UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF PREVENTION, PESTICIDE

AND TOXIC SUBSTANCES

MEMORANDUM

Date: January 30, 2010

SUBJECT: Occupational and Residential Risk Assessment to Support the Request for

Registration of Aminocyclopyrachlor. its methyl ester and potassium Slit on Turf and Non·crop

areas.

Ingredient: Aminocyclopyrachlor-methyl ester and Potassium salt

Thru:

Health Effects DIVIsion /

Registration Action Branch 4 (7509:;P':-)'1//0//\~-

Raymond Kent, Branch Chief ":;;;;:-;'<::ld.<:""""",--

Susan Hummel, Brach Senior Scientist

Health Effects Division

Registration Action Branch 4 (7509P)

To: Jessica Ryman Risk Assessor

Health Effects Division

Registration Action Branch 4 (7509P)

DP Barcode: D372493, D358166, D361326,

PC Code: 288008,288009,288010 D361329, 0361339, D361341, D361347, D361348,

D361353, D361354, D361355, D361358

Registration No, 352-TOG, 352-TOE, 352-INN, 352-

Decision No.: 400976 TOT, 352-IRL, 352-IRE, 352-TOU, 352-T1A, 352-

TIL, 352-TIT, 352-IRG, 352-IRU, 352-TOO, 352-ING,

352-INU, 352-INT, 352-IRR, 352-TOI

Petition No.: N/A Regulatory Action: Section 3 Registration

Assessment Type: ORE Re-registration Case No.: <None'

MRlD No.: 475602-09 CAS No.: 858956-08-8, 858954-83!f.'1l58956-35-1 I

TXRNo.: NA 40 CFR: 180.475 ./ /'---. 1/-

From: James S Miller, Envirorunental

. . . SCientist~'~ . .' t!'Jz-t

Introduction

The registrant, DuPont, Inc. requests the registration ofthe herbicide arninocyclopyrachlor, its

methyl ester, and potassium salt. This memorandum addresses risk from occupational and

residential exposure resulting from proposed uses.
Table of Contents 

1.0 Executive Summary.............................................................................................................3 

2.0 Use Profile ...........................................................................................................................6 

 

3.0 Hazard Profile ......................................................................................................................8 

 

4.0 Occupational Exposure and Risk.......................................................................................11 

 

5.0 Occupational Post-application Exposure and Risk............................................................18 

6.0 Non-Occupational/Residential Exposure and Risk .......................................................... 19 

7.0 Non-Occupational/Residential Post Application Exposure and Risk........................21 

8.0 Conclusion.... .....................................................................................................................25 

9.0 References...........................................................................................................................26 

Appendices.....................................................................................................................................27 

Page 2 of 27 
1.0 Executive Summary

Background and Purpose:

The enclosed occupational and residential exposure assessment is being conducted as part of 

EPA’s human health risk assessment for the proposed Section 3 registration for use of 

aminocyclopyrachlor, its methyl ester and potassium salt, on terrestrial, non-crop areas and 

lawn/turf. Aminocyclopyrachlor-methyl ester and its potassium salt, (4-Pyrimidinecarboxylic 

acid, 6-amino-5-chloro-2-cyclopropyl, - methyl) are herbicides formulated as a dispersible 

granular, a granular, and a soluble liquid for pre-, and or post-emergence control of broad leaf 

and woody species weeds; including many terrestrial, riparian invasive, and noxious weeds. 

Aminocyclopyrachlor, its methyl ester and potassium salt belong to a new chemical class of 

Auxin-type herbicides: the pyrimidine carboxylic acids. Like other auxin-type herbicides, the 

mode of action is disorganized plant growth. No toxic mode of action has been identified in 

mammalian species. 1

In this registration action aminocyclopyrachlor-methyl ester, aminocyclopyrachlor; a potassium 

salt form, and aminocyclopyrachlor; an acid form are being registered for general weed and 

brush control on private, public and military lands including sod farms, un-cultivated nonagricultural areas such as airports, highways, railroads, golf courses, lumber yards, wild life 

habitats, multi family residential complexes, recreation areas, utility rights of way, with 

residential use specified for lawn/turf. 

Use Patterns and Formulations:

Aminocyclopyrachlor-methyl is applied in three different formulations, a water dispersible 

granular, a granular, and a soluble liquid. For this registration action DuPont labels, 

(DPXKJM44 80XP Herbicide/EPA Reg. No. 352 – TOE), (DuPontTM DPX-MAT28 50SG 

Herbicide/EPA Reg No. 352-TIT), (DuPontTM DPX-MAT28 240SL Turf Herbicide/EPA Reg 

No. 352-TOG), and (DuPontTM DPX-MAT28 0.064G Lawn Herbicide + Fertilizer/EPA Reg No. 

352-TOT), were used because they represented; 

• Crop and “Non-Crop” usage 

• Conservative maximum application rates applicable to formulation 

• Complete exposure scenario explanations (equipment used for application) 

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 

 

1

 Aminocyclopyrachlor and Aminocyclopyrachlor-Methyl: Human Health Risk Assessment for Proposed Outdoor 

Uses as Herbicides. PC Codes: 288008 (aminocyclopyrachlor), 288009 (aminocyclopyrachlor-methyl), Petition No: 

XFXXXX, DP Barcode: D. Memorandum dated; 12/13/2009. 

Page 3 of 27 
LOC handgun equipment, which are typically used by a lawn care operator (landscape 

maintenance personnel). Broadcast applications may be performed by using either a single 

ground boom, a tractor type broadcast or 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 handwand, hose-end sprayer, and hand 

held spreader (belly grinder). 

Note; Applications may be applied at waters edge, however not directly to water. 

The proposed product is applied as a granular, a water dispersible granular (i.e. dry flowable), 

and a soluble liquid. 

• Occupational application rates range from a minimum of 1.5 oz. of product/ acre per 

application (0.07 lbs ae/ Acre) to a maximum of 9 oz. of product/ acre per season (0.28 

lbs ae/ Acre). 

• Residential application rates range from a minimum of 1.5 oz. of product/ acre per 

application (0.07 lbs ae/ Acre) to a maximum of 3.0 oz. of product/ acre (0.108 lbs ae/ 

Acre). 

Note; Maximum application rates (oz of product/acre/season) used in all “Non-Crop 

Occupational handler” calculations are conservative estimates, whereas typically multiple 

applications of smaller amounts are conducted, however due to the nature of a “Non-Crop” 

herbicide, label specific instruction note “one application per year” is probable. 

There is a potential for short- and intermediate-term residential and occupational exposure to 

aminocyclopyrachlor-methyl during mixing, loading, application, and post-application activities, 

however chronic exposure is not expected for the proposed use patterns. 

