Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

MEMORANDUM

Date: 06/28/2012

SUBJECT: Halosulfuron-methyl. Application for Section 3 Registration of Yukon Herbicide

(EPA Reg. No. 81880-6), Sandea Herbicide (EPA Reg. No. 81880-18), and 

GWN-3061 Herbicide (EPA Reg. No. 81880-2) to Add New Uses on Proso Millet 

and Pasture and Rangeland Grasses. Summary of Analytical Chemistry and 

Residue Data.

PC Code: 128721 DP Barcode: D393948

Decision No.: 453868 Registration Nos.: 81880-2, 81880-6, 81880-18

Petition No.: 1F7916 Regulatory Action: Section 3 Registration

Risk Assessment Type: NA Case No.: NA

TXR No.: NA CAS No.: 100784-20-1

MRID Nos.: 48583601 and 48583602 40 CFR: §180.479

FROM: Meheret Negussie, Chemist

Risk Assessment Branch III

Health Effects Division (HED) (7509P)

THROUGH: Leung Cheng, Senior Chemist

Risk Assessment Branch III

Health Effects Division (HED) (7509P)

TO: Kable Davis/Maggie Rudick RM 25

Herbicide Branch

Registration Division (7505P)

Note: This document was originally prepared under contract by Versar, Inc. (6850 Versar Center, Springfield, VA 22151; 

submitted 3/30/12). The document has been reviewed by the Health Effects Division (HED) and revised to reflect current Office 

of Pesticide Programs (OPP) policies.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Executive Summary

Halosulfuron-methyl is a selective herbicide belonging to the sulfonylurea group of herbicides. 

Its mode of action includes the inhibition of a specific plant enzyme, acetolacetate synthase. 

Halosulfuron-methyl is registered for the pre- and postemergence control of annual broadleaf 

weeds and nutsedges in selected crops, as well as residential turf grass and ornamentals. 

Halosulfuron-methyl is sold in the U.S. as a dry flowable/water-dispersible granule formulation.

The petitioner, Canyon Group LLC (agent Gowan Company) has submitted a request for 

amended registration of a 12.5% water dispersible granule (WG) formulation of halosulfuronmethyl (Yukon Herbicide; EPA Reg. No. 81880-6; MAI containing 55% dicamba) and two 75% 

WG formulations (Sandea Herbicide, EPA Reg. No. 81880-18, and GWN-3061, EPA Reg. No. 

81880-2) for use on proso millet and pasture and rangeland grasses. The proposed uses reflect

foliar broadcast application to proso millet at 0.023-0.0313 lb ai/A or to pasture and rangeland 

grasses at 0.0313-0.0625 lb ai/A. The proposed preharvest intervals (PHIs) are 0 days and 7 or 

14 days for forage and 37 days for hay (both crops); no PHI has been proposed for millet grain 

and straw.

In conjunction with the proposed uses, Canyon Group has requested the establishment of 

tolerances for the herbicide halosulfuron-methyl in/on the following commodities:

Millet, proso, forage........................................................... 7.0 ppm

Millet, proso, hay ............................................................... 0.02 ppm

Millet, proso, grain............................................................. 0.01 ppm

Millet, proso, straw ............................................................ 0.01 ppm

Grass forage, fodder, and hay, Crop group 17 forage.... 17.0 ppm

Grass forage, fodder, and hay, Crop group 17 hay...... 0.90 ppm

There are a number of discrepancies in the directions for use for this action. For millet forage, there 

is a discrepancy between the PHIs/pregrazing intervals (PGIs) for forage specified on the submitted 

draft labels (0 days for non-lactating animals and 7 days for lactating animals) and that which 

appears in the petition under Reasonable Grounds in Support of Petition (7 days for all animals). 

The available residue data will support PHIs/PGIs of 0 and/or 7 days. In addition, a PHI must be 

proposed for millet grain and straw. For grass, the use pattern for forage must be amended to specify 

a 0-day PGI for all animals. Finally, the labels specify a 30-day preslaughter interval (PSI) for both 

crops which must be removed because HED has previously concluded that a PSI of this length is not 

practical for pesticides.

Permanent tolerances are established under §180.479(a)(1) for residues of halosulfuron-methyl 

including its metabolites and degradates in livestock commodities to be determined by measuring 

only those halosulfuron-methyl residues containing the 3-chlorosulfonamide (3-CSA) moiety,

expressed as halosulfuron-methyl equivalents, for the meat byproducts of cattle, goat, hog, horse, 

and sheep at 0.1 ppm. Tolerances are established for a variety of field, fruit, and vegetable crop 

commodities under §180.479(a)(2) for residues to be determined by measuring only 

halosulfuron-methyl, at levels ranging from 0.05 to 2.0 ppm. 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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The nature of the residue in plants is adequately understood based on acceptable metabolism 

studies with corn, sugarcane, and soybean treated both pre- and postemergence. The terminal 

residue of concern in plants is halosulfuron-methyl.

The nature of the residue in ruminants and poultry is adequately understood based on acceptable 

goat and hen metabolism studies. The residue of concern in ruminants and poultry is 

halosulfuron-methyl. However, because the approved enforcement method for livestock 

commodities quantifies the parent compound and metabolites containing the 3-CSA by 

converting residues to 3-CSA, tolerances for residues in livestock commodities are expressed in 

terms of halosulfuron-methyl and its metabolites determined as 3-CSA, expressed as 

halosulfuron-methyl equivalents. 

