all rats occurred after oral gavage at the highest treatment 

level by day 4, and in 1/5 males and 5/5 females in the 1375 mg a.i./kg bw dose group. The 

resulting male and female LD50 = 1721 mg a.i./kg bw and 1016 mg a.i./kg bw, respectively. 

Clinical signs of toxicity were observed in the three highest dose groups; both males and females 

in the 750 mg ai/kg bw dose group exhibited hypoactivity, tremors, generalized leg weakness, 

ataxia, lethargy, bloody tears, colored nasal discharge, and hunched posture (females only). In 

the 1375, and 2500 mg a.i./kg bw dose groups, clonic convulsions and salivation was observed in 

all animals; other clinical signs of toxicity exhibited by some rats included coma, lethargy, 

hunched posture, immobilization, bloody tears, colored nasal discharge, poor grooming, 

piloerection, lack of feces, and anterior soiling. 

In the acute oral rat toxicity study on A-Rest* Solution® (0.0264%) (MRID 00162642), two 

groups of 5 male and 5 female rats were oral dosed with either 479 or 4965 mg form/kg bw. No 

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mortality occurred in either group. Toxic signs of dosing included leg weakness and soft stools. 

The resulting LD50 for both male and female rats was > 4965 mg form/kg bw. In an acute oral 

toxicity study on ABIDETM (0.0264%) (MRID 47331303), two groups of three female rats were 

given single oral gavage doses of 2000 mg/kg bw. There were no deaths, abnormal clinical 

signs, or treatment-related gross necropsy findings at the end of the study (end of the 14 day 

observation period). The resulting LD50 based on female rats was > 2000 mg a.i./kg bw. 

Ancymidol is classified practically non-toxic to young adult honey bees (Apis mellifera) based 

on the one acute contact toxicity study (MRID 43140504). The resulting 48-hour LD50 and 

NOAEL based on mortality in bees is >100 μg a.i./bee and 100 μg a.i./bee, respectively. Clinical 

observations in all treatment groups were comparable to the control groups. 

4.3. Incident Databases Review 

Preliminary reviews of the Ecological Incident Information System (EIIS, version 2.1) and the 

Avian Incident Monitoring System (AIMS)4

 were conducted on January 21, 2011. No incidents 

involving ancymidol were found in these databases. 

In addition to the incidents recorded in EIIS, additional incidents are reported to the Agency in 

aggregated form. Pesticide registrants report certain types of incidents to the Agency as 

aggregate counts of incidents occurring per product per quarter. Ecological incidents reported in 

aggregate reports include those categorized as ‘minor fish and wildlife’ (W-B), ‘minor plant’ (PB), and ‘other non-target’ (ONT) incidents. ‘Other non-target’ incidents include reports of 

adverse effects to insects and other terrestrial invertebrates. For ancymidol, as of January 21, 

2011, there have been no reported aggregated incidents associated with ancymidol. 

The total number of actual incidents associated with the use of ancymidol may be higher than 

what is reported to the Agency. Incidents may go unreported since effects may not be 

immediately apparent and/or readily attributed to the use of a chemical. As such, the absence of 

incident reports cannot be construed as the absence of incidents. 

4.4. Ecosystems Potentially at Risk 

The ecosystems at risk are often extensive in scope; therefore, it may not be possible to identify 

specific ecosystems during the development of a nation-wide ecological risk assessment. 

However, in general terms, terrestrial ecosystems potentially at risk from ancymidol exposure 

could include the treated nursery ground and adjacent areas that may receive drift or runoff. 

Areas adjacent to the treated containerized plants within or beyond the nursery grounds could 

include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, 

woodlands, riparian habitats and other uncultivated areas. 

 

4

 http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm 

-14 of 46-
Aquatic ecosystems potentially at risk include water bodies adjacent to, or downstream from, the 

treated area and could include impounded bodies such as ponds, lakes and reservoirs, or flowing 

waterways such as streams or rivers. For uses in coastal areas, aquatic habitat also includes 

marine ecosystems, including estuaries. 

5. Assessment Endpoints 

Assessment endpoints represent the actual environmental value that is to be protected, defined by 

an ecological entity (species, community, or other entity) and its attribute or characteristics 

(USEPA, 1998a). For ancymidol, the ecological entities may include the following: birds, 

mammals, terrestrial-phase amphibians, reptiles, freshwater fish and invertebrates, aquatic-phase 

amphibians, estuarine/marine fish and invertebrates, terrestrial plants, terrestrial invertebrates, 

and aquatic plants. The attributes for each of these entities include growth, reproduction, and 

survival. 

6. Conceptual Model 

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically 

significant concentrations. An exposure pathway is the means by which a pesticide moves in the 

environment from a source to an ecological receptor. For an ecological pathway to be complete, 

it must have a source, a release mechanism, an environmental transport medium, a point of 

exposure for ecological receptors, and a feasible route of exposure. 

The conceptual model for ancymidol provides a written description and visual representation of 

the predicted relationships between ancymidol, potential routes of exposure, and the predicted 

effects for the assessment endpoint. A conceptual model consists of two major components: risk 

hypothesis and a conceptual diagram (USEPA, 1998). 

Based on the limited submitted environmental fate data, ancymidol is not expected to volatilize 

and ancymidol persistence in surface waters is uncertain. Dissipation and degradation of 

ancymidol in aquatic environments cannot be determined due to lack of environmental fate 

studies. Column leaching study suggests that ancymidol has potential to leach through 

subsurface to ground water. Due to ancymidol’s log Kow value of 1.91, more information is 

needed to determine the potential of the chemical to bioaccumulate in aquatic or terrestrial 

environments. 

The previous ecological risk assessment for ancymidol identified minimal adverse effects to 

listed and nonlisted fish, aquatic invertebrates, aquatic plants, birds, mammals, beneficial insects, 

and terrestrial plants from nursery use on containerized plants only. However, this determination 

was based on an incomplete dataset and undetermined maximum application rates, and risks to 

most taxa (i.e., birds, mammals, fish, aquatic invertebrates, and plants) are uncertain. These 

preliminary conclusions are used to derive the risk hypothesis and conceptual diagram discussed 

below. 

-15 of 46-
6.1. Risk Hypothesis 

A risk hypothesis describes the predicted relationship among the stressor, exposure, and 

assessment endpoint response along with the rationale for their selection. Because data are either 

not available or are incomplete with which to assess acute and chronic effects across multiple 

taxa (i.e. birds, mammals, fish, aquatic invertebrates, and plants), and because exposures levels 

to non-target organisms have not been determined, there is uncertainty regarding potential risks 

to these taxa. Based on the lack of data, the following ecological risk hypothesis is being 

employed for this ecological risk assessment: 

Given the uses of ancymidol as a plant growth regulator in container-grown plants in 

nursery production and its environmental fate properties, there is potential exposure 

from ancymidol and its degradates of concern to non-target terrestrial and aquatic 

organisms. When used in accordance with the label, ancymidol and its degradates may 

result in potential adverse effects upon the survival, growth, and reproduction of nontarget terrestrial and aquatic organisms. 

6.2. Conceptual Diagram 

The environmental fate properties of ancymidol indicate that runoff, spray drift and direct spray 

represent potential transport mechanisms to aquatic and terrestrial habitats where non-target 

organisms may be either directly or indirectly exposed. These transport mechanisms (i.e., 

sources) are depicted in the conceptual diagrams below (Figures 1 and 2) along with the 

receptors of concern and the potential attribute changes in the receptors due to exposures of 

ancymidol. While not captured in Figure 2, exposure of terrestrial vertebrates from drinking 

water containing ancymidol and degradates of concern is also a route of exposure that will be 

assessed. 

-16 of 46-
Stressor

Source

Receptors

Attribute

Change

Ancymidol and Degradates of Concern applied to use site

Spray drift

Aquatic animals

Invertebrates 

Vertebrates

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in nonvascular 

and vascular plants

Reduction in prey

Modification of PCEs 

related to prey availability

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Modification of PCEs related to 

habitat

Surface water/

Sediment

Runoff

Aquatic Animals

Invertebrates

Vertebrates

Exposure

Media

Uptake/gills 

or integument

Ingestion Ingestion

Atmospheric 

transport

Wet/dry deposition

Soil Leaching to

Groundwater

Uptake/gills 

or integument

Aquatic Plants

Non-vascular

Vascular

Uptake/cell, 

roots, leaves Riparian plants

terrestrial 

exposure 

pathways see 

Figure 2

FIGURE 1. Conceptual Model for Ancymidol and Degradate Effects on Aquatic 

Organisms. Dotted Lines Indicate Exposure Pathways that Have a Low Likelihood of 

Contributing to Ecological Risk. 

-17 of 46-
Stressor

Source

Attribute

Change

Ancymidol and Degradates of Concern applied to use site

Direct

application Spray drift

Terrestrial 

vertebrates

Terrestrial 

inverts

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in prey and food

Modification of PCEs 

related to prey availability

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Modification of PCEs related

to habitat

Terrestrial plants

grasses/forbs, fruit, seeds 

(trees, shrubs)

Runoff

Terrestrial 

Vertebrates 

Exposure Media 

& Receptors Soil

Ingestion

Ingestion

Ingestion

Dermal uptake/Ingestion

Atmospheric 

transport

Root uptake/contact

Wet/dry deposition

Ingestion

Leaching to

Groundwater Irrigation 

water

FIGURE 2. Conceptual Model for Ancymidol and Degradate Effects on Terrestrial 

Organisms. Dotted Lines Indicate Exposure Pathways that Have a Low Likelihood of 

Contributing to Ecological Risk. 

