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Environmental Fate and Ecological Risk Assessment for the 

Reregistration of Chlormequat Chloride 

N

CH3

CH3

C CH3 H2C

H2

Cl Cl

+

Cycocel® CAS No. 00999-81-5 PC Code 018101 

Prepared by: 

Brian D. Kiernan, Biologist 

Marietta Echeverria, Environmental Scientist 

Reviewed by: 

Thomas Steeger, Ph.D., Senior Biologist 

R. David Jones, Ph.D., Senior Agronomist 

Elizabeth Behl, Branch Chief 

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
2 of 66 

I. Executive Summary.......................................................................................................................... 4 

A. Nature of the Chemical Stressor .................................................................................. 4 

B. Conclusions – Exposure Characterization ................................................................... 4 

C. Conclusions – Effects Characterization....................................................................... 4 

D. Potential Risks to Non-target Organisms..................................................................... 4 

E. Data Gaps and Uncertainties........................................................................................ 5 

II. Problem Formulation....................................................................................................................... 6 

A. Stressor Source and Distribution ................................................................................. 6 

1. Source and Intensity......................................................................................... 6 

2. Physical/Chemical/Fate and Transport Properties........................................... 6 

3. Pesticide Type, Class, and mode of Action ..................................................... 7 

4. Usage Overview............................................................................................... 7 

B. Receptors ..................................................................................................................... 7 

C. Assessment Endpoints ................................................................................................. 7 

D. Conceptual Model........................................................................................................ 9 

5. Diagram............................................................................................................ 9 

6. Risk Hypothesis ............................................................................................. 10 

E. Analysis Plan ............................................................................................................. 10

II. Analysis......................................................................................................................................... 11 

A. Use Characterization.................................................................................................. 11 

B. Exposure Characterization......................................................................................... 12 

1. Environmental Fate and Transport Characterization..................................... 12 

2. Aquatic Exposure........................................................................................... 14 

3. Terrestrial Exposure....................................................................................... 17 

C. Ecological Effects Characterization........................................................................... 18 

1. Aquatic Effects............................................................................................... 19 

2. Terrestrial Effects .......................................................................................... 20 

3. ECOTOX ....................................................................................................... 21 

III. Risk Characterization................................................................................................................... 21 

A. Risk Estimation.......................................................................................................... 22 

1. Aquatic Species.............................................................................................. 23 

2. Terrestrial....................................................................................................... 24 

B. Risk Description ........................................................................................................ 27 

1. Aquatic........................................................................................................... 28 

2. Terrestrial....................................................................................................... 28 

C. Uncertainties and Data Gaps...................................................................................... 31 

IV. Conclusion ................................................................................................................................... 32 

V. Threatened and Endangered Species ............................................................................................ 33 

A. Action Area................................................................................................................ 34 

B. Taxonomic Groups Potentially at Risk...................................................................... 34 

C. Indirect Effects Analysis............................................................................................ 35 

D. Critical Habitat........................................................................................................... 36 

E. Co-occurrence Analysis............................................................................................. 36 

VI.References..................................................................................................................................... 37 

VII. Appendix I. Environmental Fate and Transport Data ............................................................... 38 
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VIII. Appendix II. PRZM/EXAMS Output Files ............................................................................. 41 

IX. Appendix III. TREX Model Information.................................................................................... 45

X. Appendix IV. TerrPlant Model .................................................................................................... 46 

XI. Appendix V. Individual Effect Chance Model........................................................................... 48 

XII. Appendix VI. Endangered Species Count from the LOCATES Database by Listed Taxon for 

each Crop ............................................................................................................................... 52 
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I. EXECUTIVE SUMMARY 

 The intent of this document is to review the environmental fate and potential ecological 

effects associated with the outdoor uses of chlormequat chloride on bedding plants and 

containerized nursery crops (Cycocel®; EPA Reg. No. 241-74). 

A. Nature of the Chemical Stressor 

Chlormequat chloride is also registered for use on indoor greenhouse ornamental crops, but 

these uses are not evaluated in this assessment. Chlormequat chloride, the sole active ingredient in 

Cycocel®, is a plant growth regulator (PGR) applied as a drench or spray to greenhouse plants and 

proposed outdoor spray on containerized ornamentals. 

B. Conclusions – Exposure Characterization 

Chlormequat chloride is expected to be moderately mobile to mobile (FAO classification 

scheme) in the environment. Major routes of dissipation in the environment include microbial 

degradation in soils and aquatic systems; however, the extent to which the chemical is subject to 

abiotic routes of degradation is unknown since no data are currently available. There is uncertainty 

regarding chlormequat chlorides’ persistence in the environment. In aerobic soil metabolism 

studies, chlormequat chloride degraded with half-lives ranging from 4-6 weeks. But there were 

significant unidentified residues in these studies. Including the unidentified residues in the half-life 

estimates increases them to ~ 1-4 months. In aquatic environments, chlormequat chloride was 

short-lived, degrading with half-lives of ~ 1 week. However, significant non-extractable residues 

were detected in these studies and it is uncertain whether or not they consist of parent chlormequat 

chloride and/or residues of risk concern. 

C. Conclusions – Effects Characterization 

For aquatic organisms on an acute exposure basis, chlormequat chloride is classified as 

practically non-toxic to freshwater and estuarine/marine fish, slightly toxic to freshwater and 

estuarine/marine invertebrates, and moderately toxic to aquatic plants. For terrestrial organisms, 

chlormequat chloride is categorized as slightly toxic to birds, moderately toxic to mammals and 

practically non-toxic to honeybees on an acute exposure basis. Chronic toxicity endpoints for birds 

and mammals include decreases in weight gain. Sublethal effects in birds also included eggshell 

thinning and decreased testicular weight, effects often associated with endocrine-mediated 

processes. Sensitive terrestrial plants can be adversely affected by chlormequat chloride. 

D. Potential Risks to Non-target Organisms 

Based on this screening-level assessment, the proposed new use of chlormequat chloride 

could result in acute and chronic risk to terrestrial animals, risk to terrestrial plants and Federallylisted threatened and endangered (listed) aquatic vascular plant species. Adverse effects to 

terrestrial or aquatic plants could affect primary productivity in their respective ecosystems, leading 

to effects on higher trophic levels. The acute risk level of concern (LOC) is exceeded for birds 

foraging on short grass, tall grass and broadleaf plants/small insects and for small-sized (20g) birds 

foraging on fruits/pods/seeds/large insects (RQs 0.45-6.9). The listed species LOC is also exceeded 

for small- and medium-sized (100g) birds foraging on fruits/pods/large insects. While a NOAEC 

was not determined for birds, using the lowest dietary concentration tested indicates potential 

chronic risk to birds in all forage classes. There is potential acute risk to mammals foraging on 
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short grass, tall grass and broadleaf plant/small insects (RQs 0.45-2.2), and the listed species LOC 

is exceeded for small (15g) and medium size (35g) classes foraging on fruits/pods/large insects. 

Potential chronic risk to mammals is indicated for all size classes for the short grass, tall grass and 

broadleaf plant/small insect forage classes. Table 1 summarizes the listed taxa potentially at risk 

from direct and/or indirect effects due to the outdoor applications of chlormequat chloride. 

E. Data Gaps and Uncertainties 

There are several data gaps that increase the uncertainty of this assessment. There are 

currently no acceptable data for hydrolysis, photolysis, anaerobic soil metabolism or terrestrial field 

dissipation. In the absence of data, it was assumed that chlormequat chloride is stable to hydrolysis, 

photolysis and anaerobic metabolism. In the aerobic soil and aerobic aquatic metabolism studies all 

transformation products greater than 10% of the applied may not have been identified. A total 

residue approach was used for calculating the aerobic soil metabolism half-life for exposure 

modeling. 

There are currently no data regarding the toxicity of chlormequat chloride to freshwater fish 

on a chronic exposure basis. Although use of the acute to chronic ratio for daphnids suggests the 

likelihood of chronic risk to freshwater fish is low, potential for risk is presumed. Additionally, 

there are no data available to evaluate the potential chronic risk to estuarine/marine organisms. 

The avian reproduction study with chlormequat chloride did not determine the necessary 

NOAEC due to significant treatment-related effects at all treatment levels. The terrestrial plant 

seedling emergence study also did not establish a NOEC, also due to effects at all treatment levels. 

These deficiencies increase the uncertainty in the assessment. 

Since there are no specific nursery scenarios for aquatic exposure modeling, surrogate 

scenarios were used. The turf scenarios were chosen as surrogates because they consist of high 

organic matter top soil layers that are similar to soils used for bedding plants in nurseries. 

However, the extent to which the meteorologic, edaphic and agronomic characteristics of the 

surrogate scenarios are representative of actual use sites in nurseries is uncertain. 

Table 1. Listed species risks associated with potential direct or indirect effects due to the proposed 

applications of chlormequat chloride in containerized ornamental production. 

Listed Taxon Direct Effects 

Acute 

Direct Effects 

Chronic Indirect Effects 

Terrestrial and semi-aquatic 

plants - monocots Yes - Yes1

Terrestrial and semi-aquatic 

plants - dicots Yes - Yes1

Insects No - Yes1

Birds Yes Yes Yes1

Terrestrial phase amphibians Yes Yes Yes1

Reptiles Yes Yes Yes1

Mammals Yes Yes Yes1
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Aquatic plants Yes - Yes1

Freshwater fish No No data2 Yes1

Aquatic phase amphibians No No data Yes1

Freshwater invertebrates No No Yes1

Mollusks No data No data Yes1

Marine/estuarine fish No No data Yes1

Marine/estuarine crustaceans No No data Yes1

1

Unlisted LOC exceeded for terrestrial and aquatic vascular plants, therefore there is potential for adverse effects to 

those species that rely either on a specific plant species or multiple plant species. Plant indirect effects may include 

general habitat modification, host plant loss, and food supply disruption. 2

When data are unavailable, risk is presumed. 

II. PROBLEM FORMULATION 

A. Stressor Source and Distribution 

1. Source and Intensity 

This screening-level environmental fate and ecological risk assessment evaluates the 

potential risk to non-target organisms from the outdoor use of chlormequat chloride as a backpack 

or ground spray on containerized ornamentals and bedding plants in nurseries, shadehouses and 

other non-enclosed structures. Chlormequat chloride, the sole active ingredient in Cycocel®, is a 

plant growth regulator (PGR) registered for application as a drench or spray to greenhouse plants. 

For outdoor use of chlormequat chloride, the compound can be applied at a maximum rate of 33.3 

lbs ai/A/year. Greenhouse uses were not considered since aquatic and terrestrial exposures are 

expected to be minimal due to the closed-system nature of their operations and discharges from 

greenhouses must be regulated in accordance with a NPDES permit under the Clean Water Act. 

According to the product labels, a primary use of chlormequat chloride is as a tank mix with 

another PGR, B-nine® (daminozide; EPA Reg. No. 400-69). 

2. Physical/Chemical/Fate and Transport Properties 

Chlormequat chloride is the salt of a quaternary ammonium cation, a diverse group of 

molecules commonly known as “quats”. More specifically, chlormequat chloride has been 

classified according to the Agency’s PR Notice 88-2 (February 26, 1988) as a Group I, alkyl or 

hydroxyalkyl (straight chain) substituted quaternary ammonium compounds. Another Group I 

quaternary ammonium salt, didecyldimethylammonium chloride (DDAC) was recently reregistered 

by the Antimicrobials Division (USEPA D325481, 2006). The quaternary ammonium cations are 

permanently charged, independent of the pH of solution. 

Chlormequat chloride is expected to be moderately mobile to mobile (FAO classification 

scheme) in the environment. The major route of dissipation in the environment appears to be 
7 of 66 

microbial degradation in both soil and aquatic systems. There is uncertainty regarding chlormequat 

chloride’s persistence in the environment. 

3. Pesticide Type, Class, and mode of Action 

a) Chemical Profile 

Chemical name: 2-chloro-N,N,N-trimethylethylethanammonium chloride salt 

Common name: Chlormequat chloride 

 Chlorocholine chloride (CCC) 

CAS No. 000999-81-5 

Chemical structure: 

N

CH3

CH3

C CH3 H2C

H2

Cl Cl

+

b) Mode of Action 

Chlormequat chloride is used as a plant growth regulator (PGR), reducing internodal 

elongation and delaying flowering. The physiological causes of these effects on the plant are not 

well documented. 

4. Usage Overview 

Chlormequat chloride is currently registered for application to greenhouse ornamentals. The 

first outdoor use of this chemical was registered in November, 2006; therefore there are no 

available data on current usage for this risk assessment. 

B. Receptors 

Ecological effect endpoints are derived from registrant-submitted guideline studies as 

required for registration under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA; 40 

CFR Part 158), as well as a review of data available through acceptable open literature (ECOTOX; 

www.epa.gov/ecotox), when available. The most sensitive endpoints (described below) from 

testing of surrogate species are used to estimate risk to the taxonomic group(s) represented by the 

surrogate tested. Toxicity data reported in this document are intended to represent all terrestrial and 

aquatic organisms. However, only a few surrogate species for both freshwater fish and birds are 

used to represent all freshwater fish (2000+) and bird (680+) species in the United States. In 

addition, neither reptiles nor amphibians are tested. Birds are used as surrogates for reptiles and 

terrestrial-phase amphibians; fish are used as surrogates for aquatic-phase amphibians. The Norway 

rat is typically the surrogate for all mammals. 

C. Assessment Endpoints 

Assessment endpoints are defined, per Agency guidelines, as “explicit expressions of the 

actual environmental value that is to be protected” which are “operationally defined by an 

ecological entity and its attributes” (USEPA, 2004). The ecological entity can be a species, a 
8 of 66 

functional group of species, a community, an ecosystem, or another entity of importance or concern. 

 An attribute is the characteristic of the entity that is important to protect and is potentially at risk. 

Defining an assessment endpoint involves two steps: 1) identifying the valued attributes of the 

environment that are considered to be at risk, and 2) operationally defining the assessment endpoint 

in terms of an ecological entity (e.g., a community of fish and aquatic invertebrates) and its 

attributes (i.e., survival and reproduction). Therefore, selection of the assessment endpoints is 

based on valued entities (i.e., ecological receptors), the ecosystems potentially at risk and the routes 

by which ecological receptors are exposed to pesticide-related contamination. The selection of 

clearly defined assessment endpoints is important because they provide direction and boundaries in 

the risk assessment for addressing risk management issues of concern.

Typical assessment endpoints for screening-level pesticide ecological risk assessments 

include reduced survival and/or reproductive impairment for both aquatic and terrestrial animal 

species from direct acute or direct chronic exposures. Aquatic animal groups that are typically 

characterized in the risk assessment include: freshwater fish and invertebrates and estuarine/marine 

fish and invertebrates. Terrestrial animal groups include birds, mammals, and beneficial insects. 

All assessment endpoints are characterized at the individual level in order to protect threatened and 

endangered species. However, risks to higher biological levels (i.e., populations and communities) 

can be inferred from this approach (e.g., pesticide effects on individual survival and fecundity may 

impact population stability, growth, and/or habitat carrying capacity). A species-specific 

assessment containing characterization of indirect effects to listed species and critical habitat is the 

next step following completion of the screening-level risk assessment. 

For terrestrial and semi-aquatic plants, the screening assessment endpoint is the perpetuation 

of populations of non-target species (crops and non-crop plant species). Existing testing 

requirements only evaluate the seedling emergence and vegetative vigor of annuals. Although it is 

recognized that the endpoints of seedling emergence and vegetative vigor may not address all 

terrestrial and semi-aquatic plant life cycle components, it is assumed that impacts on plant 

emergence and/or on active growth have the potential to impact individual competitive ability and 

reproductive success, from which population effects can be inferred. 

For aquatic plants, the assessment endpoint is the maintenance and growth of standing crop or 

biomass. Measurement endpoints for this assessment focus on nonvascular, e.g., algae, and 

vascular plants, e.g., duckweed (Lemna gibba), growth rates and biomass measurements. 

The ecological relevance of the assessment endpoints assumes that complete exposure 

pathways exist for these receptors, that the receptors may be sensitive to pesticides in affected 

media and/or forage items and that the receptors could potentially inhabit areas where pesticides are 

applied, or areas where runoff and/or spray drift may impact the sites because suitable habitat is 

available. 

Ecological measurement endpoints for this screening-level risk assessment are based on a 

suite of registrant-submitted toxicity studies performed on a limited number of organisms, 

supplemented by the open literature where applicable, in the following broad groupings: 

1. Birds, e.g., Japanese quail (Coturnix coturnix japonica) and mallard duck (Anas 

platyrhynchos), also used as surrogate species for terrestrial-phase amphibians and 

reptiles, 

2. Mammals, e.g., laboratory rat (Rattus norvegicus), 

3. Freshwater Fish e.g., rainbow trout (Oncorhynchus mykiss), also used as a surrogate 

for aquatic-phase amphibians, 

4. Freshwater invertebrates, e.g., waterflea (Daphnia magna), 
9 of 66 

5. Estuarine/marine fish, 

6. Estuarine/marine invertebrates, 

7. Terrestrial plants, 

8. Vascular and nonvascular aquatic plants. 

Within each of these broad taxonomic groups, an acute and chronic endpoint is selected 

from the available test data. The selection is made from the most sensitive species tested within a 

particular surrogate group. If additional toxicity data are available from other sources, the selection 

of an endpoint may not be limited to the surrogate species listed above, but may be expanded to 

include those data for other groups or species that have been deemed of sufficient quality by the 

Agency for use in the risk assessment. 

D. Conceptual Model 

 In order for a chemical to pose an ecological risk, it must reach ecological receptors in 

biologically significant concentrations. Exposure pathways are defined as the means by which a 

contaminant moves in the environment from a source to an ecological receptor. For an ecological 

exposure pathway to be complete, it must have a source, an environmental transport medium, a 

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

1. Diagram 

The conceptual model used to depict the potential ecological risk associated with the 

proposed use of chlormequat chloride (the stressor) assumes that as a pesticide, chlormequat 

chloride can adversely affect terrestrial and aquatic organisms (the receptors) if environmental 

concentrations exceed toxic thresholds as a result of application according to the label directions 

(Figure 1). Ecological receptors that may potentially be exposed to chlormequat chloride include 

terrestrial and semi-aquatic wildlife (e.g., mammals, birds, amphibians and reptiles), terrestrial and 

semi-aquatic plants, terrestrial invertebrates (e.g., honey bees), and terrestrial soil and aquatic 

sediment invertebrates. Additionally, aquatic organisms (i.e., freshwater and estuarine/marine fish 

and invertebrates, amphibians, and aquatic plants) are potential receptors in adjacent water bodies 

through off-site transport of chlormequat chloride from the application site through runoff, erosion 

and/or spray drift. 