Adequate analytical methods are available for the enforcement of tolerances for residues of 

halosulfuron-methyl in plants (Method RES-109-97-4), and for residues of halosulfuron-methyl 

and its 3-CSA metabolites in livestock commodities (Method RES-046-93). Samples from the 

submitted field trial studies were analyzed for residues of halosulfuron-methyl using a modified 

version of the plant enforcement method (gas chromatography with nitrogen phosphorus or mass 

selective detection; GC/NPD or GC/MSD) with a petitioner-validated limit of quantitation 

(LOQ; determined as the lowest level of method validation; LLMV) of 0.01 ppm. The method 

was adequate for data collection based on acceptable concurrent method recoveries, and the 

fortification levels used in concurrent method recovery were adequate to bracket expected 

residue levels.

Residues of halosulfuron-methyl and 3-CSA are not adequately recovered by FDA Multiresidue 

Method protocols.

Adequate storage stability data are available to support the storage conditions and durations of 

samples collected from the submitted crop field trials on proso millet and grass. As residues of 

halosulfuron-methyl were found to be stable in tested crop matrices, storage stability corrections 

need not be applied.

There are animal feedstuffs associated with the proposed uses on proso millet and grasses. An 

acceptable feeding study was previously submitted reflecting dosing of lactating dairy cows with 

halosulfuron-methyl at 0.5, 1.5, and 5 ppm in the daily diet on a dry weight basis. In the study, 

no quantifiable residues (<0.01 ppm) were found in milk, muscle, or fat at any feeding level; 

quantifiable residues were found in liver and kidney at all feeding levels. With the recalculated 

dietary burden for dairy cattle (from 0.825 ppm to 20 ppm), the dose rates in the feeding study 

correspond to ~0.025x, ~0.075x, and ~0.25x the current maximum reasonable dietary burden 

(MRBD). Based on extrapolation from the highest concentration level (5 ppm) of the feeding 

study with residues at the LOQ (0.01 ppm) in milk, muscle, and fat, HED has concluded that 

tolerances at 0.05 ppm can be established for residues of halosulfuron-methyl in the milk, muscle 

and fat of cattle, goats, horses, and sheep based on the reasons stated in the ChemSAC minutes 

(ChemSAC 06/20/2012). The petitioner must propose a tolerance of 0.05 ppm for these 

livestock commodities. For future new uses that increase the dietary burden above 20 ppm, a 

new feeding study will be needed reflecting dosing at 1x, 3x, and 10x the maximum reasonable 

dietary burden (MRDB). 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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The available data for liver and kidney are sufficient to assess the existing tolerances for meat 

byproducts. The data indicate that the established tolerances of 0.1 ppm for the meat byproducts 

of cattle, goat, horse, and sheep are too low and should be increased to 1.0 ppm. No change is 

needed for the established tolerance of 0.1 ppm for hog meat byproducts, and tolerances for 

halosulfuron-methyl residues in poultry commodities are not required due to low use rates, low 

residues of halosulfuron-methyl in poultry feed items, and the low transfer rate of residues to 

poultry tissues.

Acceptable crop field trial data have been submitted on proso millet. The trials reflect a single 

foliar broadcast application of a WG formulation at a target application rate of 0.0313 lb ai/A; a

non-ionic surfactant (NIS) was used in all trials. Residues in/on proso millet hay, grain, and 

straw were below the LOQ. The available data will support tolerances at the LOQ of 0.01 ppm 

for these commodities, provided the petitioner proposes a PHI of 50 days for grain and straw. 

Quantifiable residues were observed in/on forage harvested at 0- and 7-day PHIs. The data will 

support a tolerance of 10 ppm for millet forage with a 0-day PHI.

Acceptable crop field trial data have been submitted on pasture and rangeland grasses. The trials 

reflect a single foliar broadcast application of a WG formulation of halosulfuron-methyl at a 

target application rate of 0.0625 lb ai/A; an NIS was used in all trials. The data will support 

tolerances of 20 ppm for forage (based on a 0-day PGI) and 0.50 ppm for hay. 

Differences in proposed and recommended tolerances may be attributed to the petitioner having 

used the NAFTA tolerance calculation procedures for determining the tolerance and HED’s 

having used the OECD tolerance calculation procedures; for grass hay, the petitioner used values 

below the LOQ in the tolerance calculation.

Adequate confined and limited field rotational crop data are available. HED previously 

concluded that the residue of concern in rotational crops is halosulfuron-methyl. Based on the 

absence of the parent compound in the confined studies and in the limited field rotational crop 

studies, with the exception of one forage sample, HED previously concluded that rotational crop 

tolerances and restrictions are not required for halosulfuron-methyl.

There are no Codex, Canadian, or Mexican maximum residue limits (MRLs) established for 

residues of halosulfuron-methyl in crop or livestock commodities.