7. Analysis Plan 

In order to address the risk hypothesis, the potential for adverse effects on the environment will 

be estimated. The use, environmental fate, and ecological effects of ancymidol will be 

characterized and integrated to assess the risks. Risk quotients (RQ) will be derived for 

ancymidol by dividing estimated environmental concentrations (EEC) by the most sensitive 

endpoint from the relevant, available toxicity data for ancymidol. 

This analysis plan will be revisited and may be revised depending upon a full review of the data 

available in the open literature and the information submitted by the public in response to the 

opening of the Registration Review docket. 

7.1. Stressors of Concern 

The stressors, or residues, of concern in this assessment will include ancymidol and any 

degradates determined to be of toxicological concern. Limited environmental fate data of 

-18 of 46-
ancymidol suggest that CO2 is the major degradate with six unidentified minor degradates 

formed in soil. Thus, the stressors of concern for this assessment will include ancymidol, as well 

as any other degradates determined to be of toxicological concern at the time the risk assessment 

is completed. Data sources which will be used in future assessment included: 1) registrant 

submissions in support of registration review, 2) publicly available literature on ecological 

effects, 3) monitoring data for freshwater streams, lakes, reservoirs, and estuarine areas, 4) 

incident reports of adverse effects on aquatic and terrestrial organisms associated with the use of 

ancymidol. 

 

The Agency does not routinely include an evaluation of mixtures of active ingredients in its 

ecological risk assessments, either those mixtures of multiple active ingredients in product 

formulations or those in the applicator’s tank. In the case of the product formulations of active 

ingredients (that is, a registered product containing more than one active ingredient), each active 

ingredient is subject to an individual risk assessment for regulatory decision regarding the active 

ingredient on a particular use site. If effects data are available for a formulated product 

containing more than one active ingredient, the data may be used qualitatively or quantitatively 

in accordance with the Agency’s Overview Document and the Services’ Evaluation 

Memorandum (USEPA, 2004; USFWS/NMFS, 2004). 

Ancymidol is not currently formulated with other pesticide active ingredients. An evaluation of 

environmental mixtures of ancymidol with other pesticides will not be presented as part of the 

ecological risk assessment. 

7.2. Measures of Exposure 

In order to estimate risks of ancymidol exposures in aquatic and terrestrial environments, all 

exposure modeling and resulting risk conclusions will be made based on maximum application 

rate for the currently registered use as discussed in Section 3.2. Measures of exposure are based 

on aquatic and terrestrial models that estimate environmental concentrations of ancymidol using 

the maximum labeled application rate and application methods that have the greatest potential 

for off-site transport of the chemical. The models used to generate aquatic estimated 

environmental concentrations (EEC) are the Pesticide Root Zone Model (PRZM) coupled with 

the EXposure Analysis Model System (EXAMS). The EECs will be based on the parent 

compound as well as any other degradates that are determined to be of toxicological concern 

based on information available at the time of the assessment. The model used to produce 

terrestrial EECs on food items is T-REX. The model used to derive EECs relevant to terrestrial 

and wetland plants is TerrPlant. These models are parameterized using relevant reviewed 

registrant-submitted environmental fate data. 

PRZM (v3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are screening simulation 

models coupled with the graphical user interface, PE (v5.0, November 2006) to generate daily 

exposures and 1-in-10-year EECs of ancymidol (and residues of concern) that may occur in 

surface water bodies adjacent to application sites receiving ancymidol through runoff and spray 

drift. PRZM simulates pesticide application, movement and transformation on an agricultural 

field and the resultant pesticide loadings to a receiving water body via runoff, erosion, and spray 

drift. EXAMS simulates the fate of the pesticide and resulting concentrations in the water body. 

The standard watershed geometry used for ecological pesticide assessments assumes application 

-19 of 46-
to a 10-hectare agricultural field that drains into an adjacent 1-hectare water body that is 2 meters 

deep (20,000 m3

 volume) with no outlet. The composite model PRZM/EXAMS is used to 

estimate screening-level exposure of aquatic organisms to ancymidol. The measure of exposure 

for aquatic species is the 1-in-10-year peak or rolling mean concentration. The 1-in-10-year 

peak is used for estimating acute exposures of direct effects to aquatic organisms. The 1-in-10-

year 60-day mean is used for assessing the effects to fish and aquatic-phase amphibians from 

chronic exposure. The 1-in-10-year 21-day mean is used for assessing the effects on aquatic 

invertebrates from chronic exposure. 

Exposure estimates for terrestrial animals assumed to be in the target area or in an area exposed 

to spray drift are derived using the T-REX model (version 1.4.1, 10/08/2008). This model 

incorporates the Kenaga nomograph, as modified by Fletcher et al. (1994), which is based on a 

large set of actual field residue data. The upper limit values from the nomograph represent the 

95th percentile of residue values from actual field measurements (Hoerger and Kenaga 1972). 

The Fletcher et al. (1994) modifications to the Kenaga nomograph are based on measured field 

residues from 249 published research papers, including information on 118 species of plants, 121 

pesticides, and 17 chemical classes. For input into T-REX, the default foliar dissipation half-life 

of 35 days will be used due to insufficient foliar dissipation rate data on ancymidol. If terrestrial 

plant toxicity data are available, EECs for terrestrial plants inhabiting dry and wetland areas are 

derived using TerrPlant (version 1.2.2, 12/26/2006). This model uses estimates of pesticides in 

runoff and in spray drift to calculate EECs. EECs are based upon solubility, application rate and 

minimum incorporation depth. 

The AgDRIFT spray drift model (v2.01; May, 2001) is used to assess exposures of organisms to 

ancymidol deposited on terrestrial habitats by spray drift. 

The Screening Imbibition Program (SIP v.1.0, Released June 15, 2010) was used to calculate an 

upper bound estimate of drinking water exposure alone using ancymidol’s solubility (650 mg/L 

at 20°C), the most sensitive acute and chronic avian toxicity endpoints (avian LD50 unavailable; 

avian NOAEC unavailable) and the most sensitive acute and chronic mammalian toxicity 

endpoints (laboratory rat LD50 >1,016 mg a.i./kg-bw; laboratory rat NOAEL unavailable). 

Appendix A provides a description of the model and assumptions in deriving an upper bound 

exposure estimate. Due to lack of data, SIP generated results for acute exposure to mammals, 

only. When more toxicity data become available, upper bound estimates of chronic drinking 

water exposure to mammals and acute and chronic exposure to birds will be generated. Drinking 

water exposure alone was determined to be a potential concern for mammals on an acute basis 

(see Appendix A for model results). This pathway will be explored further with the development 

of SIP v.2.0 in the Ecological Risk Assessment for ancymidol. Detailed information about the 

SIP v.1.0, as well as the tool, can be found on the EPA’s website at

http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial. 

STIR v.1.0, Screening Tool for Inhalation Risk, is used to provide an upper bound estimate of 

exposure of birds and mammals to pesticides through inhalation of spray drift or vapor. The 

upper bound exposure estimate requires a number of input parameters including the vapor 

pressure and molecular weight for the vapor-phase pesticide; additionally it requires the 

application rate and method of application (i.e., ground or aerial) for spray drift. The toxicity 

-20 of 46-
aspect of the tool requires an avian acute oral LD50 value (the model provides an estimate of 

avian inhalation toxicity in the absence of such data), the chemical specific avian allometric 

scaling factor to adjust toxicity based on body weight for the chemical (if available), the weight 

of the tested bird, a rat acute oral LD50 value, a rat acute inhalation LC50 value, the duration of 

the rat inhalation study, and the weight of the tested rat. This tool was designed for use in the 

Problem Formulation phase of the ecological risk assessment process to quantitatively evaluate 

the need for further analysis of inhalation as a potential pathway of concern for birds and 

mammals. Because the maximum application rates for ancymidol are unknown, a screening 

analysis of inhalation risk with STIR v.1.0 will be conducted at the final risk assessment stage of 

registration review once the maximum application rates for all outdoor uses have been 

determined. If further analysis of the inhalation exposure pathway is recommended, additional 

data will be requested to address uncertainty related to this route of exposure. Detailed 

information about the SIP v.1.0, as well as the tool, can be found on the EPA’s website 

(http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial). 

7.3. Measures of Effect 

 

Ecological effects data are used as measures of direct and indirect effects to biological receptors. 

As discussed previously, data are obtained from registrant-submitted studies or from literature 

studies identified by ECOTOX. The ECOTOX database provides more ecological effects data in 

an attempt to bridge existing data gaps. ECOTOX is a source for locating single chemical 

toxicity data and potential chemical mixture toxicity data for aquatic life, terrestrial plants, and 

wildlife. ECOTOX was created and is maintained by the USEPA, Office of Research and 

Development, and the National Health and Environmental Effects Research Laboratory's MidContinent Ecology Division. 

Also as discussed previously, information on the potential effects of ancymidol on non-target 

animals is also collected from the Ecological Incident Information System (EIIS; USEPA, 

2007c). The EIIS is a database containing adverse effect (typically mortality) reports on nontarget organisms where such effects have been associated with the use of pesticides. 

Incidents reported in the aggregate incident reports and the Avian Incident Monitoring System 

(AIMS) will also be searched. AIMS is a database administered by the American Bird 

Conservancy with partial funding from EPA). It contains publicly available data on reported 

avian incidents involving pesticides 

(http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm). 