Routes of exposure to terrestrial and aquatic organisms can occur from direct application, 

spray drift and/or runoff. Exposure may be through ingestion of contaminated food or water 

sources, dermal contact or absorption, and/or inhalation. 

 This assessment does not take into account potential atmospheric transport in estimating 

environmental concentrations, potential exposure via ground water, nor does it account for 

ingestion of chlormequat chloride residues by animals in contaminated grit, ingestion through 

preening activities, or uptake through inhalation or dermal absorption by terrestrial animals. 

Exposure to terrestrial animals is based primarily on dietary consumption of foliar (and insect) 

residues. Aquatic assessments assume that all potential routes of direct exposure are accounted for. 

 
10 of 66 

Figure 1. Conceptual Model for a Screening Level Assessment of Chlormequat Chloride on 

Ornamental Crops. 

2. Risk Hypothesis 

The labeled outdoor uses of chlormequat chloride may pose risk of adverse effects to 

nontarget species in the environment. 

 At maximum application rates for the outdoor uses of chlormequat chloride, exposure of 

terrestrial, aquatic and semi-aquatic wildlife and plants to chlormequat chloride may be of sufficient 

duration and intensity to result in direct effects (e.g., mortality due to acute exposure or impaired 

reproduction, growth, or survival from chronic exposure). Additionally, species may be indirectly 

affected by chlormequat chloride due to a loss of food resources and/or changes to ecologically 

critical habitat resulting from proposed uses. 

E. Analysis Plan 

The maximum outdoor label application rates for use of chlormequat chloride on bedding 

plants and containerized ornamentals were selected for modeling environmental concentrations for 

this screening-level deterministic (risk-quotient based) assessment, as the outdoor uses represent the 

greatest likelihood of non-target exposure. The most sensitive toxicity endpoints from surrogate 

test species are used to estimate treatment-related effects on growth and survival assessment 

endpoints. Estimated environmental concentrations (EECs) used in terrestrial and aquatic 

ecological risk assessments are based solely on chlormequat chloride parent compound. 

A risk quotient-based approach is used in this assessment, comparing the ratio of exposure 

concentrations to effects endpoints with predetermined levels of concern (LOCs). The use, 

laboratory environmental fate, and laboratory ecological effects data, all of which provide the basis 

for these risk quotients, are characterized in the assessment. Although risk is often defined as the 

likelihood and magnitude of adverse ecological effects, the risk quotient-based approach does not 

Residue on Plants and Animal Feed Items 

(from direct deposition or spray drift) 

Runoff and/or Spray drift to Surface 

Waters 

Plant and Animal Aquatic Species Plant and Animal Terrestrial Species

Acute and Chronic Effects Acute and Chronic Effects

Chlormequat Chloride

Application to Ornamental Crops
11 of 66 

provide a quantitative estimate of likelihood and/or magnitude of an adverse effect. At a screening 

level, RQs that fall below the Agency’s LOC (for a given taxon) indicate a low potential for risk, 

while RQs greater than the LOC indicate there is a potential for ecological effects if a sufficient 

exposure threshold is reached. 

II. ANALYSIS 

A. Use Characterization 

Chlormequat chloride is a plant growth regulator (PGR) for use on bedding plants and 

containerized ornamentals in shadehouses and nurseries as the formulated product Cycocel® (EPA 

Reg. No. 241-74). In open production areas not under cover, Cycocel® use is restricted to bedding 

plants and containerized ornamentals. Application to field-grown ornamentals is not allowed by the 

label. The label allows foliar spray applications and drench applications. Drench applications are 

only allowed for the indoor greenhouse uses. This assessment does not evaluate the indoor 

greenhouse uses because environmental exposures are expected to be limited to greenhouse 

discharge which is regulated under the National Pollutant Discharge Elimination System (NPDES). 

 The registrant stated that a majority of the outdoor uses of chlormequat chloride would be in tank 

mix with B-nine® (daminozide; 035101), which provides greater PGR effect than either product 

alone (Latimer et al., 2001). Potential synergistic effects are not considered in this risk assessment, 

as there is no available ecological effects data on the possible tank mixes. 

For the outdoor (shadehouse and nursery) uses, spray volume providing thorough plant 

coverage will vary with plant size and foliage coverage and application rates will vary according 

specific plant species. However, the label states that a single application cannot exceed a rate of 3.7 

lbs. ai/A, and the total annual rate can not exceed 33.3 lbs ai/A/year. The label also limits the 

number of applications to 3 per crop cycle. For this assessment, 3 production cycles per year are 

considered, resulting in a maximum of 9 applications per year. The interval between repeat 

applications to the same crop can range from 5 to 21 days. The proposed label also states that 

applications by mechanical (tractor) multi-nozzle sprayers may not exceed one acre of plants per 

day, per mixer/loader/applicator. Table 2 summarizes the maximum application rates used in this 

assessment. This assessment also assumes that chlormequat chloride will be applied by low-boom 

sprayer to bedding plants and by backpack sprayer to most containerized ornamentals. 

Table 2. Proposed maximum use patterns of chlormequat chloride. 

Uses App. Type Max single 

app. rate 

(lbs ai/A) 

Max # of 

app./ year 

Max annual 

app. Rate 

(lbs ai/A/yr) 

Min app. 

Interval 

(days) 

Bedding plants, 

containerized 

ornamentals 

Foliar spray; 

mechanized 

ground boom 

sprayer 

3.7 9 33.3 5 

The USDA National Agriculture Statistics Service (NASS, 2006), which collects 

information on, among other things, the numbers of farms and acreages associated with agricultural 

practices, has 2002 statistics for "nursery, greenhouse, floriculture, mushrooms, sod, and vegetable 

seeds grown for sale". This category is further divided into “under glass or other protection” acres 

and “in the open”. While it is not possible to determine the actual area likely to be treated with 

chlormequat chloride, the “in the open” category can provide a useful index of potential use area. 
12 of 66 

According to NASS, California (18,600 acres) and Florida (12,800 acres) dominate the category, 

with only two other states (Michigan and New Jersey) having more than 3,000 acres. However, all 

50 states report at least some acreage in this category. 

B. Exposure Characterization 

1. Environmental Fate and Transport Characterization 

 There are a number of data gaps in the chlormequat chloride environmental fate and 

transport dataset. In the absence of data, assumptions made regarding chlormequat chloride were 

compared to and supported by the environmental fate and transport data of DDAC (PC code 69149, 

CAS No. 007173-51-5). DDAC and chlormequat chloride are both quaternary ammonium 

compounds that have been classified according to the Agency’s PR Notice 88-2 (February 26, 

1988) as Group I, alkyl or hydroxyalkyl (straight chain) substituted quaternary ammonium 

compounds. Details of the environmental fate and transport studies can be found in Appendix I. 

 Chlormequat chloride has variable mobility in the environment. Batch equilibrium studies 

resulted in Freundlich sorption coefficients ranging 1.13 – 9.12 ml/g with corresponding 1/N values 

ranging 0.511 – 0.955 (MRIDs 46715228, 46715229). Even though chlormequat chloride is a 

cation, the correlation between cation exchange capacity (CEC) and sorption was not significant in 

the batch equilibrium studies. Chlormequat chloride is classified as moderately mobile to mobile, 

according to the FAO classification scheme. In an aged column leaching study 0.3-0.5 % of the 

applied radioactivity was found in the leachate after 48 hours of leaching with 4 pore volumes of 

0.01 M CaCl2 in a loamy sand soil (MRID 46715230). In another aged column leaching study 2.5% 

of the applied radioactivity was found in the leachate following 45 days of leaching with 0.5 inches 

of distilled water daily through a 15-inch column filled with a clay loam soil (MRID 124061). In 

an unaged column leaching study < 0.1 % of applied radioactivity was found in the leachate after 

leaching with 20 inches of distilled water at a rate not exceeding 1 inch/hour through a 15 inch 

column filled with a sand, sandy loam, silt loam and clay loam soil (MRID 124062). In both of 

these studies distilled water was used which could lead to dispersion of clays that could affect soil 

structure. Depending on soil, site and meteorological conditions chlormequat chloride may be 

transported off-site via runoff, leaching and/or erosion. 

 Overall, the major route of dissipation for chlormequat chloride appears to be microbial 

degradation. An aerobic soil metabolism study showed that chlormequat chloride degraded with 

half-lives of 30-43 d in two sandy loam and two silt loam soils (MRID 46715225). Soils were was 

sequentially extracted four times with methanol:water, then four times with acidified water (pH 2). 

Nonextractable residues increased from 0.9-6.0% at day 0 to 19.0-27.8% at 112 days. In the study, 

up to 43.7% and 10.7% of the applied radioactivity in the soil extracts was unaccounted for in two 

soils. No attempt was made to identify these transformation products and it is not known whether 

or not the residues consisted of one or more components. Consequently, all transformation products 

detected at >10% of the applied may not have been identified. Using a total residue approach that 

assumes all unidentified extractable residues are of equal toxicity to chlormequat chloride results in 

half-lives of 32 – 132 days. 

 An aerobic aquatic metabolism study showed that chlormequat chloride degraded with total 

system half-lives of 5-9 days in a river water-sandy loam sediment and pond water-silt loam 

sediment system (MRID 46715227). Even though sediments were sequentially extracted 1-3 times 

with methanol:acidified (pH 2) water, followed by 1-5 times with acidic (pH 2) water, 

nonextractable residues increased from 1.0-2.6% at time 0 to 49.0-59.2% at 30 days and were 27.7-

31.3% at 105 study termination. The nonextractable residues are uncharacterized and it is uncertain 
13 of 66 

whether or not they consist of parent chlormequat chloride and/or residues of risk concern. 

 There were no available acceptable data for degradation of chlormequat chloride by 

hydrolysis or photolysis. Comparison to DDAC data, however, suggests that chlormequat chloride 

may be hydrolytically and photolytically stable (MRID 411758-01, 411758-02). There are also no 

data for chlormequat chloride under anaerobic conditions. DDAC has, however, been shown to be 

persistent under anaerobic conditions (MRID 422538-02). Table 3 summarizes the registrantsubmitted environmental fate and transport properties of chlormequat chloride. 

Major degradates (excluding CO2) were not identified in the available metabolism studies. 

In the aerobic aquatic metabolism study, an unidentified polar compound reached a maximum of 

4.8 and 13.4 % in the total systems. Choline-chloride was also detected in the aerobic aquatic 

metabolism study at a maximum of 2.0 and 5.5% in the total systems. 

 

Table 3. Summary of environmental chemistry and fate properties of chlormequat chloride. 

Parameter Value Reference/Comments

Selected Physical/Chemical Parameters

PC code 018101 

CAS No. 999-81-5 

Physical state Liquid Product chemistry 

Chemical name 2-chloro-N,N,Ntrimethylethylethanammonium chloride 

salt 

Product chemistry 

Chemical formula C5H13Cl2N Product chemistry 

Molecular weight 158.1 g/mol Product chemistry 

Water solubility 106 mg/L Product chemistry 

Density 1.14 g/mL Product chemistry 

Boiling point Not reported Product chemistry 

Vapor pressure (20 °C) 7.5 x 10-8 mm Hg Product chemistry 

log KOW 2.51 Product chemistry 

Persistence

Hydrolysis t1/2 

 pH 5 

 pH 7 

 pH 9 

No data 

Photolysis t1/2in water No data 

Photolysis t1/2 in soil No data 

Soil metabolism aerobic t1/2 

[Total residues]1 

43.4, 29.7, 31.5, 43.0 d 

[43.4, 32.9, 36.3, 132.3 d] 

MRID 46715225 

Soil metabolism anaerobic t1/2 No data 

Aquatic metabolism aerobic t1/2 4.9, 8.7 d MRID 46715227 

Aquatic metabolism anaerobic 

t1/2

No data 
14 of 66 

Parameter Value Reference/Comments

Mobility

Batch equilibrium Soil Type Kf

2 1/N Koc3 MRIDs 46715228, 

46715229 

 Loamy sand 1.25 0.511 55 

 Sandy loam 4.57 0.691 291 

 Silt loam 1.13 0.702 81 

 Sand 1.73 0.543 93 

 Sandy loam 2.14 0.768 89 

 Loam 9.12 0.849 912 

 Silt loam 8.08 0.955 385 

 

Column leaching – aged 

residues 

0.3-0.5 % applied radioactivity in 

leachate after 48 hours of leaching with 

4 pore volumes of 0.01 M CaCl2 in a 

loamy sand soil; 

2.5% of applied radioactivity in leachate 

following 45 days of leaching with 0.5 

inches of distilled water daily in 15 inch 

column with a clay loam soil; 

MRID 46715230, 

AN124061 

Column leaching - unaged < 0.1 % of applied radioactivity in 

leachate after leaching with 20 inches of 

distilled water in 15 inch column with a 

sand, sandy loam, silt loam and clay 

loam soil. 

AN124062 

Laboratory volatility NA 

Field Dissipation

Terrestrial field dissipation No data 

Aquatic field dissipation NA 

Bioaccumulation

Accumulation in fish, BCF No data 

1. Total residue approach assumes uncharacterized extractable residues are of similar toxicity as parent chlormequat chloride. 

2. Units of (mg/kg)/(mg/L)1/N, where 1/N is the Freundlich exponent. 

3. Approximation calculated from the Freundlich coefficient, per standard EFED guidance. 

2. Aquatic Exposure 

Tier II modeling for selected scenarios representing proposed outdoor uses was used to 

generate estimated environmental concentrations (EECs). No monitoring data were available for 

the proposed new uses of chlormequat chloride. For Tier II, two models are used in tandem: the 

Pesticide Root Zone Model, (PRZM, Carsel et al., 1997) and the Exposure Analysis Modeling 

System (EXAMS, Burns, 1997). PRZM (3.12 beta dated May 24, 2001) simulates fate and 

transport on the agricultural field, and EXAMS (2.98.04, dated July 18, 2002) simulates the fate and 

resulting daily concentrations in the water body. Simulations are carried out with the linkage 

program shell, PE4V01.pl (dated 8/13/2003), which incorporates the standard crop and orchard 
15 of 66 

scenarios developed by EFED. Simulations are run for multiple (usually 30) years, and the EECs 

represent peak values that are expected once every ten years based on the thirty years of daily 

values generated during the simulation. Additional information on these models can be found at: 

http://www.epa.gov/oppefed1/models/water/index.htm. 

For aquatic endpoints, the exposure is estimated for the maximum application pattern to a 

10-ha field bordering a 1-ha pond, 2-m deep (20,000 m3

) with no outlet. Exposure estimates 

generated using this standard pond are intended to represent a wide variety of vulnerable water 

bodies that occur at the top of watersheds including prairie pot holes, playa lakes, wetlands, vernal 

pools, man-made and natural ponds, and intermittent and first-order streams. As a group, there are 

factors that make these water bodies more or less vulnerable than the standard surrogate pond. 

Static water bodies that have larger ratios of pesticide-treated drainage area to water body volume 

would be expected to have higher peak EECs than the standard pond. These water bodies will be 

either smaller in size or have large drainage areas. Smaller water bodies have limited storage 

capacity and thus may overflow and carry pesticide in the discharge, whereas the standard pond has 

no discharge. As watershed size increases beyond 10-ha, it becomes increasingly unlikely that the 

entire watershed is planted with a non-major single crop that is all treated simultaneously with the 

pesticide. Headwater streams can also have peak concentrations higher than the standard pond, but 

they likely persist for only short periods of time and are then carried and dissipated downstream. 

OPP standard PRZM crop or orchard scenarios, which consist of location-specific soils, 

weather, and cropping practices, are used in the simulations to represent proposed labeled uses of 

Cycocel®. These scenarios are developed to represent high-end exposure sites in terms of 

vulnerability to runoff and erosion and subsequent off-site transport of pesticide. Cycocel® is being 

proposed for use on containerized ornamentals and bedding plants in nurseries and shade houses. 

There are currently no PRZM scenarios for these containerized uses. For use on ornamental trees, 

the applications will be likely applied by hand-held equipment (e.g., backpack sprayer). Although 

residues may be washed from foliage following backpack sprayer application, the controlled and 

directed nature of this type of application would likely minimize both excess mass applied and 

spray drift. Therefore off-site transport resulting from these applications was not considered an 

exposure pathway for this assessment. It is assumed that applications made by tractor-pulled 

equipment will be limited to bedding plants. It is assumed that the EECs resulting from the tractorpulled spray applications will be more conservative of applications made by hand-held equipment. 

Because no specific nursery scenario has been developed, FL turf and PA turf were chosen 

as surrogate scenarios for the bedding plant use. The turf scenarios were chosen as surrogates 

because they consist of high organic matter top soil layers (designed to approximate a thatch layer 

in turf) that may be similar to soils used for bedding plants in nurseries. Additionally, the FL turf 

scenario results in the greatest upper-bound EECs because it is in a high rainfall area (1216 mm 30-

year mean annual precipitation). However, the extent to which the meteorological and agronomic 

characteristics of the surrogate scenarios are representative of actual use sites in nurseries is 

uncertain. A summary of the crop scenarios used to estimate chlormequat chloride concentrations 

in the aquatic systems for ecological risk assessment are listed in Table 4. 

Table 4. Summary of crop scenarios used in aquatic exposure modeling.

Cycocel Use Crop Scenario MLRA/ Met Station Scenario Characterization 
16 of 66 

Cycocel Use Crop Scenario MLRA/ Met Station Scenario Characterization 

FL turf: Osceola County, 

Adamsville sand 

MLRA 156A; W12834 Surrogate for bedding plants in 

southeast 

Bedding plant 

PA turf: York County, 

Glenville silt loam 

MLRA 148; W14737 Surrogate for bedding plants in midAtlantic 

 

 PRZM/EXAMS modeling was done using the proposed maximum label rate, maximum 

number of applications per year and the minimum application interval. Input parameters are listed 

in Table 5. Pesticide applications were simulated as foliar applications (PRZM chemical 

application method, CAM = 2), with an application efficiency and drift fractions equal to 0.99 and 

0.01, respectively. The condition for disposition of the pesticide remaining on foliage after harvest 

(PRZM variable IPSCND) was set to 1 (pesticide remaining on foliage is converted to surface 

application), as a protective assumption. The first date of application was chosen to be in early 

spring (April 15th), although applications are expected anytime throughout the year. 

 Based on registrant-submitted data for chlormequat chloride, an aerobic soil metabolism and 

aerobic aquatic metabolism half-life of 100 and 12.6 d (the upper 90th percentile confidence bound 

on the mean), respectively, were used for surface water modeling with PRZM/EXAMS. It was 

assumed that chlormequat chloride is stable to photolysis, hydrolysis, and anaerobic metabolism 

since there are no acceptable data for these parameters. A soil organic carbon partitioning 

coefficient (Koc) of 272 ml/goc, the mean of seven soils, was used. 

