UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF CHEMICAL SAFETY AND

                                                                        
                                   POLLUTION PREVENTION

MEMORANDUM

	Date:	August 31, 2010

	Subject:	Glufosinate Ammonium.  Petitions for the Establishment of
Permanent Tolerances in/on Citrus Fruits (Crop Group 10), Pome Fruits
(Crop Group 11), Stone Fruits (Crop Group 12), Olives and Sweet Corn. 
Summary of Analytical Chemistry and Residue Data.

PC Code:  128850	DP Barcode No.:  D372625 

Decision No.: 424397 	Registration No.: 264-646

Petition No.:  9F7655 and 9E7604	Regulatory Action: Tolerance Petition 

Risk Assessment Type: Residue Chemistry	Case No.: NA

TXR No.:  NA	CAS No.: 77182-82-2

MRID No.:  47915701, 47915702, 47915703, 47915704, 47915705, 47915706,
47915707, 47915708, 47828201, 47828202 and 47828203	40 CFR:  §180.473



From:           Ideliz Negrón-Encarnación, Ph.D., Chemist 

			     Risk Assessment Branch V		

		  	     Health Effects Division (7509P)

Through:	 William H. Donovan, Ph.D., Chemist 

			 Risk Assessment Branch V

		     Health Effects Division (7509P)

		     Jack Arthur, Chief

		     Risk Assessment Branch V

		     Health Effects Division (7509P)

TO: 		Sidney Jackson, Barbara Madden, RM Team 05

	James Stone, RM Team 23

	Registration Division (RD) (7505P)

Tom Myers, Risk Manager  

Pesticide Re-Evaluation Division (PRD) (7508P)Executive Summary

Technical glufosinate ammonium is a racemic mixture of the D and L
enantiomers; only the L enantiomer is herbicidally active.  The compound
is a non-selective herbicide and acts as an inhibitor of glutamine
synthetase which leads to poisoning of the plant by ammonia. 
Glufosinate ammonium is currently registered for use on both transgenic
and nontransgenic crops.  The transgenic plants currently registered
(canola, sugar beet, corn, soybean) and the transgenic plants requested
for registration (rice and cotton) have been engineered to express
phosphiothrion-acetyl-transferase (PAT) which enables the plant to
metabolize glufosinate ammonium into N-acetyl-glufosinate.

The petitioners have proposed application of Liberty® 280 SL (24.5%
glufosinate ammonium; soluble concentrate; EPA Reg. No. 264-829) to
Citrus Fruits (Crop Group 10), Pome Fruits (Crop Group 11), Stone Fruits
(Crop Group 12) and Olives.  However, the crop field trials were
performed with RELY 200SL (18.19% glufosinate ammonium; soluble
concentrate; EPA Reg. No. 264-660).  For the intended purpose of
establishing tolerances, the RELY 200SL data will be considered
acceptable to amend the Liberty label to included uses for the mentioned
RACs.  The Liberty® label may include use directions to support a three
applications to the soil at a maximum rate of 1.5 lb ai/A, 14-day
retreatment interval (RTI), and 14-day pre harvest interval (PHI) for
citrus fruits, pome fruits and olives for a maximum seasonal rate of 4.5
lb ai/A.  For stone fruits, the studies submitted support two
applications to the soil with a maximum rate of 1.5 lb ai/A, 28-day RTI,
and 14-PHI for a maximum seasonal rate of 3.0 lb ai/A.  The product
label prohibits application through irrigation equipment and by
aircraft.

The Interregional Research Project No 4 submitted crop field trial data
to support the use of glufosinate ammonium on transgenic sweet corn. 
Twelve crop field trials were conducted in EPA regions 1, 3, 5, 10 and
11.  Two foliar applications of Liberty Herbicide at a rate of 0.375 lb
ai/A for a total of 0.75 lb ai/A were performed with a retreatment
interval (RTI) of 14-16 days.  Ammonium sulfate was included in the tank
mix. Sweet corn ears, forage and stover were harvested 30 to 50 days
following the final application.  Stover was dried for 5 to 13 days
after harvest.

Based on the metabolism and magnitude of the residue studies, the
Metabolism Assessment Review Committee (MARC) concluded that the
residues of concern in the crops studied, for tolerance expression and
risk assessment purposes, are glufosinate ammonium,
N-acetyl-glufosinate, and glufosinate propanoic acid (D282757, T. Bloem,
9-May-2002).  HED concludes that the results from the currently
available metabolism studies may be translated to citrus fruits, pome
fruits, stone fruits, olives and sweet corn.   

Adequate enforcement and multiresidue analytical methods are available
for glufosinate ammonium, N-acetylglufosinate, and glufosinate propanoic
acid.  In the current studies, residues of glufosinate ammonium,
N-acetyl-glufosinate, and glufosinate propanoic acid were determined
using one of three methods.  A Gas Chromatography (GC) with flame
photometric detection method currently used for enforcement purposes
(BK/01/99) was used for the analysis of peach samples.  A method very
similar to the enforcement method HRVA-5 was used for the analysis of
sweet corn samples.  A Liquid Chromatography/Mass Spectrometry/Mass
Spectrometry (LC/MS/MS) method developed by Bayer was used for the
analysis of orange, lemon, grapefruit, prune, pear, cherry, olive, olive
oil, orange oil and prunes.  The method described in Bayer CropScience
report number GL-001-P07-01, “An Analytical Method for the
Determination of Residues of Glufosinate in Crop Matrices Using
LC/MS/MS” residues were quantitated by liquid chromatography/mass
spectroscopy/mass spectroscopy (LC/MS/MS).  The limit of quantitation
(LOQ) is reported to be 0.05 ppm for each analyte. The method was
adequate for data collection based on concurrent method recoveries. 
Control samples were fortified with glufosinate ammonium,
N-acetyl-glufosinate, and glufosinate propanoic acid at 0.05, 0.5 ppm
for all commodities. All recoveries were between the acceptable range of
70-120%. 

With the current petition, frozen storage stability was demonstrated for
glufosinate residues in peaches stored frozen for 730 days (24.3 months)
and N-acetylglufosinate and 3-methylphosphinico-propanoic acid residues
stored frozen for 778 days (25.9 months). Previously submitted and
reviewed frozen storage stability data indicate that glufosinate
ammonium and glufosinate propanoic acid are stable for 730 days on
frozen apples, corn grain, and soybeans (PP#8F3607, J. Garbus,
8-Aug-1990), and for 24 months on oranges and 6 months on kiwi. 
Blueberry storage stability data results showed that glufosinate
ammonium and glufosinate propanoic acid were stable in/on frozen
blueberry samples for 693 days and 664 days, respectively (D271110, T.
Bloem, 20/June/2002).  Additional storage stability data indicated that
glufosinate ammonium, N-acetylglufosinate, and glufosinate propanoic
acid are stable for 12 months on transgenic soybean seed, forage and
hay; for 3 months on soybean oil and meal; for 6 months on transgenic
corn grain, fodder and forage; and for 24 months on transgenic sugar
beet tops and roots (D211531 and D219069, M. Rodriguez, 7-Mar-1996;
D257629, T. Bloem, 9-Jul-1999).  These data are adequate to validate the
storage interval and conditions for the samples analyzed as part of the
current study. 

  SEQ CHAPTER \h \r 1 Regulatory Recommendations and Residue Chemistry
Deficiencies

Provided revised Section B and F are submitted as specified below there
are no residue chemistry deficiencies that would preclude granting a
registration for the requested uses of glufosinate ammonium on citrus
fruits, pome fruits, stone fruits, olives and sweet corn.  The submitted
data support the following tolerances for glufosinate ammonium residues
of concern in/on the following raw agricultural commodities: 

Citrus fruit (CG 10) 	... 0.15 ppm

Pome fruit (CG 11) 	0.25 ppm

Stone fruit (CG 12) 	 0.25 ppm

Olives 	0.15 ppm

Corn, sweet, kernels plus cob with husks removed	0.25 ppm

Corn, sweet, forage	1.6 ppm

Corn, sweet, stover	10 ppm

A revised human health risk assessment including glufosinate ammonium
uses on citrus fruits, pome fruits, stone fruits, olives and sweet corn
is being prepared as a separate document.