Where available, sub-lethal effects observed in both registrant-submitted and open literature 

studies will be evaluated qualitatively. Such effects may include behavioral changes (e.g., 

lethargy and changes in coloration). Quantitative assessments of risks, though, are limited to 

those endpoints that can be directly linked to the Agency’s assessment endpoints of impaired 

survival, growth and reproduction. 

-21 of 46-
The assessment of risk for direct effects to non-target organisms makes the assumption that 

toxicity of ancymidol to birds is similar to terrestrial-phase amphibians and reptiles. The same 

assumption is made for fish and aquatic-phase amphibians. 

The acute measures of effect used for animals in this assessment are the LD50, LC50 and EC50. 

LD stands for "Lethal Dose", and LD50 is the amount of a material, given all at once, that is 

estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” 

and LC50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. 

EC stands for “Effective Concentration” and the EC50 is the concentration of a chemical that is 

estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic 

measures of exposure for listed and non-listed animals are the NOAEL/NOAEC and NOEC. 

NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested dose of 

a substance that has been reported to have no harmful (adverse) effects on test organisms. The 

NOAEC (i.e., “No-Observed-Adverse-Effect-Concentration”) is the highest test concentration at 

which none of the observed effects were statistically different from the control. The NOEC is 

the No-Observed-Effects-Concentration. For non-listed plants, only acute exposures are 

assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed plants either the 

NOAEC or EC05 is used. 

 

7.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effect characterizations to 

determine the potential ecological risk from the use of ancymidol and the likelihood of direct and 

indirect effects to non-target organisms in aquatic and terrestrial habitats. The exposure and 

effects data are integrated in order to evaluate potential adverse ecological effects on non-target 

species. For the assessment of ancymidol risks, the risk quotient (RQ) method is used to 

compare estimated exposure and measured toxicity values. Acute and chronic EECs are divided 

by acute and chronic toxicity values. The resulting RQs are then compared to the Agency’s 

Levels of Concern (LOC) (USEPA 2004). These criteria are used to indicate when ancymidol’s 

use, as directed on the labels, has the potential to cause adverse direct or indirect effects to nontarget organisms. In addition, incident data from EIIS, aggregate incident reports, and AIMS 

will be considered as part of the risk characterization. 

7.5. Deterministic and Probabilistic Assessment Methods 

The quantitative assessment of risk will primarily depend on the deterministic point estimatebased approach described in the risk assessment. Depending on the risk manager’s need for 

additional information regarding risk, an effort will be made to further qualitatively describe risk 

using probabilistic tools that the Agency has developed. These tools have been reviewed by 

FIFRA Scientific Advisory Panels (http://www.epa.gov/scipoly/sap/index.htm) and have been 

deemed as appropriate means of refining assessments where deterministic approaches have 

identified risks. 

-22 of 46-
7.6. Endangered Species Assessments 

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the 

Agency will evaluate risks to Federally-listed threatened and/or endangered (listed) species from 

registered uses of ancymidol. This assessment will be conducted in accordance with the 

Overview Document (USEPA, 2004), provisions of the ESA, and the Services’ Endangered 

Species Consultation Handbook (USFWS/NMFS, 1998). 

The assessment of effects associated with the registration of ancymidol is based on an action 

area. The action area is considered to be the area directly or indirectly affected by the federal 

action, as indicated by the exceedance of Agency Levels of Concern (LOCs) used to evaluate 

direct or indirect effects. The Agency’s approach to defining the action area under the provisions 

of the Overview Document (USEPA, 2004) considers the results of the risk assessment process 

to establish boundaries for that action area with the understanding that exposures below the 

Agency’s defined LOCs constitute a no-effect threshold. For the purposes of this assessment, 

attention will be focused on the footprint of the action (i.e., the area where ancymidol application 

occurs), plus all areas where offsite transport (i.e., spray drift, runoff, etc.) may result in potential 

exposure that exceeds the Agency’s LOCs. Specific measures of ecological effect that define the 

action area for listed species include any direct and indirect effects and/or potential modification 

of its critical habitat, including reduction in survival, growth, and reproduction as well as the full 

suite of sub-lethal effects available in the effects literature. Therefore, the action area extends to 

a point where environmental exposures are below any measured lethal or sub-lethal effect 

threshold for any biological entity at the whole organism, organ, tissue, and cellular level of 

organization. In situations where it is not possible to determine the threshold for an observed 

effect, the action area will be assumed to encompass the entire United States. 

7.7. Drinking Water Assessment 

If a drinking water assessment is warranted by the Health Effects Division (HED), a drinking 

water exposure assessment using up-to-date models and data will be completed during the 

registration review process. The drinking water assessment will incorporate model estimates of 

ancymidol residues of concern, including parent and any degradates of toxicological concern, in 

surface water and ground water. Concentrations of ancymidol and its residues of concern in 

surface water will be estimated using PRZM/EXAMS (see description in Section 7.2). Ground 

water exposure estimates for ancymidol and its residues of concern will be estimated using the 

Screening Concentration in Ground Water (SCI-GROW) model (v.2.3, July 2003) followed by a 

higher tier model if necessary. The drinking water assessment will also include a summary of 

available surface and ground water monitoring data. 

7.8. Preliminary Identification of Data Gaps 

The following two sections, 7.8.1. and 7.8.2., identify the remaining fate and effect studies 

needed to complete an environmental fate and ecological risk assessment in support of the 

registration review of the labeled outdoor uses of ancymidol. No fate and effect studies are 

-23 of 46-
needed to support registration review of the labeled indoor uses (i.e., seed treatment, 

greenhouse, and/or interiorscape uses). 

 7.8.1. Environmental Fate Data 

The studies submitted to fulfill environmental fate data requirements for labeled outdoor uses of 

ancymidol are not sufficient for an environmental exposure assessment. Eight guideline 

requirements have not been satisfied: (1) There is no acceptable photolytic degradation in water; 

(2) There is no acceptable photolytic degradation in soil; (3) The current supplemental aerobic 

soil metabolism study will be used for risk assessment purposes, however an additional 

acceptable study with multiple soils is required to fulfill the guideline and better understand the 

potential variability in the biotic degradation of ancymidol in terrestrial environment; (4) There 

is no acceptable anaerobic biotic degradation in soil; (5) There is no acceptable aerobic aquatic 

metabolism study in sediment; (6) There is no anaerobic aquatic metabolism study in sediment; 

(7) There is no acceptable terrestrial field dissipation study; (8) There is no bioaccumulation 

study. 

 

Table 6 identifies studies by MRID that offer data for each guideline requirement, as well as 

study classifications and whether or not further data are needed in order to support risk 

assessment (i.e., whether there is a data gap). Draft Data Call-In (DCI) tables for requested data 

are provided in APPENDIX B. 

TABLE 6. Environmental Fate Data Requirement Table for Ancymidol. 

OPPTS 

Guideline Data Requirement 

Submitted 

Studies 

(MRID) 

Classification Data Gap? Comment 

835.2120 Hydrolysis 417235-03 Acceptable No 

835.2240 Aqueous photolysis Nneo -- Yes 

835.2410 Soil photolysis None -- Yes 

835.4100 Aerobic soil 

metabolism 420530-01 Acceptable Yes 

Aerobic soil metabolism study was performed 

on one soil only. OSCPP requires multiple 

soils to reduce uncertainty. Three more 

studies are required. 

835.4200 Anaerobic soil 

metabolism None -- Yes Data requirements include both studies. 

835.4300 Aerobic aquatic 

metabolism None -- Yes 

Multiple deficiencies including inadequate 

duration of study and failure to demonstrate 

patterns of formation and decline of 

degradates. 

835.4400 Anaerobic aquatic 

metabolism None -- Yes 

Data are needed for two additional sediment 

systems, one each at a neutral and an acidic 

pH. 

835.1230 Adsorption/ 

desorption and 

leaching 

417235-02 Acceptable 

No 

Also includes ancillary data on aerobic soil 

metabolism. 

419137-01 Acceptable Also includes ancillary data on aerobic soil 

metabolism. 

-24 of 46-
OPPTS 

Guideline Data Requirement 

Submitted 

Studies Classification Data Gap? Comment 

(MRID) 

835.6100 

Terrestrial field 

dissipation 

None -- 

Yes 

A frozen storage stability study has not been 

submitted. 

Currently under review 

Freezer storage 

stability None -- 

Data from another study (MRID 43003434) 

show extracted residues decreased as a result 

of frozen storage prior to analysis. An 

acceptable freezer storage stability study using 

the soils used in the TFD studies is needed. 

Analytical method 

– soil None -- Yes 

Analytical method 

– water None -- Yes 

Analytical method 

- sediment None -- Yes 

850.1730 Fish 

bioconcentration None -- No 

Log Kow value of 1.91 indicates a low 

potential for ancymidol to bioconcentrate in 

fish (log Kow > 3); therefore a study is not 

required under 40 CFR part 158 Subpart G. 

7.8.2. Ecological Effects Data 

Only six (6) ecological effect data requirements have been fulfilled for the currently registered 

outdoor uses of ancymidol; 15 additional data gaps remain across aquatic and terrestrial plant 

and animal taxa (Tables 7-9). Data gaps include the following tests: avian acute oral, avian subacute dietary, avian reproduction, acute freshwater and estuarine/marine fish, acute 

estuarine/marine invertebrates, chronic freshwater fish and invertebrates, algae, and terrestrial 

plants. No chronic toxicity data on ancymidol has yet been submitted the Agency. Although not 

an ecological effects data gap, a chronic 2-generation toxicity study in mammals is also 

unavailable. The data gaps are discussed in detail below. Draft Data Call-In (DCI) tables for 

requested data are provided in APPENDIX B. 

