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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF PREVENTION, PESTICIDE

AND TOXIC SUBSTANCES

MEMORANDUM

Date: 10/22/2009

SUBJECT: Aminopyralid and Aminopyralid Triisopropanolammonium (TIPA) Salt. Request 

to Add Uses on Field Corn to Milestone® (EPA Reg. No. 62719-519). Summary

of Analytical Chemistry and Residue Data.

PC Codes: 005100 (Aminopyralid) and 

005209 (Aminopyralid TIPA Salt)

DP Barcode: D360100

Decision No.: 401475 Registration No.: 62719-519

Petition No.: PP#8F7455 Regulatory Action: Section 3 Registration

Risk Assessment Type: NA Case No.: NA

TXR No.: NA CAS No.: 150114-71-9 (Aminopyralid) and 

566191-89-7 (Aminopyralid TIPA Salt)

MRID No.: 46661301, 46729001, 

46729601-03, 47572601, 47572603-04

40 CFR: 180.610

FROM: Douglas Dotson, Ph.D., Chemist

Risk Assessment Branch II

Health Effects Division, 7509P

THROUGH: Michael Doherty, Ph.D., Chemist

Richard Loranger, Ph.D., Senior Scientist

Risk Assessment Branch II

Health Effects Division, 7509P

TO: Kathryn Montague/Joanne Miller, RM 23

Herbicide Branch

Registration Division, 7505P

This document was originally prepared under contract by Dynamac Corporation (1901 Research 

Boulevard, Suite 220; Rockville, MD 20850). The document has been reviewed by the Health 

Effects Division (HED) and revised to reflect current Office of Pesticide Programs (OPP) 

policies.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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Executive Summary

Aminopyralid is a systemic postemergence herbicide which belongs to the pyridine carboxylic 

acid class of herbicides. It is currently registered for use on rangeland, permanent grass pastures, 

and wheat. In addition, it is registered for use on wildlife habitat and industrial vegetation 

management areas, including right-of-way for roads, railroads, and utility lines. 

Under PP#8F7455, Dow AgroSciences is proposing the establishment of permanent tolerances 

for aminopyralid (2-pyridine carboxylic acid, 4-amino-3,6-dichloro-), expressed as total parent, 

free and conjugated, in or on the following raw agricultural commodities:

Corn, forage ....................................................................... 0.30 ppm

Corn, grain ......................................................................... 0.20 ppm

Corn, stover........................................................................ 0.20 ppm

In conjunction with the submitted petition, Dow AgroSciences is requesting an amended Section 

3 registration to add uses on field corn to Milestone® (EPA Reg. No. 62719-519), a liquid 

soluble concentrate (SL) formulation in which aminopyralid is formulated as the 

triisopropanolammonium (TIPA) salt. The product contains 40.6% aminopyralid TIPA salt at an 

acid equivalent (ae) of 21.1% or 2 lb ae/gal. The product is proposed for postemergence foliar 

broadcast or spot applications to field corn up to the V6 growth stage at a maximum seasonal rate 

of 0.027 lb ae/A. Preharvest intervals (PHIs) of 0 days for grain and 8 days for forage or silage 

are proposed. 

Tolerances for aminopyralid are currently established under 40 CFR §180.610. Tolerances for 

residues in/on crop commodities are established under 180.610(a)(1) and are expressed in terms 

of free and conjugated residues of aminopyralid, calculated as aminopyralid. Tolerances have 

been established for aspirated grain fractions, grass forage and hay, and wheat bran, forage, grain, 

hay, and straw. Tolerances for residues in livestock commodities are established under 

180.610(a)(2) and are expressed in terms of aminopyralid. Tolerances have been established for 

milk and the fat, kidney, meat, and meat byproducts of cattle, goat, horse, and sheep. 

The qualitative nature of aminopyralid residues in field corn is adequately understood for the 

purposes of this petition based on previously submitted metabolism studies with grass and wheat. 

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 cereal grain 

commodities are free and conjugated aminopyralid. 

Previously submitted metabolism studies with lactating goats and laying hens show that most of 

the administered dose is rapidly excreted (~80% for hens and ~95% for goat). Residues in all 

poultry commodities, including eggs, were too low to allow identification of residues (residues 

were less than 0.004 ppm aminopyralid-equivalents across all commodities). In the goat, 

residues were less than 0.008 ppm aminopyralid-equivalents in all commodities except kidney. 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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In kidney, 80% of the residues (0.07 ppm) were identified as parent aminopyralid. Although 

residues in other tissues were too low to permit identification, 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. 

Adequate high performance liquid chromatography (LC) methods with tandem mass 

spectroscopy detection (MS/MS) have been submitted for tolerance enforcement for crop and 

livestock commodities. The validated limit of quantitation (LOQ) is 0.01 ppm in each matrix. 

Samples from the submitted field corn crop field trial and processing studies were analyzed using 

the crop commodity tolerance enforcement method. Samples of grass and wheat commodities 

from the submitted storage stability study were analyzed using a previous version of the crop 

commodity enforcement method. 

The submitted storage stability data are adequate to support the crop field trial study and the field 

corn processing study. 

Acceptable field corn crop field trial studies have been submitted. The proposed use on field 

corn must be amended to remove the proposed PHIs of 0 and 8 days for grain and forage, as the 

submitted data do not support these low PHIs. The data support application to field corn up to 

the V6 growth stage, with harvest of forage occurring at the dent growth stage or later. The data 

support the proposed tolerances of 0.30 ppm for field corn forage and 0.20 ppm for field corn 

grain and stover. 

The submitted field corn processing study is adequate and indicates that tolerances are not 

needed for field corn processed commodities, and that no change in the existing tolerance for 

aspirated grain fractions is needed as a result of the proposed uses on field corn. 

The nature of the residue in rotational crops is adequately understood based on a previously

submitted study with lettuce, turnip, and sorghum. No field rotational crop data have been 

submitted for aminopyralid. Although the proposed uses reflect an increased maximum seasonal 

rate, a limited field rotational crop study with aminopyralid does not need to be submitted. The 

only crops which are likely to have quantifiable residues at the requested plantback intervals 

(PBIs) are wheat, grasses, and corn, all of which will be treated as primary crops and have 

tolerances to cover the resulting residues. HED considers the rotation intervals listed on the 

supplemental label for field corn to be adequate.

No changes to the existing tolerances for livestock commodities are needed as a result of the 

proposed uses on field corn.

Codex and Canadian MRLs have been established for residues of aminopyralid; however, no 

MRLs have been established for the requested crop commodities. No Mexican MRLs have been 

established for aminopyralid.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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Regulatory Recommendations and Residue Chemistry Deficiencies

HED has examined the residue chemistry database for aminopyralid. Pending submission of a 

revised Section B (see requirements under Directions for Use) and a revised Section F (see 

requirements under Proposed Tolerances), there are no residue chemistry issues that would 

preclude granting Section 3 registration for the requested uses of aminopyralid, or establishment 

of tolerances for residues of aminopyralid, as follows:

Corn, field, forage .............................................................. 0.30 ppm

Corn, field, grain ................................................................ 0.20 ppm

Corn, field, stover .............................................................. 0.20 ppm

HED recommends that 40CFR §180.610(a)(1) be amended by replacing the tolerance expression 

with the following: “Tolerances are established for residues of aminopyalid (4-amino-3,6-

dichloro-2-pyridinecarboxylic acid), including its metabolites and degradates, in or on the 

commodities in the table below. Compliance with the tolerance levels specified below is to be 

determined by measuring only free and conjugated aminopyralid.” HED further recommends 

that 40CFR §180.610(a)(2) be amended by replacing the tolerance expression with the following: 

“Tolerances are established for residues of aminopyralid, including its metabolites and 

degradates, in or on the commodities in the table below. Compliance with the tolerance levels 

specified below is to be determined by measuring only aminopyralid.”

