Proposed Registration of 

 Aminocyclopyrachlor on Non-Crop 

 Areas, Sod Farms, Turf, and 

 Residential Lawns

June 16, 2010 

U.S. Environmental Protection Agency 

Office of Pesticide Programs 

Registration Division 

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Proposed Registration of

Aminocyclopyrachlor on Non-Crop

Areas, Sod Farms, Tu...., and

Residential Lawns

Approvedb~ f~

Date:

Lois Rossi, Director

Registration Division

~'(M'./ 1% &O/D

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TABLE OF CONTENTS 

1. REGULATORY RATIONALE........................................................................................... 4

1.1. CHEMICAL INFORMATION ............................................................................................. 4

1.1.1. Chemical Name: Aminocyclopyrachlor (parent acid) ..........................................................................4

1.1.2. Chemical Name: Aminocyclopyrachlor-methyl (methyl ester)............................................................5

1.1.3. Chemical Name: Aminocyclopyrachlor potassium salt........................................................................5

1.2. HUMAN HEALTH RISK ................................................................................................... 6

1.2.1. Toxicological Summary and Considerations.........................................................................................6

1.2.2. Toxicological End Points and Doses .....................................................................................................7

1.2.3. Consideration of Toxicity to Children ...................................................................................................8

1.2.4. Dietary Risk...........................................................................................................................................9

1.2.5. Residential Risk...................................................................................................................................10

1.2.6. Aggregate Risk ....................................................................................................................................11

1.2.7. Occupational Risk................................................................................................................................11

1.3. ENVIRONMENTAL RISK................................................................................................ 12

1.3.1. Environmental Summary and Considerations......................................................................................13

1.3.2. Environmental Fate..............................................................................................................................13

1.3.3. Ecological Risk....................................................................................................................................14

1.4. PUBLIC INTEREST......................................................................................................... 16

2. PROPOSED REGULATORY DECISION ...................................................................... 17

2.1. DATA REQUIREMENTS ................................................................................................. 17

2.1.1. Human Health Data Requirements ......................................................................................................17

2.1.2. Environmental Data Requirements......................................................................................................17

2.2. LABEL REQUIREMENTS................................................................................................ 18

2.2.1. Environmental Hazards........................................................................................................................18

2.2.2. Plant Residue .......................................................................................................................................19

2.2.3. Livestock .............................................................................................................................................20

2.2.4. Spray Drift ...........................................................................................................................................20

2.2.5. Restricted-Entry Interval (REI)............................................................................................................21

2.3. PROPOSED REGISTRATION DECISION.......................................................................... 21

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Proposed Registration of Aminocyclopyrachlor on Non-Crop Areas, 

Sod Farms, Turf, and Residential Lawns 

1. REGULATORY RATIONALE 

The Agency is proposing to conditionally grant the first non-food use registrations of the active 

ingredient aminocyclopyrachlor, formulated as 2 technical products, 3 manufacturing-use 

products, and 15 end-use products. It is a selective herbicide providing pre- and post-emergent 

control of broadleaf weeds, woody species, vines, and grasses in non-crop areas [private, public, 

and military lands: uncultivated non-agricultural areas (such as airports, highway, railroad and 

utility rights-of-way, sewage disposal areas), uncultivated non-crop agricultural areas (such as 

farmyards, fuel storage areas, fence rows, non-irrigation ditchbanks, barrier strips), outdoor 

industrial sites (such as lumberyards, pipeline, and tank farms), natural areas (such as wildlife 

management areas, wildlife openings, wildlife habitats, recreation areas, campgrounds, 

trailheads, and trails)], turf/lawns (residential, industrial, and institutional), golf courses, parks, 

cemeteries, athletic fields, and sod farms. 

Three forms of aminocyclopyrachlor are being proposed for registration: the parent acid 

(aminocyclopyrachlor), the methyl ester (aminocyclopyrachlor-methyl), and the potassium salt 

(aminocyclopyrachlor potassium salt). The parent acid, aminocyclopyrachlor, is considered the 

active ingredient. 

Aminocyclopyrachlor may be applied in three different formulations: granular, water dispersible 

granular (dry flowable), and soluble liquid. Occupational application scenarios include: aerial 

(fixed wing or helicopter), ground boom, right-of-way sprayer, push-type spreader, push cyclone 

spreader, tractor drawn broadcast spreader, and lawn care operator (LOC) handgun. Broadcast 

applications may be performed by using either a single ground boom, a tractor type broadcast, or 

as a banded application for pre-plant, pre-emergence, or early post-emergence. Pre-plant 

applications can be made as either a single or split application that is either surface applied or 

incorporated. Residential application scenarios include low pressure hand wand, hose-end 

sprayer, and hand-held spreader (i.e. belly grinder). Proposed maximum annual application rates 

range from 0.05 – 0.324 lb acid equivalent (ae)/acre/year. 

1.1. Chemical Information 

Aminocyclopyrachlor is a systemic herbicide in the pyrimidine carboxylic acids class within the 

family of synthetic auxins, which disrupts gene expression resulting in undifferentiated cell 

division and elongation. It is biologically active in soil and is rapidly absorbed by roots and 

leaves. Effects to target weeds include downward bending of leaves, severe necrosis, stem 

thickening, growth stunting, leaf crinkling and cupping, calloused stems and leaf veins, and 

enlarged roots. Symptoms may begin from a few hours to a few days after application, and plant 

death may take weeks to several months. 

1.1.1. Chemical Name: Aminocyclopyrachlor (parent acid)

 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylic acid 

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EPA PC Code: 288008 

CAS Number: 858956-08-8 

Mode of Action: Synthetic auxin-type herbicide causing disorganized plant growth 

 (pyrimidine carboxylic acid) 

Registrant: E.I. du Pont de Nemours and Company (EPA Company Number: 352) 

Products: 

EPA Reg. No. Product Name % a.i. 