Regulatory Recommendations and Residue Chemistry Deficiencies

HED has examined the residue chemistry database for halosulfuron-methyl and evaluated the 

adequacy of study submissions associated with the current action. Pending submission of a 

revised Section B, a revised Section F, and an analytical standard for the Rearrangement ester 

(RRE) of halosulfuron-methyl, there are no residue chemistry data gaps that would preclude 

granting unconditional registration for the requested use of halosulfuron-methyl on proso millet 

and pasture and rangeland grasses. The proposed uses and the submitted data support the 

following tolerances for residues of halosulfuron-methyl in/on the following commodities:

Millet, proso, forage ................................................................................10 ppm

Millet, proso, hay..................................................................................0.01 ppm
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Millet, proso, grain ..............................................................................0.01 ppm

Millet, proso, straw ..............................................................................0.01 ppm

Grass, forage, fodder, and hay, group 17, forage ....................................20 ppm

Grass, forage, fodder, and hay, group 17, hay........................................0.5 ppm

The proposed uses necessitates the establishment of tolerances as follow:

Cattle, fat ..............................................................................................0.05 ppm

Cattle, meat...........................................................................................0.05 ppm

Goat, fat................................................................................................0.05 ppm

Goat, meat ............................................................................................0.05 ppm

Horse, fat ..............................................................................................0.05 ppm

Horse, meat...........................................................................................0.05 ppm

Milk ......................................................................................................0.05 ppm

Sheep, fat..............................................................................................0.05 ppm

Sheep, meat ..........................................................................................0.05 ppm

The proposed requested use on proso millet and grasses necessitates the revision of existing 

tolerances for halosulfuron-methyl residues containing 3-CSA in/on livestock commodities as 

follow:

Cattle, meat byproducts..........................................................................1.0 ppm

Goat, meat byproducts............................................................................1.0 ppm

Horse, meat byproducts..........................................................................1.0 ppm

Sheep, meat byproducts..........................................................................1.0 ppm

A human health risk assessment is forthcoming. 

860.1200 Directions for Use

The following label revisions are needed:

For all labels, the preharvest interval (PHI) and pregrazing interval (PGI) for millet forage 

should be revised to 0-day PHI.

All labels should be revised to:

o Specify a 37-day PHI for proso millet hay and a 50-day PHI for proso millet grain 

and straw.

o Specify a 0-day PGI for grass forage for all animals (beef, lactating and nonlactating).

o Because crop oil concentrates (COC) were not used in any of the submitted crop 

field trials on proso millet or grass, the labels for the 12.5% and 75% WG 

formulations should be revised to state that only non-ionic surfactants (NIS) 

adjuvants may be added to the spray mixtures for these crops. 

o Remove the recommended 30-day pre-slaughter interval (PSI).
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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860.1550 Proposed Tolerances

The petitioner should submit a revised Section F reflecting the recommended tolerances 

and commodity definitions presented in Table 10.

860.1650 Submittal of Analytical Reference Standards

An analytical reference standard for the RRE of halosulfuron-methyl must be submitted 

to the EPA National Pesticide Standards Repository.

Background

The chemical structures and nomenclatures of halosulfuron-methyl and the 3-CSA moiety are 

presented in Table 1. The physicochemical properties of the technical grade of halosulfuronmethyl are presented in Table 2.

Table 1. Halosulfuron-methyl Nomenclature.

Chemical structure

N

N

CH3

Cl

N

N N

H

N

H

O

S

O

O

O

CH3

O

CH3

O

O

CH3

Common name halosulfuron-methyl

Company experimental name MON 12000, NC-319

IUPAC name methyl 3-chloro-5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-

methylpyrazole-4-carboxylate

CAS name methyl 3-chloro-5-[[[[(4,6-dimethoxy-2-

pyrimidinyl)amino]carbonyl]amino]sulfonyl]-1-methyl-1H-pyrazole-4-carboxylate

CAS registry number 100784-20-1

End-use product (EP) 12.5% WG (Yukon Herbicide; EPA Reg. No. 81880-6; MAI containing 55% 

dicamba)

75% WG (Sandea Herbicide; EPA Reg. No. 81880-18)

75% WG (GWN-3061; EPA Reg. No. 81880-2)

Chemical structure of

3-chlorosulfonamide moiety 

(3-CSA)

N

N

CH3

Cl

NH2

S

O

O

OH

O

3-chloro-1-methyl-5-sulfamoyl-1H-pyrazole-4-carboxylic acid
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Table 2. Physicochemical Properties of Halosulfuron-methyl.

Parameter Value Reference

Melting range 175.5-177.2oC MRID 42139403; DP#s 

173627 & 180565, 7/30/92, 

G.J. Herndon

pH 4.11 at 25oC (1% w/v slurry)

Density 1.618 g/mL at 25oC

Water solubility at 20oC pH 5 0.0015 g/100 mL

pH 7 0.165 g/100 mL

pH 9 0.747 g/100 mL

Solvent solubility at 20oC methanol 0.1616 g/100 mL

n-hexane 0.001278 g/100 mL

Vapor pressure <1 x 10-7 mm Hg at 25oC

Dissociation constant, Ka 3.61 x 10-4at 22.4oC

Octanol/water partition coefficient, 

Log(KOW) at 23oC

1.67 at pH 5

-0.0186 at pH 7

-0.542 at pH 9

UV/visible absorption spectrum Not available

860.1200 Directions for Use

In support of the proposed uses on proso millet and pasture and rangeland grasses, Canyon Group 

has submitted draft labels for the following end-use products: a 12.5% WG formulation (Yukon 

Herbicide; EPA Reg. No. 81880-6; MAI containing 55% dicamba); and two 75% WG 

formulations (Sandea Herbicide, EPA Reg. No. 81880-18, and GWN-3061, EPA Reg. No. 

81880-2). In addition, the proposed use patterns are summarized in the petition materials under 

“Residue Chemistry including Reasonable Grounds in Support of Petition.”

The proposed use pattern information is presented in Table 3. HED notes that there are 

discrepancies between the PHIs/PGIs specified on different labels and summarized in the petition 

materials.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Table 3. Summary of Directions for Use of Halosulfuron-methyl.

