Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 WASHINGTON, D.C. 20460

 OFFICE OF 

PREVENTION, PESTICIDES

 AND TOXIC SUBSTANCES 

MEMORANDUM

Date: 10/22/2009

SUBJECT: Aminopyralid Chronic Aggregate Dietary (Food and Drinking Water) Exposure 

and Risk Assessment for the Section 3 Registration on Field Corn

 

PC Code: 005100 DP Number: D369212

Decision No: 401475 Registration No: 62719-519

Petition Nos.: 8F7455 Regulatory Action: Section 3 Registration

Risk Assess Type: None Case No.: None 

TXR No.: None CAS No.: 566191-89-7

MRID No.: None 40 CFR: 180.610

 

FROM: Douglas Dotson, Ph.D., Chemist

Risk Assessment Branch II

Health Effects Division (7509P)

THROUGH: Donna Davis, Chemist

William Cutchin, Chemist

Dietary Exposure Science Advisory Council

Health Effects Division (7509P)

TO: Kathryn Montague/Joanne Miller, RM Team 23

Herbicide Branch

Registration Division (7505P)
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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Executive Summary

A chronic aggregate dietary (food and drinking water) exposure and risk assessment was

conducted for the herbicide, aminopyralid, using the Dietary Exposure Evaluation Model,

DEEM-FCIDTM, Version 2.03, which uses food consumption data from the U.S. Department of 

Agriculture’s Continuing Surveys of Food Intakes by Individuals (CSFII). The surveys were 

taken from 1994-1996 and included a supplemental children’s survey taken in 1998. The 

analysis was performed to support a Section 3 tolerance petition for the use of aminopyralid on 

field corn. An acute dietary assessment was not performed, as a toxicological endpoint 

attributable to a single dose has not been identified for aminopyralid. Aminopyralid is classified 

as “not likely to be carcinogenic to humans;” therefore, a cancer assessment was not performed.

The unrefined chronic assessment is based on the assumption that aminopyralid residues are 

present at tolerance levels in all commodities for which tolerances have been established, and 

that 100% of those crops are treated. DEEMTM Version 7.81 default processing factors were 

applied to all processed commodities for which they were available. Drinking water was 

incorporated directly into the dietary assessment using the estimated drinking water 

concentration (EDWC) for surface water generated by the Tier 1 FQPA Index Reservoir 

Screening Tool (FIRST) Model.

The resulting chronic dietary exposure estimates for food and water combined are well below 

HED’s level of concern for the general U.S. population and all population subgroups. Using the 

DEEM-FCID software, dietary exposure is estimated at 0.000703 mg/kg/day for the U.S. 

population (<1% of the chronic population adjusted dose (cPAD)) and 0.002097 mg/kg/day

(<1% of the cPAD) for children 1 to 2 years old, the population subgroup with the highest 

estimated chronic dietary exposure to aminopyralid. 

I. Introduction

Dietary risk assessment incorporates both exposure and toxicity of a given pesticide. For acute 

and chronic assessments, the risk is expressed as a percentage of a maximum acceptable dose 

(i.e., the dose which HED has concluded will result in no unreasonable adverse health effects). 

This dose is referred to as the population adjusted dose (PAD). The PAD is equivalent to the 

point of departure (PoD; e.g. NOAEL, LOAEL, etc.) divided by the required uncertainty or 

safety factors.

For acute and non-cancer chronic exposures, HED is concerned when estimated dietary risk 

exceeds 100% of the PAD. References which discuss the acute and chronic risk assessments in 

more detail are available on the EPA/pesticides website: “Available Information on Assessing 

Exposure from Pesticides, A User’s Guide,” 21-JUN-2000, web link: 

http://www.epa.gov/fedrgstr/EPA-PEST/2000/July/Day-12/6061.pdf ; or see SOP 99.6 (20-

AUG-1999).
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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II. Residue Information

Residues of Concern: The nature of the residue of aminopyralid in plants and livestock has been 

adequately delineated based on metabolism studies conducted with aminopyralid in wheat, grass, 

lactating goats, and laying hens. In metabolism studies reflecting foliar applications to grass and 

wheat, aminopyralid was found to be metabolized to a multi-component mixture of water-soluble 

complexes that consist mostly of isomeric mixtures of acid- and base-labile N-glucosides and 

glucose ester conjugates of aminopyralid. HED concluded that the residues of concern in grass 

and small grain commodities are free and conjugated aminopyralid. Metabolism studies in

lactating goats and laying hens show that most of the administered dose is rapidly excreted 

(~80% for hens and ~95% for goat). The weight of the evidence is that the limited amount of 

aminopyralid that is not excreted remains as the parent compound. Therefore, the residue of 

concern in livestock is aminopyralid (Memo, D360100, D. Dotson, 10/22/2009).