Hazard Profile:

Aminocyclopyrachlor,its methyl ester and potassium salt are classified in Toxicity Category IV 

for acute dermal and skin irritation and Category III for primary eye irritation. 

Aminocyclopyrachlor exhibits low acute and subchronic toxicity by oral, dermal, or inhalation 

exposure. The major effects across species were decreased body weight and decreased body 

weight gain at the limit dose. There is no apparent target organ. Aminocyclopyrachlor was not 

geneotoxic, neurotoxic, immunotoxic, or toxic to the reproductive system and did not cause 

developmental toxicity at doses up to the limit dose. 

Endpoint Selection:

The dose selected for short-, and intermediate-term dermal exposure is a NOAEL of 1000 

mg/kg/day, based on a 28 day dermal toxicity study. “No hazard or LOAEL was identified. 

Furthermore, for purposes of determining intermediate-term dermal exposure a 100% dermal 

Page 4 of 27 
absorption factor was used for route-to-route extrapolation from an oral study. 

The dose selected for short-, and intermediate-term inhalation and incidental oral exposure is a 

NOAEL of 350 mg/kg/day. The LOAEL is 1045 mg/kg/day, based on decreased body weights, 

body weight gains, food consumption, and food efficiency in both sexes. 

Cancer Risk:

For this registration action, no food uses were listed and “no long-term exposure is expected,” 

therefore a cancer assessment was not conducted. 

Uncertainty Factors

The uncertainty factor applied to aminocyclopyrachlor, its methyl ester and potassium salt was 

100X (10X interspecies extrapolation x 10X intra-species variability). Food Quality Protection 

Act (FQPA) considerations do not apply to aminocyclopyrachlor for the (non-food) use patterns 

described in this risk assessment. However, the HED risk assessment team has reviewed the 

toxicity database for indications that young may be particularly sensitive to the effects of 

aminocyclopyrachlor, since some products may be used in residential settings. The toxicity 

database to assess the hazard to the general population, as well as the potential susceptibility of 

children, was complete and no evidence of increased susceptibility for children was found. 

Therefore, no other uncertainty factors were required. 

Margin of Exposure

The Agency’s level of concern for non-cancer risks (i.e., target level for MOEs or Margins of 

Exposure) is defined by the uncertainty factors (noted above) that are applied to the assessment. 

The total uncertainty factors that have been applied to non-cancer risk assessments are 100 for 

occupational short-, and intermediate-term exposure scenarios. For details, see table 3.1

(Summary of Toxicological Doses and Endpoints for aminocyclopyrachlor, its methyl ester and 

potassium salt for Use in Human Risk Assessments). 

Residential Non-Cancer Risks 

• Residential Handler Risk Summary:

Quantification of dermal exposures is not required because no toxicity was observed in a dermal 

study conducted at the limit dose2

. However, residential inhalation exposures were assessed. 

All short- and intermediate-term inhalation MOEs for lawn/Turf were greater then 100 (MOE

100), and therefore not of concern for this registration action. 

 > 

Occupational Non-Cancer Risks 

• Occupational Handler Risk Summary: 

 

2

 Memorandum: Aminocyclopyrachlor: Human Health Risk Assessment for Proposed Uses as 

an Herbicide. Dated; December 1, 2009 PC Code: 288008, 288009, 288010 DP Barcode: 

D369057

Page 5 of 27 
As noted above; quantification of dermal exposures is not required because no toxicity was 

observed in a dermal study conducted at the limit dose2

. However, occupational inhalation 

exposures were assessed. All short- and intermediate-term inhalation MOEs for general weed 

and brush control on private, public and military lands including sod farms, un-cultivated nonagricultural areas such as airports, highways, railroads, golf courses, lumber yards, wild life 

habitats, multi family residential complexes, recreation areas, utility rights of way and turf were 

greater then 100 (MOE > 100), and therefore not of concern for this registration action. 

Occupational Post-Application Risks 

• Occupational Post-Application Risk Summary: 

Chemical-specific post-application exposure data were submitted (MRID # 47560209) in support 

of the registration of aminocyclopyrachlor, its methyl ester and potassium salt. Turf transferable 

residues (TTRs), were selected form three test sites located in California (Porterville), Canada 

(Branchton) and Georgia (Sycamore). Note; at the Georgia site rainfall occurred and caused 

substantial lower TTR values, therefore these data were not used in this assessment. However, 

as noted earlier quantification of dermal exposures is not required because no toxicity was 

observed in a dermal study conducted at the limit dose. 

Furthermore, HED believes that based on the occupational handler inhalation MOE values of 

(190,000 - 50,000,000), occupational post-application inhalation exposures will be negligible and 

therefore were not assessed in this memorandum. Please see table 4 for specifics. 

The draft product label of (352-TIL- DPX-KJM44 80XP) states that because this product is used 

on sod farms it is within the scope of the Workers Protection Standard (WPS) for agricultural 

pesticides (40 CFR Part 170). Label directions call for a restricted entry interval (REI) of 4 

hours, however due to a category III in acute eye irritation therefore HED maintains that a REI of 

12 hours is appropriate and that all label directions reflect this change. 

Residential Post-Application Risks 

• Residential Post-Application Risk Summary: 

As noted above; chemical-specific post-application exposure data was submitted (MRID # 

47560209) in support of the registration of aminocyclopyrachlor, its methyl ester and potassium 

salt. However, quantification of dermal exposures is not required because no toxicity was 

observed in a dermal study conducted at the limit dose. 

Therefore, residential post-application inhalation, hand to mouth, and soil ingestion exposures 

were assessed. For all exposures noted, MOEs for are greater then 100, and therefore were not 

of concern for this registration action. 

2.0 Use Profile 

A summary of the proposed use profile is presented in Table 2. Note; for aminocyclopyrachlormethyl, maximum application units are pounds of acid equivalent per acre. 