Applic. Timing, 

Type, and 

Equip.

Formulation

[EPA

Reg. No.]

Applic. 

Rate

oz/A

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. 

Seasonal 

Applic. 

Rate

oz/A

(lb ai/A)

PHI/PGI1

(Days)

Use Directions and Limitations2

Proso Millet

Post weed 

emergence and 

actively growing 

weeds;

Foliar,

Broadcast,

Ground or 

aerial;

12.5% WG

[81880-6]

3-4 oz/A 

(0.0234-

0.0313)

Not 

specified 

(NS)

4 oz/A 

(0.0313)

Forage

Beef & nonlactating:

0

Lactating 

dairy:

7

Hay

37

Apply at the 3- to 5-leaf stage. 

A PSI of 30 days is specified 

for beef and non-lactating 

animals.

Master Label:

Apply in minimum spray 

volumes of 5 - 15 gal/A (GPA)

by air or 10 GPA by ground.

Do not apply through any type 

of irrigation system. 

Avoid disturbing (cultivation) 

treated areas for at least 7-days 

following application.

A non-ionic surfactant is 

required at 0.25 to 0.5% v/v or 

a crop oil concentrate may be 

used instead at 1% v/v.

Post weed 

emergence and 

actively growing

weeds;

Foliar,

Broadcast,

ground or band 

application, 

aerial

75% WG

[81880-18]

0.5-0.67 

(0.0234-

0.0313)

NS 0.67

(0.0313)

0 Apply at the 2-leaf through 

layby stage (before grain head 

emergence).

Master Label:

Ground (min. 15 gal/A) or 

aerial (3-15 gal/A).

Do not apply using air assisted 

(air blast) field crop sprayers.

Do not apply through any type 

of irrigation system. 

Do not apply more than 2 oz/A 

per 12 month period (includes 

applications to the crop and to 

row middles/furrows).

A non-ionic surfactant is 

recommended at 0.25 to 0.5% 

v/v or a crop oil concentrate at 

1% v/v.

Use of a COC or silicone-based 

adjuvants can result in crop 

injury and reduced yields and 

are not recommended for 

postemergence.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Table 3. Summary of Directions for Use of Halosulfuron-methyl.

Applic. Timing, 

Type, and 

Equip.

Formulation

[EPA

Reg. No.]

Applic. 

Rate

oz/A

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. 

Seasonal 

Applic. 

Rate

oz/A

(lb ai/A)

PHI/PGI1

(Days)

Use Directions and Limitations2

Post weed 

emergence and 

actively growing

weeds;

Foliar,

Broadcast,

ground or band 

application, 

aerial

75% WG

[81880-2]

0.5-0.67 

(0.0234-

0.0313)

NS 0.67

(0.0313)

0 Apply at the 2-leaf through 

layby stage (before grain head 

emergence).

Master Label:

Apply in minimum 

spray volumes of 3 - 15 GPA by 

air or 10 GPA by ground.

Do not apply through any type 

of irrigation system. 

Avoid disturbing (cultivation) 

treated areas for at least 7-days 

following application.

A non-ionic surfactant is 

required at 0.25 to 0.5% v/v or 

a crop oil concentrate may be 

used instead at 1% v/v.

Pasture and Rangeland Grasses

Post weed 

emergence; 

Foliar,

Broadcast,

Ground or 

aerial;

12.5% WG

[81880-6]

4-8 oz/A

(0.0313-

0.0625)

NS 8 oz/A

(0.0625)

Forage

Beef & nonlactating:

0

Lactating 

dairy:

14

Hay

37

A PSI of 30 days is specified 

for beef and non-lactating 

animals.

Same as the master label under 

proso millet.
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Table 3. Summary of Directions for Use of Halosulfuron-methyl.

Applic. Timing, 

Type, and 

Equip.

Formulation

[EPA

Reg. No.]

Applic. 

Rate

oz/A

(lb ai/A)

Max. No. 

Applic. per 

Season

Max. 

Seasonal 

Applic. 

Rate

oz/A

(lb ai/A)

PHI/PGI1

(Days)

Use Directions and Limitations2

Postemergence3

Foliar broadcast

Ground

or aerial 

75% WG

[81880-18]

0.67-1.33

(0.0313-

0.0625

NS 1.33

(0.0625)

Forage

Beef & nonlactating:

0

Lactating 

dairy:

14

Hay

37

Apply to established pasture 

and rangeland. A PSI of 30 

days is specified for beef and 

non-lactating animals.

Ground (min. 10 gal/A) 

Same as the master label under 

proso millet, except for ground 

application use min. 10 gal/A.

Postemergence3

Foliar broadcast

Ground

or aerial 

75% WG

[81880-2]

0.67-1.33

(0.0313-

0.0625

NS 1.33

(0.0625)

Forage

Beef & nonlactating:

0

Lactating 

dairy:

14

Hay

37

Apply to established pasture 

and rangeland. A PSI of 30 

days is specified for beef and 

non-lactating animals.

Same as the master label under 

proso millet.

1 The proposed use pattern as described in the petition materials under “Residue Chemistry including Reasonable 

Grounds in Support of Petition” indicates that the proposed pregrazing intervals are: 7 days for all animals for proso 

millet; and 7 days for lactating animals and 0 days for all other animals for pasture and rangeland grasses. 

2

PSI = Preslaughter interval. 