With the review of the interference study and the final report of the grass and wheat storage 

stability study in this document, all the data requirements that were identified as conditions of 

registration in the previous aminopyralid petition (PP#4F6827; D305665, M. Doherty, 7/12/05) 

have now been satisfied.

860.1200 Directions for Use

 The proposed label must be modified to specify that spray or spot applications may not be 

made after the V6 growth stage (BBCH 16) and that forage may not be harvested prior to 

the dent stage of growth. If the petitioner wishes to support a shorter PHI for field corn 

forage (or harvest of forage at an earlier growth stage), then adequate crop field trial data 

reflecting the shorter PHI and/or earlier forage harvest must be submitted.

860.1550 Proposed Tolerances

 The proposed tolerances should be revised to reflect the correct commodity definitions as 

specified above and in Table 8.

 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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Background

Aminopyralid is a systemic postemergence herbicide that belongs to the pyridine carboxylic acid 

class of herbicides. The chemical structure and nomenclature of aminopyralid and aminopyralid 

TIPA salt are presented in Table 1. The physiochemical properties of the technical grade of 

aminopyralid are presented in Table 2.

Table 1. Aminopyralid Nomenclature.

Chemical structure

Cl N

NH2

Cl

O

OH

Common name Aminopyralid

Company experimental name XDE-750

IUPAC name 4-amino-3,6-dichloropyridine-2-carboxylic acid

CAS name 4-amino-3,6-dichloro-2-pyridinecarboxylic acid 

CAS registry number 150114-71-9

Chemical structure

Cl N

NH2

Cl

O

OH

N

HO CH3

H3C

OH

CH3

OH

.

Common name Aminopyralid, triisopropanolammonium (TIPA) salt

PC Code 005209

Company experimental name XDE-750 TIPA salt

IUPAC name 4-amino-3,6-dichloropyridine-2-carboxylic acid - (2RS,2′RS,2′′RS)-1,1′,1′′-

nitrilotripropan-2-ol (1:1)

CAS name 4-amino-3,6-dichloropyridine-2-carboxylic acid compound with 1,1′,1′′-

nitrilotris[2-propanol] (1:1)

CAS registry number 566191-89-7

End-use product (EP) Milestone® (2 lb ae/gal SL; EPA Reg. No. 62719-519)
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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TABLE 2. Physicochemical Properties of the Technical Grade of Aminopyralid.

Parameter Value Reference

Melting point/range 163.5oC MRID 46235703

pH 2.31 at 23.4oC (1% solution in water) MRID 46235703

Density 1.72 at 20oC MRID 46235703

Water solubility 2.48 g/L unbuffered water at 18oC

212 g/L pH 5 buffer at 20oC

205 g/L pH 7 buffer at 20oC

203 g/L pH 9 buffer at 20oC

MRID 46235703

Solvent solubility at 20°C methanol 52.2 g/L

acetone 29.2 g/L

n-octanol 3.9 g/L

ethyl acetate 3.9 g/L

1,2-dichloroethane 0.2 g/L

xylene 0.04 g/L

heptane <10 μg/mL

MRID 46235703

Vapor pressure 2.59 x 10-8Pa at 25oC; 9.52 x 10-9Pa at 20oC MRID 46235703

Dissociation constant, pKa 2.56 MRID 46235703

Octanol/water partition coefficient, Log(KOW) 0.201 unbuffered water at 19oC

-1.76 at pH 5

-2.87 at pH 7

-2.96 at pH 9

MRID 46235703

UV/visible absorption spectrum

Solution

Wavelength

λ max, nm

Extinction 

coefficient

L/(mol*cm)

Neutral 217 29100

Basic (pH 12.6) 220 26100

Basic (pH 12.6) 245 10150

Acidic (pH 1.4) 217 22800

Acidic (pH 1.4) 270 9140

MRID 46235703

860.1200 Directions for Use

The petitioner submitted a proposed supplemental label (pin punched with date 10/15/08) for the 

2 lb ae/gal SL product (Milestone®; EPA Reg. No. 62719-519) for use on field corn. The 

proposed use directions are presented in Table 3. The supplemental label states that use is 

subject to all use precautions and limitations imposed by the label on the parent product.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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Table 3. Summary of Directions for Use of Aminopyralid.

Applic. Timing, 

Type, and 

Equip.

Formulation

(EPA Reg. 

No.)

Applic. 

Rate 

(lb ae/A)

Max. No. 

Applic. per 

Season

Max. 

Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Field Corn and Field Corn grown for Ensilage

Postemergence,

Broadcast,

Ground

2 lb ae/gal SL 

(62719-519)

0.0089-

0.027

Not 

specified 0.027

0 (grain);

8 (forage 

or silage)

Application is to be 

made to actively 

growing corn before it 

reaches 20 inches in 

height or V6 growth 

stage. Spot treatments 

are to be made at rates 

equivalent to broadcast 

application, in a 

minimum spray volume 

of 0.5 gal/1,000 ft2.

Postemergence,

Spot treatment,

Ground

0.00021-

0.00063 lb 

ae/1,000 ft2

The label specifies that aerial applications are not to be made unless permitted by EPA-approved 

supplemental labeling. Under the mixing instructions, the master label specifies that a non-ionic 

surfactant at 0.25-0.5% v/v (1-2 quarts per 100 gallons spray) is recommended to enhance 

herbicide activity under adverse environmental conditions.

The following rotational crop restrictions are specified: 0-month plantback interval for wheat; 4-

month plantback interval for grasses and field corn; 12-month plantback interval for barley, 

canola (rapeseed), flax, grain sorghum, mustard, oats, sweet corn, and popcorn; and a 24-month 

plantback interval for crops not listed. The label also specifies that a field bioassay should be 

conducted prior to planting any broadleaf crops not listed within 18 months of application.

Conclusions. The submitted label is adequate to allow evaluation of the residue data relative to 

the proposed use. The submitted crop field trial data represent application at the proposed 

maximum seasonal rate (with a nonionic surfactant) and at the proposed growth stage. The 

proposed PHIs of 0 days for grain and 8 days for forage or silage are not supported by the 

submitted data. The proposed label should be modified to specify that spray or spot applications 

may not be made after the V6 growth stage (BBCH 16) and that forage may not be harvested 

prior to the dent stage of growth. If the petitioner wishes to support a shorter PHI for field corn 

forage (or harvest of forage at an earlier growth stage), then adequate crop field trial data 

reflecting the shorter PHI and/or earlier forage harvest must be submitted.

860.1300 Nature of the Residue - Plants

Residue Chemistry Memo DP# 305665, 7/12/05, M. Doherty (PP#4F6827)

The nature of the residue in field corn is adequately understood for the purposes of this petition 

based on previously submitted metabolism studies with grass and wheat. The major residue 

identified in these studies was the parent aminopyralid (free and conjugated). In the grass 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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metabolism study, there did not appear to be any significant metabolic alterations to the basic 

structure of the parent compound, with the exception of a minor conjugated metabolite formed by

addition of a hydroxyl group to the parent molecule and found to be present at <1% total 

radioactive residues (TRR). Aminopyralid was rapidly conjugated to yield a multi-component 

mixture of water-soluble complexes which consisted mostly of isomeric mixtures of acid- and 

base-labile N-glucosides and glucose ester conjugates of aminopyralid. In the wheat metabolism 

study, the petitioner concluded that the major metabolic pathway of aminopyralid in wheat 

proceeded via conjugation of aminopyralid and hydroxylated aminopyralid with glucose. The 

petitioner further concluded that any metabolites present in wheat which were not identified were 

believed to be conjugates of glucose or similar endogenous compounds, based on the fact that 

most of the radioactivity in the wheat samples that was not initially detected as the parent could 

be hydrolyzed to aminopyralid.