 

Page 6 of 27 
Table 2: Summary of Directions for Use of Aminocyclopyrachlor-methyl ester and potassium salt

Application 

Equipment 

Crop(s) 

Non-Crops EPA Reg. # Max Application Formulation 

Non-crop 

352-TIA 

352-TIT 

352-TIL 

0.28 

Turf/Sod Farm 352-TOE 

352-TOU 

352-TOE 

352-TOU 

Water Dispersible 

Granular 

Turf/Lawn Golf 

Course 

352-TOG 

Groundboom 

(Open Cab) 

Turf/Sod Farm. 352-TOG 

0.07 

Soluble Liquid 

Non-crop 

352-TIA 

352-TIT 

352-TIL 

0.28 Water Dispersible 

Granular 

LCO Handgun 

Turf/Lawn/Sod 

Farm/Golf Course 

352-TOG 

352-TOE 

352-TOU 

0.07 Soluble Liquid 

Aerial 

(Fixed wing) 

enclosed cockpit 

Non-crop 

352-TIA 

352-TIT 

352-TIL 

0.28 Water Dispersible 

Granular 

Push Cyclone 

Spreader 

Push Type 

Spreader 

Tractor Drawn 

Broadcast 

Spreader 

Sod Farm Golf 

Course 

352-IRU 

352-IRE 

352-IRG 

352-TOT 

0.108 Granular 

Non-crop 

352-TIA 

352-TIT 

352-TIL 

0.28 Water Dispersible 

Granular 

Right of way 

sprayer 

Turf/Lawn 

Sod Farm 

Golf Course 

352-TOG 

352-TOE 

352-TOU 

0.07 Soluble Liquid 

Page 7 of 27 
Table 2: Summary of Directions for Use of Aminocyclopyrachlor-methyl ester and potassium salt

Application 

Equipment 

Crop(s) 

Non-Crops EPA Reg. # Max Application Formulation 

Low Pressure 

Handwand 

(PHED) Soluble Liquid 

Hose-end 

Sprayer 

"mix your own" 

0.07 

Water dispersible 

granular 

Belly Grinder 

(PHED) 

Turf 

(Lawns) 

352-TOG 

352-TOE 

352-TOU 

352-TOT 

352-IRG 

352-TOI 

352-IRU 

352-TOO 

352-IRL 

352-INN 

352-ING 

352-INU 

352-INT 

352-IRR 

0.108 Granular (dry bulk 

fertilizer) 

3.0 Hazard Profile 

The toxicology database for aminocyclopyrachlor is adequate for risk assessment for non-crop 

and domestic outdoor herbicidal use. Aminocyclopyrachlor, its methyl ester and potassium salt 

exhibit low acute toxicity by oral, dermal, or inhalation exposure, and neither cause skin 

sensitization or irritation. All are rapidly absorbed, with rapid metabolic conversion of 

aminocylopyrachlor-methyl to aminocylopyrachlor. Elimimation is almost complete within 24 

hours. Due to the demonstrated rapid conversion of aminocyclopyrachlor-methyl to 

aminocyclopyrachlor in mammals, these two chemicals are toxicologically equivalent, and so the 

toxicology database for aminocyclopyrachlor-methyl can be bridged with aminocyclopyrachlor. 

 Aminocyclopyrachlor, its methyl ester and potassium salt are not toxic subchronically via the 

dermal route of exposure (no toxicity at the limit dose), and subchronic toxicity via the oral route 

is low. The major effects across species with subchronic oral administration were decreased body 

weight, body weight gains, food consumption, and food efficiency in both sexes at the limit dose. 

The most sensitive species is the rat, and the most sensitive exposure route is dietary exposure. 

The most sensitive endpoint is decreased body weight. There are no sex differences. There is no 

apparent target organ. Because toxic effects were not observed below the limit dose, there is no 

dose-response. Aminocyclopyrachlor was not geneotoxic, neurotoxic, immunotoxic, or toxic to 

the reproductive system and did not cause developmental toxicity at doses up to the limit dose. 

Endpoints have been selected to assess dietary (drinking water), residential, and occupational 

exposures to aminocyclopyrachlor. Toxicity resulting from a single exposure to 

aminocyclopyrachlor was not observed, and so quantification of acute exposures is not required. 

Quantification of dermal exposures is not required because no toxicity was observed in a dermal 

study conducted at the limit dose. Endpoints for all inhalation risk assessments were selected 

Page 8 of 27 
from oral toxicity studies, and so it is assumed that oral and inhalation absorption are equivalent. 

For short and intermediate-term inhalation exposures an endpoint was selected from a 90-Day 

Oral Toxicity Feeding-rat (870.3100), citing decreased body weights, body weight gains, food 

consumption, and food efficiency in both sexes. Quantification of human carcinogenic risk is 

not required for aminocyclopyrachlor for this use pattern. 

The dose selected for short-term dermal exposure is a NOAEL of 1000 mg/kg/day. However, 

aminocyclopyrachlor is not toxic sub-chronically via the dermal route of exposure (no toxicity at 

the limit dose); therefore a dermal assessment was not conducted for this registration action.

Endpoints for all inhalation risk assessments were selected from oral toxicity studies, and so it is 

assumed that oral and inhalation absorption are equivalent. For short and intermediate-term 

inhalation exposures an endpoint was selected from sub-chronic toxicity studies in rats in which 

decreased body weight was observed. A NOAEL of 350 mg/kg/day was selected for short-, and 

intermediate-term inhalation exposure. A LOAEL of 1045 mg/kg/day was selected based on 90-

Day Oral Toxicity Feeding-rat (870.3100). 

Furthermore, endpoints for short- and intermediate-term incidental oral were selected based on A 

NOAEL of 350 mg/kg/day was the dose selected. The LOAEL of 1045 mg/kg/day was selected 

based on decreased body weights, body weight gains, food consumption, and food efficiency in 

both sexes. Quantification of human carcinogenic risk is not required for aminocyclopyrachlor 

for this use pattern.

 The database for acute toxicity for aminocyclopyrachlor-methyl is complete and is summarized 

below. Aminocyclopyrachlor-methyl is classified as Toxicity Category IV for acute exposure 

via the oral, dermal and inhalation routes. For acute ocular, a Toxicity Category of III was 

established due to mild irritation in white New Zealand rabbits. A summary of the toxicological 

Categories, doses, and endpoints is provided in Tables 3 and 3.1 

Table 3: Acute Toxicity of Aminocyclopyrachlor-methyl ester and potassium salt

Guideline 

No. Study Type Results Toxicology Category

870.1100 Acute Oral [rat] LD50=(comb)-5000 mg/kg IV 

870.1200 Acute Dermal [rat] LD50=(comb)-5000 mg/kg IV 

870.1300 Acute Inhalation [rat] LD50 > 5.4 mg/L IV 

870.2400 Primary Eye Irritation [rabbit] Mild irritation III 

870.2500 Primary Skin Irritation [rabbit] Non-irritant IV 

870.2600 Dermal Sensitization [Guinea Pig] Non-sensitizer IV 

Page 9 of 27 
Table 3.1 Summary of Toxicological Doses and Endpoints for Aminocyclopyrachlor-methyl ester 

and potassium salt 

Exposure/ 

SceNArio 

Point of 

Departure 

Uncertainty/FQPA 

Safety Factors 

RfD, PAD, 

Level of 

Concern for 

Risk 

Assessment 

Study and Toxicological Effects 

Incidental 

Oral ShortTerm (1-30 

days) 

NOAEL= 350 

mg/kg/day 

UFA= 10 x 

UFH=10 x 

Residential 

LOC for 

MOE = 100 

90-Day Oral Toxicity Feeding-rat 

(870.3100) 

LOAEL = 1045 mg/kg/day (limit 

dose) based on decreased body 

weights, body weight gains, food 

consumption, and food efficiency 

in both sexes 

Incidental 

Oral 

IntermediateTerm (1-6 

months) 

NOAEL= 350 

mg/kg/day 

UFA= 10 x 

UFH=10 x 

Residential 

LOC for 

MOE = 100 

90-Day Oral Toxicity Feeding-rat 

(870.3100) 

LOAEL = 1045 mg/kg/day (limit 

dose) based on decreased body 

weights, body weight gains, food 

consumption, and food efficiency 

in both sexes 

Dermal 

Short-Term 

(1-30 days) 

NOAEL= 

1000 

mg/kg/day 

(limit dose) 

NA NA 

28-Day Dermal Toxicity- rat 

(870.3200) 

No hazard was identified. 