Table 5. PRZM/EXAMS input parameters for chlormequat chloride applied by ground spray 

Input Parameter Value Source Comment

Application Rate in 

lbs a.i./A (kg a.i./ha) 

3.7 (4.15) EPA Reg. No. 241-74 

Applications per Year 9 EPA Reg. No. 241-74 3 applications per crop production; 3 

crop productions per year 

Application Intervals (d) 5 EPA Reg. No. 241-74 

Date of Initial Application April 15 

Chemical Application Method 

(CAM) 2 

EPA Reg. No. 241-74 Foliar application 

IPSCND Input 1 

Spray Drift Fraction 0.01 Input parameter 

guidance.1

Ground spray default 

Application Efficiency 0.99 Input parameter 

guidance.1

Ground spray default 

Molecular Mass (g/mol) 158.1 Product chemistry data. 

Vapor Pressure (Torr) 7.5 x 10-8 Product chemistry 

Henry's Law Constant (atmm3

/mol) 

1.6 x10-15 Calculated 

Solubility in Water at 25oC (mg/L) 106 Product chemistry data. Not multiplied by 10 

Organic Carbon-Water Partition 

Coefficient (Koc, ml/goc) 

272 MRIDs 46715228, 

46715229 

mean of seven values.1

Aerobic Soil Metabolism t1/2 (d) 100 MRID 46715225 90th percentile upper confidence 

bound on the mean (43.4, 32.9, 36.3, 

132.3 d), based on total residues2 
17 of 66 

Input Parameter Value Source Comment

Aerobic Aquatic Metabolism t1/2

(d) 

12.6 MRID 46715227 90th percentile upper confidence 

bound on the mean (4.9, 8.7 d) 

Anaerobic Aquatic Metabolism t1/2

(d) 

0 MRID 422538-02 stable 

Hydrolysis t1/2 (d) 0 MRID 411758-01 stable 

Aqueous Photolysis t1/2 (d) 0 MRID 411758-02 stable 

1. EFED input parameter guidance is located at: http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm. 

2. Total residue approach assumes all unidentified extractable residues are of similar toxicity to parent chlormequat chloride.

The EECs listed in Table 6 reflect maximum 1-in-10 year upper-bound surface water 

concentrations based on the proposed maximum use rates for containerized ornamentals and 

bedding plants where ground spray applications are used. 

Table 6. Tier II surface water 1-in-10-year estimated environmental concentrations (EECs) of 

chlormequat chloride from containerized nursery use (ppb). 

PRZM 

Scenario 

App. Rate (lbs 

ai/A/yr) 

Peak 4-day 21-day 60-day 

FL turf 33.3 153 140 110 59 

PA turf 33.3 144 135 93 55 

3. Terrestrial Exposure 

a) Animals 

Terrestrial wildlife exposure estimates are typically calculated for birds and mammals 

emphasizing a dietary uptake of pesticide through residues on vegetative and insect forage items. 

Avian terrestrial EECs are considered representative of potential exposure for terrestrial-phase 

amphibians and reptiles as well, unless more appropriate data are available through ECOTOX. For 

exposure to terrestrial organisms, pesticide residues on food items are estimated, based on the 

assumption that organisms are exposed to a single pesticide residue in a given exposure scenario. 

Exposure was evaluated using EECs generated from a spreadsheet-based screening model (TREX 

v.1.2.3) that calculates the dissipation of a chemical applied to foliar surfaces for single or multiple 

applications. The terrestrial animal exposure assessment is based on the methods of Hoerger and 

Kenaga (1972) as modified by Fletcher et al. (1994). When data are absent, as in this case, EFED 

assumes a 35-day foliar dissipation half life. The predicted maximum residues of chlormequat 

chloride that may be expected to occur on selected avian or mammalian food items immediately 

following application at the maximum rate for a single growing cycle are presented in Table 7. 

Since three growing cycles per year are permitted by the label, these residues do not represent the 

maximum mass of chlormequat chloride potentially available for wildlife exposure on an annual 

basis. However, since new target plants would be present for each growing cycle, only non-target, 

presumably marginal forage items, such as weeds, would be potentially subject to multiple growing 

cycles. Further details of the model are presented in Appendix III. 
18 of 66 

Table 7. Dietary-based estimated environmental concentrations (EECs) on terrestrial animal forage 

items following applications of chlormequat chloride to a single growing cycle of ornamentals 

based on TREX (version 1.2.3). 

Application Rate Food Items Upper-bound EEC 

(ppm)a

Mean EEC 

(ppm)a

Short grass 2421 857 

Tall grass 1110 363 

Broadleaf plants/small insects 1362 454 

3.7 lbs ai/A 

3 applications 

5 day interval 

Fruits, pods, seeds, and large insects 151 71 a Predicted residues based on Hoerger and Kenaga (1972) as modified by Fletcher et al. (1994). 

b) Plants 

Exposure to upland and wetland plants is estimated using the TerrPlant (v1.2.1) screening 

model. TerrPlant estimates potential exposure from a single application using default assumptions 

for runoff and spray drift (Table 8). Multiple applications during a single growing cycle and 

multiple growing cycles are not taken into account. See Appendix IV for more information. 

Table 8. Expected environmental concentrations (EEC) on plants following label-specified 

applications of chlormequat chloride determined using the TerrPlant model (lbs ai/A).

Rate Application 

Method 

Adjacent Upland 

Loadinga

Adjacent Wetland 

Loading 

Drift Only

3.7 lbs ai/A Ground Spray 0.22 1.89 0.04 

a

Loading is runoff plus drift (lbs ai/A) 

C. Ecological Effects Characterization 

 In screening-level ecological risk assessments, the effects characterization describes the 

types of effects a pesticide can potentially produce in an animal or plant. This characterization is 

generally based on registrant-submitted studies that describe acute and chronic effects information 

for various aquatic and terrestrial animals and plants; however, these data may also be 

supplemented by data reported in ECOTOX that have met Agency criteria for acceptability. 

 Toxicity testing reported in this section does not include all species of potentially affected 

by chlormequat chloride usage. Only a few surrogate species for both freshwater fish and birds are 

used to represent all freshwater fish (2000+) and bird (680+) species in the United States. For 

mammals, toxicity studies are limited to the laboratory rat. Also, neither reptiles nor amphibians 

are tested. The risk assessment assumes that avian and reptilian and terrestrial-phase amphibian 

toxicities are similar. Fish are considered reasonable surrogates for aquatic-phase amphibians. 

Terrestrial plant data are derived from the vegetative vigor and seedling emergence tests, typically 

on 10 agricultural plant species, and do not account for potential chronic or reproductive effects. 

Typically, five aquatic plant species are used to represent potential toxicity to all aquatic plant 

species. 
19 of 66 

1. Aquatic Effects 

a) Freshwater Fish 

Two acceptable guideline studies with the bluegill sunfish (Lepomis macrochirus; 001232-

61) and rainbow trout (Oncorhynchus mykiss; 000374-33) indicate the 96-h median lethal 

concentration (LC50) is >1000 mg ai/L. One supplemental subacute 21-day toxicity study following 

OECD 204 was reviewed (MRID 467152-17). The Agency has no provision for subacute fish 

studies, but they provide supplemental information useful in this risk assessment. In that study, 

rainbow trout were exposed to chlormequat chloride concentrations of 43, 100, 250, 590, 1400 and 

3400 mg/L. By the sixth day of the study (guideline acute fish toxicity tests are 96h), 90% of the 

fish in the 3400 mg ai/L concentration were dead. No other treatment-related mortalities were 

observed. Therefore, the NOAEC for this study is 1400 mg ai/L and the LC50 is >1400 mg ai/L, 

which results in chlormequat chloride being classified as practically non-toxic to freshwater fish on 

an acute exposure basis. Additionally, ECOTOX reports LC50s of >100 mg ai/L for bluegill 

sunfish, fathead minnow (Pimephales promelas) and channel catfish (Ictalurus punctatus), also 

resulting in chlormequat chloride as being classified as practically nontoxic to freshwater fish. No 

studies are available regarding chronic toxicity of chlormequat chloride to freshwater fish. 

b) Freshwater Invertebrates 

A supplemental study assessing the acute toxicity of chlormequat chloride to Daphnia 

magna (MRID 001387-19) indicates chlormequat chloride is slightly toxic to freshwater 

invertebrates with an EC50 of 16.9 mg ai/L. In a 21-day chronic toxicity study on the water flea, 

classified as supplemental, a NOAEC of 5.0 mg ai/L (MRID 467152-16) was reported based on a 

statistically significant 20% reduction in live offspring relative to the control. 

c) Estuarine/Marine Fish 

 No acute or chronic studies regarding the toxicity of chlormequat chloride to 

estuarine/marine fish were submitted by the registrant. However, ECOTOX reports a study by 

Linden et al. (1979) which established an LC50 for the bleak (Alburnus alburnus) at 1950 mg ai/L, 

which results in chlormequat chloride being classified as practically nontoxic to estuarine/marine 

fish on an acute exposure basis. No chronic toxicity data for estuarine/marine fish are available for 

this assessment. 

d) Estuarine/Marine Invertebrates 

No acute or chronic guideline studies regarding the toxicity of chlormequat chloride to 

estuarine/marine invertebrates were available for this assessment. However, ECOTOX reports a 

study by Linden et al. (1979) which established an LC50 for the copepod Nitocra spinipes as 80 mg 

ai/L, which indicates chlormequat is slightly toxic to estuarine/marine invertebrates on an acute 

exposure basis. No chronic toxicity data for estuarine/marine invertebrates are available for this 

assessment. 

e) Aquatic Plants 

 Chlormequat is classified as moderately toxic to the aquatic vascular plant Lemna gibba

based on reductions in all measured parameters, the most sensitive being frond number, with an 

EC50 of 2.8 mg ai/L and a NOEC of 0.04 mg ai/L (MRID 467152-21). Chlormequat chloride is less 

toxic to nonvascular plants such as green algae Scenedesmus subcapitatus with a 96-hr EC50 >899 
20 of 66 

mg ai/L and a NOAEC of 233 mg ai/L (MRID 467152-22;) and blue-green algae (cyanobacteria; 

Anabaena flos-aquae) with an EC50 >207 mg ai/L and a NOAEC=207 mg ai/L (MRID 467152-23). 

2. Terrestrial Effects 

a) Avian Acute Oral, Dietary and Chronic 

The available data indicate that chlormequat chloride is slightly toxic to avian species on an 

acute exposure basis. Two acute oral toxicity studies, with the Japanese quail (Coturnix coturnix 

japonica) indicated an LD50 of 556 mg ai/kg bw (MRID 467152-10) and 1018 mg ai/A (MRID 

467152-11;), respectively. In both studies, all mortalities occurred in the first day of the 14-day 

studies. Chlormequat chloride is slightly toxic (possibly) to practically nontoxic to Japanese quail 

(LC50>3175 mg ai/kg diet; MRID 467152-12) and the mallard duck (LC50>5438 mg ai/kg diet; 

MRID 467152-13) on a subacute dietary exposure basis. 

A supplemental avian reproduction study with the Japanese quail (MRID 467152-14) was 

submitted which had mean-measured concentrations of 158, 387 and 982 mg/kg diet. The study 

was conducted with a two week pre-treatment period followed by a 6-week exposure period, rather 

than the guideline 10-week pre-laying exposure followed by a 10-week egg-laying exposure period. 

 The most sensitive endpoints were the adult parameters of food consumption and male body weight 

gain; both endpoints showed significant adverse effects at all treatment levels. As a result, the 

required NOAEC could not be statistically determined (<158 mg ai/kg diet) from this study. The 

most sensitive reproductive parameter was a significant reduction in hatchlings per eggs set and 

number of cracked eggs in the highest test concentration. Additionally, the study authors reported 

that absolute testes weight was significantly reduced (by 16%) in the 982 mg/kg group and that 

there was a significant increase in egg shell thinning and decreased egg strength at the highest test 

concentration. These reductions may reflect effects on endocrine-mediated processes. 

b) Mammalian Acute and Chronic 

Mammalian toxicity studies are normally reviewed by the Health Effects Division in support 

of the human health risk assessments conducted by that division. However, they are also used to 

characterize the toxicity to mammalian wildlife by EFED. The mammalian toxicity data (Norway 

rat study; MRID 417216-04) indicate that chlormequat chloride is moderately toxic to mammals on 

an acute oral exposure basis, with males (LD50=487 mg ai/kg bw) being slightly more sensitive than 

females (LD50=560 mg ai/kg bw). In a two-generation study with Norway rats, there were parental 

effects evident by decreased body weight at 255 mg ai/kg bw (males again slightly more sensitive 

than females), with a NOAEL of 86.4 mg ai/kg bw (MRID 467152-06). Offspring effects 

(NOAEL=86.4 mg ai/kg bw) were reduced mean litter size, body weight and delayed development 

c) Non-target Insects 

Chlormequat chloride is classified as practically nontoxic to honey bees (Apis mellifera) on 

both an acute contact and acute oral basis (LD50>100 μg ai/bee; MRID 467152-24). No sublethal 

effects were reported in the study. 

d) Terrestrial Plants 

A non-guideline seedling emergence test (MRID 467152-19) was submitted for chlormequat 

chloride, with only six plants (4 dicot, 2 monocot) tested, rather than the 10 species preferred in 

guideline studies. Species tested were oat (Avena sativa), onion (Allium cepa), carrot (Daucus 

carota), oilseed rape (Brassica napus), soybean (Glycine max) and sugar beet (Beta vulgaris). 
21 of 66 

There were five treatment levels and a control, with eight replicates per treatment, five seeds per 

replicate. There was no effect at the highest treatment level (1.9 lbs ai/A) for five of the six species. 

 The percent emergence of the dicotyledonous plant oilseed rape was significantly reduced by 38% 

at the highest level tested, resulting in an EC25 of >0.9 ai/A and a NOEC of 0.9 lb ai/A. 

A non-guideline vegetative vigor study (MRID 467152-20) was submitted for chlormequat 

chloride, only six plants (4 dicot, 2 monocot) were tested, rather than the 10 species preferred in 

guideline studies. Species tested were oat, onion, carrot, pea (Pisum sativum), sunflower 

(Helianthus annuus) and cabbage (Brassica oleracea). The study design varied with species, but 

the treatment levels were 0.21, 0.42, 0.84, 1.7 and 3.4 lb ai/A for all species. The most sensitive 

species was sunflower, with a calculated EC25 of 1.5 lb ai/A. A NOEC was not determined due to 

significant reductions in fresh weight (biomass) at all treatment levels (>25% at the lowest 

treatment). Carrot biomass was also effected, with an EC25 of 2.0 lbs ai/A and a NOEC of 0.21 lbs 

ai/A. Although the EC25 for pea was >3.4 lbs ai/A, there was a 20% biomass reduction at 3.4 lbs 

ai/A, making the NOEC 1.7 lbs ai/A. The other three species tested were unaffected at all treatment 

levels. 

Table 9. Terrestrial plant toxicity endpoints used in RQ calculations 

EC25 NOAEC Study Type Mono Dicot Mono Dicot 

Seedling Emergence >1.9 >0.9 1.9 0.9 

Vegetative Vigor >3.4 1.5 3.4 <0.21 

3. ECOTOX 

 The Agency’s ECOTOX database (www.epa.gov/ecotox) was reviewed for toxicological 

endpoints. There were several reported terrestrial studies; none were of greater sensitivity than 

those used in this assessment. The estuarine/marine fish and invertebrate endpoints reported above 

were selected from the ECOTOX report; no other reported aquatic endpoints were more sensitive 

than those used in this assessment. 

III.RISK CHARACTERIZATION 

The risk quotient (RQ) approach is used in this assessment, comparing the ratio of exposure 

concentrations to effects endpoints with predetermined levels of concern (LOCs). Laboratory 

environmental fate, laboratory ecological effects, and use data that provide the basis for these risk 

quotients have been discussed previously in the assessment. Although risk is often defined as the 

likelihood and magnitude of adverse ecological effects, the risk quotient-based approach does not 

provide a quantitative estimate of likelihood and/or magnitude of an adverse effect. Estimated 

environmental concentrations (EECs) are divided by acute and chronic toxicity values to calculate 

RQs. If the RQs exceed the LOCs, the Agency presumes potential for risk to the taxa. These LOCs 

(Table 10) are the Agency’s interpretive policy and are used to determine the need to consider 

regulatory action by indicating whether a pesticide, used as directed on the label, has the potential 

to cause adverse effects on non-target organisms. 

Table 10. Levels of concern (LOCs) for various taxa. 
22 of 66 

Risk Presumption RQ LOC

Birds 

Acute Risk EEC/LC50 or LD50/sqft or LD50/day 0.5 

Acute Restricted Use EEC/LC50 or LD50/sqft or LD50/day (or LD50 < 50 mg/kg) 0.2 

Acute Endangered Species EEC/LC50 or LD50/sqft or LD50/day 0.1 

Chronic Risk EEC/NOAEC 1 

Wild Mammals 

Acute Risk EEC/LC50 or LD50/sqft or LD50/day 0.5 

Acute Restricted Use EEC/LC50 or LD50/sqft or LD50/day (or LD50 < 50 mg/kg) 0.2 

Acute Endangered Species EEC/LC50 or LD50/sqft or LD50/day 0.1 

Chronic Risk EEC/NOAEC 1 

Aquatic Animals 

Acute Risk EEC/LC50 or EC50 0.5 

Acute Restricted Use EEC/LC50 or EC50 0.1 

Acute Endangered Species EEC/LC50 or EC50 0.05 

Chronic Risk EEC/NOAEC 1 

Terrestrial and Semi-Aquatic Plants 

Acute Risk EEC/EC25 1 

Acute Endangered Species EEC/NOAEC or EC05 1 

Aquatic Plants 

Acute Risk EEC/EC50 1 

Acute Endangered Species EEC/NOAEC or EC05 1 

A. Risk Estimation 

RQ values for the proposed use of chlormequat chloride on bedding and containerized 

nursery plants indicate potential risk to aquatic and terrestrial animals and plants. The acute and 

chronic toxicity endpoints used in this risk assessment are summarized Table 11. 

Table 11. The most sensitive endpoints used in the chlormequat chloride risk assessment. 