 

-25 of 46-
TABLE 7. Available Ecological Effects Data for Terrestrial Animals Exposed to 

Ancymidol and Remaining Data Gaps.

Guideline Description MRID/ 

Accession 

Classification Data 

Gap? 

Comments 

850.2100 Avian acute oral 

toxicity – upland game 

or waterfowl species 

None Not applicable Yes

*Avian acute oral toxicity data 

are not available for 

passerines, which are required 

under the new 40 CFR Part 

158. Therefore, this is 

identified as a data gap. 

Avian acute oral 

toxicity – passerine 

species 

None Not applicable Yes* 

850.2200 Avian sub-acute 

dietary toxicity – 

upland game species 

41670602 Acceptable No 

Avian sub-acute 

dietary toxicity – 

waterfowl species 

None Not applicable Yes 

850.2300 Avian reproduction – 

upland game species None Not applicable Yes 

Avian reproduction – 

waterfowl species None Not applicable Yes

850.3020 Honeybee acute 

contact toxicity 43140504 Acceptable No 

 

-26 of 46-
TABLE 8. Available Ecological Effects Data for Aquatic Animals Exposed to Ancymidol 

and Remaining Data Gaps.

Guideline Description MRID/ 

Accession Classification Data Gap? Comments 

850.1075 

Acute freshwater fish 

– cold water species 41670603 Acceptable No * Toxicity data for freshwater fish and invertebrates, which 

are required, are not currently 

available. Therefore, these are 

identified as data gaps. 

**Conditional data 

requirement not triggered 

based on available ecotoxicity 

data, anticipated 

environmentally relevant 

concentrations, and use pattern 

criteria; Conditional data 

requirement will be 

reconsidered once additional 

fate and toxicity data, and 

application information have 

been submitted. 

Acute freshwater fish 

– warm water species None Not applicable Yes* 

850.1010 

Freshwater 

invertebrates – 

acute toxicity 

41670601 Acceptable No 

850.1075 Acute estuarine/ 

marine fish None Not applicable Yes* 

850.1025 

850.1055 

Acute estuarine/ 

marine mollusk None Not applicable Yes*

850.1035 

850.1045 

Acute estuarine/ 

marine invertebrate None Not applicable Yes*

850.1300 

Freshwater 

invertebrate – 

 life cycle test 

None Not applicable Yes* 

850.1350 

Saltwater invertebrates 

– 

life cycle test 

None Not applicable No** 

850.1400 Freshwater fish – 

early life stage test None Not applicable Yes* 

850.1400 Saltwater fish – 

early life stage test None Not applicable No** 

850.1500 Fish life cycle test None Not applicable No** 

850.1735 

850.1740 

Whole Sediment Acute 

Invertebrates None Not Applicable No** 

 

-27 of 46-
TABLE 9. Available Ecological Effects Data for Plants Exposed to Ancymidol and 

Remaining Data Gaps.

Guideline Description MRID Classification Data 

Gap? Comments 

850.4100 

Terrestrial Plant 

toxicity: Tier I seedling 

emergence 

None Not applicable No 

Tier I toxicity data for 

terrestrial plants are not 

required for known 

phytotoxicants , such as plant 

growth regulators 

850.4225 

Terrestrial Plant 

toxicity: Tier II seedling 

emergence 

None Not applicable Yes Study is required on the TEP 

(typical end-use product) 

850.4150 

Terrestrial Plant 

toxicity: Tier I 

vegetative vigor 

None Not applicable No 

Tier I toxicity data for 

terrestrial plants are not 

required for known 

phytotoxicants, such as plant 

growth regulators 

850.4250 

Terrestrial Plant 

toxicity: Tier II 

vegetative vigor 

None Not applicable Yes Study is required on the TEP 

(typical end-use product) 

850.5400 

Aquatic Plant Growth: 

algae – freshwater green 

alga 

43140502 Acceptable No Data were submitted on P. 

subcapitata using the TGAI. 

Aquatic Plant Growth: 

algae – freshwater 

diatom 

None Not applicable Yes 

Study is required with either 

the TGAI or TEP; EFED 

prefers a representative TEP 

Aquatic Plant Growth: 

algae – saltwater diatom None Not applicable Yes 

Study is required with either 

the TGAI or TEP; EFED 

prefers a representative TEP 

Aquatic Plant Growth: 

algae –Cyanobacteria None Not applicable Yes 

Study is required with either 

the TGAI or TEP; EFED 

prefers a representative TEP 

850.4400 Aquatic Plant Growth: 

vascular plants 43140501 Acceptable No Data were submitted on L. gibba using the TGAI 

Avian Acute Oral, Sub-acute Dietary, and Reproduction Toxicity Studies 

Acute avian oral toxicity data are not available for ancymidol. Avian acute oral toxicity data on 

passerines are required under the current 40 CFR Part 158 (July 1, 2009) data requirements for 

conventional pesticides (72 FR 60934; USEPA 2007d). The Part 158 data requirements specify 

that avian acute oral toxicity data (OCSPP Guideline 850.2100) be submitted for either an upland 

game or waterfowl species and a passerine species. Due to the reported sublethal effects 

(reduction in mean body weight) in bobwhite quail to ancymidol, adverse sub-acute dietary 

effects to birds have been demonstrated and risk to birds from ancymidol use is uncertain. EFED 

recommends requesting two avian acute oral studies at this time according to the data 

requirements for an outdoor use chemical. The registrant will need to submit a passerine study 

-28 of 46-
protocol for review by the Agency prior to initiation of the passerine study. EFED will assume 

risk to birds on an acute oral basis in the absence of these data. 

Under the 40 CFR Part 158 (July 1, 2009) data requirements for conventional pesticides, avian 

sub-acute dietary toxicity data are required on waterfowl and upland game species (OCSPP 

Guideline 850.2200). Currently, an acceptable study on the bobwhite quail (upland game) is 

available (MRID 41670602), which demonstrates effects to bobwhite on a sublethal basis. Data 

should also be submitted on a waterfowl species for guideline 850.2200 to test for differences in 

interspecies sensitivity to ancymidol on a subacute dietary basis. 

Under the 40 CFR Part 158 (July 1, 2009) data requirements for conventional pesticides, avian 

reproduction data are required on waterfowl and upland game species (OCSPP Guideline 

850.2300). Because no chronic data on birds have been submitted to date, EFED recommends 

requesting two avian reproduction studies according to the data requirements for an outdoor use 

chemical. EFED will assume risk to birds on a chronic basis in the absence of these data. 

Acute and Chronic Freshwater Invertebrate and Fish Toxicity Studies 

 

Two acute freshwater fish (OCSPP Guideline 850.1075) and one acute estuarine/marine fish are 

required for registration of pesticides with outdoor uses (CFR Part 158). Both a cold and warm 

water species of freshwater fish are required for testing; to date, only data on the rainbow trout 

(MRID 41670603), a cold water species, is available. The study on rainbow trout was conducted 

as a limit test with a resulting LD50 of > 99.2 mg a.i./L. Clinical signs of toxicity exhibited by 

fish at this concentration were labored respiration, prostration, and a distended ventral surface. 

Due to these effects, and because of the uncertainty in application rates and exposure levels, 

adverse effects to listed freshwater fish cannot currently be determined; however, because 

additional information labeled application rates are being requested in addition to data on a warm 

water fish species, a second acute freshwater fish study with a cold water species is not requested 

at this time. Acute data on freshwater invertebrates, estuarine/marine invertebrates, and 

estuarine/marine mollusks are also required for registration of pesticides with outdoor uses (CFR 

Part 158). Acceptable data on the freshwater invertebrate, Daphnia magna, have already been 

submitted. Data should be submitted for the remaining two acute fish (warm freshwater species 

and marine/estuarine species) and two acute invertebrate toxicity studies (at least one mollusk 

and one as specified by the 850.1035 or 850.1045 guidelines (i.e. a species of shrimp); in the 

absence of these data, EFED will presume risk to estuarine/marine fish and invertebrates on an 

acute exposure basis. 

Chronic toxicity studies for ancymidol with freshwater fish or invertebrates are not available at 

this time and are required for registration of pesticides with outdoor uses (CFR Part 158). EFED 

will assume risk to these taxa on a chronic basis in the absence of these data. Chronic toxicity 

studies for ancymidol with estuarine/marine fish or invertebrates are conditional requirements 

and are not triggered for ancymidol based on the available ecotoxicity data, the anticipated 

environmentally relevant concentrations, and use pattern criteria; based on this information, 

chronic risk to estuarine/marine fish and invertebrates will be determined in the final risk 

assessment. EFED reserves the right to request chronic toxicity studies on these taxa in the 

future once additional fate and ecotoxicity data, as well as application information have been 

-29 of 46-
submitted. A freshwater invertebrate life cycle test (Guideline 850.1300) and a freshwater fish 

early life stage test (Guideline 850.1400) should be submitted. 