Dermal 

IntermediateTerm (1-6 

months) 

NOAEL= 

1000 

mg/kg/day 

(limit dose) 

NA NA 

28-Day Dermal Toxicity- rat 

(870.3200) 

No hazard was identified. 

Inhalation 

Short- Term 

(1-30 days) 

NOAEL=350 

mg/kg/day 

(inhalation and 

oral are 

assumed to be 

equivalent) 

UFA= 10 x 

UFH=10 x 

Residential/

Occupational 

LOC for 

MOE = 100 

90-Day Oral Toxicity Feeding-rat 

(870.3100) 

LOAEL = 1045 mg/kg/day (limit 

dose) based on decreased body 

weights, body weight gains, food 

consumption, and food efficiency 

in both sexes 

Inhalation 

IntermediateTerm (1-6 

months) 

NOAEL=350 

mg/kg/day 

(inhalation and 

oral are 

assumed to be 

equivalent) 

UFA= 10 x 

UFH=10 x 

Residential/

Occupational 

LOC for 

MOE = 100 

90-Day Oral Toxicity Feeding-rat 

(870.3100) 

LOAEL = 1045 mg/kg/day (limit 

dose) based on decreased body 

weights, body weight gains, food 

consumption, and food efficiency 

in both sexes 

Page 10 of 27 
Note: Point of Departure (POD) = A data point or an estimated point that is derived from observed doseresponse data and used to mark the beginning of extrapolation to determine risk associated with lower 

environmentally relevant human exposures. NOAEL = no observed adverse effect level. LOAEL = lowest 

observed adverse effect level. UF = uncertainty factor. UFA = extrapolation from animal to human 

(interspecies). UFH = potential variation in sensitivity among members of the human population (intraspecies). FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c = chronic). RfD = 

reference dose. MOE = margin of exposure. LOC = level of concern. N/A = not applicable 

4.0 Occupational Exposure and Risk

Handler Exposure 

The proposed uses associated with this action are for use of aminocyclopyrachlor-methyl on noncrops and lawn/turf. Aminocyclopyrachlor, its methyl ester and potassium salt, (4-

Pyrimidinecarboxylic acid, 6-amino-5-chloro-2-cyclopropyl, - methyl) is a dispersible granular, a 

granular and a soluble liquid herbicide used for pre-, and or post-emergence control of broad leaf 

and woody species weeds; including many terrestrial, riparian invasive and noxious weeds. 

In this registration action aminocyclopyrachlor-methyl ester, aminocyclopyrachlor; a potassium 

salt form, and aminocyclopyrachlor: an acid form, are being registered for general weed and 

brush control on private, public and military lands including un-cultivated non-agricultural 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. 

Based on label specific information and information provided by the registrant, handler 

exposures are expected to be short- and intermediate-term in duration. The quantitative 

exposure/risk assessment developed for commercial handlers is based on the following exposure 

scenarios: 

Groundboom:

• Mixing/loading: (dry flowable, soluble liquid) formulations to Non-crops, Golf courses, 

Sod Farms, and Lawn/Turf. 

• Applying: (dry flowable, soluble liquid) formulations to Non-crops, Golf courses, Sod 

Farms, and Lawn/Turf. 

Aerial:

• Mixing/loading: fixed and non-fixed wing (dry flowable) formulation to Non-crops. 

• Applying; fixed and non-fixed wing (dry flowable) formulation to Non-crops. 

• Flagging: fixed and non-fixed wing (dry flowable) formulation to Non-crops. 

LCO Handgun:

• Mixing/Loading: (water dispersible granules, soluble liquid) formulation to Non-crops, 

Golf courses, Sod Farms, and Lawn/Turf. 

• Applying: (water dispersible granules, soluble liquid) formulation to Non-crops, Golf 

courses, Sod Farms, and Lawn/Turf. 

Page 11 of 27 
Right of way Sprayer:

• Mixing/Loading: (water dispersible granules, soluble liquid) formulation to Non-crops, 

Golf courses, Sod Farms, and Lawn/Turf. 

• Applying: (water dispersible granules, soluble liquid) formulation to Non-crops, Golf 

courses, Sod Farms, and Lawn/Turf. 

Push Type Spreader:

• Mixing/Loading: (granular) formulation to Golf courses, Sod Farms, and Lawn/Turf. 

• Applying: (granular) formulation to Golf courses, Sod Farms, and Lawn/Turf. 

Tractor Drawn Broadcast Spreader:

• Mixing/Loading/Applying: (granular) formulation to Golf courses, Sod Farms, and 

Lawn/Turf. 

Push Cyclone Spreader

• Mixing/Loading: (granular) formulation to Golf courses, Sod Farms, and Lawn/Turf. 

No chemical-specific handler exposure data were submitted in support of this registration. It is 

the policy of the HED to use data from the Pesticide Handlers Exposure Database (PHED) 

Version 1.1 as presented in PHED Surrogate Exposure Guide (8/98). 

As noted in the Executive Summary and Hazard Profile sections, endpoints for short-, and 

intermediate-term dermal were selected, but a dermal assessment was not conducted, whereas no 

toxicity was observed. 

However, inhalation exposures were calculated and an assessment was conducted. For all 

scenarios noted above, MOEs were greater then 100 (MOE >100), and therefore not of concern. 

4.1 Data and Assumptions for Occupational Handler Exposure Scenarios 

Unit Exposures:

• Chemical-specific data for assessing exposure during pesticide handling activities were 

not submitted to the Agency in support of this Section 3 application. It is HED policy to 

use data from the Pesticide Handlers Exposure Database (PHED) Version 1.1 to assess 

handler exposures for regulatory actions when chemical-specific data are not available 

(HED Science Advisory Council for Exposure, SOP Number .007, January 1999). 