352-TIE (782) DPX-MAT28 Technical Herbicide 89.3 

352-TOA (796) DPX-MAT28 10% Manufacturing Concentrate 10.0 

352-TIT (787) DPX-MAT28 50SG Herbicide 50.0 

352-TOU (794) DPX-MAT28 50SG Turf Herbicide 50.0 

352-IRG (813) DPX-MAT28 0.05G Turf Herbicide + Fertilizer 0.05 

352-IRU (814) DPX-MAT28 0.03G Turf Herbicide + Fertilizer 0.03 

352-IRL (815) DPX-MAT28 0.068G Lawn Herbicide + Fertilizer 0.068 

1.1.2. Chemical Name: Aminocyclopyrachlor-methyl (methyl ester) 

 methyl 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylate 

EPA PC Code: 288009 

CAS Number: 858954-83-3 

Mode of Action: Synthetic auxin-type herbicide causing disorganized plant growth 

 (pyrimidine carboxylic acid) 

Registrant: E.I. du Pont de Nemours and Company (EPA Company Number: 352) 

Products: 

EPA Reg. No. Product Name % a.i. 

352-TIG (783) DPX-KJM44 Technical Herbicide 95.6 

352-TIU (784) DPX-KJM44 80 MUP Herbicide 80.0 

352-TOL (795) DPX-KJM44 10% Manufacturing Concentrate 10.0 

352-TIL (785) DPX-KJM44 80XP Herbicide 80.0 

352-TOE (792) DPX-KJM44 80XP Turf Herbicide 80.0 

352-TOT (797) DPX-KJM44 0.064G Turf Herbicide + Fertilizer 0.064 

352-INN (800) DPX-KJM44 0.073G Lawn Herbicide + Fertilizer 0.073 

352-ING (803) DPX-KJM44 0.053G Lawn Herbicide + Fertilizer 0.053 

352-INU (804) DPX-KJM44 0.049G Lawn Herbicide + Fertilizer 0.049 

352-INT (807) DPX-KJM44 0.033G Lawn Herbicide + Fertilizer 0.033 

352-IRR (811) DPX-KJM44 0.02G Lawn Herbicide + Fertilizer 0.02 

1.1.3. Chemical Name: Aminocyclopyrachlor potassium salt

 potassium 6-amino-5-chloro-2-cyclopropyl-4-pyrimidinecarboxylate 

EPA PC Code: 288010 

CAS Number: 858956-35-1 

Mode of Action: Synthetic auxin-type herbicide causing disorganized plant growth 

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 (pyrimidine carboxylic acid) 

Registrant: E.I. du Pont de Nemours and Company (EPA Company Number: 352) 

Products: 

EPA Reg. No. Product Name % a.i. 

352-TIA (786) DPX-MAT28 240SL Herbicide 25.0 

352-TOG (793) DPX-MAT28 240SL Turf Herbicide 25.0 

1.2. Human Health Risk 

A summary of the human health effects and risk of aminocyclopyrachlor as assessed in the 

Agency document titled “Aminocyclopyrachlor: Human Health Risk Assessment for Proposed 

Uses as an Herbicide” is provided below. 

1.2.1. Toxicological Summary and Considerations 

Pharmacokinetic oral studies indicate that both aminocyclopyrachlor and aminocyclopyrachlormethyl are rapidly absorbed, with rapid metabolic conversion of aminocyclopyrachlor-methyl to 

aminocyclopyrachlor. Elimination is almost complete within 24 hours. Similar acute toxicities, 

subchronic dietary, reproductive toxicity, and gene mutation studies results for both chemicals, 

along with evidence from metabolism studies form a scientific justification for considering 

aminocyclopyrachlor and aminocyclopyrachlor-methyl toxicologically equivalent, thus allowing 

bridging of the toxicity database for aminocyclopyrachlor-methyl with studies using 

aminocyclopyrachlor. 

The toxicology database for aminocyclopyrachlor is adequate for risk assessment for the 

proposed use patterns. Aminocyclopyrachlor has low acute toxicity by oral, dermal, and 

inhalation routes of exposure, and does not cause skin sensitization or irritation. However, it can 

cause mild eye irritation. Aminocyclopyrachlor and aminocyclopyrachlor-methyl have low 

subchronic toxicity via the oral route. The most sensitive species is the rat, with decreased body 

weight at the limit dose in subchronic dietary studies as the most sensitive endpoint of toxicity. 

The major effect observed across species for aminocyclopyrachlor was decreased body weight at 

the limit dose. No toxicity was observed in subchronic dietary studies in dogs at the highest dose 

of aminocyclopyrachlor tested, which was half the limit dose, but still higher than the dose at 

which no adverse effects occurred in the rat. No target organ of toxicity was identified. No sex 

differences in toxicity were observed for either aminocyclopyrachlor or aminocyclopyrachlormethyl. 

Aminocyclopyrachlor was not neurotoxic when administered acutely or subchronically via the 

oral route. Aminocyclopyrachlor-methyl showed no evidence of neurotoxicity or reproductive 

toxicity in an extended one generation reproductive toxicity study in rats. Aminocyclopyrachlor 

did not cause developmental toxicity in rats or rabbits. Therefore, there is low concern for 

reproductive, developmental, or neurotoxicity for aminocyclopyrachlor and 

aminocyclopyrachlor-methyl. 

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Aminocyclopyrachlor and aminocyclopyrachlor-methyl are considered to have low potential to 

cause chronic toxicity or carcinogenicity. No evidence of genotoxic effects was observed in 

mutagenicity studies in vitro for aminocyclopyrachlor and aminocyclopyrachlor-methyl or in 

vivo for aminocyclopyrachlor. No evidence of target organ toxicity was observed in oral 

subchronic studies for aminocyclopyrachlor and aminocyclopyrachlor-methyl at doses exceeding 

the limit dose. 

Immunotoxicity was investigated via the oral route in two species (rats and mice) for 

aminocyclopyrachlor. There was no evidence of immunotoxicity. 