Tolerances: Permanent tolerances have been established under 40 CFR §180.610(a) for free and 

conjugated residues of aminopyralid in or on grass and wheat commodities at levels ranging

from 0.04 ppm in wheat grain to 50 ppm in grass hay. Permanent tolerances have also been 

established residues of aminopyralid in or on the following animal commodities: milk 

(0.03ppm), kidney of cattle, goat, horse, and sheep (0.3 ppm), and the fat, meat, and meat 

byproducts (except kidney) of cattle, goat, horse, and sheep (0.02 ppm).

Dow AgroSciences has proposed tolerances for residues of aminopyralid on field corn grain, 

forage, and stover. HED has reviewed residue data submitted to support these uses and 

concluded that the proposed tolerances are appropriate (Memo, D. Dotson, D360100, 

10/22/2009). The tolerances are listed in Table 1, below. Field corn grain is the only human 

food item on this list.

Table 1. Aminopyralid Recommended Tolerances

Crop Commodity Recommended Tolerance (ppm)

Field Corn Grain 0.20

Field Corn Forage 0.30

Field Corn Stover 0.20

Livestock: Livestock feedstuffs associated with the proposed uses include field corn grain, 

forage, silage, stover, and milled byproducts. Tolerances are currently in effect for animal 

commodities. Based on recalculated dietary burdens and the results of ruminant and poultry

feeding studies, HED concluded that no changes need to be made to the animal commodity

tolerances.

Residue Data used for the Chronic Assessment: The unrefined chronic dietary assessment is 

based on the assumption that aminopyralid residues are present at tolerance levels in all 

commodities for which tolerances have been established and that 100% of those crops are 
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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treated. DEEMTM Version 7.81 default processing factors were applied to all processed 

commodities for which they were available. The only processed commodities in this assessment 

are corn syrup and dried beef. Processing studies for these two commodities were not submitted 

by the registrant. 

III. Drinking Water Data

The drinking water residues used in the dietary risk assessment were provided by the 

Environmental Fate and Effects Division (EFED, Memo, R. Barris, D361926, 7/24/2009). Water 

residues were incorporated directly into the DEEM-FCID assessment under the food categories 

“water, direct, all sources” and “water, indirect, all sources.” 

The residue of concern in drinking water is parent aminopyralid (Memo, D301689, M. Doherty, 

7/12/2005). EFED estimated residues of aminopyralid in surface water and groundwater using 

the FIRST and SCIGROW (Screening Concentrations in Groundwater) models, respectively. 

The models and their descriptions are available at the EPA internet site: 

http://www.epa.gov/oppefed1/models/water/. The maximum estimated drinking water 

concentrations (EDWCs) are presented below in Table 2.

Table 2. Maximum Aminopyralid EDWCs in Surface and Ground Water

Maximum Surface Water EDWC (ppb)

Maximum Ground Water 

Acute/Chronic EDWC (ppb)

Acute Value Chronic/Cancer Value

10.024 1.937 0.630

The chronic surface water EDWC was higher than the groundwater EDWC; therefore, the 

surface water value of 1.937 ppb was used in the chronic dietary assessment. The acute surface 

water value is not relevant to this dietary assessment, as a toxic effect attributable to a single 

dose has not been identified for aminopyralid.