Page 12 of 27 
Area Treated:

• HED assumed 40 acres per day for mixing/ loading, and applying; (lawn/turf/Golf 

course) with groundboom equipment (HED Exposure Science Advisory Committee SOP 

Number 9.1)

• HED assumed 80 acres per day for mixing/loading, and applying; (Non-crops/sod farms) 

with groundboom equipment (HED Exposure Science Advisory Committee SOP Number 

9.1)

• HED assumed 350 acres for mixing/loading, applying and flagging; (Non-crops) with 

aerial equipment (HED Exposure Science Advisory Committee SOP Number 9.1)

• HED assumed 5.0 acres per day for application; (Non-crop, lawn/turf, golf course, and 

sod farm ) with LOC Handgun equipment and right of way sprayers (HED Exposure 

Science Advisory Committee SOP Number 9.1)

• HED assumed 100 acres per day for mixing and loading; (Non-crop and lawn/turf) with 

LOC Handgun equipment. 

• HED assumed 5.0 acres per day for loading and applying; (sod farm/golf course) with a 

push type spreader (HED Exposure Science Advisory Committee SOP Number 9.1).

• HED assumed 40 acres per day for application; (sod farm/golf course) with a tractor 

drawn broadcast spreader, and push cyclone spreader (HED Exposure Science Advisory 

Committee SOP Number 9.1).

Note: HED maintains that the 100 acres for mixing and loading is calculated by assuming the 

following. (Mixing and loading of 20 trucks that will apply 5 acres of formulation per day). 

Application Rate:

Aminocyclopyrachlor is applied in three different formulations, a water dispersible granular, a 

granular, and a soluble liquid. For this registration action DuPont labels, (DPXKJM44 80XP 

Herbicide/EPA Reg. No. 352 – TOE), (DuPontTM DPX-MAT28 50SG Herbicide/EPA Reg No. 

352-TIT), (DuPontTM DPX-MAT28 240SL Turf Herbicide/EPA Reg No. 352-TOG), and 

(DuPontTM DPX-MAT28 0.064G Lawn Herbicide + Fertilizer/EPA Reg No. 352-TOT), were 

used because they represented; 

• Crop and “Non-Crop” usage 

• Conservative maximum application rates applicable to formulation 

• Complete exposure scenario explanations (equipment used for application) 

The labels noted above specified the distribution aminocyclopyrachlor-methyl using a broadcast 

system (groundboom, right of way sprayer, lawn care operator handgun, push type spreader, 

push cyclone spreader, tractor drawn spreader, and Aerial fixed and non-fixed wing) 

Page 13 of 27 
Occupational application rates for all occupational equipment range from a minimum of 1.5 oz. 

of product/ acre per application (0.07 lbs ae/Acre) to a maximum of 9 oz. of product/ acre per 

season (0.28 lbs ae/Acre). 

Exposure Duration:

• MOEs for both the short-term and intermediate-term scenarios have been estimated. 

Body Weight:

• The average adult body weight of 70 kg was used for estimating short- and intermediateterm inhalation exposure and risk. 

Inhalation Absorption Factor: 

• 100% 

4.2 Handler Exposure Calculations 

 

Handler risks were calculated using the Margin of Exposure (MOE) which is a ratio of the 

calculated daily dose to the NOAEL of concern. Daily dose estimates are calculated using 

relevant application parameters (i.e., rate and area treated) along with unit exposures. Exposures 

are then adjusted for body weight and absorption factors as appropriate to calculate dose levels. 

Daily Exposure: The daily exposures were calculated as described below. 

• Daily exposure = (Unit exposure x appl. rate x Daily Area Treated) 

Where: 

Daily Exposure = Amount (mg ai/day) inhaled that is available for 

inhalation absorption; 

Unit Exposure = Unit exposures (mg ai/lb ai) derived from August 1998 

PHED data, or other appropriate data; 

Application Rate = lbs ai per acre; 

Daily Area Treated = acres per day 

 

Daily Dose: The daily dose (inhalation) was calculated by adjusting the inhalation exposure 

values by body weight and accounting for inhalation absorption. For adult handlers using 

aminocyclopyrachlor, its methyl ester and potassium salt an average body weight of 70 kg was 

used. 

Page 14 of 27 
Page 15 of 27 

• Daily Dose = (Daily exposure x absorption factor)/ Bodyweight 

Where: 

Daily Dose = Absorbed dose (mg ai./kg body weight/day); 

Daily Exposure = Amount (mg ai/day) inhaled; 

Absorption Factor = 100 % (inhalation) 

Body Weight = 70 kg 

Margins of Exposure: The daily doses were then compared to the NOAELs to assess the risk as 

an MOE. The MOEs were calculated using the formula below: 

• MOE = NOAEL/Dose 

 Where: 

MOE = Margin of Exposure (unit less) 

Dose = mg/kg/day 

NOAEL = No Observed Adverse Effects Level (mg/kg/day) 

4.3 Handler Exposure Summary 

 

Exposure and risk assumptions and MOEs for occupational handlers (Agricultural and NonAgricultural use) are summarized in Table 4. 
Table 4: Occupational Short and Intermediate-Term Risk Assessment Uses of Aminocyclopyrachlor-methyl ester 

and potassium salt 

Exposure Scenario Crops

Application

Rate 

(lb ae/A)2

Area 

Treated

(A/day)3

Inhalation 

Unit 

Exposure 

(μg/lb ai) 1

Inhalation 

Daily Dose 

(mg/kg/day)4

Inhalation 

Short/Intermedia

te-term MOE5

Open Mixing and Loading 

Groundboom 

(dry flowable)6

0.77 0.0002464 1,400,000 

Applying Sprays with 

Groundboom 

(Open Cab) 

(dry flowable) 

Non-crop7. 0.28 

0.74 0.0002368 1,500,000 

Open Mixing and Loading 

Groundboom 

(dry flowable)6

0.77 0.0000616 5,700,000 

Applying Sprays with 

Groundboom 

(Open Cab) 

(dry flowable) 

Turf 9

/Sod 

Farm 

80 

0.74 0.0000592 5,900,000 

Open Mixing and Loading 

Groundboom 

(Liquid) 

0.07 

1.2 0.000048 7,300,000 

Applying Sprays with 

Groundboom 

(Open Cab) 

(Liquid) 

Turf/Lawn 

Golf 

Course2

.