Revised Section B - Label use directions should match crop field trial
use pattern to include maximum application rates, RTI, and adjuvant
uses.

Revised Section F – Proposed crop commodity definitions and tolerance
levels should be revised to those recommended in Table 9.

Background

  SEQ CHAPTER \h \r 1 The chemical structure and nomenclature of
glufosinate ammonium, N-acetyl-glufosinate, and glufosinate propanoic
acid are presented in Table 1 while the physicochemical properties are
presented in Table 2.

 

Common name	

Glufosinate ammonium

Company experimental name	

AE F039866, HOE 039866

IUPAC name	ammonium-DL-homoalanin-4-yl-(methyl)-phosphinate

CAS name	



Common name	Glu-PPA, AE F061517, Glufosinate propanoic acid, HOE 061517

Chemical name	3-methylphosphinico-propionic acid or



Common name	Glu-NAG, AE F085355, N-acetylglufosinate, HOE 099730

Chemical name	2-(Acetylamino)-4-(hydroxymethyl phosphinyl) butanoic acid



  SEQ CHAPTER \h \r 1 Table 2.  Physicochemical Properties of the
Technical Grade Test Compound.

Parameter	Value1

Melting point/range (°C)	215-218 

pH	4.7

Density (g/cm3)	1.32

Water solubility  (g/L at pH 5)	1370

Solvent solubility at room temp (g/L)	methanol: 5.73; DMSO: 0.049;
polyethylene glycol: 0.047;

acetonrile, toluene, acetone, ethyl acetate, and hexane: <0.00025

Vapor pressure at 25°C (torr)	<7.50 x 10-9 

Dissociation constant, pKa	9.15 ± 0.07

Octanol/water partition coefficient (Log KOW)	9.77 x 10-5

UV/visible absorption spectrum (nm)	>190

1 Source: DER for MRID 46573701, Tom Bloem, 2005

860.1200 Directions for Use

For the application of glufosinate ammonium in/on citrus, pome fruit,
stone fruit and olives, the petitioner has submitted undated draft
labels in conjunction with each petition for the 2.34 lb/gal SL
formulation (Liberty® 280 SL Herbicide; EPA Reg. No. 264-829).  A
summary of the proposed/registered crop use patterns in this document is
listed in Table 3.

Liberty® 280 SL Herbicide is presently registered for use on canola,
field corn, silage corn, cotton, soybean, bushberries, lingonberry,
juneberry, salal, tree nuts, grape vineyards and potato.   The
petitioner submitted residue field trials to establish tolerances for
glufosinate ammonium and two metabolites in/on citrus, pome fruit, stone
fruit and olives.  For this RELY 200, a soluble concentrate formulation
containing 1.64 lb ai/A was applied to the soil near the base of the
trees.

IR-4 submitted field trials to support the use of glufosinate ammonium
in/on transgenic sweet corn.  With this purpose, foliar applications of
Liberty® Herbicide on transgenic sweet corn were performed.  End-use
products equivalent to the Liberty® Herbicide may be registered for use
on transgenic sweet corn based on the data generated in these crop field
trials.

Table 3.   Summary of Directions for Use of Glufosinate Ammonium (2.34
lb/gal; EPA Reg. No. 352-515).1

Applic. Timing, Type, and Equip.	Applic. Rate 

(lb ai/A)	Retreat. Interval (days)	Max. No. Applic. Per Season	Max.
Seasonal Applic. Rate

(lb ai/A)	PHI

(days)	Adjuvant	Use Directions and Limitations

Broadcast, banded or spot treatment	Stone Fruit	Do not apply this
product through any type of irrigation system.

Do not apply this product aerially.

Do not graze, harvest, and/or feed treated orchard cover crops to
livestock.

Do not make spot spray applications to suckers.

	1.5	28	2	3.0	

14

	non-ionic antifoam2



Pome Fruit



1.5	14	3	4.5	

14

	non-ionic antifoam2



Citrus



1.5	14	3	4.5	

14

	non-ionic antifoam2



Olives



1.5	14	3	4.5	

14

	non-ionic antifoam2

	Foliar treatment

	Transgenic Sweet Corn	

Must be applied with ammonium sulfate.

	0.365	14	2	0.73	50	Do not use

	1 The numbers in bold are not in the label but correspond to the use
pattern proposed based on the field trials.

2 A non-ionic antifoam adjuvant may be added to the tank mixture at the
application rate used in the field trials.

Conclusions.  The proposed use directions should specify the maximum
application rate and retreatment interval; therefore, the petitioner may
revise the product label to specify the conditions used in the field
trials studies.  The Liberty® label may include use directions to
support a three applications to the soil at a maximum rate of 1.5 lb
ai/A, 14-day retreatment interval (RTI), and 14-day pre harvest interval
(PHI) for citrus fruits, pome fruits and olives for a maximum seasonal
rate of 4.5 lb ai/A.  For stone fruits, the studies submitted support
two applications to the soil with a maximum rate of 1.5 lb ai/A, 28-day
RTI, and 14-PHI for a maximum seasonal rate of 3.0 lb ai/A.  A non-ionic
antifoam adjuvant was included in the herbicide mixture in some field
trials for citrus fruits, peach, plum, pear and olives; therefore, the
use directions may include the use of this adjuvant on the crops
specified but the corresponding use rate should reflect the one used in
the crop field trials.  For transgenic sweet corn, the crop field trials
support the following use pattern: two foliar applications of Liberty
Herbicide at a maximum rate of 0.365 lb ai/A for a total seasonal
maximum rate of 0.73 lb ai/A, a 14-day RTI, and a 50-day PHI following
the final application.  Moreover, as stated in the label use directions
for sweet corn, ammonium sulfate must be added to the pesticide mixture.

860.1300 Nature of the Residue – Plants and Livestock

No plant or animal metabolism data were submitted with the subject
petitions.  The nature of the residue of glufosinate ammonium in
livestock and plants has been adequately delineated.  HED has previously
reviewed metabolism studies conducted with nontransgenic (corn, soybean,
apple, and lettuce; 8F3607, J. Garbus, 14-Oct-1988 & 8-Aug-1990) and
transgenic (corn, soybean, sugar beet, canola, and rice; D227386, M.
Rodriguez, 7-Mar-1996; D257629, T. Bloem, 9-Jul-1999; 45204405.der.wpd)
crops.  The transgenic corn, soybean, sugar beet, canola, and rice
investigated in the metabolism studies were engineered to express PAT
which acetylates glufosinate (herbicidally active) to form
N-acetyl-glufosinate (not herbicidally active).  

Based on the metabolism and magnitude of the residue studies, the
Metabolism Assessment Review Committee (MARC) concluded that the
residues of concern in the crops studied, for tolerance expression and
risk assessment purposes, are glufosinate ammonium,
N-acetyl-glufosinate, and glufosinate propanoic acid (D282757, T. Bloem,
9-May-2002).  HED concludes that the results from the currently
available metabolism studies may be translated to citrus fruit, pome
fruit, stone fruit and sweet corn.   

Glufosinate propanoic acid was the only metabolite identified in the
nontransgenic studies (2-40% total radioactive residue (TRR); only
soybean leaf, corn stover, and apples were analyzed).  The petitioner
demonstrated that 40% of the TRR in nontransgenic corn stover was
incorporated into protein, starch, cellulose, and lignin.  Glufosinate
ammonium, N-acetyl-glufosinate, and glufosinate propanoic acid were the
major residues identified in the transgenic crops (40-98% of the TRR). 
The petitioner demonstrated that for transgenic sugar beet leaves,
surface residues are composed of a nearly equal mixture of the D and L
enantiomers of glufosinate ammonium while interior residues are composed
of almost exclusively D enantiomer of glufosinate ammonium.  This
indicates that only the L enantiomer of glufosinate ammonium was
acetylated to form N-acetyl-glufosinate. 