Based on these studies, HED concluded that the residues of concern in grass and cereal grain

commodities are free and conjugated aminopyralid. Additional metabolism data will be required 

to support uses on non-grass or non-grain commodities.

860.1300 Nature of the Residue - Livestock

Residue Chemistry Memo DP# 305665, 7/12/05, M. Doherty (PP#4F6827)

The nature of the residue in livestock is adequately understood based on previously submitted 

studies with goat and hen. Although the residues in the goat and hen studies were too low to 

allow adequate characterization/identification of residues, HED concluded that new studies 

would not be needed. The available metabolism data from the goat, hen, and rat indicate that the 

majority of the administered aminopyralid is excreted as unchanged parent in all three species, 

and the small amount which is absorbed remains unchanged. Therefore, the residue of concern 

in livestock is aminopyralid. This finding is supported by the residues of concern for the related 

compounds picloram and clopyralid which, in each case, show parent compound to be the major 

residue.

860.1340 Residue Analytical Methods

Crop commodities

DER References: 46729001.der.doc

47572602.de1.doc

MRID 46729601 (no DER; reviewed herein)

MRID 46729603 (no DER; reviewed herein)

Residue Chemistry Memo DP# 305665, 7/12/05, M. Doherty (PP#4F6827)

Analytical Chemistry Branch Memo DP# 312724, 11/3/05, D. Wright

Enforcement method: Dow AgroSciences had previously proposed an LC/MS/MS method, 

Method GRM 02.31, for the enforcement of tolerances for aminopyralid residues in grass and 

wheat commodities. The method was adequately validated in barley grain, forage, and straw; 

grass forage and hay; sorghum grain, forage, and stover; and wheat grain, forage, and straw. 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 9 of 28

Adequate ILV data were submitted for the method using grass forage and wheat grain, and 

adequate radiovalidation data were submitted for the extraction procedures using samples of 

grass and wheat commodities bearing incurred residues from the metabolism studies. 

Method GRM 02.31 was sent to ACB for review. It was concluded that the method was 

adequate for enforcement purposes and that no laboratory validation at ACB was needed. ACB 

concluded that the method needed confirmatory procedures. The single ion transition monitored 

in the method is not considered sufficient for positive confirmation of analyte information. ACB 

additionally noted two errors in the analyte peak response area and quantitation ratio data 

reported in one of the representative chromatograms in the independent laboratory validation 

study (MRID 46235712). 

In review of Method GRM 02.31, HED expressed concern that the proposed enforcement method 

might not be able to differentiate between aminopyralid, picloram, and clopyralid, and requested 

that the petitioner complete an interference study using these three compounds. 

In response, the petitioner submitted a revised version of Method GRM 02.31 in MRID 

46729601. The revised method includes instructions for monitoring two additional MS/MS 

transitions for confirmation of residue identity. In addition, the petitioner submitted MRID 

46726903, a revised version of the ILV study, in which the two errors noted by ACB in the 

representative chromatogram were corrected. 

In addition, Dow AgroSciences submitted the requested interference study for the derivatization 

and LC/MS/MS analysis procedures of Method GRM 02.31. To investigate the potential 

inference of picloram and clopyralid in the determination of aminopyralid, the petitioner prepared

analytical standards of picloram and clopyralid, as well as aminopyralid, and derivatized the 

standards to form the 1-butyl esters of the compounds using the procedures of Method GRM 

02.31. The derivatized compounds were then analyzed by LC/MS/MS. 

The analysis of the 1-butyl esters of aminopyralid, clopyralid, and picloram demonstrated that the 

three compounds have different retention times and that there was no interference in the ion 

transitions. Therefore, clopyralid and picloram do not interfere in the determination of 

aminopyralid residues using Method GRM 02.31. 

The petitioner noted that, since the original aminopyralid methods were developed, minor 

changes in the LC conditions and MS/MS parameters have been made to improve the sensitivity

and selectivity of the method, including the addition of two ion transitions to monitor for the 

confirmation of aminopyralid residues. Representative chromatograms from the analysis of a 

grass forage sample were provided for the quantitation ion transition and the two confirmation 

ion transitions. The changes in the LC and MS/MS conditions are reflected in the revised 

methods that were submitted with this tolerance petition: Method GRM 07.07 for crop 

commodities and Method GRM 07.08 for livestock commodities (see below). 

With PP#8F7455, Dow AgroSciences has proposed an LC/MS/MS method, Method GRM 07.07, 

for the determination of residues of aminopyralid in crop commodities (wet, dry, acidic, and oily
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

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crops). The method description indicates that Method GRM 07.07 supersedes Method 02.31. 

The major differences between the two methods are that Method GRM 02.31 uses a different 

internal standard (13C2

15N-aminopyralid) and only includes instructions for the determination of 

residues in barley, sorghum, wheat, and grass commodities. 

Briefly, residues are extracted from homogenized agricultural commodities using 0.1 N NaOH, 

which hydrolyzes bound residues and base-labile conjugates to yield free aminopyralid. The 

hydrolysate is acidified with 2 N HCl. Oil samples are extracted with acetone and the extract is 

evaporated to dryness, redissolved in hexane, and partitioned into water. The aqueous phase is 

mixed with 0.2 N NaOH to hydrolyze bound residues and base-labile conjugates to yield free 

aminopyralid, and then acidified with 3 N HCl. For both crop samples and oil samples, the 

acidified extract is heated at 80°C for 90 minutes, which hydrolyzes acid-labile conjugates to 

yield free aminopyralid and further solubilizes bound residues. The extract is then purified by

anion-exchange solid phase extraction (SPE), using ethyl acetate:trifluoroacetic acid (99:1, v:v) 

to elute residues. An internal standard (13C2

2H15N-aminopyralid) is added to the eluate, which is 

evaporated to dryness, reconstituted in acetonitrile:pyridine:1-butanol (22:2:1, v:v:v; 

derivatization coupling reagent) and derivatized with butyl chloroformate to form the 1-butyl 

esters of the analyte and the internal standard. The mixture is diluted with a solution of 

methanol:water (40:60, v:v) containing 0.05% formic acid and 5 mM ammonium formate for 

LC/MS/MS analysis. The LOQ and limit of detection (LOD) are 0.01 and 0.003 ppm, 

respectively, for aminopyralid in each tested matrix.

Method GRM 07.07 was adequately validated using samples of untreated wet crops (broccoli and 

tomato), dry crops (wheat forage, grain, and straw, corn forage and grain, and grass forage and 

straw), acidic crops (lemon whole fruit and orange peel, pulp, and whole fruit), and oily crops 

(palm oil and sunflower seed) fortified with aminopyralid at 0.01 and 2 ppm for all crops other 

than grass forage and straw, and at 0.01 and 50 ppm for grass forage and straw. The recovery

ranges for these matrices were 75-102% for wet crops (average ± standard deviation: 86% ± 

6.6%), 70-102% for dry crops (86% ± 8.3%), 72-105% for acidic crops (88% ± 7.4%), and 82-

106% for oily crops (93% ± 6.5%). 

The fortification levels and samples used in method validation are adequate to bracket expected 

residue levels. Although field corn stover, aspirated grain fractions, and processed commodities 

were not included in the validation study, adequate concurrent method recovery data for these 

commodities were included with the field corn field trial and processing studies submitted with 

this petition. 

The method includes instructions for monitoring up to three ion transitions for aminopyralid; 

therefore, confirmatory analysis procedures are not needed.