1.2.1.1. Degradate of Concern

An environmental photodegradate of aminocyclopyrachlor present only in surface water was of 

possible concern for drinking water exposures. This photodegradate, cyclopropane carboxylic 

acid (IN-V0977), has a different mode of toxic action than aminocyclopyrachlor. Oral 

administration of cyclopropane carboxylic acid causes severe impairment of mitochondrial 

function by inhibiting the beta oxidation of fatty acids, resulting in microvesicular steatosis 

(accumulation of small fat droplets in cells). The liver is the most sensitive organ, and 

hepatocellular microvesicular steatosis is often accompanied by liver necrosis and inflammation, 

decreased hepatic glycogen, and decreased blood glucose levels. These effects have been 

observed with acute (one to three days) and longer (up to 14 days) exposure. The most sensitive 

species is the rabbit. Hepatic microvesicular steatosis in the rabbit follows a different doseresponse than body weight decreases observed with aminocyclopyrachlor and 

aminocyclopyrachlor-methyl in rats, with a lowest observed adverse effect level (LOAEL) that is 

100-fold lower. However, based on the proposed use pattern, the dietary exposure to IN-V0977 

from drinking water is below the Agency’s level of concern (LOC) (see Section 1.2.4). 

1.2.2. Toxicological End Points and Doses 

1.2.2.1. Acute Dietary 

For aminocyclopyrachlor, no acute reference dose (aRfD) or acute population adjusted dose 

(aPAD) was established because no toxicity was observed at the limit dose in the acute oral 

toxicity studies. 

For the degradate IN-V0977, the Agency has established an aRfD of 0.0026 mg/kg (body 

wt)/day, based on the LOAEL of 2.55 mg/kg/day from a rabbit study in which hepatic steatosis 

was observed and an uncertainty factor of 1000X. The 1000X uncertainty factor takes into 

account interspecies and intraspecies variability (10X for each) as well as the uncertainty 

associated with extrapolation of a no observed adverse effect level (NOAEL) from a LOAEL 

(10X). 

1.2.2.2. Chronic Dietary 

For aminocyclopyrachlor, the Agency has established a chronic reference dose (cRfD) and a 

chronic population adjusted dose (cPAD) of 0.35 mg/kg/day, based on the NOAEL of 350 

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mg/kg/day from the 90-day oral toxicity study in rats and an uncertainty factor of 1000X. In this 

study, decreased body weights, body weight gains, food consumption, and food efficiency in 

both sexes were observed at the LOAEL of 1044.6/1424.9 mg/kg/day. The 1000X uncertainty 

factor takes into account interspecies and intraspecies variability (10X for each) as well as the 

uncertainty associated with using an endpoint from a subchronic study to assess chronic 

exposure (10X). 

For the degradate IN-V0977, the Agency has established a cRfD of 0.00087 mg/kg/day, based on 

the LOAEL of 2.55 mg/kg/day from a rabbit study in which hepatic steatosis was observed and 

an uncertainty factor of 3000X. The 3000X uncertainty factor takes into account interspecies 

and intraspecies variability (10X for each), uncertainty associated with extrapolation of a 

NOAEL from a LOAEL (10X), and uncertainty arising from using a short-term study to assess 

long-term risk (3X). 

1.2.2.3. Short- and Intermediate-Term Incidental Oral and Inhalation 

The Agency has established a LOC of 3.5 mg/kg/day for the margin of exposure (MOE) of 100, 

based on the NOAEL of 350 mg/kg/day from the chronic 90-day oral toxicity study in rats and 

an uncertainty factor of 100X (10X interspecies x 10X intraspecies). In this study, decreased 

body weights, body weight gains, food consumption, and food efficiency in both sexes were 

observed at the limit dose LOAEL of 1044.6/1424.9 mg/kg/day. Long-term incidental oral 

exposures are not anticipated based on the proposed use pattern. 

1.2.2.4. Short- and Intermediate-Term Dermal 

No dermal endpoint was established because no toxicity was observed at the limit dose in the 28-

day dermal toxicity study. The 90-day dermal toxicity study was waived because the 28-day 

dermal toxicity study is considered suitable for long-term exposures and all endpoints of concern 

were assessed. 

1.2.2.5. Cancer 

The Agency has classified aminocyclopyrachlor as “Not likely to be Carcinogenic to Humans” 

based on the lack of evidence of genotoxic effects in the in vitro and in vivo mutagenicity 

studies. Aminocyclopyrachlor is considered to have low potential to cause chronic toxicity or 

carcinogenicity. No evidence of target organ toxicity was observed in oral subchronic studies at 

doses exceeding the limit dose. Therefore, cancer risk was not assessed. 

1.2.3. Consideration of Toxicity to Children 

Food Quality Protection Act (FQPA) considerations do not apply to aminocyclopyrachlor for the 

non-food use patterns described in this risk assessment. However, the Agency has reviewed the 

toxicity database and has determined that the young will not be particularly sensitive to the 

effects of aminocyclopyrachlor when used in residential settings based on the following: 

• The toxicity database is considered complete and includes acceptable developmental 

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toxicity studies in rats and rabbits, a two-generation reproductive toxicity study in rats, 

and an extended one-generation reproductive toxicity study in rats that included a 

modified functional observational battery. 

• No evidence of neurotoxicity was observed in the acute or subchronic neurotoxicity 

studies in rodents at the limit dose after exposure to aminocyclopyrachlor. Also, no 

evidence of neurotoxicity was observed in an extended one-generation reproduction study 

in rats with aminocyclopyrachlor-methyl that included a modified functional 

observational battery. 

• No evidence of developmental toxicity was observed when aminocyclopyrachlor was 

administered in the diet of rats or orally by gavage to rabbits at the limit dose. 

• No evidence of adverse effects of aminocyclopyrachlor or aminocyclopyrachlor-methyl 

on reproduction or fertility parameters was observed in dietary studies with rats. 

• No evidence of prenatal toxicity was observed following maternal exposure to 

aminocyclopyrachlor. There is no evidence of increased susceptibility following in utero 

exposure to aminocyclopyrachlor in rats or rabbits in developmental toxicity studies, 

which showed no adverse effects in offspring at the limit dose. An increase in abortions 

in maternal rabbits was observed at the limit dose, but this was considered secondary to 

decreases in body weight. There was also no evidence of increased susceptibility of 

offspring to aminocyclopyrachlor in reproduction and fertility studies in rats, for which 

adverse effects were limited to decreased body weights in both maternal animals and 

offspring at the limit dose. Therefore, the young are not considered more susceptible 

than adults to adverse effects from aminocyclopyrachlor or aminocyclopyrachlor-methyl. 