Environment Taxa Type 

of Risk 

Type of 

Endpoint Endpoint Units MRID 

Aquatic Fish Acute LC50 >1400 mg ai/L 467152-17 

 Freshwater Chronic NOAEC No data - - 

Invertebrate

s Acute EC50 16.9 mg ai/L 

001387-19 
23 of 66 

Environment Taxa Type 

of Risk 

Type of 

Endpoint Endpoint Units MRID 

 Chronic NOAEC 5 mg ai/L 467152-16 

 Plants Acute EC50 2.8 mg ai/L 467152-21 

 Listed NOAEC 0.04 mg ai/L 467152-21 

Terrestrial Avian Acute LD50 556 mg ai/kg-bw 467152-10 

 Chronic NOAEC <158 mg ai/kg-diet 467152-14 

 Mammalian Acute LD50 487 mg ai/kg-bw 417216-04 

 Chronic NOAEC 86.4 mg ai/kg-bw 467152-06 

 Plants Acute EC25 >0.9 lb ai/A 467152-19 

 Listed NOAEC 0.9 lb ai/A 467152-20 

1. Aquatic Species 

a) Freshwater Fish 

Because chlormequat chloride is classified as practically nontoxic to freshwater fish, i.e. the 

LC50 is greater than 100 mg/L, the potential for acute risk to freshwater is presumed to be low. If 

100 mg/L was the toxicity endpoint, RQs would be <0.01. There are no guideline chronic toxicity 

data available with which to evaluate potential chronic risk to freshwater fish. Chronic risk is 

presumed in the absence of data. 

b) Freshwater Invertebrates 

No acute or chronic risk LOCs are exceeded freshwater invertebrates (Table 12). 

Table 12. Risk Quotients for freshwater invertebrates 

Scenario Peak EEC 

mg/L 

Toxicity 

Endpoint 

mg/L 

RQ 

FL Turf Acute 0.153 16.9 <0.01 

PA Turf 0.143 16.9 <0.01 

 

FL Turf Chronic 0.110 5 0.02 

PA Turf 0.093 5 0.02 

c) Estuarine/Marine Fish 

 Chlormequat chloride is classified as practically nontoxic on an acute exposure basis to 

estuarine/marine fish, i.e. the LC50 is greater than 100 mg/L, and the potential for risk to estuarine 

fish is presumed to be low. There are no chronic toxicity data available with which to evaluate 

potential chronic risk to estuarine/marine fish. 

d) Estuarine/Marine Invertebrates 

No acute risk LOCs are exceeded for estuarine/marine invertebrates based on the 

estuarine/marine invertebrate endpoint found in ECOTOX (Table 13). There are no chronic 

toxicity data available with which to evaluate potential chronic risk to estuarine/marine 

invertebrates. 
24 of 66 

Table 13. Risk Quotients for estuarine/marine invertebrates. 

Scenario Peak EEC 

mg/L 

Toxicity 

Endpoint 

mg/L 

RQ 

FL Turf Acute 0.153 80 <0.01 

PA Turf 0.143 80 <0.01 

 

FL Turf Chronic 0.110 - - 

PA Turf 0.093 - - 

e) Aquatic Plants 

The acute risk LOC for non-listed vascular plant species is not exceeded for aquatic plant 

species (Table 14). The acute risk LOC for listed species is exceeded by more than a factor of 

three. RQs for aquatic nonvascular plants are <0.01. 

Table 14. Risk Quotients for the most sensitive aquatic plants. 

Scenario Peak EEC 

mg/L 

Toxicity 

Endpoint 

mg/L 

RQ 

FL Turf Unlisted 0.153 2.8 0.05 

PA Turf 0.143 2.8 0.05 

 

FL Turf Listed 0.110 0.04 3.6a

PA Turf 0.093 0.04 3.8a

exceeds acute risk LOC (RQ>1) 

2. Terrestrial 

 For terrestrial risk estimation, RQs are based on one growing cycle at the maximum label 

rate applied three times at five day intervals. Three growing cycles per year are allowed by the 

label; therefore exposure could possibly be higher. While the target plants would be different for 

each growing cycle, non-target species such as weeds could be subject to multiple growing cycles. 

a) Avian Acute 

When both dose-based and dietary-based toxicity estimates are available for birds, acute risk 

quotients are calculated using both a dose-based and dietary-based approach. The dose-based RQs 

are calculated using a body weight adjusted and consumption-weighted equivalent dose. The 

adjustments account for the fact that smaller-sized animals have to consume more food in terms of 

their body weight than larger animals and that differential amounts of food have to be consumed 

depending on the water content and nutritive value of the food. By expressing the Kenaga 

nomogram estimated residues in terms of daily equivalent dose, estimated environmental 

concentrations can then be compared to the dose-based LD50. However, in the case of chlormequat 

chloride, RQs can only be calculated from the LD50 since subacute dietary toxicity testing failed to 

establish LC50 values. Although at the highest dose tested in the Japanese quail dietary study 

chlormequat chloride would be classified as slightly toxic on a subacute dietary exposure basis to 

birds, i.e. the LC50 is >3175 mg/L, it is not known how much greater the LC50 would be, thus RQs 
25 of 66 

based on dietary exposure are not presented. 

Chlormequat chloride is classified as slightly toxic on an acute oral exposure basis. Dosebased RQs calculated using the acute oral LD50 are presented in Table 15. Dose-based RQs range 

from 6.9 for small birds (20g) foraging on short grass to 0.06 large (1000g) birds foraging on 

fruit/pods/large insects. The acute avian LOC (RQ≥0.5) is exceeded for all size classes foraging on 

short grass, tall grass and broadleaf plants/small insects. The acute risk to listed species LOC 

(RQ≥0.1) is exceeded for small- and medium-size birds foraging on fruit/pods/large insects. 

Table 15. Upper-bound dose-based avian acute risk quotient (RQ) values (LD50 = 556 mg/kg-bw). 

Forage items 

Size class 

20g 100g 1000g 

Short grass 6.9a 3.1 0.98 

Tall grass 3.2 1.4 0.45 

Broadleaf/small insects 3.9 1.7 0.55 

Fruits/pods/seeds/large insects 0.43b 0.19 0.06 a

Bold indicates exceeds acute risk to non-listed species LOC (RQ≥0.5) 

b

Italics indicates exceeds acute risk to endangered species LOC (RQ≥0.1) 

b) Avian Chronic 

 Because a NOAEC was below the lowest dose tested in the Japanese quail avian 

reproduction study, definitive chronic RQs cannot be calculated due to lack of data. However, 

calculating with the lowest dose tested provides an indication of the minimum extent to which 

LOCs are exceeded. RQ values calculated using the LOAEC from the Japanese quail study (Table 

16) exceed the chronic risk LOC (RQ≥1.0) for all forage groups. The chronic LOC is exceeded by 

a factor of greater than 15X for birds foraging on short grass. Since the actual NOAEC is likely to 

be lower, avian chronic RQs will be higher than those presented here. 

Table 16. Chronic dietary-based RQs calculated from the Japanese quail reproduction study. 

These RQs are lower than are indicated by the study (LOAEC=158).

Forage item RQ 

Short Grass >15* 

Tall Grass >7* 

Broadleaf plants/sm insects >9* 

Fruits/pods/seeds/lg insects >1* 

*Exceeds chronic risk LOC (RQ≥1.0)

c) Mammalian Acute 

Mammalian acute RQs (Table 17) range from 0.01 for large (1000g) granivorous mammals 

to 2.2 for small (15g) mammals foraging on short grass, a 4-fold exceedance of the acute risk LOC 

(RQ≥0.5). There are exceedances of the acute risk LOC for all size classes foraging on short grass 

and broadleaf plant/small insects and for small- and medium-size mammals foraging on tall grass. 

The listed species LOC is exceeded for all-sized mammals foraging on all food categories except 

seeds and for large mammals foraging of fruits/pods/lg insects 
26 of 66 

Table 17. Upper-bound dose-based mammalian acute risk quotient (RQ) values for the use 

chlormequat chloride (LD50=487 mg/kg-bw). 

Forage items Size class 

15g 35g 1000g 

Short grass 2.2a

 1.8 0.99 

Tall grass 0.99 0.84 0.45b

Broadleaf/small insects 1.2 1.0 0.56 

Fruits/pods/large insects 0.13 0.12 0.06 

Seeds 0.03 0.03 0.01 a

Bold indicates exceeds acute risk to non-listed species LOC (RQ≥0.5) 

b

Italics indicates exceeds acute risk to endangered species LOC (RQ≥0.1) 

d) Mammalian Chronic 

When assessing potential chronic risk to mammals, in accordance with the overview 

document, the dietary-based NOAEC is converted to a dose-based NOAEL using the standard 

USFDA laboratory rat conversion, which can be scaled to different mammalian size classes. The 

dose-based RQs are calculated using a body weight adjusted and consumption-weighted equivalent 

dose. The adjustments account for the fact that smaller-sized animals have to consume more food 

in terms of their body weight than larger animals and that differential amounts of food have to be 

consumed depending on the water content and nutritive value of the food. By expressing the 

Kenaga nomogram estimated residues in terms of daily equivalent dose, estimated environmental 

concentrations can then be compared to the dose-based NOAEC. Both sets of RQs are presented in 

Table 18. 

Dose-based RQs exceed the chronic risk LOC (1.0) for all size classes of mammals foraging 

on short grass, tall grass and broadleaf plants/small insects, by factors ranging from 3X to 12X . 

The only dietary-based RQ value that exceeds the chronic risk LOC is for mammals foraging on 

short grass; however, if dietary-based RQ values are adjusted to reflect that different-sized animals 

consume differing amounts of food, the dietary-based RQ values would likely be similar to the 

dose-based values. 

Table 18. Comparison of dose-based and dietary-based upper-bound mammalian chronic risk 

quotient (RQ) values for the use chlormequat chloride (NOAEC=86.4). 

Forage items Dose-based Dietarybased 

Size class 

 15g 35g 1000g 

Short grass 12a

 10 5.6 1.4 

Tall grass 5.6 4.8 2.6 0.65 

Broadleaf/small insects 6.9 5.9 3.1 0.79 

Fruits/pods/large insects 0.76 0.65 0.35 0.09 

Seeds 0.17 0.14 0.08 xx a

Bold indicates exceeds chronic risk LOC (RQ≥1.0)
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e) Non-target Plants 

For a single application of chlormequat chloride (3.7 lbs ai/A) the terrestrial plant LOC (1.0) 

is exceeded for dicotyledonous plants in wetlands adjacent to chlormequat use sites. The RQ 

(Table 19) for endangered monocotyledonous wetland plants for drift plus runoff (loading) is 1.0 

(at the highest dose tested); because there were no effects on monocots at the highest dose tested, an 

EC25 was not established, thus the RQ for non-listed plants is less than 1.0. For dicots, the listed 

species LOC is exceeded with an RQ of 2.1 and the non-listed LOC is exceeded with an RQ 

between 1.0 and 2.1. There are no exceedances for adjacent upland species or as a result of drift 

alone. 

Table 19. Risk quotients for terrestrial plants. Monocots: seedling emergence EC25>1.9 lbs ai/A, NOEC=1.9 

lbs ai/A; vegetative vigor EC25>3.4 lbs ai/A, NOEC=3.4 lbs ai/A. Dicots: seedling emergence EC25> 0.9 lbs ai/A, 

NOEC=0.9 lbs ai/A; vegetative vigor EC25=1.5 lbs ai/A, NOEC<0.21 lbs ai/A.

Application 

Method 

Adjacent Upland Adjacent 

Wetland 

Drift Only 

Monocot Dicot Monocot Dicot Monocot Dicot

Nonlisted Ground Spray <0.12 <0.25 <1.0 <2.1a <0.02 0.04 

Listed Ground Spray 0.12 0.25 1.0a

 2.1a 0.02 0.04 

a

exceeds LOC for non-listed species 

b

EC25 was determined to be between 0.9 and 1.9 lbs ai/A. c

meets or exceeds the LOC for listed species 

B. Risk Description 

Based on this screening-level deterministic risk assessment, EFED cannot refute the risk 

hypothesis that the labeled outdoor uses of chlormequat chloride may pose risk of adverse effects to 

non-target species. Chlormequat chloride is expected to be moderately mobile to mobile (FAO 

classification scheme) in the environment. Major routes of dissipation in the environment include 

microbial degradation in soils and aquatic systems. There is uncertainty regarding chlormequat 

chloride’s persistence in the environment. In aerobic soil metabolism studies, chlormequat chloride 

degraded with half-lives ranging from 4-6 weeks. But there were significant unidentified residues 

in these studies. In aquatic environments, chlormequat chloride was short-lived, degrading with 

half-lives of ~ 1 week. However, significant nonextractable residues were detected in these studies 

and it is uncertain whether or not they consist of parent chlormequat chloride and/or residues of risk 

concern. 

Although potential risk to aquatic animals appears to be low, available data indicate that the 

outdoor use of chlormequat chloride has the potential to adversely affect listed aquatic plants and 

non-target terrestrial animal and plant species. Due to important data gaps regarding Agency 

guideline studies, there is appreciable uncertainty regarding some risk conclusions. While this 

assessment uses conservative assumptions, greater refinement and additional data would be 

required to preclude potential risk given the exceedances noted in the previous section of the 

document. For terrestrial species, there is potential acute risk to birds for most size class/forage 

item categories, as well as the terrestrial-phase amphibians and reptiles for which birds are 

considered surrogates. The chronic risk LOC for birds is exceeded across all forage items; 

however, RQs for chronic effects will be higher because a NOAEC has not been determined. 

Potential acute risk is also indicated to mammals in most of the size class/forage categories, and 
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potential chronic risk to mammals is indicated for all-size classes in three of the five forage 

categories. Consistent with chlormequat being a PGR, potential risk to non-target aquatic vascular 

plants and to terrestrial plants in wetlands adjacent to use sites is indicated. 

1. Aquatic 

No aquatic animal RQ exceeded any LOC; however, chronic data are lacking for freshwater 

fish and potential risk cannot be precluded in the absence of data. However, based on the use of 

acute-to-chronic ratios for freshwater invertebrates (acute and chronic) and freshwater fish (acute), 

and using the lowest available LC50 (>100 mg/L), the chronic RQ would be <0.5, less than half the 

chronic LOC. The acute to chronic ratio for fish would have to be more than double that for the 

daphnids tested before the LOC would be exceeded. Additionally, based on the aerobic aquatic 

metabolism half-lives, chlormequat chloride is not expected to persist in most waterbodies. 

Based on submitted data, aquatic vascular plant species are potentially affected by 

chlormequat chloride. Although the unlisted species LOC is not exceeded, the listed species LOC 

is exceeded by a factor of more than three for aquatic vascular plants. Non-vascular plants are 

considerably (several orders of magnitude) less sensitive to chlormequat chloride than vascular 

plants. 

 Consistent with a screening-level approach, the aquatic exposure estimates used in this 

assessment are designed to be conservative. Major assumptions that contribute to the protective 

nature of the aquatic exposure estimates include the applicability of the standard models and 

surrogate PRZM scenarios to the nursery/shade house use, the application intervals modeled, and 

the area treated. The PRZM/EXAMS models and scenarios used in this assessment were developed 

to simulate pesticide applications in open agricultural fields and not specifically for containerized 

ornamentals and bedding plants in nurseries/shade houses. The impact of rainfall and 

corresponding pesticide transport is likely dampened due to the use of containers and/or shade 

covers relative to open agricultural fields, which leads to a protective assessment. The application 

interval was assumed to be 5 days (which is the minimum permitted by the label) for all 9 

applications. Since there is a maximum of 3 applications per crop cycle, it is likely that the interval 

between applications of subsequent crop cycles will be greater than 5 days, and thus the 5-day 

interval is likely a protective assumption. This will likely result in an overestimation of chronic 

exposure since a longer interval between applications would allow for greater degradation in the 

water body prior to subsequent applications. Also, the standard ecological aquatic modeling 

scenario consists of application to an entire 10-ha field simultaneously. The Cycocel® label, 

however, states that applications by mechanical (tractor) multi-nozzle sprayers may not exceed one 

acre of plants per day, per mixer/loader/applicator. The assumption that the entire 10-ha field of 

bedding plants is treated simultaneously with chlormequat chloride is likely a protective 

assumption. 

2. Terrestrial 

Dietary-based and dose-based avian RQ values are calculated using the sub-acute dietary 

LC50 and the acute oral LD50. The dose-based calculation takes into account that different-sized 

animals have to consume different amounts of food and the differing nutritional value of feed items. 

 The LD50 may give a better indication of inherent toxicity than the LC50 in cases where food 

avoidance may be an issue in the test animals. The greater energy demands in wild birds could 

make similar avoidance in natural settings unlikely. Because a subacute dietary LC50 for 

chlormequat chloride was not defined, and the LC50 exceeded the highest dietary test concentration 

(3175 ppm), no definitive dietary-based RQs were calculated. If the highest dose tested were used 
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to calculate RQs, the acute risk LOC would be exceeded for short grass and the restricted use and 

listed species LOCs would be exceeded for the tall grass and broadleaf plants/small insects forage 

categories. Due to the mass of chemical applied, even at the high-end regulatory limit for testing, 

5000 ppm, above which chemicals are classified as practically nontoxic, the listed species LOC 

would be exceeded in three of the four forage categories. Because of the magnitude of the EECs, 

i.e. greater than 1/10th the highest dose tested, risk to endangered species on a dietary basis cannot 

be precluded. 

Dose-based RQs result in exceedances of the acute risk LOC for all size classes of birds 

foraging on short grass, tall grass and broadleaf plants/small insects and small (20g) birds foraging 

on fruit/pods/seeds/large insects. The acute risk LOC for restricted use and listed species is also 

exceeded for medium-sized birds foraging on fruit/pods/seeds/large insects. RQs are calculated 

using upper-bound Kenaga values. If mean Kenaga values (expected to be exceeded about 50% of 

the time) were used to calculate the RQs, acute risk LOC would still be exceeded for small- and 

medium-sized birds foraging on short grass, tall grass and broadleaf plants/large insects and large 

birds foraging on short grass. The listed species LOC would be exceeded for large birds foraging 

on tall grass and broadleaf plants/large insects and for small- and medium-sized birds foraging on 

fruits/pods/seeds/large insects. 

Because a NOAEC was not determined in the avian reproduction study, definitive chronic 

RQ values could not be calculated. However, the lowest dose tested was used to give an indication 

of potential chronic risk. The chronic risk LOC is exceeded for birds across all forage items at the 

maximum application rate for one growing cycle. The chronic RQ exceeded the LOC by >15-fold 

for birds foraging on short grass. The most sensitive endpoints were reduced feed consumption and 

decreased male body weight gain. While there is generally a high-degree of variability in feed 

consumption, the reduced feed consumption in the non-guideline study may imply the birds were 

not acclimated properly. Males in all three treatment groups lost weight relative to their starting 

weight, up to an average of 4.5g in the highest treatment level. The control males gained an 

average of 2.1g. But the ecological significance of this endpoint is not clear. A loss of 4.5g 

represents a 6% reduction in weight, based on an average size Japanese quail. For male birds that 

provide parental care of the young, given the increased energy demands on the wild birds (relative 

to study conditions), this reduced weight may lead to reduced survivorship or impaired 

development of offspring. Additionally, if a wild species was more sensitive than the Japanese 

quail, the effect could be amplified. 