The method is very similar to the current enforcement method, LC/MS/MS Method GRM 02.31, 

for which adequate radiovalidation and independent laboratory validation data have been 

submitted. Because Method GRM 07.07 is considered to be an improvement to Method GRM 

02.31, no independent laboratory validation or validation by ACB is needed. 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 11 of 28

Data collection method: Method GRM 07.07 was used for data collection in samples of corn 

forage, grain, stover, aspirated grain fractions, and processed commodities from the crop field 

trial and processing studies submitted with this petition. Overall concurrent method recoveries 

ranged 69-90% from forage, 75-97% from grain, 72-94% from stover, and 75-98% from corn 

processed commodities. Samples of grass and wheat commodities from the storage stability

study were analyzed using Method GRM 02.31; overall concurrent method recoveries ranged 71-

106%.

Conclusions. The submitted crop analytical method data are adequate to satisfy data 

requirements. Method GRM 07.07 satisfies all requirements for an enforcement method for crop 

commodities. The method will be forwarded to the FDA for publication in PAM Vol. II. 

The submitted interference study satisfies the data requirements for this study identified in 

PP#4F6827 (Memo, D305665, M. Doherty, 7/12/05). 

Livestock commodities

DER References: 47572602.de2.doc

MRID 46729602 (no DER; reviewed herein)

Residue Chemistry Memo: D305665, M. Doherty, 7/12/05 (PP#4F6827)

Analytical Chemistry Branch Memo: D312724, D. Wright, 11/3/05

Enforcement method: Dow AgroSciences had previously proposed an LC/MS/MS method, 

Method GRM 03.18, for the enforcement of tolerances for aminopyralid residues in ruminant 

milk and tissues. The method was adequately validated in bovine whole milk, cream, skimmed 

milk, fat, kidney, liver, and muscle, and adequate ILV data were submitted for the method using 

bovine milk and kidney. RAB2 concluded that radiovalidation data were not needed for the 

method because the extraction procedures are very similar to those used in the goat metabolism 

study. The method was sent to ACB for review. It was concluded that the method was adequate 

for enforcement purposes and that no laboratory validation at ACB was needed. ACB concluded 

that the method needed confirmatory procedures. ACB additionally noted that step 9.3.17 of 

Method GRM 03.18 referred to Section 7.5.1 of the method, which does not exist. 

In response, the petitioner submitted a revised version of Method GRM 03.18 in MRID 

46729602. The revised method includes instructions for monitoring two additional MS/MS 

transitions for confirmation of residue identity. In addition, the erroneous reference to Section 

7.5.1 was removed. 

In review of Method GRM 03.18, HED expressed concern that the proposed enforcement method 

might not be able to differentiate between aminopyralid, picloram, and clopyralid, and requested 

that the petitioner complete an interference study using these three compounds. The requested 

inference study for Method GRM 02.31 has been submitted (see above). Because the 

derivatization and LC/MS/MS analysis procedures of Method GRM 02.31 are the same as those 

of Method GRM 03.18, the interference study is sufficient to demonstrate that clopyralid and 

picloram will not interfere in aminopyralid determination using Method GRM 03.18.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 12 of 28

With PP#8F7455, Dow AgroSciences has proposed LC/MS/MS Method GRM 07.08 for the 

determination of residues of aminopyralid in cattle and poultry tissues, milk, and eggs. The 

method description indicates that Method GRM 07.08 supersedes Method GRM 03.18. The 

major differences between the two methods are that Method GRM 03.18 uses a different internal 

standard (13C2

15N-aminopyralid) and only includes instructions for the determination of residues 

in bovine commodities (muscle, fat, liver, kidney, and milk). 

Briefly, sodium bicarbonate is added to homogenized livestock commodities and the mixture is 

extracted using methanol. The extract is purified by anion-exchange SPE, using ethyl 

acetate:trifluoroacetic acid (99:1, v:v) to elute residues. An internal standard (13C2

2H15Naminopyralid) is added to the eluate, which is evaporated to dryness, reconstituted in 

acetonitrile:pyridine:1-butanol (22:2:1, v:v:v; derivatization coupling reagent) and derivatized 

with butyl chloroformate to form the 1-butyl esters of the analyte and the internal standard. The 

mixture is diluted with a solution of methanol:water (40:60, v:v) containing 0.05% formic acid 

and 5 mM ammonium formate for LC/MS/MS analysis. The LOQ and LOD are 0.01 and 0.003 

ppm, respectively, for aminopyralid in each tested matrix.

The method was adequately validated using samples of untreated cattle milk, kidney, and fat and 

poultry egg, liver, and muscle fortified with aminopyralid at 0.01 and 2 ppm. The recovery

ranges for these matrices were 90-119% for bovine matrices (average of 98% with a standard 

deviation of 5.7%) and 82-111% for poultry matrices (average of 95% with a standard deviation 

of 5.9%). The fortification levels and samples used in method validation are adequate to bracket 

expected residue levels. Radiovalidation data are not needed for Method GRM 07.08 as the 

extraction procedures are very similar to those of Method GRM 03.18. 

The method includes instructions for monitoring up to three ion transitions for aminopyralid; 

therefore, confirmatory analysis procedures are not needed.

The method is very similar to the current enforcement method, LC/MS/MS Method GRM 03.18. 

Because Method GRM 07.08 is considered to be an improvement to Method GRM 03.18, no 

independent laboratory validation or validation by ACB is needed. 

Conclusions. The submitted livestock analytical method data are adequate to satisfy data 

requirements. Method GRM 07.08 satisfies all requirements for an enforcement method for 

livestock commodities. The method will be forwarded to FDA for publication in PAM Vol. II. 

860.1360 Multiresidue Methods

Residue Chemistry Memo D305665, M. Doherty , 7/12/05 

Adequate multiresidue method testing data have been submitted previously for aminopyralid. 

The results of the study indicate that the FDA multiresidue methods in PAM Vol. I are not 

suitable for the determination of aminopyralid. 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 13 of 28

860.1380 Storage Stability

DER Reference: 46661301.der.doc

Residue Chemistry Memo D305665, M. Doherty , 7/12/05 

Dow AgroSciences has submitted the final report of a storage stability study with aminopyralid 

on grass forage and hay, and wheat grain and straw. An interim report for this study, reflecting 

storage intervals of up to ~6 months, was previously reviewed under PP#4F6827. Samples of 

untreated grass forage, grass hay, wheat grain, and wheat straw were fortified with aminopyralid 

at 0.1 ppm and stored frozen (~-20oC). Storage intervals tested were 0, 28, 130, 187, and 488 

days (grass forage and hay) or 0, 113, 168/175, 273, and 469 days (wheat grain and straw).

Samples of grass hay and forage, and wheat grain and straw were analyzed for residues of 

aminopyralid using LC/MS/MS Method GRM 02.31. The method was adequate for data 

collection based on acceptable concurrent method recoveries; the reported LOQ was 0.01 ppm 

for each commodity.

The study results indicate that residues of aminopyralid are stable during frozen storage for up to 

~16 months in/on grass forage and hay, and for up to ~15 months in/on wheat grain and straw. 

The storage durations and conditions of samples from the crop field trial and processing studies

submitted to support this petition are presented in Table 4. 

Table 4. Summary of Storage Conditions and Durations of Samples from Field Corn Crop Field 

Trial and Processing Studies. 

Matrix Storage Temperature

(°C)

Actual Storage Duration1Interval of Demonstrated 

Storage Stability

Field corn forage ~-20 435-518 days (14.3-17.0 months) Residues of aminopyralid 

are stable during frozen 

storage for up to ~16 

months in/on grass forage 

and hay, and for up to ~15 

months in/on wheat grain 

and straw.

Field corn grain 375-448 days (12.3-14.7 months)

Field corn stover 377-448 days (12.4-14.7 months)

Field corn AGF 350 days (11.5 months) No storage stability data 

are available for field corn 

processed commodities.