Aquatic and Terrestrial Plant Toxicity Studies 

Aquatic plant toxicity studies and associated risk analysis of plants are required for registration 

of pesticides with outdoor uses. For known phytotoxicants, such as plant growth regulators, a 

Tier II aquatic vascular plant toxicity study (OCSPP Guideline 850.4400) and four Tier II nonvascular plant toxicity studies (OCSPP Guideline 850.5400) on either the TGAI or a TEP are 

required. The available Tier II vascular aquatic plant study with the TGAI using L. gibba, MRID 

43140501, was reviewed and fully meets OCSPP Guideline standards. Likewise, the available 

Tier II freshwater green alga toxicity study with the TGAI (MRID 43140502) is classified 

Acceptable. However, three more nonvascular plant studies are required, i.e., freshwater diatom, 

saltwater diatom, and a nitrifying cyanobacteria. Because ancymidol is a known phytotoxicant, 

EFED recommends requesting three additional toxicity studies on nonvascular aquatic plants. 

Because of the ingredients typically co-formulated with herbicides and plant growth regulators 

(e.g. surfactants), EFED prefers that these studies are conducted on a representative TEP (i.e.

ABIDETM or A-Rest* Solution®). EFED will assume risk to aquatic nonvascular plants in the 

absence of these data. 

Terrestrial plant toxicity studies are required for registration of pesticides with outdoor uses 

(CFR Part 158). For known phytotoxicants, such as plant growth regulators, Tier II vegetative 

vigor (OSCPP 850.4250) and Tier II seedling emergence (OCSPP 850.4225) studies are required 

on a TEP (i.e. ABIDETM or A-Rest* Solution®) to investigate the effects of the pesticide end-use 

product on the growth and survival of terrestrial plants. No data is currently available for these 

guidelines and the extent of risks to non-target (as well as target) terrestrial plants cannot be 

determined. Risk to terrestrial plants is assumed in the absence of data. 

-30 of 46-
8. References 

Hofmannova, Jana, Katerina Schwarzerova, Lenka Havelkova, Petra Borikova, Jan Petrasek, and 

Zdenek Opatrny, 2008. A novel, cellulose synthesis inhibitory action of ancymidol 

impairs plant cell expansion. Journal of Experimental Botany, Vol. 59, No.14:3963-3974. 

ChemBlink. 2011. Online database of chemicals from around the world (ancymidol structure) 

Accessed on January 21, 2011. Online at: http://www.chemblink.com/products/12771-

68-5.htm 

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, an instrument for estimating pesticide residues on 

plants. Environ. Tox. Chem. 13:1383-1391. 

Hoerger, F. and E. E. Kenaga. 1972. Pesticide Residues on Plants: Correlation of 

Representative Data as a Basis for Estimation of their Magnitude in the Environment. In

F. Coulston and F. Korte, eds., Environmental Quality and Safety: Chemistry, 

Toxicology, and Technology, Georg Thieme Publ., Stuttgart, West Germany, pp. 9-28. 

USEPA. 1995. Reregistration Eligibility Decision for Ancymidol: Division Director’s 

Concurrence Copy. U.S. Environmental Protection Agency, Office of Pesticide 

Programs. July 28, 1995. 

USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of 

Research and Development, Washington, D.C. EPA/630/R-95/002F. April 1998. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759 

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington DC. January 23, 2004. 

USEPA. 2007a. Ecological Incident Information System. 

http://www.epa.gov/espp/consultation/ecorisk-overview.pdf

USEPA. 2007b. ECOTOXicology Database. Office of Research and Development National 

Health and Environmental Effects Research Laboratory’s (NHEERL’s) Mid-Continent 

Ecology Division (MED). http://cfpub.epa.gov/ecotox/. 

USEPA. 2010. Ancymidol (108601): Screening Level Usage Analysis. U.S. Environmental 

Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Biological 

and Economic Analysis Division. Dec 01, 2010. 

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. 

Endangered Species Consultation Handbook: Procedures for Conducting Consultation 

and Conference Activities Under Section 7 of the Endangered Species Act. Final Draft. 

March 1998. 

-31 of 46-
USFWS/NMFS/NOAA.2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act 

Section 7 Consultation Regulations; Final Rule. Federal Register Volume 69. Number 

20.Pages 47731-47762. August 5, 2004. 

U.S. Geological Survey (USGS). 2010. Pesticide Use Maps. U.S. Geological Survey, National 

Water-Quality Assessment (NAWQA) Program, Pesticide National Synthesis Program. 

Accessed on January 26, 2011. Online at: 

http://water.usgs.gov/nawqa/pnsp/usage/maps/compound_listing.php?year=02

-32 of 46-
SUBMITTED ENVIRONMENTAL FATE STUDIES:

MRID: Citation: 

00162638 Day, E., 1986. Ancymidol Techincal Product chemistry Data: Report No. 

EWD8604. Unpublished study prepared by Lilly Research Laboratories. 

41723501 Kazee, B. (1990) Determination of Solubility of Ancymidol: Final Report: Lab. 

Project Number: SC900027. Unpublished study prepared by Battelle. 

41723502 Davis, M. (1990) Ancymidol: Adsorption/Desorption of Carbon 14 -Ancymidol 

on Soils by the Batch Equilibrium Method: Lab Project Number: SC900026. 

Unpublished study prepared by Battelle. 

41723503 Kazee, B. (1990) Hydrolysis of Ancymidol in Water: Lab Project Number: 

SC900028. Unpublished study prepared by Battelle. 

41821201 Chakrabarti, A. (1990) Vapor Pressure of Ancymidol Measured by the KnudsenEffusion/Weight Loss Method: Lab Project Number: ML-AL- 90-020336. 

Unpublished study prepared by Dow Chemical, Analytical Sciences Div. 

41913701 Zwick, T., Saxena, A.; Marsh, S. (1991) Mobility Study: Soil Column Leaching 

Study on a Soil Dosed With 14C-Ancymidol and Aged: LabProject Number: 

SC900025. Unpublished study prepared by Batelle Memorial Institute. 

42053001 Saxena, A., Malik, N., Lofthouse, T. (1991) Aerobic Soil Metabolism of 

Ancymidol: Lab Project Number: SC900021. Unpublished study prepared by 

Battelle Memorial Institute. 

SUBMITTED EFFECTS STUDIES:

MRID: Citation: 

00162642 Kehr, C.C., D.S. Negilski, T.L. Bridge, and T.F. Markey, 1986. The Acute Oral, 

Dermal, Ocular, and Inhalation Toxicity of A-rest® Solution, a Formulation (FN7086) Containing 0.0264% Ancymidol. Study IDs: R-O-286-85, B-D-204-85, BE-207-85, and R-H-099-85. Toxicity Division, Lilly Research Laboratories, 

Division of Eli Lilly and Company, Greenfield, IL. 44 p. 

41670601 Murray, A.; Seacat, J.; Brown, G. (1990) The Acute Toxicity of An- cymidol to 

Daphnia magna in a Static Test System: Lab Project Number: C00690. 

Unpublished study prepared by Lilly Research Laboratories. 35 p. 

41670602 Murray, A.; Seacat, J.; Grothe, D. (1990) The Toxicity of Ancymi- dol to Juvenile 

Bobwhite in a 5-Day Dietary Study: Lab Project Number: A00790. Unpublished 

study prepared by Lilly Research Laboratories. 40 p. 

-33 of 46-
41670603 Murray, A.; Seacat, J.; Brown, G. (1990) The Acute Toxicity of An- cymidol to 

Rainbow Trout (Salmo gairdneri) in a Static Test System: Lab Project Number: 

F02890. Unpublished study prepared by Lilly Research Laboratories. 38 p. 

43140501 Milazzo, D.; Servinski, M.; Hugo, J.; et al. (1994) Ancymidol: Toxicity to the 

Aquatic Plant, Duckweed, Lemna gibba L: Lab Project Number: DECO/ES/2725. 

Unpublished study prepared by The Dow Chemical Environmental Toxicology & 

Chemistry Research Lab. 31 p. 

43140502 Milazzo, D.; Servinski, M.; Hugo, J.; et al. (1994) Ancymidol: Toxicity to the 

Green Alga, Selenastrum capricornutum Printz: Lab Project Number: ES/2724. 

Unpublished study prepared by The Dow Chemical Environmental Toxicology & 

Chemistry Research Lab. 31 p. 

43140504 Palmer, S.; Beavers, J. (1993) Ancymidol: An Acute Contact Toxicity Study with 

the Honey Bee: Lab Project Number: 103/402: ES/2687. Unpublished study 

prepared by Wildlife International Ltd. 21 p. 

42480601 Wright, F.L., R.G. Poulsen, and R.L. St. Clair, 1992. The Acute Toxicity of 

Ancymidol (Compound 069231) Administered Orally to Fischer 344 Rats. 

Laboratory Project ID: R23391. Performed by Lilly Research Laboratories, 

Division of Eli Lilly and Company, Greenfield, IN. Submitted by DowElanco, 

Indianapolis, IN. Study Completed August 31, 1992. 

47331303 Farkas, Beáta, 2007. Acute Oral Toxicity Study (Acute Toxic Class Method) of 

Test Item Ancymidol (0.0264% SL Formulation in Rats. Test Performed by LAB 

International Research Centre Hungary Ltd. H-8200 Veszprém, Szabadságpuszta. 

Lab Study No: 07/395-001P. Study Sponsored by Fine Agrochemicals Ltd. 

Wocester, Worcestershire, UK. 

 

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APPENDIX A: SIP v.1.0 Description, Assumptions, Inputs and Outputs 

SIP v.1.0 provides an upper bound estimate of exposure of birds and mammals to pesticides through 

drinking water alone. This model is intended for use in problem formulation to determine whether or not 

drinking water exposure alone is a potential pathway of concern. This does not aggregate drinking water 

exposure with other exposure routes (i.e., diet, inhalation, dermal). 