3 The labels for the 75% WG formulations also include directions for spot treatment applications to grasses which 

are not presented herein.

Adjuvants: The labels for the 12.5% (81880-6) WG formulation and 75% WG formulation

(81880-2) state that an NIS is required at a rate of 0.25-0.5% v/v, and that a crop oil concentrate 

(COC) may also be used instead of an NIS, at 1% v/v. The label for the other 75% WG 

formulation (81880-18) states that use of an NIS (0.25-0.5% v/v) is recommended, and that a

COC or silicone-based adjuvant is not recommended for postemergence applications over the 

crop.

Rotational crop restrictions: Plantback restrictions are also specified for a number of crops, 

ranging from 0 months for insecticide-/imidazolidone-resistant field corn, rice, and sugarcane, to 

36 months for sugar beet in ND, MN, and the Red River Valley, and strawberry. HED 

previously determined that rotational crop tolerances/restrictions are not needed for halosulfuronmethyl. The restrictions appear to have been established for protection of the rotated crops from 

residual herbicidal activity.

Conclusions. The submitted use directions are adequate to allow evaluation of the submitted 

residue data relative to the proposed uses. The submitted field trial data for proso millet and 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

Page 11 of 30

grass reflect the maximum proposed use rate and the minimum PHI and support the use of an 

NIS spray adjuvant. 

For millet forage, there is a discrepancy between the PHIs/PGIs for forage specified on the 

submitted draft labels (0 days for non-lactating animals and 7 days for lactating animals) and that

which appears in the petition under Reasonable Grounds in Support of Petition (7 days for all 

animals). The available residue data will support PHIs/PGIs of 0 and/or 7 days. HED 

recommends a tolerance of 10 ppm based on a 0-day residue data. The petitioner should revise

the PHI/PGI for millet forage to 0-day PHI for all labels. 

For millet hay, grain, and straw, the petitioner has proposed a 37-day PHI for hay on the label for 

the 12.5% WG formulation, but has not proposed a PHI for grain and straw; the labels for the 

75% WG formulations propose a 0-day PHI for millet in general. The available residue data will 

support the proposed PHI of 37 days for hay and a 50-day PHI for millet grain and straw. The 

labels for the 75% WG formulations should be revised to specify a PHI of 37 days for hay, and 

the labels for the 12.5% and 75% WG formulations should be revised to specify a PHI of 50 days 

for grain and straw. 

For grass, although the available residue data will support a PHI/PGI for forage of 0 or 7 days, 

per OCSPP 860.1000 Table 1, a 0-day PGI is required for grass forage except for grasses grown 

for seed only. The data will support the proposed PHI of 37 days for hay. The labels for the 

12.5% and 75% WG formulations should be revised to specify a 0-day PHI/PGI for grass forage 

for all animals. 

Because crop oil concentrates were not used in any of the submitted crop field trials on proso 

millet or grass, the labels for the 12.5% and 75% WG formulations should be revised to state that 

only NIS adjuvants may be added to the spray mixtures for these crops. 

Finally, HED had previously concluded that a 30-day PSI is not practical for pesticides (refer to 

the minutes of the 12/6/06 ChemSAC meeting). The recommended 30-day PSI must be removed 

from the labels for the for the 12.5% and 75% WG formulations.

860.1300 Nature of the Residue - Plants

DP# 251007, M. Doherty, 12/10/1998

Metabolism Committee decision, G. Herndon , 5/21/1996

DP# 198361, G. Otakie, 7/21/1994

DP# s173627 & 180565, G. Herndon, 7/30/1992
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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The nature of the residue in plants is adequately understood based on acceptable metabolism 

studies reflecting pre- and postemergence modes of applications on corn, sugarcane, and 

soybean. The metabolism of halosulfuron-methyl was similar in the three tested crops but 

dependent on the mode of application. When halosulfuron-methyl was applied preemergence, 

initial breakdown of the herbicide in the soil and preferential uptake of the pyrazole moieties 

resulted in the primary residue being 3-CSA, which has been determined to be less toxic than the 

parent. With a postemergence application, the major residue was the parent compound with 

minimal translocation of the herbicide in the plant, except in grain where the major residue was 

3-CSA. 

Based on the very low toxicity of the metabolite 3-CSA, relatively low toxicity of the parent 

compound, and low residue levels of both parent compound and the 3-CSA metabolite, HED has 

previously determined that the residue of concern in plants is the parent compound, halosulfuronmethyl.

860.1300 Nature of the Residue - Livestock

DP# 223801, 11/17/1998, M. Doherty

Metabolism Committee decision, G. Herndon, 5/21/1996

DP# 204062, G. Herndon, 6/22/1994

DP# 184435, G. Herndon, 1/15/1993

DP# 181023, G. Herndon, 11/12/1992

DP#s 173627 & 180565, G. Herndon, 7/30/1992

Acceptable goat metabolism and hen metabolism studies were previously submitted and 

reviewed in conjunction with petitions for uses on corn and sorghum. In goat milk and tissues, 

the major extractable residue was the parent; acid hydrolysis released bound or conjugated 

residues of aminopyrimidine and 3-CSA. HED has previously determined that the residue of 

concern in ruminants is halosulfuron-methyl; however, because the approved enforcement 

method for livestock commodities quantifies the parent compound and metabolites containing 

the 3-chlorosulfonamide moiety (3-CSA) moiety by converting residues to 3-CSA, tolerances for 

residues in livestock commodities are expressed in terms of halosulfuron-methyl and its 

metabolites determined as 3-CSA, expressed as halosulfuron-methyl equivalents. 