There were effects seen at the highest dose tested that have could be indicative of effects on 

endocrine-mediated processes (e.g., eggshell thinning). Hypothetically ignoring effects at the 

lowest dose, using the NOAEC for these other effects (387 mg ai/kg bw), the chronic RQs would 

exceed the LOC in three of the four forage categories by 3- to 6-fold. 

Chronic values (calculated with the lowest dose tested) are based on upper-bound Kenaga 

values. The non-definitive RQs based on mean Kenaga values also exceed the chronic risk LOC for 

birds across the same forage categories. EECs exceed the lowest dose tested for more than 100 

days for all three forage categories, based on the upper-bound residues, and for more than 50 days 

based on the mean residues, indicating that residues above the chronic toxicity threshold could be 

available to foraging wildlife for an extended period. The chronic risk LOC based on mean 

residues is expected to be exceeded approximately half of the time. 

Terrestrial animal RQs are calculated using a default foliar half life of 35 days. If data were 

generated that demonstrated, hypothetically, three-day half life was appropriate, the maximum RQ 

would be reduced by roughly 50%. A reduction in the application rate would also reduce RQs. 

However, because a NOAEC is not established, it is not known how far these parameters would 
30 of 66 

have to be changed to get all RQs below the LOC. Even with a less conservative foliar dissipation 

rate of 3 days rather than the default 35-day half-life, chronic RQs would still exceed the LOC by a 

factor of 8x. 

 Because the Japanese quail reproduction study did not establish a NOAEC, the utility of the 

study was greatly reduced for this risk assessment. Additionally, the study deviates appreciably 

from EPA guidelines. The Agency typically prefers birds have a 10-week pre-laying exposure 

period followed by a 10-week exposure period during egg laying. The supplemental reproduction 

study submitted to the Agency was designed as an eight-week laying study, with a two-week pretreatment period, followed by a six week treatment period. It is not clear how the results of this 

study would relate to an Agency guideline study. 

 Avian exposure modeling considered only one growing cycle. Since three growing cycles 

are allowed per year, the mass of chlormequat chloride available may be underestimated. However, 

since target plants are different for each application cycle, only non-target forage items (e.g. weeds) 

would potentially be subjected to applications over more than one growing cycle. 

The acute risk LOC is exceeded for all size classes of mammals foraging on short grass and 

broadleaf plant/small insects, as well as small and medium size classes foraging on short grass and 

broadleaf plants/small insects. The acute risk to listed species LOC (RQ≥0.1) is exceeded for small 

and intermediate size classes foraging on fruits/pods/large insects and large mammals foraging on 

tall grass. RQs are calculated using upper bound (95%) Kenaga values. RQs calculated with mean 

Kenaga values still exceed the acute risk LOC for small and medium size classes foraging on short 

grass and the listed species LOC for all size classes foraging on short grass and small and medium 

size classes foraging on tall grass and fruit/pods/large insects; however, mean exposure values are 

expected to be higher about half of the time. 

 If the rate per application (for three applications, five days apart) was below 0.25 lbs ai/A 

only small and medium-sized mammals would exceed the listed species LOC at the upper-bound 

residues. Using a minimum application interval of 21-day or using a hypothetical three day half life 

results in lower RQs, but does not appreciably change the risk picture. However, the calculated 

RQs are for only one growing cycle, and therefore do not represent the total mass of chlormequat 

chloride potentially available for exposure. Since target plants are different for each application 

cycle, only non-target forage items (e.g. weeds) would potentially be subjected to applications over 

more than one growing cycle. 

Two methods (dietary-based and dose-based) are used to estimate chronic risk to mammals 

and can result in considerably different RQ estimates. The dose-based (LD50) calculation takes into 

account that different-sized animals have to consume different amounts of food and that the food 

itself has differing nutritional value. The acute oral LD50 is believed to provide a better indication 

of inherent toxicity than the LC50 in cases where food avoidance may be an issue in the test animals. 

 If the dietary-based RQ values are adjusted to account for these factors, it is possible that these 

RQs would be roughly similar to the dose-based RQ values. Dose-based chronic RQs using the 

upper-bound residues exceed the chronic risk LOC for all size classes foraging on short grass, tall 

grass and broadleaf plant/small insect by factors of up to 12-fold. Dietary-based chronic risk 

quotients exceed the LOC using upper-bound residue estimates for mammals foraging on short 

grass and broadleaf plants/small insects. Using the mean residues, dose-based RQs (1.0-4.3) exceed 

the LOC for all size classes foraging on short grass, tall grass and broadleaf plants/small insects, 

except large mammals on tall grass (RQ=0.8). Dietary-based RQs do not exceed the LOC based on 

mean residues; however, the mean residues are expected to be exceeded about half of the time. 

Given that chlormequat chloride is used as a PGR, effects on plants are to be expected. A 

single application of chlormequat chloride results in an exceedance of the acute risk to unlisted 
31 of 66 

species LOC for dicots and exceedance of the listed species LOC for both monocots and dicots in 

wetlands adjacent to use sites. It is not clear to what degree wetlands would be adjacent to the use 

sites, but it cannot be ruled out based on this screening level assessment. It is also not known what 

effect cumulative applications of chlormequat chloride might have on sensitive plants. Because one 

of the effects seen in the study was a reduction in number of seeds emerged, affected wetlands 

could be subject to reduced numbers of sensitive individuals through seed mortality, or a delay the 

emergence of sensitive plants. Delayed emergence may adversely affect a plant’s ability to 

reproduce or affect the availability of a plant as food source for higher trophic levels at a sensitive 

time. 

Additionally, the vegetative vigor study did not establish a NOAEC, based on >25% effects 

at the lowest dose tested. However, based on the drift RQ, the NOAEC would need to be 

approximately 5X lower than the lowest rate tested to result in an exceedance for drift alone. The 

available data, and the product label, suggest there are differences among species in sensitivity to 

chlormequat chloride, and only six species were tested for each study, rather than the 10 per study 

preferred. Because the non-listed plant LOC is exceeded for dicots, potential indirect effects on 

listed animals cannot be precluded based on this screening-level risk assessment. 

Endocrine Disruption Potential 

In a non-guideline avian reproduction study, chronic exposure to chlormequat chloride 

resulted in increased numbers of cracked eggs in birds and a significant decrease in testes weight, 

increased eggshell thinning and reduced eggshell strength at the highest dose tested. Additionally, 

delayed development is reported in mammalian chronic studies. While these effects are often 

associated with effects on endocrine-mediated pathways, it is unclear from the submitted study 

whether chlormequat chloride has the capacity to act on endocrine-mediated processes. 

The EPA is required under the FFDCA, as amended by FQPA, to develop a screening 

program to determine whether certain substances (including all pesticide active and other 

ingredients) “may have an effect in humans that is similar to an effect produced by a naturally 

occurring estrogen, or other such endocrine effects as the Administrator may designate.” 

Following the recommendations of its Endocrine Disruptor Screening and Testing Advisory 

Committee (EDSTAC), EPA determined that there was scientific basis for including, as part of the 

program, the androgen and thyroid hormone systems, in addition to the estrogen hormone system. 

EPA also adopted EDSTAC’s recommendation that the Program include evaluations of potential 

effects in wildlife. For pesticide chemicals, EPA will use FIFRA and, to the extent that effects in 

wildlife may help determine whether a substance may have an effect in humans, FFDCA authority 

to require the wildlife evaluations. As the science develops and resources allow, screening of 

additional hormone systems may be added to the Endocrine Disruptor Screening Program (EDSP). 

When the appropriate screening and/or testing protocols being considered under the Agency’s 

EDSP have been developed, chlormequat chloride may be subjected to additional screening and/or 

testing to better characterize effects related to endocrine disruption. 

C. Uncertainties and Data Gaps 

 The environmental fate dataset for chlormequat chloride is incomplete. There are no 

acceptable data for hydrolysis, photolysis, anaerobic soil metabolism and terrestrial field 

dissipation. It was assumed that chlormequat chloride is stable with respect to these degradation 

pathways. In the aerobic soil and aerobic aquatic metabolism studies all transformation products 

greater than 10% of the applied may not have been identified. A total residue approach, which 
32 of 66 

assumed that all unidentified extractable residues are of similar toxicity to parent chlormequat 

chloride, was used for modeling. 

 The extent to which the species tested, which are generally chosen for traits that make them 

suitable for use in laboratory testing, represent the sensitivity spectrum of non-target organisms is 

not clearly understood. It is possible that the laboratory tests represent a relatively insensitive 

portion of the non-target organisms that could be potentially exposed. If that were the case, the 

potential risk to animals would be underestimated. 

 The environmental effects database contains areas of uncertainty. In the avian reproduction 

studies with the Japanese quail, deviations from Agency guidelines range from fairly minor, such as 

the use of a test species other than those preferred by the Agency, to an appreciable difference in 

study design. Agency guideline avian reproduction studies, conducted with the mallard duck and/or 

northern bobwhite quail, are conducted for 20-22 weeks, with a 10-week pre-laying exposure 

followed by a 10-week egg laying exposure period. The submitted study was conducted with a two 

week pre-treatment period followed by a 6-week exposure period, all with laying birds. It is 

uncertain how the results of this study would relate to a guideline study. The submitted study did 

not establish a NOAEC, an important assessment endpoint, as statistically significant effects (feed 

consumption, adult male weight gain) were seen at the lowest dose tested. 

Additionally, there are no data regarding chronic effects to fish and a NOEC was not defined in the 

vegetative vigor study. Given the propensity of chlormequat to persist under some environmental 

conditions, there is a potential for chronic exposure. The lack of chronic toxicity data is a major 

impediment to estimating potential risk. 

The T-REX model uses conservative screening-level assumptions, such as the use of 

Hoerger-Kenaga upper-bound residues and that 100% of the animals’ diet consists of contaminated 

food. In this case, chlormequat chloride will be used in nurseries and shadehouses and applied 

primarily to relatively high-value plants. It seems logical that operators will employ various 

methods to limit browse on the target plants. However, weeds, seeds and insects could be 

contaminated via direct deposition and spray drift and make up an appreciable portion of an 

animal’s diet. It is not possible in this screening-level assessment to determine the likelihood of 

sufficient exposure to pose risk. 

It is unlikely that the base assumption in TerrPlant for channelized runoff to wetlands will 

be met in the case of chlormequat chloride. The model assumes 10 acres draining to one acre, but 

the label limits application to one acre per day. Although it is possible for 10 contiguous acres to be 

treated, or even for the same acre to be treated 10 times over 10 days, this temporal element is not 

accounted for by TerrPlant. Further, application of chlormequat chloride is limited to containerized 

ornamentals and bedding plants, providing for at least a minimal disconnect from the greater 

watershed. This represents a source of uncertainty in the assessment. 

IV.CONCLUSION 

This screening-level risk assessment for the proposed outdoor use of chlormequat chloride 

indicates potential risk to aquatic and terrestrial plants, birds, and mammals. It is not clear what 

potential effects may occur in reptiles or terrestrial-phase amphibians, although there are indications 

of risk to their surrogate taxon, birds. Based on potential risk to sensitive plant species, there is a 

potential for indirect effects to most terrestrial animals given chlormequat chloride’s potential effect 

on primary productivity and wetland habitat. Indirect effects to species with obligate relationships 

to aquatic vascular plants cannot be ruled out based on this assessment. 
33 of 66 

V. THREATENED AND ENDANGERED SPECIES 

Levels of concern for threatened and endangered species are exceeded for several types of 

wildlife, including birds, mammals and both aquatic and terrestrial plants. Because potential risk is 

indicated in their surrogates, there is potential risk to listed amphibians and reptiles. Exceedance of 

LOCs for plants indicate concern for indirect effects on listed terrestrial animal species reliant on 

susceptible plant communities, or those solely dependent on a sensitive plant for some portion of 

their life cycle (obligate relationships). Due to lack of data, chronic risk to freshwater fish is 

presumed. 

The Overview of Ecological Risk Assessment Process in the Office of Pesticide Programs, 

U.S. Environmental Protection Agency (USEPA 2004, the ‘Overview Document’) discusses 

methods for providing the U.S. Fish and Wildlife Service (USFWS) and the National Marine 

Fisheries Service (NMFS), collectively ‘the Services’, with additional information regarding the 

listed animal species acute levels of concern (LOCs). A tool has been developed by EFED in 

consultation with the Services to evaluate the chance of an individual organism being affected given 

the toxicity of the chemical to the organism and the dose-response curve (see Appendix IV for 

more detail). For the present time, the Excel spreadsheet tool IECV1.1 will allow for such 

calculations by entering in the mean slope estimate and the 95 percent confidence bounds of that 

estimate as the slope parameter for the spreadsheet. It is important to note that the model output can 

go as low as 10-16 in estimating the event probability. This cut-off is a limit in the Excel 

spreadsheet environment and should not be interpreted as an agreed upon lower bound threshold for 

concern for individual effects in any given listed species. The toxicity studies used in this risk 

assessment do not report dose-response curves, and due to resource limitations, it was not possible 

to determine if the data are available to calculate the curves. In cases where dose-response curves 

are unavailable, event probabilities are calculated for the listed species LOC based on a default 

slope assumption of 4.5 as per original Agency assumptions of typical dose-response slope cited in 

Urban and Cook (1986). 

For birds and mammals, the listed species LOC is 0.1. The chance of one individual being 

affected at an RQ equal to the LOC is 1 in 294,000. For birds, the highest acute RQ in this 

assessment is 6.9, for small-sized birds foraging on short grass. If listed birds are as sensitive to 

chlormequat chloride as the endpoint used in the model indicates, and exposed to the concentration 

modeled, the chance of an individual being affected is approximately 1 in 1. Large-sized birds 

foraging on fruits/pods/large insects (RQ = 0.55) results in the potential for 1 in 8 individuals to be 

affected. The highest acute mammalian RQ in this assessment is 2.2, for small-sized mammals 

foraging on short grass. If listed mammals are as sensitive to chlormequat as the endpoint used in 

the model indicates, and exposed to the concentration modeled, the chance of an individual being 

affected is approximately 1 in 1. For medium-sized mammals foraging on fruits/pods/large insects 

(RQ = 0.12; lowest mammal RQ exceeding the LOC), the chance of an individual effect is about 1 

in 58,000. 

Because the screening-level risk assessment indicates that the outdoor chlormequat chloride 

uses exceed the endangered species LOC for birds (terrestrial-phase amphibians, reptiles), 

mammals, and plants, a ‘may affect’ designation can not be precluded based on this assessment. 

Due to lack of data, chronic risk to freshwater fish is presumed. Additionally, the acute risk LOC 

for terrestrial plants is exceeded. The Agency considers this to be indicative of a potential for 

adverse effects to those listed species that rely either on a specific plant species (plant species 

obligate) or multiple plant species (plant dependant) for some important aspect of their life cycle 

(indirect effects). Indirect effects may include general habitat modification, host plant loss, and 

food supply disruption. Further analysis regarding the overlap of individual species with each use 
34 of 66 

site is required prior to determining the likelihood of potential impact to listed species. Such a 

refinement is outlined in the following sections. 

A. Action Area 

For listed species assessment purposes, the action area is considered to be the area affected 

directly or indirectly by the Federal action and not merely the immediate area involved in the 

action. At the initial screening-level, the risk assessment considers broadly described taxonomic 

groups and so conservatively assumes that listed species within those broad groups are co-located 

with the pesticide treatment area. This means that terrestrial plants and wildlife are assumed to be 

located on or adjacent to the treated site and aquatic organisms are assumed to be located in a 

surface water body adjacent to the treated site. The assessment also assumes that the listed species 

are located within an assumed area, which has the relatively highest potential exposure to the 

pesticide, and that exposures are likely to decrease with distance from the treatment area. 

If the assumptions associated with the screening-level action area result in RQs that are 

below the listed species LOCs, a "no effect" determination conclusion is made with respect to listed 

species in that taxa, and no further refinement of the action area is necessary. Furthermore, RQs 

below the listed species LOCs for a given taxonomic group indicate no concern for indirect effects 

upon listed species that depend upon the taxonomic group covered by the RQ as a resource. 

However, in situations where the screening assumptions lead to RQs in excess of the listed species 

LOCs for a given taxonomic group, a "may affect" designation cannot be precluded and may be 

associated with direct effects on listed species belonging to that taxonomic group or may extend to 

indirect effects upon listed species that depend upon that taxonomic group as a resource. In such 

cases, additional information on the biology of listed species, the locations of these species, and the 

locations of use sites need to be considered along with available information on the fate and 

transport properties of the pesticide to determine the extent to which screening assumptions 

regarding an action area apply to a particular listed organism. These subsequent refinement steps 

could delineate how this information would impact the action area for a particular listed organism 

and may potentially include areas of exposure that are downwind and downstream of the pesticide 

use site. 

B. Taxonomic Groups Potentially at Risk 

The RQs calculated based on the ratio of EECs to toxicity endpoints, in this case the LD50

and NOAEC from animal toxicity studies and NOEC from plant toxicity studies, indicate potential 

risk to listed birds (terrestrial-phase amphibians, reptiles), mammals, and plants (aquatic vascular 

and terrestrial; Table 20). Due to lack of data, chronic risk to fish is presumed. Appendix VI

provides a tabulation of species for each taxon that may be affected by this action. 

Should estimated exposure levels occur in proximity to listed resources, the available 

screening-level information suggests a potential concern for direct effects on some listed species 

associated with the proposed new uses of chlormequat chloride. This Level I screening assessment 

is based on the initial assumption that listed species within the taxonomic groups of concern are 

actually present in areas for which the estimated exposure levels used for RQ calculation can be 

expected to occur. A specific determination of “may affect” for any RQ in excess of listed species 

LOCs cannot be made until a determination of the co-occurrence of the listed species with the 

action area has been determined. This was not done for this assessment. 

Table 20. Listed species risks associated with potential direct or indirect effects due to the 

proposed applications of chlormequat chloride in containerized ornamental production. 
35 of 66 

Listed Taxon Direct Effects 

Acute 

Direct Effects 

Chronic Indirect Effects 

Terrestrial and semi-aquatic 

plants - monocots Yes - Yes1

Terrestrial and semi-aquatic 

plants - dicots Yes - Yes1

Insects No - Yes1

Birds Yes Yes Yes1

Terrestrial phase amphibians Yes Yes Yes1

Reptiles Yes Yes Yes1

Mammals Yes Yes Yes1

Aquatic plants Yes - Yes1

Freshwater fish No No data2 Yes1

Aquatic phase amphibians No No data Yes1

Freshwater invertebrates No No Yes1

Mollusks No data No data Yes1

Marine/estuarine fish No No data Yes1

Marine/estuarine crustaceans No No data Yes1

1

Nonlisted LOC exceeded for terrestrial and semi-aquatic plants (monocots and dicots), therefore potential for adverse 

effects to those species that rely either on a specific plant species or multiple plant species. Plant indirect effects may 

include general habitat modification, host plant loss, and food supply disruption. 2

Lack of data does not preclude potential risk. 