Assumptions:

 

SIP employs the following conservative assumptions to derive upper bound exposure 

estimates: 

1) The chemical concentration in drinking water is at the solubility limit in water (at 25oC). 

2) The assessed animals obtain 100% of their daily water needs through drinking water. 

3) The daily water need is equivalent to the daily water flux rate as calculated by Nagy and 

Peterson (1988). 

4) The body weight of the assessed bird is equivalent to the smallest generic bird modeled in 

T-REX (i.e., 20 g). This assumption results in the highest ratio of exposure to toxicity for the 3 

assessed avian body weights of T-REX (i.e., 20, 100, 1000 g). 

5) The body weight of the assessed mammal is equivalent to the largest generic mammal 

modeled in T-REX (i.e., 1000 g). This results in the highest ratio of exposure to toxicity for the 3 

assessed mammalian body weights of T-REX (i.e., 15, 35, 1000 g). 

Table 1. Inputs 

Parameter Value 

Chemical name Ancymidol 

Solubility (in water at 25oC; mg/L) 650 

 

Mammalian LD50 (mg/kg-bw) 1016 

Mammalian test species laboratory rat 

Body weight (g) of "other" mammalian species 

 

Mammalian NOAEL (mg/kg-bw) 0 

Mammalian test species laboratory rat 

Body weight (g) of "other" mammalian species 

 

Avian LD50 (mg/kg-bw) 0 

Avian test species mallard duck 

Body weight (g) of "other" avian species 

Mineau scaling factor 1.15 

 

Mallard NOAEC (mg/kg-diet) 0 

Bobwhite quail NOAEC (mg/kg-diet) 0 

NOAEC (mg/kg-diet) for other bird species 0 

Body weight (g) of other avian species 0 

NOAEC (mg/kg-diet) for 2nd other bird species 0 

Body weight (g) of 2nd other avian species 0 

 

 

 

 

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Table 2. Mammalian Results 

Parameter Acute Chronic 

Upper bound exposure (mg/kg-bw) 111.8000 111.8000 

Adjusted toxicity value (mg/kg-bw) 781.4671 0.0000 

Ratio of exposure to toxicity 0.1431 0.0000 

Conclusion* 

Exposure through 

drinking water alone 

is a potential concern 

for mammals 

Due to insufficient data, 

risk cannot be precluded 

 

Table 3. Avian Results 

Parameter Acute Chronic 

Upper bound exposure (mg/kg-bw) 526.5000 526.5000 

Adjusted toxicity value (mg/kg-bw) 0.0000 0.0000 

Ratio of exposure to acute toxicity 0.0000 0.0000 

Conclusion* 

Due to insufficient 

data, risk cannot be 

precluded 

Due to insufficient data, 

risk cannot be precluded 

 

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. 

Therefore, when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through 

drinking water may contribute to a total exposure that has potential for effects to non-target animals. 

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APPENDIX B: Data Call-In Tables 

The Environmental Fate and Effects Division (EFED) has completed a Data Call-In (DCI) table 

for the ancymidol environmental fate and effects data gaps identified in Registration Review. 

The attached DCI table, which includes the guideline number and study title for required data, 

also provides a rationale for requiring the data, an explanation of how the data will be used, and a 

brief description of how the data could impact the Agency’s future decision-making. 

Guideline Number: 835.2240

Study Title: Photodegradation in water

Rationale for Requiring the Data

Acceptable data on the photodegradation in water of ancymidol are required under 40 CFR Part 158, 

Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. Currently, there are no 

submitted studies that satisfy the guideline. Therefore, the Agency has a limited understanding of the 

how ancymidol behaves in aquatic environments in presence of light. Photodegradation studies 

determine the potential to degradate in when exposed to sunlight. During these studies, data are also 

collected concerning the identity, formation and persistence of major degradates. Depending on how 

quickly, to what extent, and to which transformation products the compound degrades, ancymidol may or 

may not pose a potential for surface water contamination. Because photodegradation of ancymidol in 

water is not well understood, the Agency is requiring an OCSPP guideline-compliant photodegradation in 

water study.

Practical Utility of the Data

How will the data be used?

Photolytic degradation data will facilitate a better understanding of the fate of ancymidol residues in 

aquatic environment. If data indicate that degradation in water occurs rapidly and produces nontoxic 

transformation products, then the Agency could potentially determine that ancymidol residues of concern 

do not persist in aquatic systems. If data indicate that degradation is not appreciable in aquatic systems or 

that the transformation products are of similar or higher toxicity than the parent compound, then the 

Agency could conclude that ancymidol residues of concern persist in aquatic systems. 

How could the data change the Agency’s decision or impact the Agency’s future decision-making? 

In the absence of the requested data, ancymidol photolytic degradation half-lives will be conservatively 

assumed stable. If the required data indicate that ancymidol is rapidly degrade in presence of sunlight to 

nontoxic degradation products, then risk assessment conclusions and associated labeled use precautions 

and/or restrictions could be made less restrictive.

Guideline Number: 835.2410

Study Title: Photodegradation in soil

Rationale for Requiring the Data

Acceptable data on the photodegradation in soil of ancymidol are required under 40 CFR Part 158, 

Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. Currently, there are no 

submitted studies that satisfy the guideline. Therefore, the Agency has a limited understanding of the 

how ancymidol behaves in soil in presence of sunlight. This study provides data on photolytic 

degradation and on nature and persistence of photoproducts formed on soil surface through photolysis. 

During these studies, data are also collected concerning the identity, formation and persistence of major 

degradates. Depending on how quickly, to what extent, and to which transformation products the 

compound degrades, ancymidol may or may not pose a potential exposure on soil surface. Because 

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photo-degradation of ancymidol in soil is not well understood, the Agency is requiring an OCSPP 

guidelinecompliant photodegradation in soil study.

Practical Utility of the Data

How will the data be used?

Photolytic degradation data will facilitate a better understanding of the fate of ancymidol residues in soil 

surface. If data indicate that degradation in soil surface occurs rapidly and produces nontoxic 

transformation products, then the Agency could potentially determine that ancymidol residues of concern 

do not persist in soil surface. If data indicate that degradation is not appreciable in soil surface or that the 

transformation products are of similar or higher toxicity than the parent compound, then the Agency 

could conclude that ancymidol residues of concern persist in terrestrial environment. 

How could the data change the Agency’s decision or impact the Agency’s future decision-making? 

In the absence of the requested data, ancymidol photolytic degradation half-lives will be conservatively 

assumed stable. If the required data indicate that ancymidol is rapidly degrade in presence of sunlight to 

nontoxic degradation products, then risk assessment conclusions and associated labeled use precautions 

and/or restrictions could be made less restrictive.

Guideline Number: 835.4100

Study Title: Aerobic Soil Metabolism

Rationale for Requiring the Data

Four acceptable data on the aerobic soil metabolism of ancymidol are required under 40 CFR Part 158, 

Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. Currently, one submitted 

studies that satisfy the guideline to evaluate the rate of transformation of ancymidol in soil. Therefore, 

the Agency has a limited understanding of how ancymidol behaves in aerobic soil environments once 

applied. Because ancymidol degradation in aerobic soil systems is not fully understood, the Agency is 

requiring an OCSPP guideline-compliant additional aerobic soil metabolism studies. 

Practical Utility of the Data

How will the data be used?

Additional aerobic soil metabolism data will facilitate a better understanding of the fate of ancymidol 

residues in soil. If data indicate that degradation in aerobic conditions occurs rapidly and produces 

nontoxic transformation products, then the Agency could potentially determine that ancymidol residues 

of concern do not persist in these systems. If data indicate that degradation is not appreciable in aerobic 

soil systems or that the transformation products are of similar or higher toxicity than the parent 

compound, then the Agency could conclude that ancymidol residues of concern persist in aerobic soil 

systems. 

How could the data change the Agency’s decision or impact the Agency’s future decision-making? 

In the absence of the requested additional data, currently available aerobic soil metabolism half-live for 

ancymidol will be multiplied by to reduce uncertainty. If the required data indicate that ancymidol in 

aerobic soil environments is rapidly biodegraded to nontoxic degradation products, then risk assessment 

conclusions and associated labeled use precautions and/or restrictions could be made less restrictive.

Guideline Number: 835.4200

Study Title: Anaerobic Soil Metabolism

Rationale for Requiring the Data

Acceptable data on the anaerobic soil metabolism of ancymidol are required under 40 CFR Part 158, 

Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. Currently, there are no 

submitted studies that satisfy the guideline. Therefore, the Agency has a limited understanding of how 

ancymidol behaves in anaerobic soil environments once applied. Depending on how quickly, to what 

-38 of 46-
extent, and to which transformation products the compound degrades, ancymidol may or may not pose a 

potential for ground water contamination. Because ancymidol degradation in anaerobic soil systems is 

not well understood, the Agency is requiring an OCSPP guideline-compliant anaerobic soil metabolism 

study.

Practical Utility of the Data

How will the data be used?

Anaerobic soil metabolism data will facilitate a better understanding of the fate of ancymidol residues in 

subsurface soil, and anaerobic sediments. If data indicate that degradation in anaerobic conditions occurs 

rapidly and produces nontoxic transformation products, then the Agency could potentially determine that 

ancymidol residues of concern do not persist in these systems. If data indicate that degradation is not 

appreciable in anaerobic systems or that the transformation products are of similar or higher toxicity than 

the parent compound, then the Agency could conclude that ancymidol residues of concern persist in 

anaerobic soil systems. 