• There are no residual uncertainties identified in the exposure databases. EPA made 

conservative (protective) assumptions in the ground and surface water modeling used to 

assess exposure to aminocyclopyrachlor in drinking water. EPA used similarly 

conservative assumptions to assess post-application exposure of children including 

incidental oral exposure of toddlers. These assessments will not underestimate the 

exposure and risks posed by aminocyclopyrachlor. 

1.2.4. Dietary Risk 

Dietary risk assessment addresses exposure that individuals receive through food consumption 

and drinking water. Since there are no proposed food uses for aminocyclopyrachlor, only dietary 

exposure to aminocyclopyrachlor and its environmental degradates from drinking water were 

considered. 

 

For aminocyclopyrachlor, no acute dietary risk assessment was performed since no acute toxicity 

endpoint was identified. Cancer risks from dietary exposure to aminocyclopyrachlor and the 

degradate IN-V0977 in drinking water were not assessed since no cancer dietary endpoint was 

identified. Risks for chronic dietary exposures to aminocyclopyrachlor from drinking water 

were considered, and the risk estimates for the general U.S. population and all other regulated 

population subgroups are below the Agency’s LOC of greater than 100% of the cRfD. Chronic 

exposure to aminocyclopyrachlor from drinking water will occupy <1% of the cRfD for infants 

less than 1 year old, the population subgroup with the highest estimated exposure. 

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The major route of environmental degradation of aminocyclopyrachlor is aqueous photolysis, 

which produces five degradates. Of these, one environmental degradate, IN-V0977 

(cyclopropane carboxylic acid), was of concern. Dietary assessments of acute and chronic 

dietary exposures of cyclopropane carboxylic acid from drinking water were performed, and are 

below the Agency’s LOC of greater than 100% of the aRfD/cRfD. Acute exposure to the 

degradate IN-V0977 from drinking water will occupy 13% of the aRfD and 9.9% of the cRfD for 

infants less than 1 year old, the population subgroup with the highest estimated exposure. 

1.2.5. Residential Risk 

Residential risk assessment addresses exposures that individuals receive through their use of 

consumer products and exposures that individuals receive from frequenting areas that have been 

previously treated with aminocyclopyrachlor. 

1.2.5.1. Residential Handler Risk

Residential handler exposure to aminocyclopyrachlor may occur dermally and by inhalation. No 

dermal risk was assessed because no toxicity was observed at the limit dose in the subchronic 

dermal toxicity study. Inhalation risk was assessed by analysis of short-term and intermediateterm exposures using the lawn/turf products with the highest application rates (0.07 - 0.10 lb 

ae/A) and hazards identified in subchronic oral toxicity studies. 

The Agency has identified the following residential exposure scenarios from applications to 

lawns/turf: 

Mixing/Loading/Applying 

• Low Pressure Handwand (dry flowable and soluble liquid) 

• Hose-End Sprayer (dry flowable and soluble liquid) 

• Hand-Held Spreader/Belly Grinder (granular) 

The margins of exposure (MOEs) for the three inhalation exposure scenarios range from 

7,300,000 to 41,200,000. Since the Agency’s LOC is for MOEs less than 100, residential 

handler exposures are not of concern. 

1.2.5.2. Residential Post-Application Risk

Residential post-application exposure to aminocyclopyrachlor may occur dermally and orally for 

a variety of populations. No dermal risk was assessed because no toxicity was observed at the 

limit dose in the subchronic dermal toxicity study. Oral risk in toddlers was assessed by analysis 

of short-term and intermediate-term post-application exposures using the lawn/turf product with 

the highest application rate (0.10 lb ae/A). 

The Agency has identified the following residential post-application exposure scenarios from 

applications to lawns/turf: 

Toddlers 

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• Hand-to-Mouth Activity on Lawn/Turf 

• Object-to-Mouth Activity on Lawn/Turf 

• Soil Ingestion 

The single and combined MOEs for short-term and intermediate-term oral exposures range from 

234,000 to 70,000,000. Since the Agency’s LOC is for MOEs less than 100, residential postapplication exposures are not of concern for any population, including toddlers. 

1.2.6. Aggregate Risk 

Aggregate risk assessment addresses combined exposures that individuals receive from dietary 

and residential exposures to aminocyclopyrachlor. Quantitative, aggregate exposure and risk 

assessments for aminocyclopyrachlor are not required for the proposed non-food use patterns 

because Food Quality Protection Act (FQPA) considerations do not apply. However, the 

potential for significant aggregate exposures to aminocyclopyrachlor from dietary (drinking 

water) and residential uses relative to non-aggregate exposures was considered. The highest 

estimated residential exposure (0.000048 mg/kg/day via inhalation during mixing, loading, and 

applying a granular formulation with a belly grinder) was combined with the highest estimated 

dietary exposure (0.002778 mg/kg/day for all infants < 1 year old). This combined value of 

0.003 mg/kg/day was over 1000- fold lower than the point of departure of 3.5 mg/kg/day, based 

on the most conservative LOC for MOE (350 mg/kg/day with MOE =100). This estimate 

indicates that aggregate exposures to aminocyclopyrachlor will not result in significantly 

increased risk relative to non-aggregate exposure. 

1.2.7. Occupational Risk 

Occupational risk assessment addresses risks to individuals who are exposed to 

aminocyclopyrachlor as part of their employment, via contact while using commercial products 

(handler) or by being in areas that have been previously treated (post-application). 

1.2.7.1. Occupational Handler Risk 

Occupational handler exposure to aminocyclopyrachlor may occur dermally and by inhalation. 

No dermal risk was assessed because no toxicity was observed at the limit dose in the subchronic 

dermal toxicity study. Inhalation risk was assessed by analysis of short-term and intermediateterm exposures using the products with the highest application rates (0.07 - 0.28 lb ae/A) and 

hazards identified in subchronic oral toxicity studies. 