IV. DEEM-FCIDTM Program and Consumption Information

An aminopyralid chronic dietary exposure assessment was conducted using the Dietary Exposure 

Evaluation Model software with the Food Commodity Intake Database DEEM-FCIDTM, Version 

2.03, which incorporates consumption data from USDA’s Continuing Surveys of Food Intakes 

by Individuals (CSFII), 1994-1996 and 1998. The 1994-96, 98 data are based on the reported 

consumption of more than 20,000 individuals over two non-consecutive survey days. Foods “as 

consumed” (e.g., apple pie) are linked to EPA-defined food commodities (e.g. apples, peeled 

fruit - cooked; fresh or N/S; baked; or wheat flour - cooked; fresh or N/S, baked) using publicly 
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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available recipe translation files developed jointly by USDA/ARS and EPA. For chronic

exposure assessment, consumption data are averaged for the entire U.S. population and within 

population subgroups, but for acute exposure assessment are retained as individual consumption 

events. Based on analysis of the 1994-96, 98 CSFII consumption data, which took into account 

dietary patterns and survey respondents, HED concluded that it is most appropriate to report risk 

for the following population subgroups: the general U.S. population, all infants (<1 year old), 

children 1-2, children 3-5, children 6-12, youth 13-19, adults 20-49, females 13-49, and adults 

50+ years old.

For chronic dietary exposure assessment, an estimate of the residue level in each food or foodform (e.g., orange or orange juice) on the food commodity residue list is multiplied by the 

average daily consumption estimate for that food/food form to produce a residue intake estimate. 

The resulting residue intake estimate for each food/food form is summed with the residue intake 

estimates for all other food/food forms on the commodity residue list to arrive at the total 

average estimated exposure. Exposure is expressed in mg/kg body weight/day and as a percent 

of the cPAD. This procedure is performed for each population subgroup.

V. Toxicological Information

Reference: Aminopyralid. Human Health Risk Assessment for the Proposed Use on Field Corn 

(PP#8F7455), D359088, D. Dotson, et al., 10/22/2009.

HED has evaluated the available toxicity data for aminopyralid and determined that the 

following endpoints and doses are appropriate for use in the dietary risk assessment:

Table 3. Summary of Toxicological Doses and Endpoints for Aminopyralid for Use in

Dietary Human Health Risk Assessments

Exposure/

Scenario

Point of 

Departure

Uncertainty/

FQPA Safety 

Factors

RfD, PAD, 

Level of 

Concern for 

Risk 

Assessment

Study and Toxicological Effects

Acute Dietary 

(General 

Population, 

including 

Infants and 

Children and 

females 13-49)

N/A N/A N/A

A toxic effect attributable to a single 

exposure was not seen in the toxicity 

database; therefore, an acute endpoint has 

not been identified. 

Chronic 

Dietary (All 

Populations)

NOAEL= 50 

mg/kg/day

UFA= 10 x

UFH=10 x

FQPA SF=1x

Chronic RfD = 

RfD=0.5 

mg/kg/day

cPAD 0.5

mg/kg/day

Chronic toxicity/carcinogenicity study

LOAEL=500mg/kg/day

based on cecal enlargement, slight 

mucosal hyperplasia in males and slightly 

decreased body weights

Cancer (oral, 

dermal, 

inhalation)

Classification: “Not likely to be Carcinogenic to Humans” based on the absence of significant 

tumor increases in two adequate rodent carcinogenicity studies.
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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Point of Departure (PoD) = A data point or an estimated point that is derived from observed dose-response 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. N/A = not applicable.

The FQPA Safety Factor has been reduced to 1x for all population subgroups for the following 

reasons: 1) there is no evidence of increased pre- and/or post-natal sensitivity/susceptibility to 

aminopyralid, 2) there is no evidence of neurotoxicity in the database (so a developmental 

neurotoxicity (DNT) study has not been required), and 3) the exposure values that are used in the 

risk assessment are conservative and are unlikely to underestimate risk.

VI. Results/Discussion 

As stated above, for chronic assessments, HED is concerned when dietary risk exceeds 100% of 

the cPAD. The DEEM-FCIDTM analyses estimate the dietary exposure of the U.S. population 

and various population subgroups. The results reported in Table 3 are for the general U.S. 

Population, all infants (<1 year old), children 1-2, children 3-5, children 6-12, youth 13-19,

females 13-49, adults 20-49, and adults 50+ years. 

Aminopyralid chronic dietary (food + water) exposure estimates using the DEEM-FCIDTM 

software are well below HED’s level of concern for the U.S. population and each of the 

population subgroups. Dietary exposure was estimated to be 0.000703 mg/kg/day for the U.S. 

population (<1% of the cPAD) and 0.002097 mg/kg/day (<1% of the cPAD) for the most highly

exposed population subgroup (children, 1-2 years old). The estimated exposures and risks from 

residues of aminopyralid in food and water are summarized in Table 4.