Flour 355 days (11.7 months)

Grits 384 days (12.6 months)

Meal 355 days (11.7 months)

Starch 341 days (11.2 months)

Refined oil (wet milled) 387 days (12.7 months)

Refined oil (dry milled) 350 days (11.5 months)

1

 From harvest/collection to extraction for analysis.

Conclusions. The submitted storage stability study is adequate to fulfill data requirements for 

samples of field corn forage, grain, and stover from the submitted field trial and processing 

studies. The data indicate that no correction for residue decline during storage will be needed for 

these commodities. 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 14 of 28

The data are also adequate to support the storage conditions and durations of field corn processed 

commodities from the processing study submitted to support this petition. Although a storage 

stability study with aminopyralid residues in field corn processed commodities was not 

submitted, the available storage stability data for the wheat and grass commodities will be 

considered to be adequate to support the field corn processing study. The OECD guideline 

“Stability of Pesticide Residues in Stored Commodities” (adopted 10/16/2007) states that storage 

stability data for processed foods are not needed if residue decline is not observed across the 

range of five commodity categories. In this case, HED considers the data for grain and grass 

commodities to be adequate in light of the minimal metabolism of aminopyralid in living plants. 

Conjugation is the only significant metabolic pathway, and the resulting conjugates are 

determined by the analytical method.

The dates of analysis were not provided for the subject field trial and processing studies. For 

future submissions, the petitioner should note that dates of extraction and analysis should be 

provided for all samples.

Submission of the final report of the grass and wheat storage stability study satisfies the data 

requirements for storage stability identified in PP#4F6827 (Memo, D305665, M. Doherty, 

7/12/05). No correction for residue decline is needed for any of the grass or wheat commodity

samples submitted under PP#4F6827.

860.1400 Water, Fish, and Irrigated Crops

There are no proposed uses that are relevant to this guideline topic.

860.1460 Food Handling

There are no proposed uses that are relevant to this guideline topic.

860.1480 Meat, Milk, Poultry, and Eggs

Residue Chemistry Memo: D305665, M. Doherty, 7/12/05

There are several livestock feedstuffs associated with the registered and proposed uses of 

aminopyralid, including AGF (and milled byproducts); grass forage, grass hay, field corn grain, 

field corn forage, field corn stover, wheat grain, wheat forage, wheat hay, and wheat straw. The 

dietary burdens of aminopyralid to livestock, based on reasonably balanced diets, are presented in 

Table 5. The estimated dietary burdens are 8.7 ppm for beef cattle, 45 ppm for dairy cattle, 0.15 

ppm for poultry, and 0.17 ppm for swine. 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 15 of 28

Table 5. Calculation of Dietary Burdens of Aminopyralid Residues to Livestock.

Feedstuff Type1 % Dry 

Matter2 % Diet2

Established/

Recommended 

Tolerance (ppm)

Dietary Contribution 

(ppm)

3

Beef Cattle

Grass hay R 88 15 50 8.5

Corn, field, grain CC 88 80 0.20 0.18

PC without registered uses PC -- 5 -- --

TOTAL BURDEN -- -- 100 -- 8.7

Dairy Cattle

Grass, forage R 25 45 25 45

Corn, field, grain CC 88 45 0.20 0.10

PC without registered uses PC -- 10 -- --

TOTAL BURDEN -- -- 100 -- 45

Poultry

Corn, field, grain CC 88 75 0.20 0.15

PC without registered uses PC -- 25 -- --

TOTAL BURDEN -- -- 100 -- 0.15

Swine

Corn, field, grain CC 88 85 0.20 0.17

PC without registered uses PC -- 15 -- --

TOTAL BURDEN -- -- 100 -- 0.17

1

 R: Roughage; CC: Carbohydrate concentrate; PC: Protein concentrate.

2

 OPPTS 860.1000 Table 1 Feedstuffs (June 2008). 

3

 Contribution = ([tolerance/% DM] X % diet) for beef and dairy cattle; contribution = ([tolerance] X % diet) for 

poultry and swine.

Ruminants: The dietary burdens of aminopyralid to livestock were previously calculated to be 60 

ppm for beef and dairy cattle and 0.075 ppm for swine. Based on an adequate dairy cattle 

feeding study, reflecting dosing of dairy cattle with aminopyralid at levels of 32.8, 64.5, 181.5, or 

644.7 ppm in the diet, RAB2 concluded that tolerances were needed for livestock commodities at 

0.03 ppm for milk; 0.02 ppm for the meat and meat byproducts, excluding kidney, of cattle, 

goats, horses, and sheep; 0.02 ppm for the fat of cattle, goats, horses, and sheep; and 0.30 ppm 

for the kidney of cattle, goats, horses, and sheep. It was also concluded that no tolerances were 

needed for swine commodities. Because the re-calculated dietary burdens for beef and dairy

cattle are lower than the previously calculated values, no changes to the existing tolerances for 

cattle, goat, horse, and sheep commodities are needed to support the proposed uses.

The lowest dosing level in the cattle feeding study represents 190x the maximum theoretical 

dietary burden to swine. Aminopyralid residues in milk and tissues from the lowest dosing level 

in the cattle feeding study were ≤0.01 ppm in all commodities except kidney and were 0.10 ppm 

in kidney. HED concludes that tolerances for hog commodities are not needed to support the 

proposed and registered uses of aminopyralid.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 16 of 28

Poultry: No poultry feeding study with aminopyralid has been submitted. RAB2 previously

concluded that tolerances for poultry commodities were not needed based on the results of the 

poultry metabolism study and the previously calculated dietary burden of 0.075 ppm. 

The poultry metabolism study represented a dosing level of 12 ppm and TRR were <0.01 ppm in 

eggs and all poultry tissues at this dosing level. The dosing level corresponds to 80x the current 

dietary burden aminopyralid to poultry. Therefore, HED concludes that the proposed and 

registered uses of aminopyralid result in a 40 CFR §180.6(a)(3) situation for poultry

commodities; i.e., there is no reasonable expectation of finite residues in poultry commodities. 

No poultry feeding study is needed to support the subject petition. If additional uses of 

aminopyralid with significant poultry feed items are proposed in the future, then a poultry

feeding study might be required.

860.1500 Crop Field Trials

DER Reference: 47572601.de1.doc (includes review of MRID 47572603)

Dow AgroSciences submitted field trial data for aminopyralid on field corn. Twenty field corn 

trials were conducted in the United States during the 2006 growing season. One trial each was 

performed in Zones 1 (PA), 2 (GA), and 6 (TX). Seventeen trials were performed in Zone 5 (IA 

(3), IL (3), IN (1), MI (1), MN (2), MO (1), ND (2), NE (2), OH (1), and WI (1)).

Each treated plot received a single foliar application of an SL formulation containing the TIPA

salt of aminopyralid at 2 lb ae/gal. Applications were made at the 4- to 6-leaf growth stage 

(BBCH 14-16 or V4-V6). There were two treated plots at each location. One treated plot 

received an application at ~0.031 lb ae/A (~1x the proposed maximum seasonal rate) and the 

other plot received an application at ~0.062 lb ae/A (~2x). Applications were made in ~15-24 

gal/A spray volumes, using ground equipment. A non-ionic surfactant was added to the spray

mixture at ~0.25% (v/v). Field corn commodities were harvested at normal harvest times. 

Forage was harvested at the dent stage, at a 60- to 87-day preharvest interval (PHI), and grain and 

stover were harvested at maturity, at a 105- to 138-day PHI. In addition, to evaluate residue 

decline, forage samples were harvested at the Wisconsin trial and at one of the Illinois trials at 0-, 

7-, 13- to 14-, 21-, and 28-day PHIs.