There are no feedstock items associated with this petition; however, the
nature of the residue in livestock commodities has been assessed and
have been determined to be the same as in plants (D271110, T. Bloem,
20/June/2002).

860.1340 Residue Analytical Methods

Enforcement methods

D335330, T. Bloem, 09/12/2007

Two analytical methods have been validated by the Analytical Chemistry
Branch (ACB) for enforcement of the currently established tolerances: 
(1) method HRAV-5A was validated by ACB for the determination of
glufosinate ammonium and glufosinate propanoic acid in/on apple, grape,
almond, soybean seed, corn grain, and corn forage (PP# 8F3607, J.
Garbus, 14-Sep-1989) and (2) method BK/01/99 was validated by ACB for
determination of glufosinate ammonium, N-acetyl-glufosinate, and
glufosinate propanoic acid in/on canola seed and sugar beet root
(D258420, T. Bloem, 19-Aug-2000).  Both methods involve extraction with
water, anion-exchange chromatography, derivatization with
trimethylorthoacetate, silica-gel column clean-up, and quantification
via gas chromatography with flame photometric detection (residues
expressed as glufosinate free acid equivalents).  Method BK/01/99
includes a cation ion-exchange column prior to derivatization which
fractionates glufosinate ammonium and N-acetyl-glufosinate and allows
for speciation of these compounds (both compounds are derivitized to the
same compound).  This step can be eliminated if separation of these two
compounds is unnecessary.  The methods do not distinguish between the D
and L enantiomers of glufosinate ammonium and N-acetyl-glufosinate. 

 

Based on the similarity in the two methods and the results from the
petition method validations (PMVs), HED concludes that method BK/01/99
is a suitable method for enforcement of sweet corn, stone fruit, pome
fruit, citrus fruit and olive tolerances.  

Data-collection methods

Three methods were used for quantitation of glufosinate ammonium and its
two metabolites.  For peach samples, residues of glufosinate ammonium
and its two metabolites, 3-methylphosphinico-propanoic acid and
N-acetylglufosinate were analyzed from their derivatives AE F064706 and
AE F070951 by using a gas chromatograph equipped with a flame
photometric detector operating in the phosphorous mode.  This method is
equivalent to the enforcement method BK/01/99 but instead of following
the general procedure, the optional speciation process (optional method,
Section 3.2) is followed to quantify the parent and its two metabolites
separately.  Quantitation is based on the use of a calibration curve. 
The limit of quantitation for each analyte is 0.05 ppm.  Concurrent
recovery data was obtained for peach samples by spiking the samples with
the corresponding standards before the extraction process.

For sweet corn, a similar method to the enforcement method HRVA-5 was
used for quantitation.  In this method the analytes were extracted from
samples with deionized water, the sample was cleaned through an anion
exchange resin, derivatized with trimethylorthoacetate/glacial acetic
acid to AE F064706 and AE F070951, and cleaned through a silica solid
phase extraction column. The parent and N-acetylglufosinate are
derivatized to the same analyte, AE F064706, while glufosinate propanoic
acid is derivatized to AE F070951.  The residues were subsequently
measured by gas chromatography with flame photometric detection in
phosphorous mode, and reported as glufosinate free acid equivalents.
Modifications were performed to add clarity to the extraction procedure.
 To prove the extraction efficiency in sweet corn, this method was
validated by obtaining recoveries of glufosinate ammonium and
glufosinate propanoic acid but to support it use in transgenic sweet
corn IR-4 submitted with the current petition recovery data for
N-acetylglufosinate.  The method was validated with triplicate samples
of sweet corn ears at levels 0.0480 and 0.480 ppm, forage at 0.048 and
1.06 ppm, and stover at 0.048, 0.480 and 5.32 ppm.  The recoveries of
N-acetylglufosinate in/on sweet corn were between 78% and 113% for all
matrices.  The method LOQ was determined to be 0.05 ppm for each
analyte.

For orange, lemon, grapefruit, cherry, plum, pear and olive, residues
were determined using a method described in Bayer Report Number
GL-001-P07-01, “An Analytical Method for the Determination of Residues
of Glufosinate in Crop Matrices Using LC/MS/MS”.  Orange, lemon,
grapefruit, cherry, plum, pear and olive raw agricultural commodities
and processed samples were analyzed for residues of glufosinate ammonium
and its two metabolites, glufosinate propanoic acid and
N-acetylglufosinate using liquid chromatography with tandem
mass-spectral detection (LC/MS-MS) (Method Number GL-001-P07-01).  

Briefly, for extraction from orange, lemon, grapefruit, cherry, plum,
pear and olive RACs and prunes process commodity, a sub-sample was
extracted by shaking the sample in the presence of water for 30 minutes
at room temperature. An internal standard was added to the sample vial
and then an aliquot of the extract was mixed with methanol and purified
through a SAX SPE column. The eluent was dried, reconstituted, and
injected onto the LC/MS/MS for quantification of the residues.  For
extraction of the olive oil and citrus oil matrix, an oil aliquot was
dissolved into hexane and shake in the presence of water at room
temperature two separate times. The water layers were decanted and
combined. An aliquot of the water extract was mixed with acetone and
evaporated to dryness. The residue was reconstituted into 1 mL diluting
solvent (85:15 mixture of acetonitrile/diluting buffer) and injected
onto LC/MS/MS.  An electrospray interphase in positive mode was used for
ionization of the sample.  Since the analytes elute at a similar
retention time, specificity is achieved by multiple reaction monitoring
of glufosinate ammonium (152.7/134.0 m/z), N-acetylglufosinate
(223.7/117.0 m/z) and glufosinate propanoic acid (155.7/137.0 m/z). 
Quantification of the residues was based on the use of a calibration
curve and the deuterated analytes as internal standards.  Based on the
lowest level of method validation (LLMV), the limit of quantitation
(LOQ) was 0.05 ppm for each analyte. Concurrent method recovery data was
obtained for citrus, pome fruit, stone fruit and olive raw agricultural
and processed commodities. 

The recovery of the parent and its two metabolites was based on relative
recovery studies in which a known amount of the analyte and deuterated
analyte were added during the sample preparation process and the
recovery was calculated by measuring the response of the analyte with
respect to its deuterated form. For orange, lemon, grapefruit, cherry,
plum, pear, peach and olive, the method was validated for glufosinate
ammonium and its two metabolites at levels of 0.05 ppm and 0.50 ppm. 
The average recoveries obtained from these commodities were between
78.7% and 110%.  For orange oil, olive oil and plums, the method was
validated at 0.05 ppm and at 0.8 ppm only for plum.  The average
recoveries were within 80.3% and 112%.  Average recoveries for all RAC
and processed commodities were within the acceptable range of 70-120%.  

Conclusions.  There are adequate residue analytical methods for
tolerance enforcement. Also, the methods used for data collection was
adequate based on the method recoveries, precision and the range of
levels tested which included the LOQ and tolerance level.  

860.1360 Multiresidue Methods

Glufosinate ammonium, glufosinate propanoic acid, and
N-acetyl-glufosinate were not quantitatively recovered from any of the
FDA Multiresidue Testing Protocols.  This information has been forwarded
to FDA (PP#8F3607, J. Garbus, 14-Aug-1988; PP#5F4578, M. Rodriguez,
10-Oct-1995).

860.1380 Storage Stability

Reference DERs:  47828201.der.doc and 47915705.der.doc.