HED previously concluded (PP#2G4073) that tolerances for halosulfuron-methyl residues in 

poultry commodities were not required due to low use rates, low residues of halosulfuron-methyl 

in poultry feed items, and the low transfer rate of residues to poultry tissues. 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

Page 13 of 30

860.1340 Residue Analytical Methods

DP# 250584, G. Herndon, 10/28/1998

DP# 214890, G. Herndon, 5/3/1995

DP# 202131, G. Herndon, 10/4/1994

Plants

Enforcement method: An adequate analytical method is available for enforcement of tolerances 

for halosulfuron-methyl residues in plants. The GC/TSD method quantifies halosulfuron-methyl 

as its rearrangement ester (1-H-pyrazole-4-carboxylic acid, 3-chloro-5-[(4,6-dimethoxy-2-

pyrimidinyl)amino]-1-methyl, methyl ester). Monsanto Analytical Method RES-109-97-4 

(MRID 44495801) has been validated as an enforcement method by the Analytical Chemistry 

Branch (ACB)/BEAD. The LOQ on rice straw, sugarcane, milo grain, field corn grain, cotton 

gin byproducts, and almond nutmeats was 0.05 ppm (DP# 250584, G. Herndon, 10/28/1998). 

N

N

O

CH3

O

CH3

N

H

N

N

CH3

Cl

O

O

CH3

Rearrangement ester (RRE) of halosulfuron-methyl

Data collection methods: Samples collected from the field trial studies associated with this 

action were analyzed for residues of halosulfuron-methyl using the available tolerance 

enforcement method, Method RES-109-97-4, with modifications. Briefly, samples were 

extracted with acetonitrile (ACN)/water, filtered, and partitioned with dichloromethane (DCM). 

The DCM extract was evaporated to dryness and redissolved in 15% methanol/DCM for clean-up 

through a Florisil solid phase extraction (SPE) cartridge. The eluate was mixed with 0.5 M 

potassium carbonate to convert halosulfuron-methyl residues to its rearrangement ester (RRE). 

The reaction mixture was then extracted with DCM, and the DCM extract was evaporated to 

dryness; residues were reconstituted in ethyl acetate for further clean-up through a silica SPE 

column. The eluate was evaporated to dryness and redissolved in 50% ethyl acetate/isooctane for 

analysis by GC/NPD or GC/MSD. The LOQ (determined as the LLMV) was 0.01 ppm in all 

proso millet and grass matrices.

Conclusions. The residue analytical methods data are adequate to satisfy data requirements for 

the subject action. An acceptable residue analytical method is available for tolerance 

enforcement purposes for residues in/on crop commodities. Residues of halosulfuron-methyl

in/on the crop commodities from the magnitude of the residue studies were determined using an 

acceptable data collection method.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Livestock

Enforcement method: An adequate analytical method is available for enforcement of tolerances 

for secondary residues of halosulfuron-methyl in livestock commodities. Monsanto Analytical 

Method RES-046-93 quantifies halosulfuron-methyl and metabolites containing the 3-CSA 

moiety, expressed as parent equivalents. Residues of halosulfuron-methyl and 3-

chlorosulfonamide ester are hydrolyzed to 3-CSA, which is extracted with ACN/DCM and then 

methylated with trimethylsilyl-diazomethane. The methyl ester is analyzed by GC/ECD after 

cleanup with an alumina/carbon column. The petitioner-validated LOQ was 0.01 ppm. The 

method has been validated as an enforcement method by the ACB/BEAD at an LOQ of 0.01 ppm 

in milk and liver (D. Swineford, 4/28/1995).

860.1360 Multiresidue Methods

DP# 189198, G.Herndon, 3/8/1994

Adequate multiresidue method data for halosulfuron-methyl and 3-CSA were submitted 

previously in conjunction with PP#3F4193. Residues of halosulfuron-methyl and 3-CSA are not 

recoverable by the FDA Multiresidue Protocols A through E. The results have been forwarded to 

FDA.

860.1380 Storage Stability

DP# 189189, 3/8/94, G. Herndon

DP# 243050, 1/5/99, M. Doherty

Adequate storage stability data were previously submitted which indicate that halosulfuronmethyl residues are stable during freezer storage for up to 800 days in/on corn grain, forage, 

fodder, and silage (DP# 189198, 3/8/94, G. Herndon) and 996 days in/on soybean (DP# 243050, 

1/5/99, M. Doherty). 

The storage durations and conditions of crop samples from the submitted crop field trials are 

presented in Table 4. No concurrent storage stability information was provided.

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

Matrix Storage 

Temperature 

(°C)

Actual Storage Duration

(days)

Interval of Demonstrated 

Storage Stability for Halosulfuronmethyl

(days)

Millet forage -20 ± 5 171-237 days (5.6-7.8 months) Residues of halosulfuron-methyl are stable 

during freezer storage for up to 800 days in 

corn grain, forage, fodder, and silage and 996 

days in soybean.

Millet hay 120-186 days (3.9-6.1 months)

Millet grain 142-177 days (4.7-5.8 months)

Millet straw 99-157 days (3.3-5.2 months)

Grass forage -20 ± 5 95-275 days (3.1-9.0 months)

Grass hay 55-236 days (1.8-7.8 months)

Conclusions. Adequate storage stability data are available to support the storage conditions and 

durations of samples collected from the magnitude of the residue studies on proso millet and 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

Page 15 of 30

grass. As residues of halosulfuron-methyl were found to be stable in some related crop matrices, 

storage stability corrections need not be applied.