Samples of field corn forage, grain, and stover were analyzed for residues of aminopyralid using 

LC/MS/MS Method GRM 07.07. The validated LOQ was 0.01 ppm for each matrix. The 

method was adequate for data collection based on acceptable concurrent method recovery data. 

Sample storage conditions and durations are reported in Table 4. Adequate storage stability data 

are available to support the storage conditions and durations of samples from the submitted field 

corn study.

A summary of the study results is presented in Table 6. Following foliar application of the 2 lb 

ae/gal SL formulation at approximately a 1x application rate (0.030-0.034 lb ae/A), maximum 

residues of aminopyralid were 0.262 ppm in/on forage (60- to 87-day PHI), 0.164 ppm in/on 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 17 of 28

grain (105- to 138-day PHI), and 0.176 ppm in/on stover (105- to 138-day PHI). Following foliar 

application at approximately a 2x application rate (0.060-0.069 lb ae/A), maximum residues of 

aminopyralid were 0.293 ppm in/on forage, 0.212 ppm in/on grain, and 0.387 ppm in/on stover. 

In the four forage residue decline trials, average residues of aminopyralid decreased from the 0-

day to either the 14-day PHI or 21-day PHI and then generally did not decrease further (from the 

14- or 21-day PHI to harvest at 66 or 72 days posttreatment).

Table 6. Summary of Residue Data from Crop Field Trials with Aminopyralid.

Crop matrix PHI 

(days)

Total Applic. 

Rate

(lb ai/A)

Residue Levels (ppm)

n Min. Max. HAFT1 Median Mean Std. 

Dev.

FIELD CORN

(proposed use = 0.027 lb ai/A total application rate, 0-day PHI for grain and 8-day for forage and silage)

Field corn 

forage

60-87 0.030-0.034 40 <0.01 0.262 0.226 0.041 0.059 0.053

0.060-0.069 39 0.018 0.293 0.240 0.083 0.105 0.069

Field corn 

grain

105-138 0.030-0.034 40 <0.01 0.164 0.155 0.090 0.036 0.032

0.060-0.069 40 <0.01 0.212 0.209 0.049 0.060 0.048

Field corn 

stover

105-138 0.030-0.034 40 <0.01 0.176 0.153 0.032 0.048 0.041

0.060-0.069 40 0.020 0.387 0.360 0.059 0.084 0.077

1

 HAFT = Highest average field trial result.

Conclusions. The submitted field corn crop field trial data are adequate to fulfill data 

requirements provided the proposed use is amended as requested under 860.1200. The number 

and locations of the corn field trials are in accordance with those specified in OPPTS Guideline 

860.1500 for use on field corn. Field trials were conducted at ~1x the proposed maximum 

seasonal rate, and application was made at the growth stage specified on the proposed label. 

However, it should be noted that the proposed PHIs of 0 days for grain and 8 days for forage and 

silage are not supported. 

The available data support the proposed tolerances of 0.30 ppm for field corn forage, 0.20 ppm 

for field corn grain, and 0.20 ppm for field corn stover. Refer to Appendix I for the tolerance 

calculation.

Residue data for field corn aspirated grain fractions were submitted and are discussed below with 

the field corn processing data.

860.1520 Processed Food and Feed

DER Reference: 47572601.de2.doc (includes review of MRID 47572604)

Dow AgroSciences submitted a processing study for aminopyralid on field corn. During the 

2006 growing season, a single field corn trial was conducted in the United States in Zone 5 

(Illinois). A single foliar broadcast application of an SL formulation containing the TIPA salt of 

aminopyralid at 2 lb ae/gal was made to field corn at the BBCH 14-15 growth stage at 0.060 lb 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 18 of 28

ae/A (~2x the proposed maximum seasonal rate). The application was made using ground 

equipment in a 17.4 gal/A spray volume and a non-ionic surfactant was added to the spray

mixture. A single bulk sample of field corn grain was harvested at a 138-day PHI, and processed 

using simulated commercial procedures into aspirated grain fractions (AGF), as well as flour, 

grits, meal, and refined oil (dry milling), and starch and refined oil (wet milling).

Samples of field corn grain raw agricultural commodity (RAC) and processed fractions were 

analyzed for residues of aminopyralid using LC/MS/MS Method GRM 07.07. The validated 

LOQ was 0.01 ppm for each matrix. The method was adequate for data collection based on 

acceptable concurrent method recovery data. 

Sample storage conditions and durations are reported in Table 4. Adequate storage stability data 

are available to support the storage conditions and durations of samples of field corn grain and 

processed commodities from the processing study.

Residues of aminopyralid were 0.0787 ppm in field corn grain (RAC) harvested 138 days after a 

single foliar application of aminopyralid at 0.060 lb ae/A. Residues of aminopyralid were 0.0270 

ppm in AGF, 0.0747 ppm in flour, 0.0886 ppm in grits, 0.1019 ppm in meal, and <0.01 ppm in 

starch and wet and dry milled refined oil. The processing factors for field corn processed 

commodities are presented in Table 7. Residues of aminopyralid did not concentrate in corn 

AGF (0.3x), flour (0.9x), starch (<0.1x), or refined oil (<0.04x for both wet and dry milled), but 

concentrated slightly in corn grits (1.1x) and meal (1.3x).

The observed processing factors are below the maximum theoretical concentration factor of 25x 

for corn (OPPTS 860.1520, Table 1). 

Table 7. Summary of Processing Factors for Aminopyralid.

RAC Processed Commodity Processing Factor

Field corn, grain Aspirated grain fractions 0.3x

Flour 0.9x

Grits 1.1x

Meal 1.3x

Refined oil (dry milling) <0.04x

Refined oil (wet milling) <0.04x

Starch <0.1x

Conclusions. The submitted processing data are adequate to satisfy data requirements.

The processing data indicate that no tolerances are needed for field corn flour, starch, or refined 

oil, and that no change in the existing tolerance for aspirated grain fractions, at 0.20 ppm, is 

needed as a result of the proposed uses on field corn.

The processing data indicate that aminopyralid residues might concentrate in field corn grits and 

meal. Based on the HAFT residues for aminopyralid in/on field corn grain (0.155 ppm), and the 

processing factors, expected residues of aminopyralid in corn grits and meal following treatment 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 19 of 28

at 1x would be 0.17 and 0.20 ppm, respectively. Because these values are not greater than the 

proposed tolerance of 0.20 ppm for field corn grain, no tolerances are needed for grits and meal. 

860.1650 Submittal of Analytical Reference Standards

An analytical standard for aminopyralid is currently available in the EPA National Pesticide 

Standards Repository, with an expiration date of 8/28/2010 (electronic communication, Dallas 

Wright (ACB) to D. Dotson, 9/15/2009). 

860.1850 Confined and Field Accumulation in Rotational Crops

Residue Chemistry Memo: D305665, M. Doherty, 7/12/05 (PP#4F6827)

A confined rotational crop study was submitted previously. In that study, [2,6-

14C]aminopyralid 

was applied directly to sandy loam soil in lined wooden boxes at 0.009 lb ai/A, which was 1x the 

proposed maximum seasonal rate for wheat (the only annual crop in PP#4F6827), and rotational 

lettuce, sorghum, and turnips were planted at plantback intervals (PBIs) of 90 and 120 days. 