Previously submitted and reviewed frozen storage stability data indicate
that glufosinate ammonium and glufosinate propanoic acid are stable for
24 months on frozen apples, corn grain, and soybeans (PP#8F3607, J.
Garbus, 8-Aug-1990), for 24 months on oranges and 6 months on kiwi
(study pending approval).  Moreover, blueberry storage stability data
was submitted with the petition for tolerances in the bushberries crop
group (D271110, T. Bloem, 20/June/2002).  The results showed that
glufosinate ammonium and glufosinate propanoic acid were stable in/on
frozen blueberry samples for 693 days and 664 days, respectively. 
Additional storage stability data indicated that glufosinate ammonium,
N-acetylglufosinate, and glufosinate propanoic acid are stable for 12
months on transgenic soybean seed, forage and hay; for 3 months on
soybean oil and meal; for 6 months on transgenic corn grain, fodder and
forage; and for 24 months on transgenic sugar beet tops and roots
(D211531 and D219069, M. Rodriguez, 7-Mar-1996; D257629, T. Bloem,
9-Jul-1999).  

Frozen storage stability for glufosinate residues was investigated in
peaches stored frozen for 730 days (24.3 months) and N-acetylglufosinate
and 3-methylphosphinico-propanoic acid residues stored frozen for 778
days (25.9 months) under the same storage conditions as those of the
field samples. The storage stability study started when the field
samples arrived at the analytical laboratory the fortified samples were
stored under the same conditions as the field samples. Average storage
stability results ranged from 87% to 95% for glufosinate ammonium, from
70% to 78% for 3-methylphosphinico-propanoic acid, and from 77% to 80%
for N-acetylglufosinate.  However, the storage stability period do not
cover the actual storage duration for peaches, 791 days (26 months). 
The number of days not covered by the storage stability studies was 61
for glufosinate ammonium and, 13 for 3-methylphosphinico-propanoic acid
and N-acetylglufosinate.  Since the storage stability recoveries for
glufosinate ammonium were quite high and just a few days were not
covered for the two metabolites, on this time HED will considered the
peach storage period covered by the interval of demonstrated storage
stability. 

Storage stability was also demonstrated in sweet corn ears (765 and 914
days)), forage (793 days) and stover (812 days) spiked with glufosinate
ammonium and glufosinate propionic acid at < -10 ºC.  Average storage
stability results were from 64.2 to 92.4% while the results corrected
for the mean concurrent recoveries were from 89.1 to 112% after over two
years of frozen storage.  This storage stability study support the
stability of glufosinate and glufosinate propionic acid for 914 days for
ears, and 793 days for forage and 812 days for stover.  Based on the
storage stability results the interval of demonstrated storage stability
will be considered to cover the sweet corn storage period for ears
(197-950 days), forage (146-788 days) and stover (143-810 days) samples.
 The stability of the N-acetylflufosinate was not assessed during this
study which is a metabolite relevant to transgenic sweet corn.  Previous
storage stability studies performed up to 6 months on nontransgenic
field corn show the stability of this residue but this interval do not
covers the study period.  However, the stability of N-acetylglufosinate
in peach samples was demonstrated up to 778 days which covers the
storage period of 10 of the 12 samples of sweet corn ears and most of
the forage and stover samples; therefore, the sweet corn data will be
considered acceptable for the current petition.

To translate storage stability data to all RACs, HED guidelines require
that stability is proven for at least five diverse crops.  Indeed, the
data available covers this requirement: oilseed (transgenic soybean
seed, 12 months), nonoily grain (transgenic corn grain for 6 months and
nontransgenic corn grain for 24 months (N-acetylglufosinate not
assessed)), fruit or fruiting vegetable (orange for 24 months and
blueberries for 21.8 months, N-acetylglufosinate not assessed), leafy
vegetable (sugar beet tops, 24 months), and root crop (sugar beet root,
24 months).

Based on the available storage stability data and since acceptable
percent recoveries were attained for fortified samples run concurrent to
the treated samples, HED concludes that the storage intervals and
conditions for the samples collected as part of the orange, lemon,
grapefruit, cherry, plum, pear, peach and olive field trials are
acceptable.  The storage durations and conditions of samples from the
crop field trials submitted to support these petitions are presented in
Table 4.

The storage stability of glufosinate ammonium, glufosinate propanoic
acid and N-acetylglufosinate has been established in some processed
commodities.  These are stable under frozen conditions for 3 months on
soybean oil and meal, and for 9 months on sugar beet pulp, molasses, and
sugar beet refined sugar (D211531 and D219069, M. Rodriguez, 7-Mar-1996;
D286447, T. Bloem, 11-Dec-2002).  Storage stability studies for olive
oil, orange oil and prunes processed commodities haven’t been
submitted with the current petition.  These studies are recommended in
OPPTS 860.1380 and OPPTS 860.1520 guidelines.  However, under certain
circumstances HED waives these studies.  The storage intervals for olive
oil (3.7 months) and prunes (4.4 months) can be supported based on the
available storage stability studies for soybean oil and a wide variety
of RACs.  The orange oil commodity was stored for 9.2 months.  Storage
stability for orange oil will not be requested at this time based on the
following: residue levels were <LOQ in the RAC and processed commodity
after applying exaggerated rates (5x) of the end use product, and
storage stability has been demonstrated on a wide variety of RACs for at
least 2 years and some processed commodities for at least 9 months. 

TABLE 4.	Summary of Storage Conditions.

Matrix  (RAC)	Analytes	Storage Temp (°C)	Actual Storage Duration1
Interval of Demonstrated Storage Stability (months)

Citrus, fruit	

Glufosinate ammonium, and Glufosinate Propanoic Acid

	

<0	336 days

(11.2 months)	

Concurrent storage stability data was submitted for residues in/on peach
showing a stability period of 730 days for glufosinate ammonium, and 778
days for glufosinate propanoic acid, and N-acetylglufosinate (MRID
47915705).  In addition, concurrent studies in transgenic sweet corn
were submitted showing stability of glufosinate and glufosinate
propanoic acid for 914 days in ears, 793 days in forage and 812 days in
stover (MRID 47828201).

Glufosinate ammonium and glufosinate propanoic acid: Apple, corn grain,
and soybean for 730 days (PP#8F3607, J. Garbus, 8-Aug-1990), blueberries
for 664 days (D271110, T. Bloem, 20/June/2002), orange for 24 months and
kiwi for 6 months (study pending approval).

Glufosinate ammonium, glufosinate propanoic acid, and
N-acetylglufosinate: 12 months on transgenic soybean seed, forage, and
hay; for 3 months on soybean oil and meal; for 6 months on transgenic
corn grain, fodder, and forage; and for 24 months on transgenic sugar
beet tops and roots; for 9 months on sugar beet pulp, molasses, and
sugar beet refined sugar (D211531 and D219069, M. Rodriguez, 7-Mar-1996;
D257629, T. Bloem, 9-Jul-1999; D286447, T. Bloem, 11-Dec-2002).



Trans. Sweet Corn, Ears

	197-950 days

(9.6-31.2 months)

	Trans. Sweet Corn, Forage

	146-788 days

(4.9-26.3 months)

	Trans. Sweet Corn, Stover

	143-810 days

(4.8-27 months)

	Pear	

Glufosinate ammonium, 3-methylphosphinico-propanoic acid, and
N-acetylglufosinate



224 days

(7.5 months)

	Cherry

	332 days

(11.1 months)

	Plum

	281 days

(9.4 months)

	Olive

	259 days

(8.6 months)

	Orange, Fruit (Processing Studies)

	176 days 

(5.9 months)

	Orange, Oil

	274-277 days 

(9.1-9.2 months)

	Plum (Processing Studies)

	135-146 days 

(4.5-4.9 months)

	Prune

	128-133 days 

(4.3-4.4 months)

	Olive Fruit (Processing Studies)

	122-125 days 

(4.1-4.2 months)

	Olive Oil

	109-111 days 

(3.6-3.7 months)

	1Actual storage duration from harvest to extraction.  