C. Indirect Effects Analysis 

Because terrestrial plant RQs are above non-endangered species LOCs, the Agency 

considers this to be indicative of a potential for adverse effects to those listed species that are plant 

species obligates or plant dependant for some important aspect of their life cycle. The extent to 

which the new uses of chlormequat chloride will indirectly affect listed animal species will require 

identification of listed species that co-occur in areas of chlormequat chloride use and an evaluation 

of critical habit as described below. Because of the potential extent of the proposed uses of 

chlormequat chloride, EFED cannot preclude the possibility of a ‘may affect’ designation for listed 

species based on this assessment. 
36 of 66 

D. Critical Habitat 

The screening-level risk assessment has identified potential concerns for direct and indirect 

effects on listed species associated with action areas where chlormequat chloride is used. In light of 

the potential for effects on listed species, the next step for EPA and the Services is to identify which 

listed species and critical habitat are potentially implicated. Analytically, the identification of such 

species and critical habitat can occur in either of two ways. First, the agencies could determine 

whether the action area overlaps critical habitat or the occupied range of any listed species. If so, 

EPA would examine the potential impact of the use of chlormequat chloride on listed species and 

whether impacts on non-endangered species would affect the listed species indirectly or directly 

affect a constituent element of the critical habitat. Alternatively, the agencies could determine 

which listed species depend on biological resources, or have constituent elements that fall into, the 

taxa that may be directly or indirectly impacted by the pesticide. Then EPA would determine 

whether use of the pesticide overlaps the critical habitat or the occupied range of those listed 

species. At present, the information reviewed by EPA does not permit use of either analytical 

approach to make a definitive identification of species that are potentially impacted indirectly or 

critical habitats that are potentially impacted directly by the use of the pesticide. EPA and the 

Services will work together to conduct the necessary analysis. 

This screening-level risk assessment provides a table of potential biological entities that, if 

they are constituent elements of one or more critical habitats, would be of potential concern 

(Appendix VI). These correspond to the taxa identified above as being of potential concern for 

indirect effects and include freshwater fish (aquatic-phase amphibians) (presumption of chronic 

risk), birds (terrestrial-phase amphibians, reptiles), and mammals, as well as terrestrial and aquatic 

plants. These tables should serve as an initial step in problem formulation for further assessment of 

critical habitat impacts outlined above. 

E. Co-occurrence Analysis 

The goal of the analysis for co-location is to determine whether sites of pesticide use are 

geographically associated with known locations of listed species. At the screening level, this 

analysis is accomplished using the Agency’s LOCATES (v. 2.10.3) database. The database uses 

location information for listed species at the county level and compares it to agricultural census data 

for crop production at the same county level of resolution. The database contains Federally-listed 

species that are located within states known to produce the crop upon which the pesticide will be 

used. Because the Level-I screening assessment considers both direct and indirect effects across 

generic taxonomic groupings, it is not possible to exclude any taxonomic group from a LOCATES 

database query for a screening-level risk assessment. The utility of the database is limited in the 

case of chlormequat chloride by the lack of resolution in the data regarding containerized nurseries 

and bedding plant production sites. 

Because the outdoor uses of chlormequat chloride are new, the extent of its potential use has 

not yet been determined. As noted previously, at the screening level, it is not possible to evaluate 

all the potential direct and indirect effects that could impact endangered animals. Therefore, a ‘may 

effect’ designation cannot be precluded for listed animals based on this assessment.
37 of 66 

VI.REFERENCES 

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. 

Toxicol. 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. Environmental Quality and Safety.

1: 9-28. 

Latimer, J.G., H.L. Scoggins and T.J. Banko. 2001. Using Plant Growth Regulators on 

Containerized Herbaceous Perennials. Virginia Cooperative Extension Service. Publication 430-

103. 16pp. 

Linden, E., B.E. Bengtsson, O. Svanberg, and G. Sundstrom. 1979. The Acute Toxicity of 78 

Chemicals and Pesticide Formulations Against Two Brackish Water Organisms, the Bleak 

(Alburnus alburnus) and the Harpacticoid Nitocra spinipes. Chemosphere 8(11/12):843-851 

NASS. 2006. 2002 Census of Agriculture. U.S. Department of Agriculture, National Agricultural 

Statistics Service. Online at: http://www.nass.usda.gov/Census_of_Agriculture/index.asp. 

Accessed on August 27, 2006. 

Urban D.J. and N.J. Cook. 1986. Hazard Evaluation Division Standard Evaluation Procedure 

Ecological Risk Assessment. EPA 540/9-85-001. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Washington, DC. 

USEPA. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides. U.S. Environmental Protection Agency, Office of Prevention, Pesticides 

and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects Division. Feb. 

28, 2002. Online at: http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm/. 

USEPA. 2004. Overview of 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. 

USEPA. 2006. Water Models. U.S. Environmental Protection Agency, Pesticides: Science and 

Policy. Last updated May 2, 2006. Online at: http://www.epa.gov/oppefed1/models/water/. 

Willis, Guye H., and Leslie.L. McDowell. 1987. Pesticide Persistence on Foliage. in Reviews of 

Environmental Contamination and Toxicology. 100:23-73. 

Yeager T., C. Gilliam, T. Bilderback, D. Fare, A. Niemiera, K. Tilt. 2000. Best Management 

Practices: Guide for Producing Container-Grown Plants. Southern Nursery Association. 69 pp. 
38 of 66 

VII. APPENDIX I. ENVIRONMENTAL FATE AND TRANSPORT DATA 

Abiotic Degradation 

Hydrolysis 

 There are no acceptable data to fulfill this guideline requirement. 

Aqueous Photolysis 

There are no acceptable data to fulfill this guideline requirement. 

Soil Photolysis 

There are no acceptable data to fulfill this guideline requirement. 

Metabolism 

Aerobic Soil Metabolism 

In an aerobic soil metabolism study classified as supplemental (MRID 46751225), 

chlormequat chloride decreased from 91-103% at day 0 to 47-60% at day 28, 22-37% at day 56, 

and was 11-17% at day 112 in two loamy sand soils and two silt loam soils. Soils were was 

sequentially extracted four times with methanol:water (1:1, v:v), then four times with acidified 

water (pH 2). Nonextractable residues increased from 0.9-6.0% at day 0 to 19.0-27.8% at 112 days. 

 Chlormequat chloride degraded with log-linear half-lives of 34-43 d. There were no identified 

major degradates; however up to 10.7% and 43.7% of the applied radioactivity in the soil extracts 

of two soils was unaccounted for and no attempt was made to identify the transformation 

product(s). Consequently, all transformation products detected at >10% of the applied may not 

have been identified. Using a total residue approach that assumes all uncharacterized extractable 

residues are of equal toxicity to chlormequat chloride results in half-lives of 32 – 132 d. 

 

Anaerobic Soil Metabolism 

There are no acceptable data to fulfill this guideline requirement. 

Aerobic Aquatic Metabolism 

 In an aerobic aquatic metabolism study classified as supplemental (MRID 46715227), 

chlormequat chloride decreased in the total systems from 105-108% at day 0 to 37-92% at day 7, 

1.4-20% at day 14, 1.7-6.3% at day 30 and was 0.1-0.6% at study termination in a river water-sandy 

loam and pond water-silt loam system. Sediment were sequentially extracted 1-3 times with 

methanol:acidified (pH 2) water (1:1, v:v), followed by 1-5 times with acidic (pH 2) water. There 

were no identified major degradates; however there was an unidentified TLC fraction at a maximum 

of 11.1 and 13.4% of the applied radioactivity in the sediment and total system of the river watersandy loam system. Nonextractable residues increased from 1.0-2.6% at time 0 to 49.0-59.2% at 30 

days and were 27.7-31.3% at 105 study termination. Chlormequat chloride degraded with total 

system half-lives of 4.9-8.7d. 

Anaerobic Aquatic Metabolism 

Not required 
39 of 66 

Mobility 

Batch Equilibrium 

 In a batch equilibrium study classified as acceptable (MRID 46715228), following 16 hours 

of equilibration, 11.6-65.3%, 38.9-78.0%, 13.8-40.2%, and 16.2-72.7% of the applied 

[

14C]chlormequat chloride was adsorbed to a Speyer 2.2 loamy sand, Sisseln sandy loam, Les 

Evouettes silt loam, and Wilson sand soils, respectively. Following the second desorption step, the 

percent of [14C]chlormequat chloride desorbed from the test soils, as percent of the radioactivity 

adsorbed, was 11.7-47.2% for the Speyer 2.2 loamy sand, 14.7-58.2% for the Sisseln I sandy loam, 

22.0-63.6% for the Les Evouettes silt loam, and 13.4-43.6% for the Wilson sand soils. Freundlich 

adsorption and desorption coefficients are listed in the table below.

Adsorption Desorption Soil 

KF 1/n r2 KFoc KF 1/n r2 KFoc

Speyer 2.2 

Loamy sand 1.25 0.5109 0.9899 54.6 1.93 0.4695 0.9841 84.3 

Sisseln I Sandy 

loam 4.57 0.6905 0.9984 291 5.29 0.6187 0.9982 337 

Les Evouettes 

Silt loam 1.13 0.7015 0.9913 81.2 1.54 0.5909 0.9783 110 

Wilson Sand 1.73 0.5433 0.9939 92.7 2.99 0.5346 0.9944 160 

In a batch equilibrium study classified as acceptable (MRID 46715229), 5 or 16 hours of 

equilibration, 22.4-49.0%, 59.9-76.9%, and 58.1-63.5% of the applied [14C]chlormequat chloride 

was adsorbed to the Breda sandy loam, Westmaas loam, and Itingen silt loam soils.. Following the 

second desorption step, the percent of [14C]chlormequat chloride desorbed from the test soils, as 

percent of the radioactivity adsorbed, was 40.6-68.8% for the Breda sandy loam, 21.9-34.6% for the 

Westmaas loam, and 20.7-55.0% for the Itingen silt loam soils. Freundlich adsorption and 

desorption coefficients are listed in the table below.

Adsorption Desorption Soil 

KF 1/N r2 KFoc KF 1/N r2 KFoc

Breda Sandy 

loam 2.14 0.7680 0.9998 89.4 3.18 0.7629 0.9996 133 

Westmaas Loam 9.12 0.8486 0.9999 912 12.5 0.8590 0.9996 1249 

Itingen Silt loam 8.08 0.9553 1.0000 385 10.8 0.8618 0.9997 514 

Column Leaching 

In an aged column leaching study classified as supplemental (MRID 46715230), following 

15 days of aging, the mass balance was 98 -105% of the applied radioactivity. Extractable and 

unextractable residues accounted for 46-49 % and 18-23% of the applied, respectively. Cumulative 

[

14C]CO2 comprised 33-34% of the applied, collected on days 7 and 15 of aging. A mass balance 

following the 2-day leaching period was not determined. The pooled leachates contained 0.29-

0.49% of the applied radioactivity. Data characterizing the radioactivity in the soil columns were 

not provided. 
40 of 66 

In an aged column leaching study classified as supplemental (MRID 124061), following 30 

days of aging, 69% of the initial radioactivity was recovered, of which 43% was recovered from the 

soil inside the nylon mesh bag and 26% was recovered from the untreated soil outside of the nylon 

mesh bag. Following 45 days of leaching with distilled water, an average of 79% of the applied 

was recovered in the 0-3 inch segment, 2% in the 3-6 inch segment, 1% in the 6-9 inch segment, 

and <0.1% in the 9-12 inch segment. Radioactivity in the leachate volumes totaled 2.5% of the 

applied. In the leachates, an average of <0.02% of the applied was recovered on days 0-3, 2.0% on 

day 4, 0.4% on day 5, 0.1% on day 6, <0.02% on days 8-35 days, and 0.02% on days 36-45. A 

maximum of 2.5% of the applied was recovered in the leachates on days 4-6. The soil was too 

coarsely sieved (12.7 mm), so that gravel might still have been present. In addition, the temperature 

of the soil column during leaching was not reported, and it was not stated whether leaching was 

conducted in the dark. Also, distilled water was used which could lead to dispersion of clays that 

could affect soil structure. 

In an unaged column leaching study classified as supplemental (MRID 124062), following 

leaching with 20 inches of distilled water, at a rate not exceeding 1 inch/hour, through a 15 cm 

column, 75-103% of the applied was recovered in the 0-3 inch segment, 1.6-14% in the 3-6 inch 

segment, 0.5-2.6% in the 6-9 inch segment, and <0.1-1.0% in the 9-12 inch segment for the sand 

soil. Radioactivity in the leachate samples was <0.1% of the applied. The test soils were too 

coarsely sieved (12.7 mm) prior to use in the study, so that gravel might still have been present. In 

addition, the temperature of the soil column during leaching was not reported, and it was not stated 

whether leaching was conducted in the dark. Also, distilled water was used which could lead to 

dispersion of clays that could affect soil structure. 

Terrestrial Field Dissipation 

There are no acceptable data to fulfill this guideline requirement. 

Bioaccumulation 

Not required.
41 of 66 

VIII. APPENDIX II. PRZM/EXAMS OUTPUT FILES 

FL turf 

stored as FLturf TR_RED.out 

Chemical: chlormequat chloride 

PRZM environment: FLturfC.txt modified Monday, 16 June 2003 at 12:48:06 

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 15:33:30 

Metfile: w12834.dvf modified Wedday, 3 July 2002 at 08:04:28 

Water segment concentrations (ppb) 

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly 

1961 53.26 47.55 31.56 16.87 14.31 4.268 

1962 96.08 86.64 56.71 31.53 22.88 6.633 

1963 68.32 61.26 50.6 36.67 27.78 7.914 

1964 98.01 88.49 70.06 37.34 35.78 10.2 

1965 153 136 102 54.05 38.18 10.79 

1966 98.58 87.91 65.06 51.35 39.55 10.96 

1967 81.87 73.5 49.17 26.33 19.74 5.828 

1968 184 165 111 59.08 41.8 11.4 

1969 63.35 56.93 50.42 32.5 23.46 6.644 

1970 15.45 14.1 9.588 6.682 5.579 1.64 

1971 84.94 75.54 47.7 32.64 26.74 7.588 

1972 93.18 82.98 53.04 34.56 26.31 7.469 

1973 9.025 8.125 7.009 5.355 4.02 1.465 

1974 41.41 36.77 23.51 16.67 13.13 3.782 

1975 19.95 17.66 11.74 8.305 7.126 2.086 

1976 78.69 71.13 62.76 44.1 31.91 8.564 

1977 61.67 56.67 37.62 18.64 14.48 4.836 

1978 136 119 77.82 38.25 31 8.648 

1979 122 111 75.93 39.09 33.61 9.689 

1980 27.55 25.61 20.69 14.31 11.61 3.407 

1981 33.94 30.62 19.29 11.34 10.08 3.6 

1982 72.13 63.89 40.99 32.14 23.75 6.709 

1983 153 140 116 60.28 42.66 11.76 

1984 309 281 189 94.81 66.46 17.82 

1985 37.9 33.24 20.43 12.77 10.3 3.147 

1986 44.13 40.14 26.05 13.82 10.73 3.472 

1987 15.82 13.96 10.82 7.674 6.934 2.102 

1988 33.74 29.83 18.81 11.19 8.961 2.623 

1989 30.26 27.57 21.14 12.25 8.819 2.416 

1990 7.688 6.856 6.366 4.846 3.999 1.312 

Sorted results 

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly 

0.032258064516129 309 281 189 94.81 66.46 17.82 

0.0645161290322581 184 165 116 60.28 42.66 11.76 

0.0967741935483871 153 140 111 59.08 41.8 11.4 

0.129032258064516 153 136 102 54.05 39.55 10.96 

0.161290322580645 136 119 77.82 51.35 38.18 10.79 

0.193548387096774 122 111 75.93 44.1 35.78 10.2 

0.225806451612903 98.58 88.49 70.06 39.09 33.61 9.689 

0.258064516129032 98.01 87.91 65.06 38.25 31.91 8.648 

0.290322580645161 96.08 86.64 62.76 37.34 31 8.564 

0.32258064516129 93.18 82.98 56.71 36.67 27.78 7.914 

0.354838709677419 84.94 75.54 53.04 34.56 26.74 7.588 

0.387096774193548 81.87 73.5 50.6 32.64 26.31 7.469 

0.419354838709677 78.69 71.13 50.42 32.5 23.75 6.709 

0.451612903225806 72.13 63.89 49.17 32.14 23.46 6.644 

0.483870967741936 68.32 61.26 47.7 31.53 22.88 6.633 

0.516129032258065 63.35 56.93 40.99 26.33 19.74 5.828 

0.548387096774194 61.67 56.67 37.62 18.64 14.48 4.836 
42 of 66 

0.580645161290323 53.26 47.55 31.56 16.87 14.31 4.268 

0.612903225806452 44.13 40.14 26.05 16.67 13.13 3.782 

0.645161290322581 41.41 36.77 23.51 14.31 11.61 3.6 

0.67741935483871 37.9 33.24 21.14 13.82 10.73 3.472 

0.709677419354839 33.94 30.62 20.69 12.77 10.3 3.407 

0.741935483870968 33.74 29.83 20.43 12.25 10.08 3.147 

0.774193548387097 30.26 27.57 19.29 11.34 8.961 2.623 

0.806451612903226 27.55 25.61 18.81 11.19 8.819 2.416 

0.838709677419355 19.95 17.66 11.74 8.305 7.126 2.102 

0.870967741935484 15.82 14.1 10.82 7.674 6.934 2.086 

0.903225806451613 15.45 13.96 9.588 6.682 5.579 1.64 

0.935483870967742 9.025 8.125 7.009 5.355 4.02 1.465 

0.967741935483871 7.688 6.856 6.366 4.846 3.999 1.312 

0.1 153 139.6 110.1 58.577 41.575 11.356 

 Average of yearly averages: 6.2924 

Inputs generated by pe4.pl - 8-August-2003 

Data used for this run: 

Output File: FLturf TR_RED 

Metfile: w12834.dvf 

PRZM scenario: FLturfC.txt 

EXAMS environment file: pond298.exv 

Chemical Name: chlormequat chloride 

Description Variable Name Value Units Comments 

Molecular weight mwt 158.1 g/mol 

Henry's Law Const. henry 1.6e-15 atm-m^3/mol 

Vapor Pressure vapr 7.5e-8 torr 

Solubility sol 10e6 mg/L 

Kd Kd mg/L 

Koc Koc 272 mg/L 

Photolysis half-life kdp 0 days Half-life 

Aerobic Aquatic Metabolism kbacw 12.6 days Halfife 

Anaerobic Aquatic Metabolism kbacs 0 days Halfife 

Aerobic Soil Metabolism asm 100 days Halfife 

Hydrolysis: pH 7 0 days Half-life 

Method: CAM 2 integer See PRZM manual 

Incorporation Depth: DEPI cm 

Application Rate: TAPP 4.15 kg/ha 

Application Efficiency: APPEFF .99 fraction 

Spray Drift DRFT .01 fraction of application rate applied to pond 

Application Date Date 15-4 dd/mm or dd/mmm or dd-mm or dd-mmm 

Interval 1 interval 5 days Set to 0 or delete line for single app. 