The Agency has identified the following occupational exposure scenarios from applications to 

private, public and military lands including un-cultivated non-agricultural (non-crop) areas such 

as airports, highways, railroads, golf courses, lumber yards, wild life habitats, multi family 

residential complexes, recreation areas, sod farms, utility rights of way, and residential lawns: 

Mixing/Loading 

• Groundboom (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

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• Aerial (fixed and non-fixed wing) (dry flowable) to non-crop areas 

• LCO handgun (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

• Right-of-way sprayer (dry flowable and soluble liquid) to non-crop areas, golf 

courses, sod farms, and lawn/turf 

• Push-type spreader (granular) to golf courses, sod farms, and lawn/turf 

• Tractor drawn broadcast spreader (granular) to golf courses, sod farms, and lawn/turf 

• Push cyclone spreader (granular) to golf courses, sod farms, and lawn/turf 

Applying 

• Groundboom (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

• Aerial (fixed and non-fixed wing) (dry flowable) to non-crop areas 

• LCO handgun (dry flowable and soluble liquid) to non-crop areas, golf courses, sod 

farms, and lawn/turf 

• Right-of-way sprayer (dry flowable and soluble liquid) to non-crop areas, golf 

courses, sod farms, and lawn/turf 

• Tractor drawn broadcast spreader (granular) to golf courses, sod farms, and lawn/turf 

Flagging 

• Aerial (fixed and non-fixed wing) (dry flowable) to non-crop areas 

The MOEs for the identified inhalation exposure scenarios range from 190,000 to 50,000,000. 

Since the Agency’s LOC is for MOEs less than 100, occupational handler exposures are not of 

concern. 

1.2.7.2. Occupational Post-Application Risk

Occupational post-application exposure to aminocyclopyrachlor may occur dermally and by 

inhalation. No dermal risk was assessed because no toxicity was observed at the limit dose in the 

subchronic dermal toxicity study. A quantitative post-application inhalation risk assessment was 

not deemed necessary, based on the high occupational handler MOE values. Post-application 

exposures would be lower than those for handlers due to aminocyclopyrachlor’s low vapor 

pressure and dilution in outdoor air. Therefore, occupational post-application exposures are not 

of concern. 

1.3. Environmental Risk 

A summary of the environmental fate and ecological effects and risks of aminocyclopyrachlor as 

assessed in the Agency document titled “Ecological Risk Assessment for the Section 3 New 

Chemical Registration of Aminocyclopyrachlor on Non-crop Areas and Turf” is provided below. 

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1.3.1. Environmental Summary and Considerations 

A dissociation constant study indicated that the potassium salt form of aminocyclopyrachlor 

rapidly dissociates to the acid when it is mixed with water prior to application. This similarity in 

behavior once the potassium salt is dissociated in water allows bridging of the environmental fate 

and toxicity database for aminocyclopyrachlor potassium salt with studies using 

aminocyclopyrachlor. 

Laboratory and field dissipation studies indicated that aminocyclopyrachlor-methyl rapidly 

hydrolyzes to aminocyclopyrachlor in alkaline aquatic environments, moist soils, and soil/water 

slurries. Degradation under environmentally-relevant pH conditions is primarily microbe 

mediated. Therefore, aminocyclopyrachlor-methyl applications may result in short-term 

exposures to the methyl ester form prior to hydrolysis to the acid. Aquatic studies on freshwater 

fish and invertebrates for aminocyclopyrachlor-methyl showed higher toxicity than 

aminocyclopyrachlor. As a result, with the exception of acute aquatic toxicity data, 

acute/chronic terrestrial and chronic aquatic toxicity data may be bridged for 

aminocyclopyrachlor-methyl with studies using aminocyclopyrachlor. 

1.3.1.1. Degradates of Concern

Model estimates suggest that degradates IN-LXT69 and IN-YY905 may be more toxic than 

aminocyclopyrachlor to daphnids on a chronic basis. Based on human health effects evaluation 

of degradates (see Sections 1.2.1.1 and 1.2.4), the degradate IN-V0977 may be more toxic than 

aminocyclopyrachlor to birds and mammals. However, by comparing the concentrations 

expected in the environment to the effects thresholds, IN-V0977 would have to be more than two 

orders of magnitude more toxic than aminocyclopyrachlor to exceed the Agency’s LOC. Also, 

since aqueous photolysis is the only significant rapid degradation pathway of 

aminocyclopyrachlor, aquatic exposure to the three degradates of concern would not result in any 

additional risks over those presented from exposure to aminocyclopyrachlor unless the 

degradates were considerably more toxic. 

1.3.2. Environmental Fate 

Aminocyclopyrachlor is non-volatile, highly soluble in water, and highly mobile to mobile in 

soils. Dissipation in the environment is expected to occur predominantly via aqueous photolysis, 

runoff, and leaching. Terrestrial field dissipation occurred with half-lives ranging from 22 to 126 

days. Aminocyclopyrachlor was detected at soil depths of 70 – 90 cm at 365 days, indicating 

that leaching of residues into groundwater may occur. 

Aminocyclopyrachlor is environmentally persistent in diverse environments. It persists in 

aerobic aquatic environments with a dissipation time of greater than 100 days and in aerobic 

terrestrial environments with a half-life of 373 days. It is also stable in anaerobic aquatic 

environments with a half life of 1733 days and in anaerobic terrestrial environments with a halflife of 6932 days. It has a low tendency for bioaccumulation. 

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The major route of degradation of aminocyclopyrachlor is abiotic via aqueous photolysis with a 

half-life of l.2 days in shallow, clear, and well-lit natural (pH 6.2) water bodies and 7.8 days in 

pH 4 buffer solution. However, it is slowly photolyzed on soil, with a half-life of 129 days. 

Aminocyclopyrachlor is stable to hydrolysis at pH 4, 7, and 9. 

To address concerns with the potential leaching of aminocyclopyrachlor that may result from the 

persistence and mobility described above, end-use product labels will be required to include 

surface and ground water advisories that stress the potential of runoff after treatment and 

descriptions of conditions that may promote leaching to groundwater (see Section 2.2.1). 

1.3.3. Ecological Risk 

Ecological risk assessment addresses exposures that non-target aquatic and terrestrial organisms 

and plants receive through the use of aminocyclopyrachlor. 