40 

0.74 0.0000296 12,000,000 

Open Mixing and Loading 

Groundboom 

(Liquid) 

1.2 0.000096 3,600,000 

Applying Sprays with 

Groundboom 

(Open Cab) 

(Liquid) 

Turf/Sod 

Farm 

0.07 

80 

0.74 0.0000592 5,900,000 

Mixing/Loading 

LOC Handgun 

(dry flowable) 

Non-crop 0.28 1008 0.77 0.000308 1,100,000 
Table 4: Occupational Short and Intermediate-Term Risk Assessment Uses of Aminocyclopyrachlor-methyl ester 

and potassium salt 

Application Inhalation Area Inhalation Inhalation 

Exposure Scenario Crops Rate Unit 

(lb ae/A)2 Treated

(A/day)3 Exposure 

(μg/lb ai) 1

Daily Dose Short/Intermedia

(mg/kg/day)4 te-term MOE5

Applying 

LOC Handgun 

(dry flowable) 

Non-crop 0.28 5 1.4 0.000028 13,000,000 

Mixing/Loading 

LOC Handgun 

(Liquid) 

1008 1.2 0.00012 2,900,000 

Applying 

LOC Handgun 

(Liquid) 

Turf/Lawn 

Sod farm 

Golf 

Course 

0.07 

5 1.4 0.000007 50,000,000 

Mixing/Loading 

Aerial 

(Dry Flowable) 

0.77 0.001078 320,000 

Applying Sprays 

Aerial 

(enclosed Cockpit) 

(dry flowable) 

1.3 0.00182 190,000 

Aerial 

Flagging 

Non-Crop7 0.28 350 

0.15 0.00021 1,700,000 

Mixing /Loading 

Push Type Spreader 

(granular) 

1.7 0.00001 27,000,000 

Applying 

Push Type Spreader 

(granular) 

5 

1.2 0.0000093 38,000,000 

Mixing/Loading/Applying 

Tractor Drawn Broadcast 

Spreader 

(granular) 

Sod farm 

Golf 

Course2

0.108 

40 7.3 0.000451 780,000 

Applying 

Right of Way Sprayer 

(Dry Flowable) 

Non-Crop 0.28 5 3.9 0.000078 4,500,000 

Page 17 of 27 
Table 4: Occupational Short and Intermediate-Term Risk Assessment Uses of Aminocyclopyrachlor-methyl ester 

and potassium salt 

Application Inhalation Area Inhalation Inhalation 

Exposure Scenario Crops Rate Unit 

(lb ae/A)2 Treated

(A/day)3 Exposure 

(μg/lb ai) 1

Daily Dose Short/Intermedia

(mg/kg/day)4 te-term MOE5

Mixing/Loading 

Right of Way Sprayer 

(Dry Flowable) 

Non-Crop 0.28 0.77 0.0000154 23,000,000 

Applying 

Right of Way Sprayer 

(Soluble Liquid) 

Turf/Lawn/

Sod 

Farm/Golf 

Course 

0.07 

5 

3.9 0.0000195 18,000,000 

Note: 

1. Inhalation unit exposure values represent no respirator. Values are reported in the PHED Surrogate Exposure Guide dated August 1998. 

2. Application rates are based on maximum values found in proposed labels (ae = acid equivalent) 

3. Daily area treated is based on the area or gallons that can be reasonably applied in a single day or “one time application-(non-crop)” for 

each exposure scenario of concern based on the application method and formulation/packaging type. (standard EPA/OPP/HED values). 

 4. Daily Dose (mg/kg/day) was calculated by Unit Exposure * % Absp * Appl. rate * Area treated} / 70 kg. {Where: inhalation absp. is 

assumed to be 100%} Short and Intermediate-term endpoints are the same, thus one column. 

5. Short-/Intermediate-Term MOE = Inhalation NOAEL (350 mg/kg/day). The LOC is 100. 

6. Note: Open mixing and loading formulation was calculated using a “dry-flowable” exposure scenario. See PHED version 1.1 for details. 

7. Non-Crop: Weeds /non-agricultural item. Max. "Yearly" application label rate for (Non-Crop) only: 9 oz./Acre/application.: (9oz./Acre x 

1lb/16 oz) x .50% ae = .28 lbs ae/ Acre) "One time Application" Reference label [352-TIT] . 

8. 100 acres represents an individual mixing and loading 20 trucks that will apply 5 acres 

9. Max. Application label rate for (Turf only): 1.5 oz./Acre/ application.: (1.5oz./Acre x 1lb/16 oz) x .75% ae = .07 lbs ae/ Acre) 

Reference label [352-TOE] 

5.0 Occupational Post-application Exposure and Risk 

This registration action for aminocyclopyrachlor, its methyl ester and potassium salt involves 

application to agricultural and non-agricultural crops/non-crops. Chemical-specific post-application 

exposure data was submitted (MRID # 47560209) in support of this registration action. Turf 

transferable residues (TTRs), were selected form three test sites located in California (Porterville), 

Canada (Branchton), and Georgia (Sycamore). 3

At the Georgia site, the average total TTR value was 

0.0009 μg/cm2 at the first post application sampling interval which took place 2 hours after the 

application. By the next sampling interval at 1 DAT, total residues had declined to <LOQ. Based on 

rainfall data reported in the Study Report, there was a rainfall event almost immediately after 

application and before the first post application sampling (0.02 inches). This appears to have caused 

rapid dissipation of the residues at the Georgia site. DPX-KJM44, DPX-MAT28, and total TTR 

residues were considerably lower than those observed at the other two test sites. 

 

3

 DFR study: (MRID # 47560209) 

Page 18 of 27 
At the Ontario site, the average total TTR value at the first post application sampling interval was 

0.0035μg/cm2

. Total TTR values declined gradually to an average of 0.0002 μg/cm2 by 7 DAT and 

fell below the LOD by 14 DAT. 

At the California site, total TTR values declined rapidly from an average of 0.0070μg/cm2 at the first 

post application sampling interval to less than the LOQ by 3 DAT. 

 

Note; at the Georgia site rainfall occurred and caused substantial lower TTR values, therefore this data 

was not used in this assessment. However, as noted earlier quantification of dermal exposures is not 

required because no toxicity was observed in a dermal study conducted at the limit dose. 

 

Furthermore, HED believes that based on the occupational handler inhalation MOE values of (190,000 

– 50,000,000), occupational post-application inhalation exposures will be negligible and therefore 

were not assessed in this memorandum. Please see table 4 for specifics. 

Aminocyclopyrachlor, its methyl ester and potassium salt are classified in Toxicity Category IV for 

acute dermal and skin irritation and Category III for primary eye irritation. The draft product label of 

(352-TIL- DPX-KJM44 80XP) states that because this product is used on sod farms it is within the 

scope of the Workers Protection Standard (WPS) for agricultural pesticides (40 CFR Part 170). 

Therefore the restricted entry interval (REI) is 4 hours, however due to a toxicology category of III for 

ocular irritation HED maintains that a 12 hour REI is appropriate.

5.1 Occupational Post-application Exposure Summary 

Quantification of dermal exposures is not required because no toxicity was observed in a dermal study 

conducted at the limit dose; therefore a dermal post-application assessment was not conducted. 

Furthermore, HED believes that based on the occupational handler inhalation MOE values range of 

(190,000 - 50,000,000), occupational post-application inhalation exposures will be negligible and 

therefore were not assessed in this memorandum. Please see table 4 for specifics. 