Conclusions.  There are adequate storage stability data available in a
wide variety of crops which can be translated in the current petitions
for orange, lemon, grapefruit, cherry, plum, pear, peach and olive RACs,
and citrus oil, prunes and olive oil processed commodities to validate
sample storage conditions and durations.  However, the petitioner is
reminded that storage stability studies are recommended for processed
commodities.  In addition, these studies should cover the period of time
in which the RAC or processed commodity was stored.  For
N-acetylglufosinate in/on transgenic sweet corn, the concurrent and
previous storage stability studies do not cover the storage interval. 
This deficiency needs to be resolved.

860.1400 Water, Fish, and Irrigated Crops

There are no proposed uses that are relevant to this guideline topic. 
However, glufosinate ammonium has uses registered for rice (D271110, T.
Bloem, 20-June-2002).

860.1460 Food Handling

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

860.1480 Meat, Milk, Poultry, and Eggs

No new animal feeding studies were submitted with these petitions and
only sweet corn forage and stover are associated with feedstuff items. 
In addition, glufosinate ammonium has uses registered for feedstuff
(D271110, T. Bloem, 20-June-2002).  In June 2008 an update to the Table
1 of OPPTS 860.1000 was issued.  Therefore, the dietary burden to
livestock was calculated based on the updated values of Table 1 and the
use of sweet corn feedstuff.

Table 5.  Calculation of Maximum Livestock Dietary Burden for
Glufosinate Ammonium.



Feedstock	Tolerance	%Dry Matter	

% of Diet	

Burden (ppm)2

Dairy Cattle

Sweet Corn Stover (R)	10	83	15	1.81

Field Corn Forage (R)	4.0	40	30	0.03

Field Corn Grain (CC)	0.20	88	15	3.00

Beet Sugar Molasses (CC)	5.0	75	10	0.67

Rice Grain (CC)	1.0	88	20	0.45

Undelinted Cottonseed (PC)	4.0	88	10	0.23

TOTAL	100	6.19

Beef Cattle

Field Corn Forage (R)	4.0	40	10	1.00

Cotton Gin Byproducts (R)	15	90	5	0.83

Aspirated Grain Fractions (CC)	25	85	5	1.47

Beet Sugar Molasses (CC)	5.0	75	10	0.67

Field Corn Grain (CC)	0.2	88	45	0.10

Rice Grain (CC)	1.0	88	20	0.23

Soybean Seed (PC)	2.0	89	5	0.11

TOTAL	100	4.41

Poultry

Field Corn Grain (CC)	0.2	NA	55	0.11

Rice Grain (CC)	1.0	NA	20	0.20

Soybean Seed (PC)	2.0	NA	20	0.40

Soybean Meal (PC)	2.0	NA	5	0.10

TOTAL	100	0.81

Swine

Field Corn Grain (CC)	0.2	NA	65	0.13

Rice Grain (CC)	1.0	NA	20	0.20

Soybean Seed (PC)	2.0	NA	15	0.30

TOTAL	100	0.63

	NA = Not Applicable

	1   As per Revised Table 1 (OPPTS Guideline 860.1000).

	2   For beef and diary cattle: Burden = [Tolerance ( % DM] x % Diet;
for poultry and swine: Burden = Tolerance x % Diet / 100.

The dietary burden calculated with the % of dry matter and % of diet
values from the updated Table 1 of OPPTS 860.0000 is shown in Table 5. 
The previously calculated dietary burden for beef cattle, dairy cattle,
poultry and swine is 15.38, 15.22, 3.33 and 8.89 ppm, respectively
(D271110, T. Bloem, 20/June/2002).  These values are higher than the
dietary burden calculated for this new petition; therefore, currently
the tolerances for livestock are covered by the feeding studies
previously performed with diary cow and poultry.

860.1500 Crop Field Trials

Reference DERs:  47915701.der.doc, 47915702.der.doc, 47915703.der.doc,
47915704.der.doc, and 47915705.der.doc.

Twenty three crop field trials were performed in the corresponding
regions, according to OPPTS guidelines, to evaluate the magnitude of
residue for orange, lemon and grapefruit.  A summary of the residue data
is presented in Table 6. Eight of the 23 trials used a non-ionic
antifoam. Each trial consisted of one treated plot and one control plot.
 Following three broadcast applications of RELY at the target rate of
1.50 lb ai/A/application residues of glufosinate ammonium and its two
metabolites, glufosinate propanoic acid and N-acetylglufosinate were not
detected above the LOQ (0.05 ppm) in/on oranges, lemons and grapefruit  
SEQ CHAPTER \h \r 1 harvested at a PHI of 14 (-1) days.  No effect of
the adjuvant on the residue levels was observed since the residues were
below the method LOQ for applications with and without the non-ionic
antifoam.  Moreover, results from the residue decline study performed on
each of the three crop types at five intervals corresponding to PHIs of
7, 11, 14, 17, and 21 days indicated that residues of glufosinate
ammonium, glufosinate propanoic acid and N-acetylglufosinate were below
the LOQ at all PHIs used.  

  

For plum commodities, six crop field trials were performed according to
OPPTS guidelines.  For cherries, sweet cherries or tart cherries can be
selected as a Stone Fruit crop group representative.  The registrant
submitted data with both crops and the regions were selected to
represent both commodities.  Five of the 12 trials for plum and cherries
used a non-ionic antifoam.  Each trial consisted of one treated plot and
one control plot.  Following three broadcast applications of RELY at the
target rate of 1.50 lb ai/A/application residues of glufosinate ammonium
and N-acetylglufosinate in/on cherries and plum were not detected above
the LOQ (0.05 ppm). However, 3-methylphosphinico-propanoic acid was at
quantifiable levels in/on these commodities.  One trial of the six field
trials for cherries and for plum showed total residues above the LOQ.
For cherries, the highest average field trial (HAFT) was 0.083 ppm with
a maximum residue of 0.098 ppm. The HAFT for total glufosinate ammonium
residue was 0.183 ppm with a maximum residue of 0.198 ppm.  For plums,
the HAFT for 3-methylphosphinico-propanoic acid residue was 0.066 ppm
with a maximum residue of 0.066 ppm. The HAFT for total glufosinate
ammonium residue was 0.166 ppm with a maximum residue of 0.166 ppm.  Any
effect of the adjuvant (non-ionic antifoam) on the residue levels can
not be established with this data; however, the tolerance for stone
fruit commodities will be set based on the HAFT of the field trials with
residues above the LOQ.  Results from the residue decline study
performed on both crop types at five intervals corresponding to PHIs of
7, 11, 14, 17, and 21 days indicated that total glufosinate ammonium
residues in cherry and plum were found to below or close to the LOQ at
all PHIs; therefore, a trend was not observed.  

For peach, nine crop field trials were performed in the corresponding
regions according to OPPTS guidelines.  Each trial consisted of one
treated plot and one control plot.  No adjuvants were added to the
herbicide mixture.  Following two broadcast applications of RELY at the
target rate of 1.50 lb ai/A/application there were no apparent residues
of glufosinate ammonium, 3-methylphosphinico-propanoic acid and
N-acetylglufosinate detected above the LOQ (0.05 ppm) in/on peach
samples collected from the treated and untreated plots at a target PHI
of 14 days.  There were no residue decline studies performed for this
commodity but were performed for other stone fruits, plum and cherry.

For pear, six crop field trials were performed in the corresponding
regions according to OPPTS guidelines.  Each trial consisted of one
treated plot and one control plot.  In all trials, ammonium sulfate was
added to each tank mixture and applied at a rate of 3 lb/A.  Two sites
received a non-ionic antifoam adjuvant.  Following three broadcast
applications of RELY at the target rate of 1.50 lb ai/A/application
residues of glufosinate ammonium and N-acetylglufosinate in/on pear were
not detected above the LOQ (0.05 ppm). However,
3-methylphosphinico-propanoic acid was at quantifiable levels in one of
the six field trials. Any effect of the adjuvant (non-ionic antifoam) on
the residue levels can not be established with this data; however, the
tolerance for Pome Fruit crop group will be set based on the HAFT of the
field trials with residues above the LOQ. Results from the residue
decline study with five sampling intervals corresponding to PHIs of 7,
9, 14, 16, and 21 days indicated that residues of glufosinate ammonium,
glufosinate propanoic acid and N-acetylglufosinate were below the LOQ at
all PHIs. 

