Document ID: EPA-HQ-OPP-2009-0141-0008
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-04-07T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

	OFFICE OF PREVENTION, PESTICIDE

	AND TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 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  SEQ CHAPTER \h \r 1 		

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		  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h
\r 1 

		

  SEQ CHAPTER \h \r 1 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.

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.  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.

  SEQ CHAPTER \h \r 1 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.

  

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.

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)



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

Parameter	Value	Reference

Melting point/range	  SEQ CHAPTER \h \r 1 163.5ºC	  SEQ CHAPTER \h \r 1
MRID 46235703

pH	  SEQ CHAPTER \h \r 1 2.31 at 23.4ºC (1% solution in water)	MRID
46235703

Density	  SEQ CHAPTER \h \r 1 1.72 at 20ºC	MRID 46235703

Water solubility	  SEQ CHAPTER \h \r 1 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	  SEQ CHAPTER \h \r 1 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	  SEQ CHAPTER \h \r 1 2.59 x 10-8 Pa at 25ºC; 9.52 x
10-9 Pa at 20ºC	MRID 46235703

Dissociation constant, pKa	  SEQ CHAPTER \h \r 1 2.56	MRID 46235703

Octanol/water partition coefficient, Log(KOW)	  SEQ CHAPTER \h \r 1
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	  SEQ CHAPTER \h \r 1 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.

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
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.  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 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 (13C215N-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 (13C22H15N-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.  

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.

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 (13C215N-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
(13C22H15N-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 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.   

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 Duration1	Interval 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.  

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.  

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.

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 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 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).  

  SEQ CHAPTER \h \r 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 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.  

  SEQ CHAPTER \h \r 1 860.1650 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)

umulated 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.  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.

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

  SEQ CHAPTER \h \r 1 Attachments:  

International Residue Limit Status sheet

Appendix I - Tolerance Assessment Calculations



INTERNATIONAL RESIDUE LIMIT STATUS

Chemical Name:  4-amino-3,6-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.

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.



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0.056	0.021	0.060

	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.

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

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

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

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

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

Page   PAGE  1  of   NUMPAGES  28 

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