6.0 Non-Occupational/Residential Exposure and Risk 

Handler Exposure 

The proposed uses associated with this action are for use of aminocyclopyrachlor, its methyl ester and 

potassium salt on lawn/turf. Aminocyclopyrachlor-methyl, (4-Pyrimidinecarboxylic acid, 6-amino-5-

chloro-2-cyclopropyl, - methyl) are herbicides formulated as a dispersible granular, a granular, and a 

soluble liquid for pre-, and or post-emergence control of broad leaf and woody species weeds; 

including many terrestrial, riparian invasive, and noxious weeds. 

 

Concerning application use as it applies to residential exposure and risk; label specific directions state 

that the residential use pattern is primarily focused on “residential lawn and turf”. Furthermore the 

labels noted within (352-TOG, 352-TOE, 352-TOU, 352-TOT, 352-IRG, 352-TOI, 352-IRU, 352-

TOO, 352-IRL, 352-INN, 352-ING, 352-INU, 352-INT, 352-IRR, 352-IRE) are comprised of the 

Page 19 of 27 
three different formulations (dispersible granular, granular, and a soluble liquid) and all were assessed, 

however according to label terminology, the granular formulation seems to be the product most 

highlighted for residential lawn and turf application. 

 

Based on the number of seasonal applications indicated on this product label (every other month 

interval), and information provided by the registrant, residential handler exposures are expected to be 

short- (1-30 days) and intermediate-term (1-6 months) in duration. The quantitative exposure/risk 

assessment developed for residential handlers is based on the following exposure scenarios: 

 

Exposure Scenarios: Open mixing, loading, and applying:

• Low Pressure Handwand (dry flowable and soluble liquid) formulation to Lawn/Turf. 

• Hose-end Sprayer (dry flowable and soluble liquid) formulation to Lawn/Turf. 

• Hand Held Spreader [Belly Grinder- (granular)] formulation to Lawn/Turf. 

Note: Quantification of dermal exposures is not required because no toxicity was observed in a dermal 

study conducted at the limit dose; therefore a dermal assessment was not conducted. However, an 

inhalation exposure assessment was conducted and noted in table 5. 

6.1 Data and Assumptions for Residential Handler Exposure Scenarios 

The data and assumptions are consistent with the occupational handler section (5.0), however the area 

treated and unit exposure have been adjusted for residential applications.

Area Treated:

• HED assumed 0.5 acre lawn/turf were treated per day while using the following residential 

equipment (HED Exposure Science Advisory Committee SOP Number 9.1). 

o Low pressure handwand 

o Hose-end sprayer

o Hand Held Spreader (Belly grinder)

Unit Exposures: See table #5 for details. 

6.2 Non-Occupational/Residential Handler Exposure Calculations 

Please see section 4.0 (Occupational Handler Exposure Calculations), for details. 

6.3 Non-Occupational/Residential Handler Exposure Summary 

 

Exposure and risk assumptions and MOEs for non-occupational handlers (Non-Agricultural use) are 

summarized in Table 5. 

Page 20 of 27 
Table 5: Residential Short and Intermediate-Term Risk Assessment Uses of Aminocyclopyrachlormethyl ester and potassium salt 

Exposure Scenario Crops

2Application

Rate 

(lb ae/A) 

3Area 

Treated

(A/day)

1Inhalation 

Unit 

Exposure 

(μg/lb ai) 

5

Inhalation 

Daily Dose 

(mg/kg/day)

4

Inhalation 

Short/Intterm MOE

Open Mixing, Loading and 

Applying 

Low Pressure Handwand 

(Soluble Liquid) 

30 0.000015 23,000,000 

Open Mixing, Loading, and 

Applying 

Hose-end Sprayer 

(Dry Flowable) 

.07 

17 0.0000085 41,200,000 

Open Mixing, Loading, and 

Applying 

Belly Grinder 

(Granular) 

Lawn/ 

Turf 

0.10 

0.5 

62 0.000048 7,300,000 

 Note: 

 1. Inhalation unit exposure values represent no respirator. Values are reported in the PHED Surrogate Exposure Guide dated August 1998. 

 2. Application rates are based on maximum values found in proposed labels (ae = acid equivalent) daily area treated is based on the area or 

gallons that can be reasonably applied in a single day for each exposure scenario of concern based on the application method and 

formulation/packaging type. (Standard EPA/OPP/HED values). 

 4. Short-/Intermediate-Term MOE = Inhalation NOAEL (350 mg/kg/day). The LOC is 100. 

 5. Note. Daily Dose (mg/kg/day) was calculated by Unit Exposure * % Absp * Appl. rate * Area treated} / BW-70 kg. {Where: inhalation 

absp. is assumed to be 100%} Short and Intermediate-term endpoints are the same, thus one column. 

7.0 Non-Occupational/Residential Post-application Exposure and Risk 

A wide array of individuals of varying ages can potentially be exposed to aminocyclopyrachlor, its 

methyl ester and potassium salt, when they do activities in areas that has been previously treated. 

Post-application exposure scenarios were developed for each residential setting where 

aminocyclopyrachlor, its methyl ester and potassium salt can be used. Current label guidelines state 

that treatment is to occur at residential homes and multi family residential complexes. 

7.1 Data and Assumptions for Non-Occupational/Residential Handler Exposure Scenarios 

• Residential exposure assessments for aminocyclopyrachlor, its methyl ester and potassium 

salt were classified as short-, and intermediate-term exposure scenarios due to the number of 

seasonal applications. 

• Dermal exposures for children as well as adults were not assessed. 

 

Page 21 of 27 
• Non-dietary ingestion exposures to toddlers were calculated (i.e., soil ingestion, hand-/objectto-mouth). 

• Body weight use for calculations (15kg/day). HED relies on a standardized approach for 

completing residential risk assessments that is based on current aminocyclopyrachlor labels. 

• Standard Operating Procedures for Residential Exposure Assessment (Dec. 1997). This 

document provides the overarching guidance for developing residential risk assessments 

including scenario development, algorithms, and values for inputs. 

7.2 Post-Application Dermal Exposure 

As note in previous sections, a quantification of dermal exposures is not required because no toxicity 

was observed in a dermal study conducted at the limit dose; therefore a dermal assessment was not 

conducted. However, an incidental oral (hand to mouth, object to mouth, and soil ingestion) exposure 

assessment was conducted and noted below in table 6. 

Chemical-specific post-application exposure data was submitted (MRID # 47560209) in support of the 

registration of aminocyclopyrachlor, its methyl ester and potassium salt. Turf transferable residues 

(TTRs), were selected form three test sites located in California (Porterville), Canada (Branchton) and 

Georgia (Sycamore). Note; at the Georgia site rainfall occurred and caused substantial lower TTR 

values, therefore this data was not used in this assessment.