Table 4. Chronic Aggregate Dietary (Food + Drinking Water) Exposure and Risk for Aminopyralid

Population Subgroup Exposure

(mg/kg/day) % cPAD

General U.S. Population 0.000703 <1

All Infants (< 1 year old) 0.001081 <1

Children 1-2 years old 0.002097 <1

Children 3-5 years old 0.001827 <1

Children 6-12 years old 0.001266 <1

Youth 13-19 years old 0.000822 <1

Adults 20-49 years old 0.000515 <1

Adults 50+ years old 0.000359 <1

Females 13-49 years old 0.000516 <1
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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VII. Characterization of Inputs/Outputs

These chronic dietary exposure and risk estimates are highly conservative. They are based on 

the assumption that 100% of crops with tolerances are treated with aminopyralid, and that 

residues in foods “as eaten” are present at tolerance levels. In addition, drinking water exposure 

estimates are screening level estimates generated by the Tier 1 FIRST Model.

Dietary exposure estimates could be refined through the use of anticipated residues, percent crop 

treated data, and/or refined estimated drinking water concentrations. However, as estimated 

exposures and risks using conservative assumptions are well below HED’s level of concern, no 

refinements are needed at the present time.

VIII.Conclusions

This unrefined chronic dietary exposure analysis using DEEM-FCIDTM indicates that chronic 

dietary exposure of humans to aminopyralid from food and drinking water is well below HED’s 

level of concern. Estimated chronic dietary exposures are less than 1% of the cPAD for the 

general U.S. population and all population subgroups. This assessment is unlikely to 

underestimate risk.

IX. List of Attachments

1. Aminopyralid Chronic Dietary Residue Input File

2. Results of Aminopyralid Chronic Dietary Exposure Analysis
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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Attachment 1: Aminopyralid Chronic Dietary Residue Input File