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

DP# 367058, D. Rate, 3/30/2010

DP#s 189198 & 198051, G. Herndon, 3/8/1994 

DP#s 173627 & 180565, G. Herndon, 7/30/1992 

The livestock feedstuffs associated with the proposed uses on proso millet and grasses are: 

millet forage, hay, and straw; and grass forage, hay, and silage. The feedstuffs derived from 

registered uses include those commodities derived from alfalfa, almond, apple, corn, cotton, dry 

and snap beans, potato, rice, sorghum, soybean, and sugarcane. 

Maximum reasonable dietary burdens (MRDBs) for ruminants were most recently calculated for 

halosulfuron-methyl under PP#9E7577 (DP# 367058) reflecting proposed uses on apple and 

potato. The calculated dietary burdens were 0.468 ppm for beef cattle and 0.825 ppm for dairy 

cattle.

The addition of uses on millet and grasses will have a significant impact on the dietary burden to 

dairy cattle. The addition of grass and/or millet feedstuffs to the dietary burden calculations for 

beef cattle, even at the maximum potential contribution for each, will not increase the dietary 

burden. Similarly, the addition of millet grain to the dietary burden calculations for poultry and 

swine will not increase the dietary burden; no significant intake was previously found for poultry 

or swine.

The MRDB calculations reflecting the addition of millet and grass feedstuffs are presented in 

Table 5. The dietary burden for ruminants remains unchanged at 0.468 ppm; the current dietary 

burden for dairy cattle is 19.9 ppm. 

Table 5. Calculation of Dietary Burdens of Halosulfuron-methyl Residues to Livestock.

Feedstuff Type1 % Dry 

Matter2 % Diet2

Recommended 

Tolerance/HAFT3

(ppm)

Dietary Contribution 

(ppm)4

Beef Cattle

Alfalfa, hay R 89 15 2.0 (Tolerance) 0.337

Potato, processed waste CC 15 30 0.05 (Tolerance) 0.100

Corn, field, grain CC 88 50 0.05 (Tolerance) 0.028

Soybean, meal PC 92 5 0.05 (Tolerance) 0.003
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Table 5. Calculation of Dietary Burdens of Halosulfuron-methyl Residues to Livestock.

Feedstuff Type1 % Dry 

Matter2 % Diet2

Recommended 

Tolerance/HAFT3

(ppm)

Dietary Contribution 

(ppm)4

Beef Cattle

TOTAL BURDEN -- -- 100 -- 0.468

Dairy Cattle

Grass, forage/silage R 25 45 11.0 (HAFT) 19.8

Potato, processed waste CC 15 10 0.05 (Tolerance) 0.033

Corn, field, grain CC 88 35 0.05 (Tolerance) 0.020

Cotton, meal PC 89 10 0.05 (Tolerance) 0.006

TOTAL BURDEN -- -- 100 -- 19.9

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

2 OPPTS 860.1000 Table 1 Feedstuffs (June 2008).

3 The HAFT from the crop field trials was used for grass forage; tolerances were used for all other commodities.

4 Contribution = ([tolerance /% DM] X % diet) for dairy cattle.

Dairy Cattle

An adequate dairy cattle feeding study was submitted under PP#3F4193 (DP#s 189198 and 

198051). Halosulfuron-methyl was administered in gelatin capsules to lactating dairy cattle (four 

animals/dose group) once daily for 28 consecutive days at three dose levels roughly equivalent to 

0.5, 1.5, and 5 ppm in the daily diet on a dry weight basis (corresponding to ~0.025x, ~0.075x, 

and ~0.25x the current MRBD for dairy cattle). Samples were analyzed for residues of 

halosulfuron-methyl and metabolites determined as the 3-chlorosulfonamide moiety (3-CSA) and 

expressed in parent equivalents. No quantifiable residues (<0.01 ppm) were found in milk, 

muscle, or fat of cattle at feeding levels of 0.5, 1.5, and 5.0 ppm. Quantifiable residues were 

found in liver and kidney at all feeding levels. The results of the cattle feeding study are 

summarized in Table 6.

Table 6. Maximum Residues of Halosulfuron-methyl and Metabolites in Dairy Cattle Tissues and Milk.

Dose

(ppm)

Maximum residues of total CSA, expressed as halosulfuron-methyl equivalents (ppm)

Whole Milk Raw Cream Raw Skim Milk Muscle Fat Liver Kidney

0.5 NA1 NA NA NA NA 0.01 0.02

1.5 NA NA NA <0.01 <0.01 0.04 0.11

5.0 <0.01 <0.01 <0.01 <0.01 <0.01 0.11 0.24

1 NA = Not analyzed.

To assess the need for tolerances for cattle commodities, the results of the cattle feeding study are

summarized in Table 7, reflecting extrapolation of residues found to a 1x feeding level for dairy 

cattle.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Table 7. Extrapolation of Residues found in the Ruminant Feeding Study to a 1x Feeding Level.1

Matrix

Residues of total CSA, expressed as halosulfuron-methyl equivalents (ppm)