A screening-level risk assessment based on proposed uses suggests that aminocyclopyrachlor 

presents potential risk to terrestrial and semi-aquatic plants and to organisms that depend on the 

plants for habitat and forage. 

To better characterize and confirm chronic risks to birds and freshwater invertebrates, additional 

data will be required as a condition of registration (see Section 2.1.2). To mitigate potential risk 

to non-target terrestrial and semi-aquatic plants, end-use product labels will be required to 

include language that is intended to keep the pesticide on the treatment area (see Section 2.2.4). 

1.3.3.1. Aquatic Risk

The highest surface water estimated environmental concentration (EEC) values resulted from 

proposed aerial non-crop applications at 0.284 lb ae/A. This conservative approach of using an 

EEC of 0.284 lb ae/A will also cover turf applications, which resulted in lower EECs. EECs 

were compared to toxicity endpoints to derive risk quotients (RQs), which is then compared to 

the Agency’s LOC. 

 

1.3.3.1.1. Fish Risk

Aminocyclopyrachlor is practically non-toxic to freshwater and estuarine/marine fish on an acute 

basis. Acute risk was not quantified since no toxicity was observed at the highest concentration 

tested; therefore, RQs are not expected to exceed LOCs. Aminocyclopyrachlor-methyl is 

slightly toxic to freshwater fish on an acute basis; however, the RQ of <0.01 does not exceed the 

LOC. Chronic risk to freshwater fish resulted in a RQ of <0.01 and does not exceed the LOC. 

1.3.3.1.2. Aquatic Invertebrate Risk

Aminocyclopyrachlor and aminocyclopyrachlor-methyl are slightly toxic to freshwater 

invertebrates on an acute basis; however, RQs of <0.01 do not exceed LOCs. 

Aminocyclopyrachlor is practically non-toxic to estuarine/marine invertebrates on an acute basis; 

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where the RQ <0.01 does not exceed the LOC. 

In the chronic freshwater invertebrate (daphnid) study, non dose-response mortalities were 

observed at the three lowest treatment levels. Therefore, the resulting toxicity values could not 

be used quantitatively to assess chronic risk to aquatic invertebrates. Despite the lack of valid 

data, chronic risk to freshwater invertebrates is not expected to exceed the Agency’s LOC. 

Environmental concentrations of aminocyclopyrachlor in surface waters from applications at the 

proposed maximum rates are expected to be in the parts per billion (ppb) range; whereas all 

aquatic toxicity studies were conducted at concentrations in the parts per million (ppm) range. 

Based on the results of chronic studies in freshwater fish, where the no observed adverse effect 

concentration (NOAEC) is 11 ppm, EPA also expects the freshwater invertebrate NOAEC to be 

in the ppm range, well above the expected environmental concentrations. A repeated Freshwater 

Invertebrate Life Cycle Toxicity Test (Guideline 850.1300) is expected to be confirmatory and 

will be required as a condition of registration (see Section 2.1.2). 

1.3.3.1.3. Aquatic Plant Risk

Risks to aquatic vascular and non-vascular plants resulted in RQs <0.01, which do not exceed the 

Agency’s LOC. 

1.3.3.2. Terrestrial Risk

Terrestrial wildlife EECs are estimated emphasizing a dietary exposure route for uptake of 

pesticide residues on vegetative matter and insects. Birds are used as surrogates for terrestrialphase amphibians and reptiles. Honey bee is used as a surrogate for terrestrial invertebrates. 

1.3.3.2.1. Avian Risk

Aminocyclopyrachlor and aminocyclopyrachlor-methyl are practically non-toxic to birds (also 

terrestrial-phase amphibians and reptiles) on an acute basis. Acute risk was not quantified since 

no toxicity was observed; therefore, RQs are not expected to exceed LOCs. 

The submitted avian reproduction studies were invalid due to improper husbandry practices 

(small cage sizes) that may have caused incidental mortalities in quails and reduced egg 

production in mallards. Despite the improper husbandry conditions, there was no evidence in 

either study of adverse treatment-related effects, including overt toxicity, mortality, effects on 

feed consumption and body weight, macroscopic findings, or reproductive effects. A repeated 

Avian Reproduction Toxicity Test (Guideline 850.2300) is expected to be confirmatory and will 

be required as a condition of registration (see Section 2.1.2). 

1.3.3.2.2. Mammalian Risk

Aminocyclopyrachlor and aminocyclopyrachlor-methyl are practically non-toxic to mammals on 

an acute basis. Acute risk was not quantified since no toxicity was observed; therefore, RQs are 

not expected to exceed LOCs. Chronic risks to mammals resulted in RQs of <0.1 and do not 

exceed the LOC. 

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1.3.3.2.3. Terrestrial Invertebrate Risk

Aminocyclopyrachlor is practically non-toxic to terrestrial invertebrates, due to lack of mortality 

and sublethal effects in the honey bee study for aminocyclopyrachlor. An acute earthworm 

toxicity study for aminocyclopyrachlor-methyl also showed no mortalities or behavioral 

abnormalities, but the study is classified as supplemental since the Agency does not currently 

have an OPPTS guideline for earthworms. The Agency does not routinely quantify risks to 

terrestrial invertebrates. 

1.3.3.2.4. Terrestrial Plant Risk

As expected for herbicides, terrestrial and semi-aquatic plants are sensitive to 

aminocyclopyrachlor, where RQs exceeded the LOC. Non-target terrestrial and semi-aquatic 

plants may be exposed to aminocyclopyrachlor via runoff and spray drift, with dicots being more 

susceptible than monocots. To mitigate potential risk to non-target terrestrial and semi-aquatic 

plants, end-use product labels will be required to include language that is intended to keep the 

pesticide on the treatment area (see Section 2.2.4). 

1.4. Public Interest 

Aminocyclopyrachlor poses very low risk to humans, including workers and the general 

population, due to its low toxicity and low volatility. Similarly, because of its low toxicity to 

terrestrial and aquatic non-target organisms other than plants, aminocyclopyrachlor poses low 

environmental risks. 