Chronic NOAEL: 50 mg/kg bw/day

Chronic PAD (cPAD): 0.50 mg/kg bw/day

DEEM FCID (Version 2.03), 1994-1996 data and 1998 Supplemental Children’s Survey

Filename: C:\Documents and Settings\ddotson\My 

Documents\Deemfcid\Aminopyralid\AminopyralidCHR.R98

Date created/last modified: 09-15-2009/16:34:553/8

--------------------------------------------------------------------------------

 EPA Crop Def Res Adj.Factors Comment

 Code Grp Commodity Name (ppm) #1 #2 

-------- ---- ------------------------------- ---------- ------ ------ -------

15001200 15 Corn, field, flour 0.200000 1.000 1.000 

15001201 15 Corn, field, flour-babyfood 0.200000 1.000 1.000 

15001210 15 Corn, field, meal 0.200000 1.000 1.000 

15001211 15 Corn, field, meal-babyfood 0.200000 1.000 1.000 

15001220 15 Corn, field, bran 0.200000 1.000 1.000 

15001230 15 Corn, field, starch 0.200000 1.000 1.000 

15001231 15 Corn, field, starch-babyfood 0.200000 1.000 1.000 

15001240 15 Corn, field, syrup 0.200000 1.500 1.000 

15001241 15 Corn, field, syrup-babyfood 0.200000 1.500 1.000 

15001250 15 Corn, field, oil 0.200000 1.000 1.000 

15001251 15 Corn, field, oil-babyfood 0.200000 1.000 1.000 

15004010 15 Wheat, grain 0.040000 1.000 1.000 

15004011 15 Wheat, grain-babyfood 0.040000 1.000 1.000 

15004020 15 Wheat, flour 0.040000 1.000 1.000 

15004021 15 Wheat, flour-babyfood 0.040000 1.000 1.000 

15004030 15 Wheat, germ 0.040000 1.000 1.000 

15004040 15 Wheat, bran 0.100000 1.000 1.000 

21000440 M Beef, meat 0.020000 1.000 1.000 

21000441 M Beef, meat-babyfood 0.020000 1.000 1.000 

21000450 M Beef, meat, dried 0.020000 1.920 1.000 

21000460 M Beef, meat byproducts 0.020000 1.000 1.000 

21000461 M Beef, meat byproducts-babyfood 0.020000 1.000 1.000 

21000470 M Beef, fat 0.020000 1.000 1.000 

21000471 M Beef,fat-babyfood 0.020000 1.000 1.000 

21000480 M Beef, kidney 0.300000 1.000 1.000 

21000490 M Beef, liver 0.020000 1.000 1.000 

21000491 M Beef, liver-babyfood 0.020000 1.000 1.000 

23001690 M Goat, meat 0.020000 1.000 1.000 

23001700 M Goat, meat byproducts 0.020000 1.000 1.000 

23001710 M Goat, fat 0.020000 1.000 1.000 

23001720 M Goat, kidney 0.300000 1.000 1.000 

23001730 M Goat, liver 0.020000 1.000 1.000 

24001890 M Horse, meat 0.020000 1.000 1.000 

26003390 M Sheep, meat 0.020000 1.000 1.000 

26003391 M Sheep, meat-babyfood 0.020000 1.000 1.000 

26003400 M Sheep, meat byproducts 0.020000 1.000 1.000 

26003410 M Sheep, fat 0.020000 1.000 1.000 

26003411 M Sheep, fat-babyfood 0.020000 1.000 1.000 

26003420 M Sheep, kidney 0.300000 1.000 1.000 

26003430 M Sheep, liver 0.020000 1.000 1.000 

27002220 D Milk, fat 0.030000 1.000 1.000 

27002221 D Milk, fat - baby food/infant for 0.030000 1.000 1.000 

27012230 D Milk, nonfat solids 0.030000 1.000 1.000 

27012231 D Milk, nonfat solids-baby food/in 0.030000 1.000 1.000 

27022240 D Milk, water 0.030000 1.000 1.000 

27022241 D Milk, water-babyfood/infant form 0.030000 1.000 1.000 

27032251 D Milk, sugar (lactose)-baby food/ 0.030000 1.000 1.000 

86010000 O Water, direct, all sources 0.001937 1.000 1.000 

86020000 O Water, indirect, all sources 0.001937 1.000 1.000 
Aminopyralid Dietary Exposure and Risk Assessment DP Number: 369212

PC Code: 005100 

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Attachment 2: Results of Aminopyralid Chronic Dietary Exposure Analysis

Chronic NOAEL: 50 mg/kg bw/day

Chronic PAD (cPAD): 0.50 mg/kg bw/day

Adjustment factor #2 NOT used.

Residue file name: Aminopyralid\AminopyralidCHR.R98

Analysis Date 09-15-2009/16:35:19 Residue file dated: 09-15-2009/16:34:55/8

===============================================================================

 Total exposure by population subgroup

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 Total Exposure

 -----------------------------------

 Population mg/kg Percent of 

 Subgroup body wt/day Rfd 

-------------------------------------- ------------- ---------------

U.S. Population (total) 0.000703 0.1%

U.S. Population (spring season) 0.000709 0.1%

U.S. Population (summer season) 0.000716 0.1%

U.S. Population (autumn season) 0.000699 0.1%

U.S. Population (winter season) 0.000688 0.1%

Northeast region 0.000651 0.1%

Midwest region 0.000753 0.2%

Southern region 0.000681 0.1%

Western region 0.000732 0.1%

Hispanics 0.000820 0.2%

Non-hispanic whites 0.000686 0.1%

Non-hispanic blacks 0.000715 0.1%

Non-hisp/non-white/non-black 0.000669 0.1%

All infants (< 1 year) 0.001081 0.2%

Nursing infants 0.000319 0.1%

Non-nursing infants 0.001370 0.3%

Children 1-6 yrs 0.001877 0.4%

Children 7-12 yrs 0.001208 0.2%

Females 13-19 (not preg or nursing) 0.000705 0.1%

Females 20+ (not preg or nursing) 0.000421 0.1%

Females 13-50 yrs 0.000568 0.1%

Females 13+ (preg/not nursing) 0.000598 0.1%

Females 13+ (nursing) 0.000603 0.1%

Males 13-19 yrs 0.000937 0.2%

Males 20+ yrs 0.000494 0.1%

Seniors 55+ 0.000354 0.1%

Children 1-2 yrs 0.002097 0.4%

Children 3-5 yrs 0.001827 0.4%

Children 6-12 yrs 0.001266 0.3%

Youth 13-19 yrs 0.000822 0.2%

Adults 20-49 yrs 0.000515 0.1%

Adults 50+ yrs 0.000359 0.1%

Females 13-49 yrs 0.000516 0.1%

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