Interval 2 interval 5 days Set to 0 or delete line for single app. 

Interval 3 interval 5 days Set to 0 or delete line for single app. 

Interval 4 interval 5 days Set to 0 or delete line for single app. 

Interval 5 interval 5 days Set to 0 or delete line for single app. 

Interval 6 interval 5 days Set to 0 or delete line for single app. 

Interval 7 interval 5 days Set to 0 or delete line for single app. 

Interval 8 interval 5 days Set to 0 or delete line for single app. 

Record 17: FILTRA 

 IPSCND 1 

 UPTKF 

Record 18: PLVKRT 

 PLDKRT 

 FEXTRC 0.5 

Flag for Index Res. Run IR Pond 

Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run) 

PA turf 
43 of 66 

stored as PAturfTR_RED.out 

Chemical: chlormequat chloride 

PRZM environment: PAturfC.txt modified Satday, 12 October 2002 at 15:27:02 

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 15:33:30 

Metfile: w14737.dvf modified Wedday, 3 July 2002 at 08:06:12 

Water segment concentrations (ppb) 

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly 

1961 62.26 56.13 41.81 22.7 16.27 5.878 

1962 68.36 62.26 43.4 24.06 18.81 6.969 

1963 11.47 10.81 9.817 7.707 6.072 3.266 

1964 20.89 19.68 17.55 13.6 11.17 3.579 

1965 10.33 9.601 8.811 6.919 5.428 1.983 

1966 11.6 10.95 9.901 7.616 5.912 2.653 

1967 130 118 84.63 47.68 40.89 13.03 

1968 109 102 75.52 46.27 38.37 11.72 

1969 22.57 20.51 14.71 8.259 7.348 3.782 

1970 10.99 10.3 9.386 7.378 5.893 2.466 

1971 32.25 29.87 26.02 18.17 13.92 4.581 

1972 157 146 108 72.84 52.78 15.6 

1973 73.16 69.02 49.05 37.63 28.79 9.521 

1974 51.33 48.64 40.42 28.38 21.6 7.116 

1975 26.1 23.9 17.72 11.97 10.08 3.431 

1976 18.71 17.31 12.1 7.344 5.88 3.273 

1977 15.75 14.45 10.37 8.809 7.427 2.659 

1978 53.68 51.87 42.58 24.72 18.75 5.809 

1979 82.3 78.14 59.75 33.93 25.89 8.128 

1980 14.42 13.42 12.65 9.357 7.295 2.485 

1981 51.56 48.12 41.39 25.2 18.76 5.456 

1982 96.31 90.07 71.71 48.36 35.65 10.85 

1983 17.17 15.69 13.04 11.5 10.64 3.653 

1984 146 137 94.63 56.14 42.91 12.22 

1985 47.76 45.32 36.63 26.46 20.45 6.596 

1986 38.97 36.61 27.68 20.8 16.84 5.219 

1987 23.25 21.11 14.37 9.757 9.001 3.539 

1988 148 140 107 59 43.12 12.46 

1989 64.75 60.7 53.95 38.65 28.79 8.719 

1990 123 115 81.47 45.44 35.14 10.74 

Sorted results 

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly 

0.032258064516129 157 146 108 72.84 52.78 15.6 

0.0645161290322581 148 140 107 59 43.12 13.03 

0.0967741935483871 146 137 94.63 56.14 42.91 12.46 

0.129032258064516 130 118 84.63 48.36 40.89 12.22 

0.161290322580645 123 115 81.47 47.68 38.37 11.72 

0.193548387096774 109 102 75.52 46.27 35.65 10.85 

0.225806451612903 96.31 90.07 71.71 45.44 35.14 10.74 

0.258064516129032 82.3 78.14 59.75 38.65 28.79 9.521 

0.290322580645161 73.16 69.02 53.95 37.63 28.79 8.719 

0.32258064516129 68.36 62.26 49.05 33.93 25.89 8.128 

0.354838709677419 64.75 60.7 43.4 28.38 21.6 7.116 

0.387096774193548 62.26 56.13 42.58 26.46 20.45 6.969 

0.419354838709677 53.68 51.87 41.81 25.2 18.81 6.596 

0.451612903225806 51.56 48.64 41.39 24.72 18.76 5.878 

0.483870967741936 51.33 48.12 40.42 24.06 18.75 5.809 

0.516129032258065 47.76 45.32 36.63 22.7 16.84 5.456 

0.548387096774194 38.97 36.61 27.68 20.8 16.27 5.219 

0.580645161290323 32.25 29.87 26.02 18.17 13.92 4.581 

0.612903225806452 26.1 23.9 17.72 13.6 11.17 3.782 

0.645161290322581 23.25 21.11 17.55 11.97 10.64 3.653 

0.67741935483871 22.57 20.51 14.71 11.5 10.08 3.579 
44 of 66 

0.709677419354839 20.89 19.68 14.37 9.757 9.001 3.539 

0.741935483870968 18.71 17.31 13.04 9.357 7.427 3.431 

0.774193548387097 17.17 15.69 12.65 8.809 7.348 3.273 

0.806451612903226 15.75 14.45 12.1 8.259 7.295 3.266 

0.838709677419355 14.42 13.42 10.37 7.707 6.072 2.659 

0.870967741935484 11.6 10.95 9.901 7.616 5.912 2.653 

0.903225806451613 11.47 10.81 9.817 7.378 5.893 2.485 

0.935483870967742 10.99 10.3 9.386 7.344 5.88 2.466 

0.967741935483871 10.33 9.601 8.811 6.919 5.428 1.983 

0.1 144.4 135.1 93.63 55.362 42.708 12.436 

 Average of yearly averages: 6.57936666666666 

Inputs generated by pe4.pl - 8-August-2003 

Data used for this run: 

Output File: PAturfTR_RED 

Metfile: w14737.dvf 

PRZM scenario: PAturfC.txt 

EXAMS environment file: pond298.exv 

Chemical Name: chlormequat chloride 

Description Variable Name Value Units Comments 

Molecular weight mwt 158.1 g/mol 

Henry's Law Const. henry 1.6e-15 atm-m^3/mol 

Vapor Pressure vapr 7.5e-8 torr 

Solubility sol 10e6 mg/L 

Kd Kd mg/L 

Koc Koc 272 mg/L 

Photolysis half-life kdp 0 days Half-life 

Aerobic Aquatic Metabolism kbacw 12.6 days Halfife 

Anaerobic Aquatic Metabolism kbacs 0 days Halfife 

Aerobic Soil Metabolism asm 100 days Halfife 

Hydrolysis: pH 7 0 days Half-life 

Method: CAM 2 integer See PRZM manual 

Incorporation Depth: DEPI cm 

Application Rate: TAPP 4.15 kg/ha 

Application Efficiency: APPEFF .99 fraction 

Spray Drift DRFT .01 fraction of application rate applied to pond 

Application Date Date 15-4 dd/mm or dd/mmm or dd-mm or dd-mmm 

Interval 1 interval 5 days Set to 0 or delete line for single app. 

Interval 2 interval 5 days Set to 0 or delete line for single app. 

Interval 3 interval 5 days Set to 0 or delete line for single app. 

Interval 4 interval 5 days Set to 0 or delete line for single app. 

Interval 5 interval 5 days Set to 0 or delete line for single app. 

Interval 6 interval 5 days Set to 0 or delete line for single app. 

Interval 7 interval 5 days Set to 0 or delete line for single app. 

Interval 8 interval 5 days Set to 0 or delete line for single app. 

Record 17: FILTRA 

 IPSCND 1 

 UPTKF 

Record 18: PLVKRT 

 PLDKRT 

 FEXTRC 0.5 

Flag for Index Res. Run IR Pond 

Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run) 
45 of 66 

IX.APPENDIX III. TREX MODEL INFORMATION 

Points to Consider in Development of Risk Description for Birds and Mammals

Acute and Reproduction Dietary Discussions

The risk assessment includes numerous calculations of dietary exposure for multiple weight classes 

of animals. However, there are energetic considerations that suggest that some weight class/food 

item combinations are not likely to naturally occur. For example, there are not likely to be many 15 

g mammals or 20 g birds that exclusively feed on vegetation. The risk assessor is urged to consult 

such texts as the Wildlife Exposure Factors Handbook (USEPA 1993), which provides more 

comprehensive approaches to consider energy requirements and energy availability to estimate 

dietary exposure. In addition, age of individuals may also play an important role in the types and 

relative amounts of food items selected. This should also be taken into account when describing 

dietary risks. 

Acute Toxicity RQ Approaches

Dose-based and dietary-based acute RQs should be provided to risk managers whenever effects data 

allow. There are limitations to each approach. The dose-based approach considers that the uptake 

and absorption kinetics of a gavage toxicity study to approximate exposure associated with uptake 

from a dietary matrix. Toxic response is a function of duration and intensity of exposure. For many 

compounds a gavage dose represents a very short-term high intensity exposure, where dietary 

exposure may be of a more prolonged nature. The dietary-based approach assumes that animals in 

the field are consuming food at a rate similar to that of confined laboratory animals. Energy content 

in food items differs between the field and the laboratory as does the energy requirements of wild 

and captive animals. The Wildlife Exposure Factors Handbook can provide insights into energy 

requirements of animals in the wild as well as energy content of their diets 

Reproduction RQ Approach

The typical 21-week avian reproduction study does not address the exposure duration needed to 

elicit the observed responses. The study protocol was designed to establish a steady-state tissue 

concentration for bioaccumulative compounds. For other pesticides it is entirely possible that 

steady-state tissue concentrations are achieved earlier than the 21-week exposure period. 

Moreover, pesticides may exert effects at critical periods of the reproduction cycle and so long term 

exposure may not be necessary to elicit the effect observed in the 21-week protocol. The EFED risk 

assessment uses the single-day maximum estimated EEC as a conservative approach. The degree to 

which this exposure is conservative cannot be determined by the existing reproduction study. 

However, risk assessment discussions should be accompanied by the graphics from T-REX model 

regarding the number of days dietary exposure is above the NOAEC. The greater number of days 

EECs exceed the NOAEC, the greater the confidence in predictions of reproductive risk concerns. 
46 of 66 

X. APPENDIX IV. TERRPLANT MODEL 

Exposure to Terrestrial Plants including Wetlands (August 8, 2001; version 1.0) 

Terrestrial plants inhabiting dry and semi-aquatic (wetland) areas may be exposed to pesticides from 

runoff and/or spray drift. Semi-aquatic areas are low-lying wet areas that may dry up at times 

throughout the year. 

EFED's runoff scenario is (1) based on a pesticide's water solubility and the amount ot pesticide 

present on the soil surface and its top one inch, (2) characterized as "sheet runoff" (one treated acre 

to an adjacent acre) for dry areas, (3) characterized as "channel runoff" (10 acres to a distant 

low-lying acre) for semi-aquatic or wetland areas, and (4) based on percent runoff values of 0.01, 

0.02, and 0.05 for water solubilities of <10, 10-100, and >100 ppm, respectively. 

EFED's Spray Drift scenario is assumed as (1) 1% for ground application, and (2) 5% for aerial, 

airblast, forced air, and spray chemigation applications. The spray drift ratio used here is in 

agreement with the policy procedures at the time the worksheet was designed. 

Currently, 1) this worksheet is designed to derive the plant exposure concentrations from a single, 

maximum application rate only. 2) For pesticide applications with incorporation of depth of less than 

1 inch, the total loading EECs derived for the incorporation method will be same as the 

unincorporated method. 

To calculate RQ values for Non-Endangered Terrestrial Plants: 

Terrestrial Plants Inhabiting Areas Adjacent to Treatment Site: 

Emergence RQ = Total Loading to Adjacent Area or EEC/Seedling Emergence EC25 

Drift RQ = Drift EEC/Vegetative Vigor EC25 

Terrestrial Plants Inhabiting Semi-aquatic Areas Adjacent to Treatment Site: 

 

Emergence RQ = Total Loading to Semi-aquatic Area or EEC/Seedling Emergence EC25 

 Drift RQ = Drift EEC/Vegetative Vigor EC25 

To calculate RQ values for Endangered Terrestrial Plants: 

Endangered Terrestrial Plants Inhabiting Areas Adjacent to Treatment Site: 

 

Emergence RQ = Total Loading to Adjacent Area or EEC/Seedling Emergence EC05 

Drift RQ = Drift EEC/Vegetative Vigor EC05 or NOAEC 

Endangered Terrestrial Plants Inhabiting Semiaquatic Areas Near Treatment Site: 

 

Emergence RQ = Total Loading to Semiaquatic Area or EEC/Seedling Emergence EC05 
47 of 66 

Drift RQ = Drift EEC/Vegetative Vigor EC05 or NOAEC 

Formulas used to calculate EEC values (8/08/01; version 1.0) 

To calculate EECs for terrestrial plants inhabiting in areas adjacent to treatment sites 

 

Un-incorporated Ground Application (Non-granular): 

Sheet Runoff = Application Rate (lb ai/A) x Runoff Value 

Drift = Application Rate (lb ai/A) x 0.01 

Total Loading = EEC = Sheet Runoff + Drift 

Incorporated Ground Application with Drift (Non-granular): 

Sheet Runoff = [Application Rate (lb ai/A)/Incorporation Depth (inch)] x Runoff Value 

 

Drift = Application Rate (lb ai/A) x 0.01 

Total Loading = EEC = Sheet Runoff + Drift 

Un-incorporated Ground Application (Granular): 

Sheet Runoff = EEC = Application Rate (lb ai/A) x Runoff Value 

Incorporated Ground Application without Drift (Granular): 

Sheet Runoff = EEC = [Application Rate (lb ai/A)/Incorportion Depth (inch)] 

 

x Runoff Value 

Aerial/Airblast/Spray Chemigation Applications: 

Sheet Runoff = Application Rate (lb ai/A) x Runoff Value x Application Efficiency of 0.6 

 

Drift = Application Rate (lb ai/A) x 0.05 

Total Loading = EEC = Sheet Runoff + Drift 

Runoff Value = 0.01, 0.02, or 0.05 when the solubility of the chemical is <10 ppm, 10-100 ppm, 

or>100 ppm, respectively 

Incorporation Depth: Use the minimum incorporation depth reported on the label. 
48 of 66 

XI.APPENDIX V. INDIVIDUAL EFFECT CHANCE MODEL 

Use of the Probit Dose Response Relationship to Provide Information on the Endangered 

Species Levels of Concern 

Introduction 

The document entitled Overview of Ecological Risk Assessment Process in the Office of Pesticide 

Programs, U.S. Environmental Protection Agency (USEPA 2004, the Overview Document) 

discusses methods for providing the U.S. Fish and Wildlife Service (USFWS) and the National 

Marine Fisheries Service (NMFS) with additional information regarding the listed animal species 

acute levels of concern (LOCs). This document provides (1) the background information on how 

agreements were reached between the services and USEPA for methods to provide additional LOC 

information, and (2) a discussion of issues concerning those methods and their resolution. Risk 

Assessors within the Environmental Fate and Effects Division (EFED) should use the Overview 

Document as well as the following information as guidance for using the probit dose response 

relationship as a tool for providing additional information on the listed species LOCs

Effective immediately, all screening-level risk assessments (REDS, Section 3's, Section 18's, etc.) 

using risk quotient (RQ) methods will incorporate this analysis, regardless of whether listed species 

LOCs are exceeded or not.

Background on Discussion of LOCs with USFWS and NMFS 

Over the course of negotiations with the USFWS and NMFS, one topic of discussion centered on the 

risk quotient values established as screening thresholds for consideration of direct toxic effects on 

listed species (i.e., the acute listed species LOCs of 0.1 and 0.05 used for terrestrial and aquatic 

animals, respectively). The Agency provided the Services with the mathematical interpretations of 

these LOC values, which was documented in the background information supplied to the Services 

and is included in the Overview Document CD distributed to all employees in EFED. In short, the 

interpretation of the LOCs was discussed in terms of best estimates of the chance of an individual 

event (mortality or immobilization) should exposure at the estimated environmental concentration 

actually occur for a species with sensitivity to the pesticide on par with the toxicity endpoint selected 

for RQ calculation. 

The mathematics were based on a long-held assumption of a probit dose-response relationship for 

acute toxicity endpoints. The listed species LOCs or the fraction (0.05 or 0.1) of the dose estimated 

to produce 50% mortality were used to interpolate from a probit dose response curve to estimate the 

associated ECx, LDx, or LCx. These values were then used to estimate the chance of an individual 

event. 

Two issues were identified over the course of discussions with the Services in regard to the Agency's 

presentations of the math and the interpretation of the LOCs. First was the issue that the chance of 

individual event was highly dependant upon the assumed shape and slope of the dose-response 

relationship. Second was that the Services were unwilling to present a generic threshold of the 

chance of an individual event, below which the Services would not have a concern for listed species 
49 of 66 

impacts The services indicated that the baseline conditions of a species and it's biology would 

dictate species-specific concerns for tolerated effects. Further discussion on the confidence of 

extreme value extrapolations for probit dose response did not achieve an agreement between all 

parties on what the lower limit of cutoff in reporting extreme events should be for interpretation of 

listed species acute LOCs. Even consideration of using the most intolerant listed species within 

taxonomic groups as a screening basis for other more tolerant listed species was not accepted as a 

viable strategy for establishing generic effects thresholds for listed species. 

Consequently, it was accepted by all parties that the Agency would provide in its risk assessments an 

interpretation of the listed species LOCs in terms of the chance of an individual effect should 

organisms be exposed to a media concentration or dose corresponding to 1/10 or 1/20 of the LC50, 

LD50, or EC50 used as the acute toxicity measurement endpoint for a particular animal taxonomic 

group. To accomplish this interpretation, the Agency would use (1) the slope of the dose response 

relationship available from the toxicity study used to establish the acute toxicity measurement 

endpoints for each animal taxonomic group; (2) an assumption of a probit dose response 

relationship; (3) a mean estimate of slope consistent with current Agency statistical procedures; and 

(4) a lower limit to the estimate of individual effect chance based on what could be calculated by 

Excel spreadsheet "Normdist" function. 