For olives, three crop field trials were performed in the corresponding
regions according to OPPTS guidelines.  Each trial consisted of one
treated plot and one control plot.  In all trials, ammonium sulfate was
added to each tank mixture and applied at a rate of 3 lb/A.  In two of
the trials, a non-ionic antifoam was also added to the tank mixture. 
Following three broadcast applications of RELY at the target rate of
1.50 lb ai/A/application there were no apparent residues of glufosinate
ammonium, 3-methylphosphinico-propanoic acid and N-acetylglufosinate
detected above the LOQ (0.05 ppm) in/on olive samples collected from the
treated and untreated plots at the PHI of 14 days.  No effect of the
adjuvant on the residue levels was observed since the residues were
below the method LOQ for applications with and without the non-ionic
antifoam.  There were no residue decline studies performed for this
commodity.

For sweet corn, twelve crop field trials were conducted in EPA regions
1, 3, 5, 10 and 11.  Two of the field trials in region five were
performed in the same location at Arlington, Wisconsin; therefore,
eleven field trials would represent the geographic diversity recommended
by HED.  Each trial consisted of one treated plot and one control plot. 
In all trials at region 5, ammonium sulfate was added to each tank
mixture.  Stover was dried for 5 to 13 days after harvest.   Following
two foliar applications of Liberty Herbicide at a rate of 0.375 lb ai/A
for a total rate of 0.75 lb ai/A (one trial received an overapplication
of 1.2 lb ai/A) with a retreatment interval (RTI) of 14-16 days and a
PHI of 30-50 days, HAFT residue values in/on sweet corn ears, forage and
stover were 0.06, 0.74 and 3.55 ppm for the glufosinate acid equivalent
from glufosinate ammonium and N-acetylglufosinate, 0.135, 0.14, and 0.49
ppm for glufosinate acid equivalent from glufosinate propanoic acid and
0.185, 0.79, and 3.72 ppm for total glufosinate acid, respectively.  No
residue decline data was collected.  

TABLE 6.  Summary of Residue Data from Crop Field Trials with
Glufosinate ammonium and its Two Metabolites.

Commodity	Total Applic. Rate (lb ai/A)

[kg ai/ha]	PHI (days)	Residue Levels1 (ppm)



	n	Min.	Max.	HAFT2	Median	Mean	Std. Dev.

Glufosinate ammonium

Orange	4.38 to 4.61

[4.91 to 5.16]	14	24	<0.05	<0.05	<0.05	NA	NA	NA

Lemon	4.50 to 4.53

[5.05 to 5.07]	14	10	<0.05	<0.05	<0.05	NA	NA	NA

Grapefruit	4.47 to 4.58

[5.01 to 5.14]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Pear	4.45 to 4.57

[4.99 to 5.12]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Cherry	3.00 to 3.11

[3.37 to 3.49]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Plum	2.92 to 3.03

[3.27 to 3.40]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Olive	4.50 to 4.52

[5.05 to 5.07]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Glufosinate propanoic acid

Orange	4.38 to 4.61

[4.91 to 5.16]	14	24	<0.05	<0.05	<0.05	NA	NA	NA

Lemon	4.50 to 4.53

[5.05 to 5.07]	14	10	<0.05	<0.05	<0.05	NA	NA	NA

Grapefruit	4.47 to 4.58

[5.01 to 5.14]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Pear	4.45 to 4.57

[4.99 to 5.12]	14	12	<0.05	0.089	0.081	0.05	0.053	0.007

Cherry	3.00 to 3.11

[3.37 to 3.49]	14	12	<0.05	0.098	0.083	0.05	0.056	0.013

Plum	2.92 to 3.03

[3.27 to 3.40]	14	12	<0.05	0.066	0.066	0.05	0.053	0.007

Olive	4.50 to 4.52

[5.05 to 5.07]	14	12	<0.05	<0.05	<0.05	NA	NA	NA



TABLE 6.  Summary of Residue Data from Crop Field Trials with
Glufosinate ammonium and its Two Metabolites.

Commodity	Total Applic. Rate (lb ai/A)

[kg ai/ha]	PHI (days)	Residue Levels1 (ppm)



	n	Min.	Max.	HAFT2	Median	Mean	Std. Dev.

N-Acetylglufosinate

Orange	4.38 to 4.61

[4.91 to 5.16]	14	24	<0.05	<0.05	<0.05	NA	NA	NA

Lemon	4.50 to 4.53

[5.05 to 5.07]	14	10	<0.05	<0.05	<0.05	NA	NA	NA

Grapefruit	4.47 to 4.58

[5.01 to 5.14]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Pear	4.45 to 4.57

[4.99 to 5.12]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Cherry	3.00 to 3.11

[3.37 to 3.49]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Plum	2.92 to 3.03

[3.27 to 3.40]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Olive	4.50 to 4.52

[5.05 to 5.07]]	14	12	<0.05	<0.05	<0.05	NA	NA	NA

Total Glufosinate ammonium

Orange	4.38 to 4.61

[4.91 to 5.16]	14	24	<0.15	<0.15	<0.15	NA	NA	NA

Lemon	4.50 to 4.53

[5.05 to 5.07]	14	10	<0.15	<0.15	<0.15	NA	NA	NA

Grapefruit	4.47 to 4.58

[5.01 to 5.14]	14	12	<0.15	<0.15	<0.15	NA	NA	NA

Pear	4.45 to 4.57

[4.99 to 5.12]	14	12	<0.15	0.189	0.181	0.15	0.155	0.013

Cherry	3.00 to 3.11

[3.37 to 3.49]	14	12	<0.15	0.198	0.183	0.15	0.156	0.013

Plum	2.92 to 3.03

[3.27 to 3.40]	14	12	<0.15	0.166	0.166	0.15	0.153	0.007

Olive	4.50 to 4.52

[5.05 to 5.07]	14	12	<0.15	<0.15	<0.15	NA	NA	NA



TABLE 7.  Summary of Residue Data from Crop Field Trials with
Glufosinate ammonium in/on Sweet Corn

Commodity	Total Applic. Rate (lb ai/A)	PHI (days)	Residue Levels1 (ppm)



	n	Min.	Max.	HAFT2	Median	Mean	Std. Dev.

Glufosinate ammonium and N-Acetylglufosinate

Sweet Corn, Ears	0.75	30-50	24	<0.05	0.06*	0.06	0.05	0.513	0.003

Sweet Corn, Forage	0.75	30-50	24	0.08	0.74*	0.74	0.19	0.32	0.23

Sweet Corn, Stover	0.75	30-50	24	0.33	3.55*	3.55	1.12	1.20	1.12

Glufosinate propanoic acid

Sweet Corn, Ears	0.75	30-50	24	<0.05	0.135*	0.135	0.05	0.06	0.03

Sweet Corn, Forage	0.75	30-50	24	<0.05	0.14*	0.14	0.05	0.06	0.03

Sweet Corn, Stover	0.75	30-50	24	<0.05	0.49*	0.49	0.09	0.12	0.09

Total Glufosinate

Sweet Corn, Ears	0.75	30-50	24	0.10*	0.19*	0.19*	0.10	0.11	0.02

Sweet Corn, Forage	0.75	30-50	24	0.18*	0.79*	0.79*	0.28	0.44	0.23

Sweet Corn, Stover	0.75	30-50	24	0.16*	3.7*	3.7*	1.43	1.16	1.05

*The average residue of each analyte in each field trial were added and
the total residue value of each trial was used to select the maximum and
minimum values.  In a similar way the HAFT was selected from the sum of
the average values of each analyte from each field trial.  In the study
provided, the residues from each field trial were reported in pairs;
therefore, is not possible to identify the residue from each one of the
duplicate samples analyzed in each field trial. 