How could the data change the Agency’s decision or impact the Agency’s future decision-making? 

In the absence of the requested data, ancymidol anaerobic soil metabolism half-lives will be 

conservatively assumed stable. If the required data indicate that ancymidol in anaerobic soil 

environments is rapidly biodegraded to nontoxic degradation products, then risk assessment conclusions 

and associated labeled use precautions and/or restrictions could be made less restrictive.

Guideline Number: 835.4300

Study Title: Aerobic Aquatic Metabolism

Rationale for Requiring the Data

Acceptable data on the aerobic aquatic metabolism of ancymidol in two sediment systems are required 

under 40 CFR Part 158, Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. No 

aerobic aquatic metabolism study was submitted. The Agency has a limited understanding of how 

ancymidol behaves in aerobic aquatic environments once applied. Data are needed for two sedimentwater systems conducted (one each) at neutral and acidic pHs. 

Practical Utility of the Data

How will the data be used?

Aerobic aquatic metabolism data will facilitate a better understanding of the fate of ancymidol residues in 

water. If data indicate that degradation in aerobic conditions occurs rapidly in neutral and acidic aquatic 

systems and produces nontoxic transformation products, then the Agency could potentially determine that 

ancymidol residues of concern do not persist in these systems. If data indicate that degradation is not 

appreciable in aquatic systems or that the transformation products are of similar or higher toxicity than 

the parent compound, then the Agency could conclude that ancymidol residues of concern persist in 

acidic aquatic systems under anaerobic conditions. 

How could the data change the Agency’s decision or impact the Agency’s future decision-making? 

In the absence of the requested data, ancymidol aerobic aquatic metabolism half-lives will be 

conservatively assumed to be stable at a neutral pH, or less conservatively at two times the aerobic soil 

metabolism half-life modeling input value. If the required data indicate that ancymidol in aerobic aquatic 

environments is rapidly biodegraded to nontoxic degradation products, then risk assessment conclusions 

and associated labeled use precautions and/or restrictions could be made less restrictive. 

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Guideline Number: 835.4400 

Study Title: Anaerobic Aquatic Metabolism

Rationale for Requiring the Data

Acceptable data on the anaerobic aquatic metabolism of ancymidol are required under 40 CFR Part 158, 

Subpart N (revised July 1, 2009) for labeling that includes terrestrial uses. Currently, there are no 

submitted studies that satisfy the guideline. The Agency has a limited understanding of how ancymidol 

behaves in anaerobic aquatic environments once applied. Thus, the Agency is requiring an OCSPP 

guideline-compliant anaerobic aquatic metabolism study with two systems, one each at a neutral pH and 

one at an acidic pH. 

Practical Utility of the Data

How will the data be used?

Anaerobic aquatic metabolism data will facilitate a better understanding of the fate of ancymidol residues 

in water. If data indicate that degradation in anaerobic conditions occurs rapidly in acidic and/or neutral 

aquatic systems and produces nontoxic transformation products, then the Agency could potentially 

determine that ancymidol residues of concern do not persist in these systems. If data indicate that 

degradation is not appreciable in aquatic systems or that the transformation products are of similar or 

higher toxicity than the parent compound, then the Agency could conclude that ancymidol residues of 

concern persist in acidic aquatic systems under anaerobic conditions. 

How could the data change the Agency’s decision or impact the Agency’s future decision-making? 

In the absence of the requested data, ancymidol anaerobic aquatic metabolism half-lives will be 

conservatively assumed to be stable at a neutral pH If the required data indicate that ancymidol in 

anaerobic aquatic environments is rapidly biodegraded to nontoxic degradation products, then risk 

assessment conclusions and associated labeled use precautions and/or restrictions could be made less 

restrictive.

Guideline Number: 850.2100 

Study Title: Avian Acute Oral Toxicity Test 

Rationale for Requiring the Data 

Acceptable avian acute oral toxicity data were not submitted for exposures of either bobwhite quail or 

mallard ducks to ancymidol; additionally, data are not available for a passerine species, which is now 

required under the 40 CFR Part 158 (Oct. 26, 2007) data requirements for conventional pesticides. The 

new Part 158 data requirements specify that acute avian oral toxicity data be submitted for either mallard 

duck or bobwhite quail and a passerine species. Therefore, an avian oral toxicity test is required for 

either mallard duck or bobwhite quail and a passerine species, as specified in 40 CFR Part 158. A 

passerine study protocol must be submitted for review by the Agency prior to initiation of this study. 

Practical Utility of the Data 

How will the data be used? 

Avian acute oral toxicity data will be used to determine the lethal dose of ancymidol to birds on a body 

weight basis. Acute oral toxicity information accounts for eating differences among birds, which cannot 

be estimated based on the available subacute dietary data for ancymidol. Additionally, data on avian 

species in two different taxa will determine whether there are differences in sensitivity to ancymidol 

between passerines and upland game or waterfowl species. If oral acute toxicity data are not submitted, 

risk will be assumed for all avian species. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that ancymidol “may affect” listed birds directly (and listed species from other taxa indirectly), 

and use of ancymidol and its formulated products may need to be restricted in areas where listed species 

could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in 

coming into compliance with the Endangered Species Act and could result in use restrictions for 

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ancymidol use that are unnecessarily severe. 

Guideline Number: 850.2200 

Study Title: Avian Subacute Dietary Toxicity Test 

Rationale for Requiring the Data 

Acceptable avian subacute dietary toxicity data were submitted for exposures of bobwhite quail to 

ancymidol; no data are available for exposures of mallard duck to ancymidol. Based on the results of the 

available bobwhite quail study, the LC50 > 5192 mg a.i/kg diet and the NOAEC = 2638 mg a.i/kg diet due 

to reductions in body weight. A second subacute dietary study on mallard duck is required for pesticides 

with outdoor uses, as specified in 40 CFR Part 158. 

Practical Utility of the Data 

How will the data be used? 

Avian subacute dietary toxicity data for mallard duck will be used to refine the screening-level 

assessment by determining whether there are differences in avian species sensitivity to ancymidol 

between upland game and waterfowl species. If subacute dietary toxicity data are not submitted, risk will 

be assumed for certain avian species. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that ancymidol “may affect” listed birds directly (and listed species from other taxa indirectly), 

and use of ancymidol and its formulated products may need to be restricted in areas where listed species 

could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in 

coming into compliance with the Endangered Species Act and could result in use restrictions for 

ancymidol use that are unnecessarily severe. 

Guideline Number: 850.2300 

Study Title: Avian Reproduction Test 

Rationale for Requiring the Data

Under the 40 CFR Part 158 (July 1, 2009) data requirements for conventional pesticides, avian 

reproduction data are required on waterfowl and upland game species (OCSPP Guideline 850.2300). No 

data are available to assess chronic or reproductive effects of ancymidol exposure to any species of bird. 

Based on the results of the available bobwhite quail dietary study, the LC50 > 5192 mg a.i/kg diet and the 

NOAEC = 2638 mg a.i/kg diet due to reductions in body weight. These sublethal effects suggest that 

birds may be sensitive to ancymidol on a reproductive or chronic basis. Therefore, two avian onegeneration reproduction studies of bobwhite quail and mallard duck are recommended.

Practical Utility of the Data

How will the data be used?

Due to lack of data, chronic risk to birds has not been quantitatively assessed. Neither has 

chronic risk to mammals, which may have provided inferences into potential chronic effects in 

birds. The avian reproduction studies are needed to allow the Agency to quantify the potential for 

chronic risk, as measured by effects on reproduction and hatchling survival, from the use of ancymidol. 

Without this data, chronic risk to birds will be assumed for outdoor ancymidol uses.

How could the data impact the Agency’s future decision-making?

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that ancymidol “may affect” listed birds, reptiles, and terrestrial-phase amphibians directly 

(and listed species from other taxa indirectly), and use of ancymidol and its formulated products may 

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need to be restricted in areas where listed species could be exposed. The lack of these data will limit the 

flexibility the Agency and registrants have in coming into compliance with the Endangered Species Act 

and could result in use restrictions for ancymidol use that are unnecessarily severe.

Guideline Number: 850.1025 

Study Title: Estuarine/marine Mollusk (Oyster)Acute Toxicity Test (Shell Deposition) 

or 

Guideline Number: 850.1055 

Study Title: Bivalve acute (embryo-larval) EC50

Rationale for Requiring the Data

The CFR Part 158 data requirements specify that acute toxicity data on estuarine/marine mollusks are 

required for the registration of pesticides with outdoor uses. Scientifically valid acute toxicity data are 

not available for this taxon. Either an acute estuarine/marine oyster (OCSPP 850.1025) or 

estuarine/marine bivalve (OCSPP 850.1055) toxicity test is requested at this time. 

Practical Utility of the Data

How will the data be used?

Acute freshwater invertebrate toxicity data will be used to determine the potential for ancymidol to affect 

mollusk and other invertebrate species in saltwater environments. Marine/estuarine invertebrates are 

likely to be exposed to ancymidol because of its use in nurseries. The data will inform the current risk 

assessment for estuarine/marine invertebrates and will improve the Agency’s understanding of the 

potential effects of ancymidol on aquatic animals. In the absence of data specific for these invertebrates, 

risk to freshwater invertebrates will be presumed.

How could the data impact the Agency’s future decision-making?

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that ancymidol “may affect” listed freshwater invertebrates directly (and listed species from 

other taxa indirectly), and use of ancymidol and its formulated products may need to be restricted in areas 

where listed species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for ancymidol use that are unnecessarily severe.