TRR accumulated at ≥0.01 ppm in 90- and 120-day PBI early sorghum forage (0.027 ppm and 

0.017 ppm, respectively), 90-day PBI sorghum stover (0.027 ppm), and 120-day PBI mature 

turnip tops (0.010 ppm); residues in all other rotational crop commodities ranged <0.001-0.007 

ppm. TRR were generally found to decrease from the 90-day PBI to the 120-day PBI. Total 

identified residues ranged from 17 to 44% TRR in sorghum early forage and stover as well as in 

turnip tops, and consisted entirely of free aminopyralid. Residue profiles were similar between 

the matrices. Aminopyralid was found at 0.012 ppm in 90-day PBI sorghum early forage, 0.005 

ppm in 120-day PBI sorghum early forage, 0.005 ppm in 90-day PBI sorghum stover, and 0.002 

ppm in 120-day PBI turnip tops. In PP#4F6827, HED concluded that the residues of concern in 

rotational crop commodities are the same as for primary crop commodities, free and conjugated 

aminopyralid. HED further concluded that there is potential for quantifiable residues of 

aminopyralid in rotated cereal grain forage at a 3-month PBI. No field rotational crop study was 

submitted. It was concluded that the available rotational crop data support a 0-day plantback 

interval for wheat and a 4-month plant-back interval for barley, canola, flax, grasses, field corn, 

grain sorghum, oats, mustard, popcorn, and sweet corn (the requested rotated crops in 

PP#4F6827).

With the proposed use on field corn, the maximum seasonal rate to annual crops has increased 

from 0.009 lb ai/A to 0.027 lb ai/A. The available rotational crop data reflect application at a 

rate of 0.3x the proposed maximum seasonal rate. Because the identified residues in the 

confined rotational crop study consisted solely of free and conjugated aminopyralid, a new 

confined rotational crop study (conducted at 0.027 lb ai/A) will not be required to support the 

proposed use. Although the available confined data indicate that quantifiable residues of 

aminopyralid could occur in grasses and cereal grain foliage with a PBI of 4 months, the only

crops with requested PBIs of less than one year (i.e., wheat, grasses, and field corn) will be 

treated as primary crops and will have tolerances. Therefore, the petitioner does not need to

submit a limited field rotational crop study for aminopyralid reflecting a PBI of 4 months. HED 

considers the rotation intervals listed on the supplemental label for field corn to be adequate. 
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 20 of 28

The supplemental label specifies that wheat may be planted at any time after harvest. Grasses 

and field corn may be planted at a 4-month plantback interval. Barley, canola (rapeseed), flax, 

grain sorghum, mustard, oats, sweet corn, and popcorn may be planted at a 12-month plantback 

interval. The crop rotational interval for all other crops not listed on the label is 24 months.

860.1550 Proposed Tolerances

DowAgroSciences has proposed tolerances for residues of aminopyralid (2-pyridine carboxylic 

acid, 4-amino-3,6-dichloro-), expressed as total parent, free and conjugated, in/on field corn 

commodities. The proposed tolerances are listed in Table 8.

HED recommends that 40CFR §180.610(a)(1) be amended by replacing the tolerance expression 

with the following: “Tolerances are established for residues of aminopyalid (4-amino-3,6-

dichloro-2-pyridinecarboxylic acid), including its metabolites and degradates, in or on the 

commodities in the table below. Compliance with the tolerance levels specified below is to be 

determined by measuring only free and conjugated aminopyralid.” HED further recommends 

that 40CFR §180.610(a)(2) be amended by replacing the tolerance expression with the following: 

“Tolerances are established for residues of aminopyralid, including its metabolites and 

degradates, in or on the commodities in the table below. Compliance with the tolerance levels 

specified below is to be determined by measuring only aminopyralid.” 

Codex and Canadian MRLs have been established for residues of aminopyralid; however, no 

MRLs have been established for the requested crop commodities. No Mexican MRLs have been 

established for aminopyralid.

Adequate field trial data have been submitted for field corn. The Agency’s Guidance for Setting 

Pesticide Tolerances Based on Field Trial Data was used for determining appropriate tolerance 

levels for field corn raw agricultural crop commodities. See Appendix I for tolerance 

calculations. The available data will support the proposed tolerances of 0.30 ppm for field corn 

forage, 0.20 ppm for field corn grain, and 0.20 ppm for field corn stover.

The field corn processing study is adequate. It indicates that no tolerances are required for field 

corn flour, grits, meal, refined oil, or starch, and that no change in the existing tolerance for 

aspirated grain fractions, at 0.20 ppm, is needed as a result of the proposed uses on field corn. 

No changes to the existing tolerances for livestock commodities are needed as a result of the 

proposed uses.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 21 of 28

The proposed tolerances should be revised to reflect the correct commodity definitions as 

specified in Table 8.

Table 8. Tolerance Summary for Aminopyralid.

Commodity Proposed Tolerance 

(ppm)

Recommended 

Tolerance (ppm)

Comments; Correct Commodity 

Definition

Corn, forage 0.30 0.30 Corn, field, forage

Corn, grain 0.20 0.20 Corn, field, grain

Corn, stover 0.20 0.20 Corn, field, stover

References

D305665, Aminopyralid. Petition for the Establishment of Permanent Tolerances for Use of 

Aminopyralid on Grasses and Wheat. Summary of Analytical Chemistry and Residue Data. 

PP#4F6827, M. Doherty, 7/12/05, MRIDs: 46235708-46235712, 46235714, 46235716-

46235719, 46235721-46235725

D312724, PP# 4F6827. Review of Method for the Establishment of Permanent Tolerances in 

Aminopyralid in/on Plant and Livestock Commodities. ACL Project #:B05-12, D. Wright, 

11/3/05, MRIDs: 46235712, 46235714, 46235716, 46235717

Attachments: 

International Residue Limit Status sheet

Appendix I - Tolerance Assessment Calculations
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 22 of 28

INTERNATIONAL RESIDUE LIMIT STATUS

Chemical Name: 4-amino3,6-dichloro-2-

pyridinecarboxylic acid

Common Name:

Aminopyralid

X Proposed tolerance

 Reevaluated tolerance

 Other

Date: 5/8/09

Codex Status (Maximum Residue Limits) U. S. Tolerances

 No Codex proposal step 6 or above

X No Codex proposal step 6 or above for the crops 

requested

Petition Number: PP#8F7455

DP#: 360100

Other Identifier: Decision # 401475

Residue definition (step 8/CXL): aminopyralid and its 

conjugates that can be hydrolysed, expressed as 

aminopyralid

Reviewer/Branch: D. Dotson/C.Swartz/RAB1

Residue definition: Aminopyralid, free and conjugated 

residues

Crop (s) MRL (mg/kg) Crop(s) Tolerance (ppm)

Corn, forage 0.30

Corn, grain 0.20

Corn, stover 0.20

Limits for Canada Limits for Mexico

No Limits

X No Limits for the crops requested

X No Limits

 No Limits for the crops requested

Residue definition: 4-amino-3,6-dichloro-2-

pyridinecarboxylic acid (free and conjugated)

Residue definition: N/A

Crop(s) MRL (mg/kg) Crop(s) MRL (mg/kg)

Notes/Special Instructions: S.Funk, 05/13/2009.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 23 of 28

Appendix I. Tolerance Assessment Calculations.

For the field corn commodities listed below, the Guidance for Setting Pesticide Tolerances 

Based on Field Trial Data (SOP), along with the tolerance spreadsheet (January 2008 version), 

was used for calculating recommended tolerances. As specified in the SOP, the minimum of the 

95% upper confidence limit (UCL) on the 95th percentile and the point estimate of the 99th

percentile was selected as the tolerance value because the datasets were large (40 samples each) 

and reasonably lognormal. The rounding procedures specified in the SOP were also used.

The datasets used to establish tolerances for aminopyralid on field corn forage, grain, and stover 

consisted of field trial data representing application rates of 0.03-0.034 lb ae/A (single 

application) with a 60- to 87-day PHI for forage and a 105- to 138-day PHI for grain and stover. 