Conclusions.  The number and location of field trials for orange, lemon,
grapefruit, pear, cherry, plum and olive comply with the requirements of
OPPTS 860.1500 guideline.  The data are adequate to establish tolerances
for these RACs.  The residue decline studies in all the commodities
tested showed that residues were below or close (for plum) to the LOQ at
all PHIs; therefore, residues are not expected to be higher at longer
PHIs than those established for the RACs under this petition.

860.1520 Processed Food and Feed

Processing studies were performed for orange, plum and olive
commodities.  Detailed reviews concerning the processing studies
submitted in support of the current petitions can be found in the
following reviews:  orange (47915706.der.wpd), plum (47915707.der.wpd)
and olive (47915708.der.wpd).  A summary of the results obtained is
summarized in Table 8.

Oranges were treated with three applications of RELY herbicide at 7.5
lbs ai/A (14-day RTI; 22.73 lbs ai/A total; 5x the maximum proposed
seasonal application rate).  Oranges were harvested 14 days after the
last application and processed into dried pulp, oil, juice
(pasteurized), peels, and peeled fruit.  However, only the orange RAC
and orange oil (the processed commodity with the highest theoretical
processing factor) were analyzed for residues of glufosinate ammonium,
N-acetyl-glufosinate and glufosinate propanoic acid.  After using
exaggerated rates, the residues in the orange RAC were below the method
LOQ.  Under this condition tolerances and processing studies are not
required with the exception of those for commodities with very high
processing factors, citrus oil (1000x) and mint oil (330x).  The orange
oil processed commodity resulted in combined residues of glufosinate
ammonium, N-acetyl-glufosinate and glufosinate propanoic acid below the
method LOQ; therefore, these didn’t concentrated in orange oil (1x). 
Orange juice and orange dried pulp were prepared by the registrant but
not analyzed.  Based on the guidelines, the analysis of these processed
commodities is not required when the residues are below LOQ in the RAC
after applying 5x exaggerated rates.  

Plums were treated with two applications of RELY herbicide at 7.5 lbs
ai/A (28-day RTI; 15 lbs ai/A total; 5x the maximum proposed seasonal
application rate).  Plums were harvested 14 days after the last
application and processed into prunes.  Plums and prunes were analyzed
for residues of glufosinate ammonium, N-acetyl-glufosinate and
glufosinate propanoic acid.  Only residue levels of glufosinate
propanoic acid were above the method LOQ in the plums and prunes
samples.  The total average residue level in the prune samples was 0.433
ppm.  After correction for the exaggerated application rate (5x) the
residue level (0.0866 ppm) will be below the method total LOQ (0.15
ppm); therefore, no tolerance is required for the prune RAC.  However, a
processing factor of 1.8x can be set for the prunes RAC by assuming that
glufosinate ammonium, N-acetyl-glufosinate and glufosinate propanoic
acid are at LOQ levels when these were not detected.  This processing
factor is below the theoretical concentration factor of 3.4x which is
based on loss of water.  

Olives were treated with three applications of RELY herbicide at 7.5 lbs
ai/A (14-day RTI; 22.5 lbs ai/A total; 5x the maximum proposed seasonal
application rate).  Olives were harvested 14 days after the last
application and processed into olive oil.  Samples of olives and olive
oil were analyzed for residues of glufosinate ammonium,
N-acetyl-glufosinate and glufosinate propanoic acid.  Only residue
levels of glufosinate propanoic acid were above the method LOQ in the
olive samples.  The total average residue level in the olive oil sample
was below the method LOQ; therefore, no tolerance is required for the
olives RAC.  However, a processing factor of 0.6x can be set for the
olives by assuming that glufosinate ammonium, N-acetyl-glufosinate and
glufosinate propanoic acid are at LOQ levels when these were not
detected.   This processing factor is below the theoretical
concentration factor of 108x which is based on separation of components.
 

The orange, prunes and olive oil processing studies will be considered
adequate at this time but for future studies the registrant is
recommended to analyze the washed RAC if this is washed during the
processing studies.  The current practice of using the unwashed RAC
residue levels may result in a sub estimation of the processing factor.

TABLE 8.	Residue Data from Orange, Plum and Olive Processing Study with
Glufosinate Ammonium.

Trial: City, State; Year (Trial ID#)	Processed Commodity	Total Rate

(lb ai/A) 	PHI 

≤1x	<LOD	≤1x	<LOD	≤1x	<0.15	≤1x

Live Oak, CA; 2008 (GL025-08PA)	Plum RAC (unwashed)	15.0	14	0.0704, 

<LOQ (0.0229), <LOD

Avg. <LOQ 	--	0.142, 

0.126,

 0.131

Avg. 0.13	--	<LOQ (0.0358), <LOD, 

<LOD 

Avg. <LOQ 	--	0.262

0.226

0.231

Avg. 0.240	--

	Prune

	<LOD, 

<LOD,

<LOD

Avg. <LOD	<1.0X	0.393, 

0.344, 

0.263

Avg. 0.33	2.5X	<LOD, 

<LOD,

<LOD

Avg. <LOD	<1.0X	0.493

0.444

0.363

Avg. 0.433	1.8X

Corning, CA; 2008 (GL047-08PA)	Olive RAC	22.5	14	<LOD, <LOD, <LOD

Avg. <LOD	--	0.132, 

0.142, 

0.134

Avg. 0.136	--	<LOD, <LOD, <LOD

Avg. <LOD	--	0.232

0.242

0.234

Avg. 0.236 	--

	Olive Oil

	<LOD, <LOD, <LOD

Avg. <LOD	<1.0x	<LOD, <LOD, <LOD

Avg. <LOD	<0.2x	<LOD, <LOD, <LOD

Avg. <LOD	<1.0x	<LOD, <LOD, <LOD

Avg. <LOD	<0.6x

1  LOQ = 0.05 ppm for glufosinate ammonium, Glu-PPA and Glu-NAG. 
Residues in parenthesis are values between the LOD and LOQ. 

2  The processing factor was calculated by dividing the residues in the
processed sample by the residues in the unprocessed RAC sample.  Values
<LOQ and <LOD were assigned a value of the LOQ (0.05 ppm) for
calculations. 

3 The total glufosinate ammonium residue is the sum of the individual
measured residue for the analytes of glufosinate ammonium, Glu-NAG and
Glu-PPA.  Values <LOQ and <LOD were assigned a value of the LOQ (0.05
ppm) for calculations.

Conclusions: The processed commodities required under OPPTS 860.1520
guidelines for the corresponding RACs were prepared and analyzed.  These
studies are considered acceptable.  However, the petitioner is advised
to wash the RAC before analysis if it will be washed during processing.

860.1850 / 860.1900 Confined / Field Accumulation in Rotational Crops

D271110, T. Bloem, 20/June/2002

A confined rotational crop study has been submitted and reviewed
(D211531 and D219069, M. Rodriquez, 7-Mar-1996).  Lettuce, radish, and
spring wheat were planted 28 and 119 days after the soil was treated
with [3,4-14C]-HOE-039866 at 0.9 lbs ai/acre (1.2x the maximum proposed
application rate for sweet corn).  All samples planted 28 days after
treatment were analyzed.  HOE 061517 (5-57% TRR) and HOE 064619 (6-10%
TRR) were the only compounds identified (a total of 32-64% of the TRR
was identified).  Except for the wheat commodities, TRRs were (0.02 ppm
for the samples planted 120 days after treatment (wheat commodities
0.06-0.15 ppm).  

A wheat field rotational crop study has also been submitted and reviewed
(P. Errico [RD], 6-May-1998). Wheat was planted 73 - 90 days after the
soil was treated with glufosinate ammonium at 0.8 lbs ai/acre (1.2x the
maximum proposed application rate for sweet corn).  Wheat forage, hay,
straw, and grain were harvested at maturity and analyzed for residues of
glufosinate ammonium and HOE 061517 (residues were < LOQ; LOQ = 0.05
ppm).       