Guideline Number: 850.1035

Study Title: Mysid Acute Toxicity Test 

or 

Guideline Number: 850.1045

Study Title: Penaeid Acute Toxicity Test

Rationale for Requiring the Data

Under the 40 CFR Part 158 (July 1, 2009), data are required on an estuarine/marine invertebrate other 

than a mollusk for pesticides with outdoor uses. The data will inform the current risk assessment for 

estuarine/marine invertebrates and will improve the Agency’s understanding of the potential effects of 

ancymidol on aquatic animals. As a result, one freshwater invertebrate life-cycle study on mysid or 

penaeid shrimp, OCSPP 850.1035 or 8501045, respectively, is required to support all outdoor use 

patterns. 

Practical Utility of the Data

How will the data be used?

The data would allow the Agency to quantify the potential for risk to saltwater invertebrates. 

Marine/estuarine invertebrates are likely to be exposed to ancymidol because of its use in nurseries. 

Because of the lack of marine/estuarine toxicity data, the Agency is unable to definitively determine 

whether ancymidol exposure will pose a risk to aquatic invertebrates inhabiting marine/estuarine water 

bodies. In the absence of data specific for these invertebrates, risk to freshwater invertebrates will be 

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presumed.

How could the data impact the Agency’s future decision-making?

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that ancymidol “may affect” listed freshwater invertebrates directly (and listed species from 

other taxa indirectly), and use of ancymidol and its formulated products may need to be restricted in areas 

where listed species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for ancymidol use that are unnecessarily severe.

Guideline Number: 850.1075

Study Title: Fish Acute Toxicity Test, Freshwater

Rationale for Requiring the Data

Acceptable freshwater fish acute toxicity data were submitted for exposures of rainbow trout, a cold 

water species, to ancymidol; data were not submitted for a warm water species, required under the 40 

CFR Part 158 (July 1, 2009) data requirements for conventional pesticides. The available data show that 

test fish exhibited sublethal effects at the limit dose. A second dose-response study on a warm water 

species should be submitted to the Agency under OCSPP Guideline 850.1075. 

Practical Utility of the Data

How will the data be used?

Acute freshwater fish toxicity data with a warm water species will be used to refine the screening-level 

assessment by determining whether there are differences in fish species sensitivity to ancymidol. If acute 

toxicity data are not submitted, risk may be assumed for listed freshwater fish species. 

How could the data impact the Agency’s future decision-making?

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that ancymidol “may affect” listed freshwater invertebrates directly (and listed species from 

other taxa indirectly), and use of ancymidol and its formulated products may need to be restricted in areas 

where listed species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for ancymidol use that are unnecessarily severe.

Guideline Number: 850.1075

Study Title: Fish Acute Toxicity Test, Estuarine/Marine

Rationale for Requiring the Data

The CFR Part 158 data requirements specify that acute toxicity data on estuarine/marine fish are required 

for the registration of pesticides with outdoor uses. No data has been submitted on the acute exposure of 

ancymidol to estuarine/marine fish. A fish acute toxicity test under OCSPP Guideline 850.1075 with an 

estuarine/marine fish species is requested at this time. 

Practical Utility of the Data

How will the data be used?

The data would allow the Agency to quantify the potential for risk to saltwater fish. Marine/estuarine 

fish are likely to be exposed to ancymidol because of its use in nurseries. Because of the lack of 

marine/estuarine toxicity data, the Agency is unable to definitively determine whether ancymidol 

exposure will pose a risk to fish inhabiting marine/estuarine water bodies. In the absence of data specific 

for this taxon, risk to estuarine/marine fish will be presumed.

How could the data impact the Agency’s future decision-making?

If future endangered species risk assessments are performed without these data, the Agency would have 

to assume that ancymidol “may affect” listed freshwater invertebrates directly (and listed species from 

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other taxa indirectly), and use of ancymidol and its formulated products may need to be restricted in areas 

where listed species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for ancymidol use that are unnecessarily severe.

Guideline Number: 850.4225

Study Title: Terrestrial Plant Seedling Emergence Test (Tier II) 

Rationale for Requiring the Data

Terrestrial plant toxicity studies are required for registration of pesticides with outdoor uses (CFR Part 

158). For known phytotoxicants, a Tier II seedling emergence study (OCSPP 850.4225) is required on a 

TEP (i.e. ABIDETM or A-Rest* Solution®) to investigate the effects of the pesticide end-use product 

on the emergence, growth, and survival of terrestrial plants. No data is currently available for this 

guideline and the extent of risks to non-target terrestrial plants cannot be determined. 

Practical Utility of the Data

How will the data be used?

Tier II seedling emergence data for terrestrial plants will be used to determine the potential for ancymidol 

to affect non-target plant species in the terrestrial environment and to reduce uncertainties associated with 

the current risk assessment to terrestrial plants. In the absence of data specific to the emergence and 

initial growth life stages, the spatial extent of risk to terrestrial plants off the application site cannot be 

determined.

How could the data impact the Agency’s future decision-making?

Because plants form the basis of most habitats and significantly contribute to overall environmental 

quality, a solid understanding of the potential risks to terrestrial plants is essential for sound 

environmental management. If the data indicate that registered ancymidol usage poses an even greater 

risk of adverse effects to non-target terrestrial plants above the Agency Level of Concern, the Agency 

may further explore decision options to mitigate this risk. The lack of data on the spatial extent of risk 

will limit the flexibility the Agency and registrants have in coming into compliance with the Endangered 

Species Act. 

Guideline Number: 850.4250

Study Title: Terrestrial Plant Vegetative Vigor Test (Tier II)

Rationale for Requiring the Data

Terrestrial plant toxicity studies and associated risk analysis of plants are required for registration of 

pesticides with outdoor uses (CFR Part 158). For known phytotoxicants, a Tier II vegetative vigor study 

(OSCPP 850.4250) is required on a TEP (i.e. ABIDETM or A-Rest* Solution®) to investigate the 

effects of the pesticide end-use product on the growth and survival of terrestrial plants. No data is 

currently available for this guideline and the extent of risk of spray drift to non-target terrestrial 

plants cannot be determined. 

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Practical Utility of the Data

How will the data be used?

Tier II vegetative vigor data for terrestrial plants will be used to determine the potential for ancymidol to 

affect non-target plant species in the terrestrial environment and to reduce uncertainties associated with 

the current risk assessment to terrestrial plants. In the absence of data specific to the emergence and 

initial growth life stages, the spatial extent of risk to terrestrial plants off the application site cannot be 

determined.

How could the data impact the Agency’s future decision-making?

Because plants form the basis of most habitats and significantly contribute to overall environmental 

quality, a solid understanding of the potential risks to terrestrial plants is essential for sound 

environmental management. If the data indicates that registered ancymidol usage poses an even greater 

risk of adverse effects to non-target terrestrial plants above the Agency Level of Concern, the Agency 

may further explore decision options to mitigate this risk. The lack of data on the spatial extent of risk 

will limit the flexibility the Agency and registrants have in coming into compliance with the Endangered 

Species Act. 

Guideline Number: 850.5400 

Algal Toxicity Tier II Study

Rationale for Requiring the Data

Aquatic (both vascular and non-vascular species) toxicity studies and associated risk analysis of plants 

are required for registration of pesticides with outdoor uses (CFR Part 158). For known phytotoxicants, 

four Tier II nonvascular toxicity studies (OCSPP Guideline 850.5400) on either the TGAI or 

TEP are required. There is currently only one available study on freshwater green algae for the TGAI 

to determine levels of ancymidol that could result in effects to aquatic non-vascular plants. Three more 

nonvascular plant studies are required as specified in 40 CFR Part 158; these include a study on a 

freshwater diatom, saltwater diatom, and nitrifying cyanobacteria. Because of potential changes in 

novaluron’s bio-availability in water while formulated as an end-use product, EFED prefers these studies 

be conducted with a representative TEP (i.e. ABIDETM or A-Rest* Solution®) instead of the TGAI. 

Practical Utility of the Data

How will the data be used? 

This Tier II data will be used to adequately assess risks to aquatic nonvascular plants from ancymidol 

exposure. The data will reduce uncertainties associated with the current risk assessment for aquatic 

nonvascular plants based currently on only one species and will improve our understanding of the 

potential effects of ancymidol use to aquatic plants. In the absence of data specific to freshwater diatoms, 

saltwater diatoms, and a nitrifying cyanobacteria, the extent of effects to nonvascular plants would be 

unknown and the extent of risk to aquatic plants could potentially be underestimated. Because plants 

form the basis of most habitats and significantly contribute to overall environmental quality, a solid 

understanding of the potential risks to aquatic plants is essential for sound environmental management. 

As a known phytotoxicant, risk to aquatic plants from ancymidol use would be presumed in the absence 

of these data. The data will also be used in determining whether a “may affect” to Federally-listed 

threatened and endangered species is likely under the Endangered Species Act.

How could the data impact the Agency’s future decision-making?

Without additional nonvascular aquatic plant toxicity data for ancymidol, the Agency cannot determine 

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with certitude the levels of ancymidol that result in effects to nonvascular aquatic plants. If this data is 

not available, the extent of risk to aquatic nonvascular plants from ancymidol use could potentially be 

underestimated. The lack of these data will limit the flexibility the Agency and registrants have in 

coming into compliance with the Endangered Species Act, and could result in severe use restrictions for 

ancymidol, a known phytotoxicant, which may otherwise be avoided.