The field trial application rates are within 25% of the maximum label application rate; however, 

the PHIs are much greater than the proposed PHIs of 0 days for grain and 8 days for forage and 

silage. No residue data were submitted for field corn commodities reflecting the proposed PHIs. 

The residue values that were entered into the tolerance spreadsheet are provided in Table I-1.

For forage and stover, 39 out of 40 field trial sample results for aminopyralid were above the 

LOQ (LOQ = 0.01 ppm), and for field corn grain, 35 out of 40 field trial results were above the 

LOQ. Visual inspection of the lognormal probability plot (Figures I-1, I-3, and I-5) and the 

results from the approximate Shapiro-Francia test statistic (Figures I-2, I-4, and I-6) indicated 

that the datasets were reasonably lognormal. 

Using the tolerance spreadsheet, the recommended tolerances are 0.25 ppm for field corn forage, 

0.15 ppm for field corn grain, and 0.20 ppm for field corn stover. However, for both forage and 

grain, the recommended tolerances are slightly less than the highest residue value observed in the 

field trials, of 0.262 ppm and 0.164 ppm, respectively. Therefore, HED recommends in favor of 

tolerances of 0.30 ppm for field corn forage and 0.20 ppm for field corn grain.
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 24 of 28

Table I-1. Residue data used to calculate tolerances for residues of aminopyralid on field corn forage, 

grain, and stover.

Regulator: EPA EPA EPA

Chemical: Aminopyralid Aminopyralid Aminopyralid

Crop: Field corn forage Field corn grain Field corn stover

PHI: 60-87 Days 105-138 Days 105-138 Days

App. Rate: 0.030-0.034 lb ae/A 0.030-0.034 lb ae/A 0.030-0.034 lb ae/A

Submitter: Dow AgroSciences Dow AgroSciences Dow AgroSciences

MRID Citation: MRID 47572601 MRID 47572601 MRID 47572601

Residues of Aminopyralid (ppm)

0.045 0.015 0.019

0.041 0.026 0.020

0.039 0.043 0.036

0.022 0.021 0.017

0.065 0.052 0.068

0.042 0.030 0.030

0.113 0.033 0.176

0.057 0.030 0.029

0.012 0.015 0.014

0.119 <0.01 0.091

0.189 0.145 0.167

0.035 0.023 0.064

0.021 0.053 <0.01

<0.01 <0.01 0.012

0.035 0.038 0.060

0.021 0.020 0.028

0.037 0.012 0.021

0.036 <0.01 0.035

0.046 0.031 0.033

0.084 0.051 0.071

0.034 0.014 0.018

0.024 0.032 0.030

0.041 0.047 0.034

0.050 0.025 0.012

0.086 0.052 0.108

0.044 0.032 0.021

0.128 0.037 0.131

0.052 0.028 0.037

0.030 0.016 0.029

0.145 0.081 0.075

0.262 0.164 0.107

0.056 0.021 0.060
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 25 of 28

Table I-1. Residue data used to calculate tolerances for residues of aminopyralid on field corn forage, 

grain, and stover.

Regulator: EPA EPA EPA

Chemical: Aminopyralid Aminopyralid Aminopyralid

Crop: Field corn forage Field corn grain Field corn stover

PHI: 60-87 Days 105-138 Days 105-138 Days

App. Rate: 0.030-0.034 lb ae/A 0.030-0.034 lb ae/A 0.030-0.034 lb ae/A

Submitter: Dow AgroSciences Dow AgroSciences Dow AgroSciences

MRID Citation: MRID 47572601 MRID 47572601 MRID 47572601

Residues of Aminopyralid (ppm)

0.016 0.031 0.011

0.012 <0.01 0.011

0.045 0.035 0.046

0.042 0.020 0.046

0.025 0.011 0.025

0.016 <0.01 0.028

0.038 0.036 0.023

0.149 0.056 0.072

Figure I-1. Lognormal probability plot of aminopyralid field trial data for field corn forage.

Lognormal Probability Plot

0.1 1 2 5 10 20 30 50 70 80 90 95 98 99 99.9

1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

y = 0.771x - 3.1294

R

2

 = 0.9729

Percentiles

Concentrations

EPA Aminopyralid Field corn forage 60-87 Days 0.030-0.034 lb ae/A Dow AgroSciences
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 26 of 28

Figure I-2. Tolerance spreadsheet summary of aminopyralid field trial data for field corn forage.

Regulator: EPA

Chemical: Aminopyralid

Crop: Field corn forage

PHI: 60-87 Days

App. Rate: 0.030-0.034 lb ae/A

Submitter: Dow AgroSciences

n: 40

min: 0.01

max: 0.26

median: 0.04

average: 0.06

95th Percentile 99th Percentile 99.9th Percentile

0.15 0.20 0.25

(0.20) (0.25) (--)

0.20 0.30 0.50

(0.25) (0.45) (--)

0.15

0.25

0.25

0.9729

p-value > 0.05 : Do not reject lognormality assumption

Approximate 

Shapiro-Francia 

Normality Test 

EU Method I

Normal

UCLMedian95th

95/99 Rule

EU Method II

Distribution-Free

Mean+3SD
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 27 of 28

Figure I-3. Lognormal probability plot of aminopyralid field trial data for field corn grain.

Lognormal Probability Plot

0.1 1 2 5 10 20 30 50 70 80 90 95 98 99 99.9

1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

y = 0.6917x - 3.5939

R

2

 = 0.9544

Percentiles

Concentrations

EPA Aminopyralid Field corn grain 105-138 Days 0.030-0.034 lb ae/A Dow AgroSciences

Figure I-4. Tolerance spreadsheet summary of aminopyralid field trial data for field corn grain.

Regulator: EPA

Chemical: Aminopyralid

Crop: Field corn grain

PHI: 105-138 Days

App. Rate: 0.030-0.034 lb ae/A

Submitter: Dow AgroSciences

n: 40

min: 0.01

max: 0.16

median: 0.03

average: 0.04

95th Percentile 99th Percentile 99.9th Percentile

0.09 0.15 0.15

(0.15) (0.15) (--)

0.09 0.15 0.25

(0.15) (0.25) (--)

0.09

0.15

0.15

0.9544

p-value > 0.05 : Do not reject lognormality assumption

Approximate 

Shapiro-Francia 

Normality Test 

EU Method I

Normal

UCLMedian95th

95/99 Rule

EU Method II

Distribution-Free

Mean+3SD
Aminopyralid Summary of Analytical Chemistry and Residue Data DP#: 360100

Page 28 of 28

Figure I-5. Lognormal probability plot of aminopyralid field trial data for field corn stover.

Lognormal Probability Plot

0.1 1 2 5 10 20 30 50 70 80 90 95 98 99 99.9

1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

y = 0.7799x - 3.3341

R

2

 = 0.9762

Percentiles

Concentrations

EPA Aminopyralid Field corn stover 105-138 Days 0.030-0.034 lb ae/A Dow AgroSciences

Figure I-6. Tolerance spreadsheet summary of aminopyralid field trial data for field corn stover.

Regulator: EPA

Chemical: Aminopyralid

Crop: Field corn stover

PHI: 105-138 Days

App. Rate: 0.030-0.034 lb ae/A

Submitter: Dow AgroSciences

n: 40

min: 0.01

max: 0.18

median: 0.03

average: 0.05

95th Percentile 99th Percentile 99.9th Percentile

0.15 0.15 0.20

(0.15) (0.20) (--)

0.15 0.25 0.40

(0.20) (0.35) (--)

0.15

0.20

0.20

0.9762

p-value > 0.05 : Do not reject lognormality assumption

Approximate 

Shapiro-Francia 

Normality Test 

EU Method I

Normal

UCLMedian95th

95/99 Rule

EU Method II

Distribution-Free

Mean+3SD