The benefits afforded by registration of aminocyclopyrachlor may be substantial. Along with 

other herbicides in the same chemical family, this herbicide will be an important component in 

integrated pest management programs for both non-crop and turf areas. Aminocyclopyrachlor 

controls a broad spectrum of weeds, including difficult to manage invasive and noxious brush 

and herbicide-resistant species. In particular, aminocyclopyrachlor demonstrates very good 

long-term control of Leafy Spurge, considered one of the most difficult to control invasive weeds 

in the western United States. Leafy Spurge is listed as a noxious weed in 22 states, making 

control mandatory by legal statute in those areas. Very few alternative chemicals provide 

effective long-term control of Leafy Spurge, which reproduces aggressively, actively destroying 

native biodiversity and rendering pastures and rangelands unfit for cattle and horses grazing due 

to its unpalatability and toxicity. A single application of aminocyclopyrachlor will provide longlasting control, obviating the need for multiple applications of the current alternatives and 

thereby reducing the pesticide load in the environment. Aminocyclopyrachlor will also provide 

the commercial turf industry with an important tool. Because of its low volatility, it can be used 

in turf applications around valuable ornamental plants with less risk of damage than the current 

staples of the industry, 2,4-D and dicamba. 

Based on these considerations, the Agency believes that the registration of aminocyclopyrachlor 

is in the public’s interest. 

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2. PROPOSED REGULATORY DECISION

The Agency is proposing to grant the first registrations of the active ingredient 

aminocyclopyrachlor, formulated as 2 technical products, 3 manufacturing-use products, and 15 

end-use products. It is a selective herbicide providing pre-emergence and post-emergence 

control of broadleaf weeds, woody species, vines, and grasses in non-crop areas [private, public, 

and military lands: uncultivated non-agricultural areas (airports, highway, railroad and utility 

rights-of-way, sewage disposal areas), uncultivated non-crop agricultural areas (farmyards, fuel 

storage areas, fence rows, non-irrigation ditchbanks, barrier strips), outdoor industrial sites 

(lumberyards, pipeline, and tank farms), natural areas (wildlife management areas, wildlife 

openings, wildlife habitats, recreation areas, campgrounds, trailheads, and trails)], turf/lawns 

(residential, industrial, and institutional), golf courses, parks, cemeteries, athletic fields, and sod 

farms. 

In the Federal Register of January 27, 2010 (75 FR 4384), EPA issued a notice pursuant to 

section 3(c)(4) of FIFRA entitled “Pesticide Products; Registration Applications” in the docket 

EPA-HQ-OPP-2009-0789 announcing receipt of applications to register pesticide products 

containing the new active ingredient, aminocyclopyrachlor, by E.I. du Pont de Nemours and 

Company. There were no comments received in response to the notice of receipt. 

2.1. Data Requirements

The Agency has determined that additional data are required in order to better characterize risk. 

The studies identified below will be required as a condition of the registration of 

aminocyclopyrachlor. 

2.1.1. Human Health Data Requirements

The human health risk assessment concluded that the following study is required in support of 

the proposed uses: 

• A repeated-dose study in a sensitive species is required to address the hazard of 

subchronic/chronic exposure to the environmental degradate cyclopropane carboxylic 

acid (IN-V0977): To account for the lack of this study, EPA applied an additional 3X 

uncertainty factor (UF) to the point of departure (POD) used in the chronic exposure 

assessment for drinking water. Even with the additional UF and the conservative 

assumptions of the drinking water models used to estimate concentrations of 

aminocyclopyrachlor in drinking water, estimated chronic risk is well below the LOC 

(<10% of the cPAD for all population groups).

2.1.2. Environmental Data Requirements

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The ecological risk assessment concluded that the following studies are required in support of the 

proposed uses: 

• Avian Reproduction Toxicity Test (850.2300): 

Data are required for both an upland game and waterfowl species for the proposed use 

patterns. The submitted studies were invalid due to improper husbandry practices that 

may have caused incidental mortalities in quails and reduced egg production in 

mallards. Despite the improper husbandry conditions, there was no evidence in either 

study of adverse treatment-related effects, including overt toxicity, mortality, effects on 

feed consumption and body weight, macroscopic findings, or reproductive effects. 

Therefore, submission of a repeat-study performed under proper husbandry conditions is 

expected to be confirmatory and will better characterize chronic risk to birds. 

• Freshwater Invertebrate Life-Cycle Toxicity Test (850.1300): 

Non dose-response mortalities were observed in the three lowest treatment levels for the 

submitted freshwater daphnid study. Therefore, the resulting toxicity values could not be 

used quantitatively to assess chronic risk to aquatic invertebrates. Despite the lack of 

valid data, chronic risk to freshwater invertebrates is not expected to exceed the Agency’s 

LOC. Environmental concentrations of aminocyclopyrachlor in surface waters from 

applications at the proposed maximum rates are expected to be in the parts per billion 

(ppb) range; whereas all aquatic toxicity studies were conducted at concentrations in the 

parts per million (ppm) range. Based on the results of chronic studies in freshwater fish, 

where the NOAEC is 11 ppm, EPA also expects the freshwater invertebrate NOAEC to be 

in the ppm range, well above the expected environmental concentrations. Therefore, 

submission of a repeat-study is expected to be confirmatory and will better characterize 

chronic risk to freshwater invertebrates. 

 

2.2. Label Requirements

2.2.1. Environmental Hazards 

Based on potential leaching and runoff that may result from the persistence and mobility of 

aminocyclopyrachlor, the following surface and ground water advisories must be placed on all 

aminocyclopyrachlor end-use product labels. 