Issues with the LOC Interpretation Method and Their Resolution 

Discussion within the Agency has identified three issues with regard to the calculation of the chance 

of individual event corresponding to the listed species acute LOCs. The largest issue is the 

extrapolation to extremely low probability events, referring to the very large confidence intervals 

surrounding such estimates. A secondary issue, but still very important, is the extent to which probit 

dose response slopes can be calculated for existing studies (i.e., the fitting of a probit dose response 

relationship to available data). The third issue is how to proceed when information is unavailable to 

estimate a slope. The following guidance information will address these issues: 

Extrapolation to Extremely Low Probability Events

The nature of this issue centers on the fact that slope estimates are accompanied by a corresponding 

variance in the slope term. This variance in the slope term and to some extent the variance in the 

median lethal dose estimate, can result in wide variations of effects probabilities at the upper and 

lower tails of the dose range. While the Agency has agreed to present the effects probability 

associated with the LOCs based on the mean estimate of slope, it is evident that expression of this 

single estimate of the corresponding effects probability would suggest that the Agency has 

inordinately high confidence in this estimate, when in fact there is likely considerable variability in 

the estimate. Consequently, for the short term, it is recommended that both the estimate of effects 

probability be calculated for the mean slope estimate and listed species LOC and available 

information on the 95% confidence interval of the slope estimate be used to calculate an upper and 

lower estimate of the effects probability. It is important to note that interpretation of these results is 

not required under agreement with the Services. The Services have requested that the results be 

made available in the screening assessment reports. It is recommended that reporting minimally 

include the following discussion: 
50 of 66 

" Based on an assumption of a probit dose response relationship with a mean 

estimated slope of (enter slope here), the corresponding estimated chance of 

individual mortality associated with the listed species LOC of (0.1 or 0.05) the acute 

toxic endpoint for (enter appropriate animal taxonomic group) is (enter value). It 

is recognized that extrapolation of very low probability events is associated with 

considerable uncertainty in the resulting estimates. To explore possible bounds to 

such estimates, the upper and lower values for the mean slope estimate (enter the 95 

percent confidence interval for the slope) were used to calculate upper and lower 

estimates of the effects probability associated with the listed species LOC. These 

values are (enter the upper and lower estimates)." 

For the present time, the Excel spreadsheet tool IECV1.1 will allow for such calculations by entering 

in the mean slope estimate and the 95 percent confidence bounds of that estimate as the slope 

parameter for the spreadsheet. It is important to note that the model output can go as low as 10 E-16 

in estimating the event probability. This cut-off is a limit in the Excel spreadsheet environment and 

is not to be interpreted as an agreed upon lower bound threshold for concern for individual effects in 

any given listed species. 

EFED will continue to work on establishing subsequent approaches to account for both the variance 

in the slope and the median lethal dose estimate when establishing this upper and lower estimates of 

effects estimates associated with the listed species LOCs. 

Probit Slopes for Existing Studies

Slope information may or may not be estimated for a given study upon which RQs were calculated. 

When the available data evaluation records (DERs) or study reports provide the slope information 

(i.e., mean slope estimate, p-value of estimate, and 95% confidence interval of the estimate) , it 

should be used as reported once these reported values have been carefully reviewed to ensure their 

accuracy. However, there are likely to be situations where slope information is not provided in the 

DERs. For such situations, the raw data from the study must be entered into and analyzed by the 

EFED current statistical package for acute effects studies. See the EFED Statistical Workgroup for 

assistance with accessing these software. Probit slope information will be used from these analyses. 

 However, there are two distinctions that must be made in the reporting of these results for listed 

species evaluation. First, studies with good probit fit characteristics can be used as reported 

accompanied with a statement that the probit dose response relationship was statistically appropriate 

for the data set. Alternatively, if the assumption of a probit dose response was shown to be 

statistically unsupported, the slope estimates are still used in the listed species LOC interpretation 

(remember we have in our policy assumed probit dose response when LOCs were established), but 

the statistical rejection criteria must be presented along with a statement : 

"Although the Agency has assumed a probit dose response relationship in establishing 

the listed species LOCs, the available data for the toxicity study generating RQs for 

this taxonomic group do not statistically support a probit dose response relationship 

(enter the p-value from the statistical package) and so the confidence in estimated 

event probabilities based on this dose response relationship and the listed species 

LOC is low." 
51 of 66 

EFED will continue to work on the development of statistical tools to explore alternative dose 

response relationships in situations where the assumption of probit dose response relationship is not 

upheld by available data. 

How to Proceed When Information is Unavailable to Estimate a Slope 

State in the assessment that information is unavailable to estimate a slope from the available toxicity 

study and the reason why re-analysis of raw data is not possible. Then state that a event probability 

was calculated for the listed species LOC based on a default slope assumption of 4.5 as per original 

Agency assumptions of typical slope cited in Urban and Cook (1986). 

References

United States Environmental Protection Agency (USEPA). 2004. Overview of 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. 

Urban D.J. and N.J. Cook. 1986. Hazard Evaluation Division Standard Evaluation Procedure 

Ecological Risk Assessment. EPA 540/9-85-001. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Washington, DC. 
52 of 66 

XII. APPENDIX VI. ENDANGERED SPECIES COUNT FROM THE LOCATES 

DATABASE BY LISTED TAXON FOR EACH CROP 

Species Counts by State for Indicated Crops

No species were excluded.

Minimum of 1 Acre.

All Medium Types Reported

floriculture crops - bedding/garden plants, cut flowers& florist greens, 

foliage and potted flowering plants- total, nursery and greenhouse crops - 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

Alabama

The taxa Amphibian has 2 species co-occurring with indicated crops.

The taxa Bird has 4 species co-occurring with indicated crops.

The taxa Bivalve has 28 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 9 species co-occurring with indicated crops.

The taxa Ferns has 2 species co-occurring with indicated crops.

The taxa Fish has 15 species co-occurring with indicated crops.

The taxa Gastropod has 10 species co-occurring with indicated crops.

The taxa Mammal has 4 species co-occurring with indicated crops.

The taxa Monocot has 3 species co-occurring with indicated crops.

The taxa Reptile has 5 species co-occurring with indicated crops.

Arizona

The taxa Amphibian has 2 species co-occurring with indicated crops.

The taxa Bird has 8 species co-occurring with indicated crops.

The taxa Dicot has 14 species co-occurring with indicated crops.

The taxa Fish has 17 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Mammal has 8 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

The taxa Reptile has 2 species co-occurring with indicated crops.

Arkansas

The taxa Bird has 3 species co-occurring with indicated crops.

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53 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Bivalve has 5 species co-occurring with indicated crops.

The taxa Crustacean has 2 species co-occurring with indicated crops.

The taxa Dicot has 4 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 3 species co-occurring with indicated crops.

California

The taxa Amphibian has 6 species co-occurring with indicated crops.

The taxa Bird has 16 species co-occurring with indicated crops.

The taxa Conf/cycds has 2 species co-occurring with indicated crops.

The taxa Crustacean has 9 species co-occurring with indicated crops.

The taxa Dicot has 161 species co-occurring with indicated crops.

The taxa Fish has 29 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Insect has 22 species co-occurring with indicated crops.

The taxa Mammal has 20 species co-occurring with indicated crops.

The taxa Marine mml has 2 species co-occurring with indicated crops.

The taxa Monocot has 18 species co-occurring with indicated crops.

The taxa Reptile has 8 species co-occurring with indicated crops.

Colorado

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Dicot has 6 species co-occurring with indicated crops.

The taxa Fish has 6 species co-occurring with indicated crops.

The taxa Insect has 2 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Connecticut

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 1 species co-occurring with indicated crops.

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54 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

Delaware

The taxa Bird has 2 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

Florida

The taxa Amphibian has 1 species co-occurring with indicated crops.

The taxa Bird has 10 species co-occurring with indicated crops.

The taxa Bivalve has 7 species co-occurring with indicated crops.

The taxa Conf/cycds has 1 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 49 species co-occurring with indicated crops.

The taxa Fish has 4 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Lichen has 1 species co-occurring with indicated crops.

The taxa Mammal has 13 species co-occurring with indicated crops.

The taxa Marine mml has 1 species co-occurring with indicated crops.

The taxa Monocot has 3 species co-occurring with indicated crops.

The taxa Reptile has 10 species co-occurring with indicated crops.

Georgia

The taxa Amphibian has 1 species co-occurring with indicated crops.

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55 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Bird has 5 species co-occurring with indicated crops.

The taxa Bivalve has 16 species co-occurring with indicated crops.

The taxa Conf/cycds has 1 species co-occurring with indicated crops.

The taxa Dicot has 9 species co-occurring with indicated crops.

The taxa Ferns has 2 species co-occurring with indicated crops.

The taxa Fish has 8 species co-occurring with indicated crops.

The taxa Mammal has 3 species co-occurring with indicated crops.

The taxa Marine mml has 1 species co-occurring with indicated crops.

The taxa Monocot has 6 species co-occurring with indicated crops.

The taxa Reptile has 2 species co-occurring with indicated crops.

Hawaii

The taxa Arachnid has 1 species co-occurring with indicated crops.

The taxa Bird has 32 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 233 species co-occurring with indicated crops.

The taxa Ferns has 12 species co-occurring with indicated crops.

The taxa Gastropod has 39 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Marine mml has 1 species co-occurring with indicated crops.

The taxa Monocot has 22 species co-occurring with indicated crops.

The taxa Reptile has 2 species co-occurring with indicated crops.

Idaho

The taxa Bird has 1 species co-occurring with indicated crops.

The taxa Dicot has 3 species co-occurring with indicated crops.

The taxa Fish has 8 species co-occurring with indicated crops.

The taxa Gastropod has 2 species co-occurring with indicated crops.

The taxa Mammal has 3 species co-occurring with indicated crops.

Illinois

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56 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 7 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 7 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Insect has 2 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Indiana

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 11 species co-occurring with indicated crops.

The taxa Dicot has 4 species co-occurring with indicated crops.

The taxa Insect has 2 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

Iowa

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 2 species co-occurring with indicated crops.

The taxa Dicot has 3 species co-occurring with indicated crops.

The taxa Ferns has 1 species co-occurring with indicated crops.

The taxa Fish has 2 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

Kansas

The taxa Bird has 4 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Fish has 4 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

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57 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Kentucky

The taxa Bird has 7 species co-occurring with indicated crops.

The taxa Bivalve has 22 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 9 species co-occurring with indicated crops.

The taxa Fish has 3 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 3 species co-occurring with indicated crops.

Louisiana

The taxa Bird has 5 species co-occurring with indicated crops.

The taxa Bivalve has 2 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Ferns has 1 species co-occurring with indicated crops.

The taxa Fish has 2 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Marine mml has 1 species co-occurring with indicated crops.

The taxa Reptile has 7 species co-occurring with indicated crops.

Maine

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Fish has 2 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

Maryland

The taxa Bird has 2 species co-occurring with indicated crops.

The taxa Bivalve has 1 species co-occurring with indicated crops.

The taxa Dicot has 4 species co-occurring with indicated crops.

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AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Fish has 2 species co-occurring with indicated crops.

The taxa Insect has 2 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

Massachusetts

The taxa Bird has 4 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Insect has 3 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

The taxa Reptile has 2 species co-occurring with indicated crops.

Michigan

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 2 species co-occurring with indicated crops.

The taxa Dicot has 4 species co-occurring with indicated crops.

The taxa Ferns has 1 species co-occurring with indicated crops.

The taxa Insect has 4 species co-occurring with indicated crops.

The taxa Mammal has 3 species co-occurring with indicated crops.

The taxa Monocot has 3 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

Minnesota

The taxa Bird has 2 species co-occurring with indicated crops.

The taxa Bivalve has 2 species co-occurring with indicated crops.

The taxa Dicot has 2 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

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59 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Monocot has 2 species co-occurring with indicated crops.

Mississippi

The taxa Amphibian has 1 species co-occurring with indicated crops.

The taxa Bird has 6 species co-occurring with indicated crops.

The taxa Bivalve has 7 species co-occurring with indicated crops.

The taxa Dicot has 2 species co-occurring with indicated crops.

The taxa Ferns has 1 species co-occurring with indicated crops.

The taxa Fish has 3 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Reptile has 7 species co-occurring with indicated crops.

Missouri

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 6 species co-occurring with indicated crops.

The taxa Dicot has 6 species co-occurring with indicated crops.

The taxa Fish has 5 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Insect has 2 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Montana

The taxa Bird has 2 species co-occurring with indicated crops.

The taxa Dicot has 2 species co-occurring with indicated crops.

The taxa Fish has 4 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

Nebraska

The taxa Bird has 4 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Fish has 2 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

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60 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Nevada

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Dicot has 7 species co-occurring with indicated crops.

The taxa Fish has 15 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

New Hampshire

The taxa Bird has 1 species co-occurring with indicated crops.

The taxa Bivalve has 1 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

New Jersey

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Dicot has 2 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 3 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

New Mexico

The taxa Amphibian has 1 species co-occurring with indicated crops.

The taxa Bird has 7 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 10 species co-occurring with indicated crops.

The taxa Fish has 9 species co-occurring with indicated crops.

The taxa Gastropod has 2 species co-occurring with indicated crops.

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61 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Mammal has 5 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

New York

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 1 species co-occurring with indicated crops.

The taxa Dicot has 4 species co-occurring with indicated crops.

The taxa Ferns has 1 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

North Carolina

The taxa Arachnid has 1 species co-occurring with indicated crops.

The taxa Bird has 5 species co-occurring with indicated crops.

The taxa Bivalve has 8 species co-occurring with indicated crops.

The taxa Dicot has 20 species co-occurring with indicated crops.

The taxa Fish has 4 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Lichen has 1 species co-occurring with indicated crops.

The taxa Mammal has 4 species co-occurring with indicated crops.

The taxa Marine mml has 1 species co-occurring with indicated crops.

The taxa Monocot has 5 species co-occurring with indicated crops.

The taxa Reptile has 5 species co-occurring with indicated crops.

North Dakota

The taxa Bird has 4 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

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62 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

Ohio

The taxa Bird has 2 species co-occurring with indicated crops.

The taxa Bivalve has 6 species co-occurring with indicated crops.

The taxa Dicot has 3 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Insect has 4 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

The taxa Reptile has 2 species co-occurring with indicated crops.

Oklahoma

The taxa Bird has 6 species co-occurring with indicated crops.

The taxa Bivalve has 2 species co-occurring with indicated crops.

The taxa Fish has 4 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 3 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

Oregon

The taxa Bird has 5 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 11 species co-occurring with indicated crops.

The taxa Fish has 22 species co-occurring with indicated crops.

The taxa Insect has 2 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

Pennsylvania

The taxa Bird has 2 species co-occurring with indicated crops.

The taxa Bivalve has 2 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

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63 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Reptile has 1 species co-occurring with indicated crops.

Rhode Island

The taxa Bird has 1 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

South Carolina

The taxa Amphibian has 1 species co-occurring with indicated crops.

The taxa Bird has 5 species co-occurring with indicated crops.

The taxa Bivalve has 1 species co-occurring with indicated crops.

The taxa Dicot has 12 species co-occurring with indicated crops.

The taxa Ferns has 1 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Lichen has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Marine mml has 6 species co-occurring with indicated crops.

The taxa Monocot has 6 species co-occurring with indicated crops.

The taxa Reptile has 5 species co-occurring with indicated crops.

South Dakota

The taxa Bird has 4 species co-occurring with indicated crops.

The taxa Fish has 2 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Tennessee

The taxa Arachnid has 1 species co-occurring with indicated crops.

The taxa Bird has 4 species co-occurring with indicated crops.

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64 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Bivalve has 38 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 16 species co-occurring with indicated crops.

The taxa Ferns has 1 species co-occurring with indicated crops.

The taxa Fish has 16 species co-occurring with indicated crops.

The taxa Gastropod has 2 species co-occurring with indicated crops.

The taxa Lichen has 1 species co-occurring with indicated crops.

The taxa Mammal has 3 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Texas

The taxa Amphibian has 4 species co-occurring with indicated crops.

The taxa Arachnid has 10 species co-occurring with indicated crops.

The taxa Bird has 13 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 20 species co-occurring with indicated crops.

The taxa Fish has 4 species co-occurring with indicated crops.

The taxa Insect has 8 species co-occurring with indicated crops.

The taxa Mammal has 5 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

The taxa Reptile has 6 species co-occurring with indicated crops.

Utah

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Dicot has 19 species co-occurring with indicated crops.

The taxa Fish has 8 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

Vermont

The taxa Bird has 1 species co-occurring with indicated crops.

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65 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Bivalve has 1 species co-occurring with indicated crops.

The taxa Dicot has 1 species co-occurring with indicated crops.

The taxa Mammal has 1 species co-occurring with indicated crops.

The taxa Monocot has 1 species co-occurring with indicated crops.

Virginia

The taxa Amphibian has 1 species co-occurring with indicated crops.

The taxa Bird has 3 species co-occurring with indicated crops.

The taxa Bivalve has 13 species co-occurring with indicated crops.

The taxa Crustacean has 1 species co-occurring with indicated crops.

The taxa Dicot has 12 species co-occurring with indicated crops.

The taxa Fish has 5 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Insect has 3 species co-occurring with indicated crops.

The taxa Mammal has 5 species co-occurring with indicated crops.

The taxa Monocot has 4 species co-occurring with indicated crops.

The taxa Reptile has 1 species co-occurring with indicated crops.

Washington

The taxa Bird has 5 species co-occurring with indicated crops.

The taxa Dicot has 7 species co-occurring with indicated crops.

The taxa Fish has 18 species co-occurring with indicated crops.

The taxa Insect has 1 species co-occurring with indicated crops.

The taxa Mammal has 4 species co-occurring with indicated crops.

West Virginia

The taxa Amphibian has 1 species co-occurring with indicated crops.

The taxa Bird has 1 species co-occurring with indicated crops.

The taxa Bivalve has 5 species co-occurring with indicated crops.

The taxa Dicot has 4 species co-occurring with indicated crops.

The taxa Gastropod has 1 species co-occurring with indicated crops.

The taxa Mammal has 4 species co-occurring with indicated crops.

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66 of 66 

AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, 

MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VT, 

VA, WA, WV, WI, WY

The taxa Monocot has 1 species co-occurring with indicated crops.

Wisconsin

The taxa Bird has 4 species co-occurring with indicated crops.

The taxa Bivalve has 2 species co-occurring with indicated crops.

The taxa Dicot has 4 species co-occurring with indicated crops.

The taxa Insect has 2 species co-occurring with indicated crops.

The taxa Mammal has 2 species co-occurring with indicated crops.

The taxa Monocot has 2 species co-occurring with indicated crops.

Wyoming

The taxa Bird has 1 species co-occurring with indicated crops.

The taxa Dicot has 2 species co-occurring with indicated crops.

The taxa Fish has 1 species co-occurring with indicated crops.

The taxa Mammal has 4 species co-occurring with indicated crops.

No species were excluded.

Dispersed species included in report.

9/21/2006 1:45:26 PM Ver. 2.10.3 Page 15 of 15