7.3 Post-Application Incidental Oral Exposure 

Incidental Oral exposure was assessed for toddlers. Please table 6 for details. 

7.3.1 Incidental Oral Exposure Calculations 

Non-dietary Ingestion Exposure from Treated Turf: Non-dietary ingestion exposure from treated 

turf was calculated using the following equations. 

• Hand-to-mouth Transfer of Pesticide Residues on Lawns (toddler) 

The approach used to calculate the non-dietary ingestion exposures that are attributable to hand-tomouth behavior on treated turf is: 

ADD = (TTR0 * SA * FQ * ET * SE * CF1) / BW 

Where: 

ADD = average daily dose (mg/kg/day); 

TTRt = turf transferable residue on day "0" (μg/cm2 ); 

SA = surface area of the hands (20 cm2

/event); 

Page 22 of 27 
FQ = frequency of hand-to-mouth activity 

 (Short-term 20/Intermediate-term 9.5 events/hr); 

ET = exposure time (2 hr/day); 

 SE = extraction by saliva (50%); 

CF1 = weight unit conversion factor to convert μg units in the DFR value to mg for the 

daily exposure (0.001 mg/μg); and 

BW = body weight (15 kg). 

• Object-to-mouth Transfer of Pesticide Residues on Lawns (toddler) 

The approach used to calculate exposures that are attributable to object-to-mouth behavior on treated 

turf that is represented by a child mouthing on a handful of turf is: 

ADD = (TTR0 * IgR* CF1) / BW 

Where: 

ADD = average daily dose (mg/kg/day); 

TTRt = turf transferable residue on day "0" (μg/cm2); 

IgR = ingestion rate of grass (25 cm2/day); 

CF1 = weight unit conversion factor to convert the μg of residues on the grass to mg to 

provide units of mg/day (1E-3 mg/μg); 

BW = body weight (15 kg). 

• Incidental Ingestion of Soil from Pesticide-Treated Residential Areas (toddler). 

The approach used to calculate exposures that are attributable to soil ingestion is: 

ADD = (SR0 * IgR * CF1) / BW 

Where: 

ADD = average daily dose (mg/kg/day); 

SR0t = soil residue on day "0" (0.0022 μg/g); 

Page 23 of 27 
IgR = ingestion rate of soil (100 mg/day); 

CF1 = weight unit conversion factor to convert the μg of residues on the soil to grams 

to provide units of mg/day (1E-6 g/μg); and 

BW = body weight (15 kg). 

7.4 Non-Occupational/Residential Post-Application Exposure Summary 

 Detailed risk calculations for the various residential aminocyclopyrachlor assessments are included in 

Appendices D. A summary of risk estimates for residential post-application risks for children is 

provided in table 6. Additionally, HED combines risk values resulting from separate post-application 

exposure scenarios when it is likely they can occur simultaneously based on the use-pattern and the 

behavior associated with the exposed population (see Table 6). 

Table 6: Toddler Residential Risk Estimates for Post-application Exposure to Aminocyclopyrachlor-methyl 

ester and potassium salt

Exposure Scenario TC 

cm2/hr 

Route of 

Exposure Application Rate 5

MOE at Day 0 

1 Combined MOE 

Ingestion 

 Outdoors S-Term Int-Term 

2Hand to Mouth Activity 

on Turf 234,000 493,000 

3Object to Mouth 

Activity on Turf 938,000 

4

Soil Ingestion 

N/A Oral 0.1 

70,000,000 

322,000 

1Combined MOE = NOAEL/ (ADDhand-to-mouth + ADDobject-to-mouth + ADDincidental soil ingestion ) Intermediate.-term ADD used to calculate 

combined MOE: (most conservative) : Level of Concern: MOE = 100 

 2 Hand-to-mouth Transfer of Pesticide Residues on Lawns (toddler): ADD = (TTR0 * SA * FQ * ET * SE * CF1) / BW 

 * FQ: (Short-term 20/Intermediate-term 9.5 events/hr); 

 3 Object-to-mouth Transfer of Pesticide Residues on Lawns (toddler): ADD = (TTR0 * IgR* CF1) / BW 

 4

Incidental Ingestion of Soil from Pesticide-Treated Residential Areas (toddler): ADD = (SR0 * IgR * CF1) / BW 5 Short-/Intermediate-Term MOE = Inhalation NOAEL (350 mg/kg/day). The LOC is 100. 

8.0 Conclusion 

This registration action for aminocyclopyrachlor, its methyl ester and potassium salt involves 

application to non-agricultural crops, exclusively (Lawn/Turf). Chemical-specific post-application 

exposure data was submitted (MRID # 47560209) in support of the registration of 

aminocyclopyrachlor, its methyl ester and potassium salt. Turf transferable residues (TTRs), were 

selected form three test sites located in California (Porterville), Canada (Branchton), and Georgia 

(Sycamore). Note; at the Georgia site rainfall occurred and caused substantial lower TTR values, 

therefore this data was not used in this assessment. However, as noted earlier quantification of dermal 

exposures is not required because no toxicity was observed in a dermal study conducted at the limit 

dose. 

Page 24 of 27 
Page 25 of 27 

For all Occupational and Non-Occupational/Residential handler and post application exposure 

scenarios, Margins of Exposure (MOEs) were ≥100 and therefore risks were not observed at these 

application rats. 

Lastly, label directions call for a restricted entry interval (REI) of 4 hours, however due to a category 

III in acute eye irritation, HED maintains that a REI of 12 hours is appropriate and that all label 

directions reflect this change.
9.0 References 

• Label Use Patterns; (EPA registration #’s 352-TOG, 352-TOE, 352-INN, 352-TOT, 352-

IRL, 352-IRE, 352-TOU, 352-TIA, 352-TIL, 352-TIT, 352-IRG, 352-IRU, 352-TOO, 352-

ING, 352-INU, 352-INT, 352-IRR, 352-TOI) 

• Pesticides Handlers Exposure Database (PHED)Version 1.1; dated 8/98 (HED Science 

Advisory Council for Exposure Draft Policy #7; dated 1/28/99 

• End Point Selection; [(see Memorandum, DP # 369507 titled, Aminocyclopyrachlor: 

Human Health Risk Assessment for Proposed Uses as an Herbicide. PC Code: 288008, 

288009, 288010 DP Barcode: D369057 

• HED: Exposure Science Advisory Counsel 

• Chemical-specific post-application exposure data, (MRID # 47560209). 

Page 26 of 27 
Page 27 of 27 

Appendices

A) Commercial Handler (inhalation 

B) Residential Handler (inhalation) 

C) Residential Post-Application (Incidental Oral)