Based on the confined and field rotational crop studies, the MARC
determined that the residues of concern in rotational crops, for
tolerance expression and risk assessment purposes, are glufosinate
ammonium, HOE 061517, and HOE 064619 (D282757, T. Bloem, 9-May-2002). 
The Liberty Herbicide label indicates that plant rotation to other crops
after treatment of sweet corn can occur with a Plant Back Interval (PBI)
of 120 days with the exception of wheat, barely, buckwheat, millet,
oats, rye sorghum, and triticale for which a PBI of 70 days is allowed. 
Based on the results from the confined and field rotational studies, HED
concludes that the proposed rotational crop restrictions are appropriate
for sweet corn.  

  SEQ CHAPTER \h \r 1 860.1650 Submittal of Analytical Reference
Standards

Analytical standards for the herbicide glufosinate ammonium,
N-acetylglufosinate and 3-methylphosphinico-propanoic acid are to be
kept available in the EPA National Pesticide Standards Repository. 
These analytical reference standards must be replenished as requested by
the Repository.  If requested, reference standards should be sent to the
Analytical Chemistry Laboratory located in Fort Meade to the attention
of either Theresa Cole at the following address:

	U.S. EPA

	National Pesticide Standards Repository/ Analytical Chemistry
Branch/OPP

	701 Mapes Road

	Fort George G. Meade, MD 20755-5350

Please note that mail will be returned if the entire extended zip code
is not used when addressing correspondence to the Repository. 

860.1550 Proposed Tolerances

  SEQ CHAPTER \h \r 1 Glufosinate ammonium tolerances are established
under 40 CFR §180.473 and are currently expressed in terms of
glufosinate ammonium and two of its metabolites.  On 27-MAY-2009 HED
established interim guidance on writing tolerance expressions for
enforcement purposes.  In order to add clarity to the language used to
establish the coverage of the tolerance expression and measurement of
the level of the residue in the RACs the text in the 40 CFR § 180.533
should read:  “(a) General. (1) Tolerances are established for
residues of glufosinate ammonium, 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 glufosinate ammonium (butanoic acid,
2-amino-4-(hydroxymethylphosphinyl)-monoammonium salt) and its
metabolites, 2-acetamido-4-methylphosphinico-butanoic acid and
glufosinate propanoic acid, expressed as
2-amino-4-(hydroxymethylphosphinyl)butanoic acid equivalents.”

The residue values obtained in the A summary of the recommended
tolerances for the crop commodities discussed in this Summary Document
is presented in Table 9.

Table 9.   Tolerance Summary for Glufosinate Ammonium.

Commodity	Current §180.533

Tolerance (ppm)	Proposed 

Tolerance (ppm)	Recommended §180.533

Tolerance (ppm)	Comments

Citrus (CG 10)	None	0.05	0.15	Fruit, citrus, group 10*

Pome Fruit (CG 11)	None	0.10	0.25	Fruit, pome, group 11*

Stone Fruit (CG 12)	None	0.10	0.25	Fruit, stone, group 12

Olives	None	0.05	0.15

	Corn, sweet, kernels plus cob with husks removed	None	0.2	0.25

	Corn, sweet, forage	None	4.0	1.6

	Corn, sweet, stover	None	6.0	10

	Plum, prune, dried	None	0.20	N/A	Covered by the Stone Fruit tolerance.

* Or Group 10-10 and Group 11-10 when these new crop groups are
officially established.

The NAFTA calculator was used to establish the tolerance for sweet corn
forage and stover.  The maximum residues from each field trial location
were selected from each analyte and then summed to obtain the total
residue value used to establish the tolerance.  A lognormal distribution
was assumed and the 95/99 rule was used to calculate the tolerance for
sweet corn forage and the UPL median 95 method for sweet corn stover. 
The latter method is used as an alternative to the 95/99 rule when the
standard deviation of the field trials is high.  For the remaining
commodities the tolerance was estimated based on the HAFT.  

The Codex Alimentarius Commission has not established maximum residue
limits (MRLs) for glufosinate ammonium in/on olives and sweet corn
commodities.  However, for glufosinate ammonium in/on Citrus, Pome Fruit
and Stone Fruit the Codex have set a MRL of 0.1, 0.05, and 0.05 ppm,
respectively.  The US tolerance for Citrus, Pome Fruit and Stone Fruit,
is 0.15, 0.25 and 0.25 ppm, respectively.  The US tolerance values for
these commodities is higher than the Codex MRL; therefore, harmonization
of the US tolerances with the Codex MRLs is not possible with this
petition, see Attachment 1.  There are no MRLs established in Mexico or
Canada for the use of glufosinate ammonium on the commodities under the
current petition.

References

Tom Bloem, Glufosinate Ammonium (PC Code: 128850). Label Amendment for
Pre-Plant Application of Glufosinate Ammonium to Transgenic and
Non-transgenic Field Corn, Non-transgenic Canola, and Non-transgenic
Soybean. Residue Chemistry Summary., D335330, 09/12/2007.

Tom Bloem, Glufosinate Ammonium (PC Code 128850). Section 3
Registrations for Transgenic Cotton (ID# - 0F06140), Transgenic Rice
(ID# - 0F06210), and Bushberry (ID# - 2E06404). Summary of Analytical
Chemistry and Residue Data., D271110, 20/June/2002.

M. Rodriguez, PP5G4466 & PP5F4578: Glufosinate-ammonium in/on Transgenic
Corn and Soybeans. Experimental Use Permit, Temporary Tolerance and
Permanent Tolerance Petitions. Evaluation of Analytical Method and
Residue Data., D219069 and D211531, 03/07/1996.

  SEQ CHAPTER \h \r 1 Attachments

Attachment 1:  International Residue Limit Status 

Attachment 2:  NAFTA Calculator Results 



Attachment 1: International Residue Limit Status 

Glufosinate Ammonium (PC Code 128850; Aug 10, 2010)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition: 

US	Canada	Mexico2	Codex3

40 CFR 180.473

Plant and Livestock: glufosinate ammonium (butanoic acid,
2-amino-4-(hydroxymethylphosphinyl)-monoammonium salt) and its
metabolites, 2-acetamido-4-methylphosphinico-butanoic acid and
3-methylphosphinico-propionic acid, expressed as
2-amino-4-(hydroxymethylphosphinyl)butanoic acid equivalents
ammonium(±)-2-amino-4-(hydroxymethylphosphinyl)butanoate, including the
metabolite propanoic acid, 3-(hydroxymethylphosphinyl)

Sum of glufosinate-ammonium, 3-[hydroxy(methyl)phosphinoyl]propionic
acid and N-acetyl-glufosinate, calculated as glufosinate (free acid).

Commodity1	Tolerance (ppm) /Maximum Residue Limit (mg/kg)

	US	Canada	Mexico2	Codex

Citrus (CG10)	0.15*

	Citrus fruits 0.1

Pome Fruit (CG 11)	0.25

	Pome fruits 0.05 (*)

Stone Fruit (CG 12)	0.25

	Stone fruits 0.05 ( *)

Olives	0.15*



	Corn, Sweet, Ears	0.25



	Corn, Sweet, Forage	1.6



	Corn, Sweet, Stover	10



























	Completed:  M. Negussie; 08/10/2010

1 Includes only commodities of interest for this action.  Tolerance
values should be the HED recommendations and not those proposed by the
applicant.

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.

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* = absent at the limit of quantitation; Po = postharvest treatment,
such as treatment of stored grains.  PoP = processed postharvest treated
commodity, such as processing of treated stored wheat. (fat) = to be
measured on the fat portion of the sample. MRLs indicated as proposed
have not been finalized by the CCPR and the CAC.

Attachment 2.1: NAFTA Calculator Results for Sweet Corn Forage

Attachment 2.2:  NAFTA Calculator Results for Sweet Corn Stover

Page   PAGE  1  of   NUMPAGES  26 

Glufosinate Ammonium	Summary of Analytical Chemistry and Residue Data
D372625 