Surface Water Advisory

Products Primarily Intended for Commercial Use on Non-Crop Areas, Sod Farms, and 

Turf/Lawns 

“This Product may impact surface water quality due to spray drift and runoff of rain water. This 

is especially true for poorly draining soils and soils with shallow ground water. This product is 

classified as having high potential for reaching surface water via runoff for several months after 

application. A level, well-maintained vegetative buffer strip between areas to which this product 

is applied and surface water features such as ponds, streams, and springs will reduce the 

potential loading of aminocyclopyrachlor from runoff water and sediment. Runoff of this 

product will be reduced by avoiding applications when rainfall is forecasted to occur within 48 

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hours. See manual at the following Internet address: 

http://www.wsi.nrcs.usda.gov/products/W2Q/pest/core4.html” 

Products Primarily Intended for Consumer Use on Residential Lawns 

“This Product may impact surface water quality due to spray drift and runoff of rain water. This 

is especially true for poorly draining soils and soils with shallow ground water. This product is 

classified as having high potential for reaching surface water via runoff for several months after 

application. Avoid accidental or intentional application of this product to ditches, swales, 

drainage ways or impervious surfaces such as driveways. Runoff of this product to surface water 

will be reduced by avoiding applications when rainfall is forecasted to occur within 48 hours.” 

Ground Water Advisory

All End-Use Products

“This chemical has properties and characteristics associated with chemicals detected in ground 

water. This chemical may leach into ground water if used in areas where soils are permeable, 

particularly where the water table is shallow.” 

2.2.2. Plant Residue 

Although no incidents have been reported for aminocyclopyrachlor, a pyrimidine carboxylic 

acid, because it is a new chemical; several incidents have been reported for a similar class of 

chemicals, the pyridine carboxylic acids, which includes herbicides such as aminopyralid, 

clopyralid, and picloram. Incidents were reported where treated plant residues or manure from 

animals which were fed treated residues were used in compost, which caused desirable crop or 

lawn damage. Some states as well as the United Kingdom were prompted to take regulatory 

action due to these incidents. Since aminocyclopyrachlor also shares the persistent and systemic 

nature in soil and the high seedling emergence toxicity with these similar chemicals, similar 

incidents could occur following application of aminocyclopyrachlor. Therefore, the Agency is 

requiring that the following language be placed on all aminocyclopyrachlor end-use product 

labels: 

 

Plant Residue Restrictions

Products Primarily Intended for Commercial Use on Non-Crop Areas 

“Do not use plant material treated with this product for mulch or compost.” 

Products Primarily Intended for Commercial Use on Sod Farms and Turf/Lawns 

“Do not send grass clippings from treated areas to a composting facility or use grass clippings 

from treated areas for mulch or compost. Applicators must give notice to property 

owner/property manager/residents to not use grass clippings from treated turf for mulch or 

compost.” 

Products Primarily Intended for Consumer Use on Residential Lawns 

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“Do not use grass clippings from treated areas for mulch or compost. Grass clippings must 

either be left on the treated lawn or if allowed by local yard waste regulations, disposed of in the 

trash” 

2.2.3. Livestock 

 

Aminocyclopyrachlor can be applied in uncultivated agricultural areas and other areas with 

potential exposure to livestock via feeding or grazing. Since aminocyclopyrachlor is proposed 

for non-food use and no tolerances have been established on livestock commodities, the 

following restriction is required on all end-use labels to protect feeding exposure to livestock. 

Livestock Restriction

Products for Use on Non-Crop Areas 

“Do not graze or feed forage, hay, or straw from treated areas to livestock.” 

2.2.4. Spray Drift 

As expected for an herbicide, aminocyclopyrachlor presents potential risk to terrestrial plants, 

particularly through spray drift (see Section 1.3.3.2.4). In order to mitigate risk to non-target 

plants and keep the pesticide on the intended treatment area, the following spray drift language 

must be placed on all aminocyclopyrachlor end-use product labels: 

Spray Drift Management

The phrase “(>150 – 200 microns)” must be removed from the current spray drift management 

statement so that it reads “The most effective way to reduce spray drift potential is to apply large 

droplets. The best drift management strategy is to apply the largest droplets that provide 

sufficient coverage and control.”

Products Primarily Intended for Commercial Use on Non-Crop Areas

Aerial Application Restriction 

“When applying by air, maintain a 50-foot buffer around non-target aquatic areas and between 

the point of direct application and the closest downwind edge of non-target terrestrial areas. 

Apply only using nozzles which will deliver coarse or greater (VMD >350 microns) droplets as 

defined by ASABE S572 standard. Do not release spray at a height greater than 10 feet above 

the ground or crop canopy unless a greater height is required for aircraft safety. Do not apply 

when wind speed is greater than 10 mph. Do not apply during a temperature inversion.” 

Ground Application Restriction 

“When applying by ground, maintain a 50-foot buffer around non-target aquatic areas and 

between the point of direct application and the closest downwind edge of non-target terrestrial 

areas. Apply only using nozzles which will deliver coarse or greater (VMD >350 microns) 

droplets as defined by ASABE S572 standard. Do not apply with a nozzle height greater than 4 

feet above the ground or crop canopy. Do not apply when wind speed is greater than 10 mph. 

Do not apply during a temperature inversion.” 

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Products Primarily Intended for Commercial Use on Sod Farms and Turf/Lawns 

(Ground Applications Only)

Application Restriction 

“Maintain a 25-foot buffer around non-target aquatic areas and between the point of direct 

application and the closest downwind edge of non-target terrestrial areas. Apply only using 

nozzles which will deliver coarse or greater (VMD >350 microns) droplets as defined by ASABE 

S572 standard. Do not apply with a nozzle height greater than 4 feet above the ground or crop 

canopy. Do not apply when wind speed is greater than 10 mph. Do not apply during a 

temperature inversion.” 

2.2.5. Restricted-Entry Interval (REI) 

The REI must be changed to 12 hours from the proposed REI of 4 hours. The minimum standard 

REI for agricultural pesticides is 12 hours. EPA allows a reduced REI of 4 hours for certain 

minimum-risk pesticides that meet low-toxicity standards and that have not been reported to 

cause illness or injury due to post-application exposure. Since aminocyclopyrachlor is a new 

pesticide with no history of actual use, incident information (illness or injury reports) is not 

available for this chemical. Therefore, EPA believes the minimum standard REI of 12 hours is 

appropriate for aminocyclopyrachlor. 

2.3. Proposed Registration Decision

In accordance with FIFRA Section 3(c)(7)(C), the Agency believes that the conditional 

registration of aminocyclopyrachlor will not cause any unreasonable adverse effects to human 

health or to the environment and that the use of the pesticide is in the public’s interest; and is 

therefore proposing to grant the conditional registration.