Feeding level = 0.5 ppm

0.025x MRDB

Feeding level = 1.5 ppm

0.075x MRDB

Feeding level = 5.0 ppm

0.25x MRDB Maximum 

expected at 

1x Residues 

found

Expected at 

1x

Residues 

found

Expected at 

1x

Residues 

found

Expected at 

1x

Milk -- -- -- -- <0.01 <0.04 <0.04

Skim milk -- -- -- -- <0.01 <0.04 <0.04

Cream -- -- -- -- <0.01 <0.04 <0.04

Liver 0.01 0.40 0.04 0.53 0.11 0.44 0.44

Kidney 0.02 0.79 0.11 1.46 0.24 0.95 0.95

Muscle -- -- <0.01 <0.13 <0.01 <0.04 <0.13

Fat -- -- <0.01 <0.13 <0.01 <0.04 <0.13

1 Based on the MRBD to dairy cattle of 19.9 ppm

Evaluation of the current dietary burden for dairy cattle in conjunction with the cattle feeding 

study indicates that expected residues in liver and kidney will increase to 0.44 and 0.95 ppm, 

respectively, as a result of the proposed use on grass. Residues in milk, skim milk, cream, 

muscle, and fat were below the LOQ at all dosing levels in the feeding study. Based on 

extrapolation from the highest concentration level (5 ppm) of the feeding study with residues at 

the LOQ (0.01 ppm) in milk, muscle, and fat, HED has concluded that tolerances at 0.05 ppm 

can be established for residues of halosulfuron-methyl in the milk, muscle and fat of cattle, goats, 

horses, and sheep based on the reasons stated in the ChemSAC minutes (ChemSAC 06/20/2012). 

For future new uses that increase the dietary burden above 20 ppm, a new feeding study will be 

needed.

Conclusions. The available ruminant feeding study which corresponds to 0.25x the current 

MRDB of dairy cattle is acceptable to support the proposed new uses of halosulfuron-methyl on 

millet and grasses. In support of the proposed uses, tolerances need to be established at 0.05 ppm 

on milk, muscle, and fat of cattle, goats, horses, and sheep. The petitioner must propose a 

tolerance of 0.05 ppm on these livestock commodities. For future new uses that increase the 

dietary burden above 20 ppm, a new feeding study will be needed reflecting dosing at 1x, 3x, and 

10x the maximum reasonable dietary burden (MRDB). 

The available data for liver and kidney are sufficient to assess the existing tolerances for meat 

byproducts. The data indicate that the established tolerances of 0.1 ppm for the meat byproducts 

of cattle, goat, horse, and sheep are too low and should be increased to 1.0 ppm. 

No change is needed for the established tolerance of 0.1 ppm for hog meat byproducts. 

HED previously concluded (PP#2G4073) that tolerances for halosulfuron-methyl residues in 

poultry commodities were not required due to low use rates, low residues of halosulfuron-methyl 

in poultry feed items, and the low transfer rate of residues to poultry tissues. This conclusion 

remains unchanged.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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860.1500 Crop Field Trials

DER Reference: 48583601.der (Proso millet)

DER Reference: 48583602.der (Pasture and rangeland grass)

Canyon Group LLC (agent Gowan Company) submitted magnitude of the residue studies on 

proso millet and pasture and rangeland grass. The results from these field trials are discussed 

below, and the residue data are summarized in Tables 8 and 9.

Proso Millet

Gowan Company has submitted field trial data for halosulfuron-methyl on proso millet. Five 

field trials were conducted in the United States during the 2009 growing season in the North 

American Free Trade Agreement (NAFTA) Growing Zones 5 (NE; 1 trial), 7 (NE and ND; 2 

trials), and 8 (KS; 2 trials). Two pairs of trials (Trials -01/-02 in NE and Trials -04/-05 in KS) 

were each conducted by the same principle field investigator. Examination of the field trial 

records indicates that there were sufficient distinguishing characteristics between the trials in 

each pair that each trial constitutes a separate trial for purposes of 860.1500 data requirements. 

For the NE trials, distinguishing characteristics include irrigation (overhead at Trial -01 and none 

at Trial -02), spray volume (>25% difference), distance (>20 miles apart), and NAFTA zone. For 

the KS trials, distinguishing characteristics include irrigation (subsurface at Trial -04 and none at 

Trial -05) and distance (~40 miles apart). 

Each trial consisted of one untreated plot and one treated plot. At each trial location, the treated 

plots received a single foliar broadcast application of a 12.5% WG formulation of halosulfuronmethyl (Yukon Herbicide) at 0.0310-0.0314 lb ai/A (0.0347-0.0352 kg ai/ha; ~1x the maximum 

proposed seasonal application rate). The 12.5% WG formulation is an MAI formulation that also 

contains 55% dicamba; only data for halosulfuron-methyl are presented herein. All applications 

were made using ground equipment in spray volumes of 10-15 gal/A (94-140 L/ha). An NIS was 

added to the spray mixture for each of the applications for all trials. In addition, the spray 

solutions included urea ammonium nitrate (UAN). 

Samples of forage were harvested at normal crop maturity at a 0-day PHI and again at a 7-day 

PHI. Hay samples were harvested at a 36- to 37-day PHI; hay was dried in the field for 3-8 days 

prior to collection. Grain and straw samples were harvested at normal crop maturity (51- to 67-

day PHIs); straw was dried in the field for 2-7 days at two trial sites prior to collection. To assess 

residue decline, additional samples were harvested from one trial in NE (Trial -02) at PHIs of 3 

and 14 days for forage, 31, 44, and 52 days for hay, and 52, 65, and 72 days for grain and straw.

Samples were analyzed for residues of halosulfuron-methyl using the tolerance enforcement 

method, and the study is supported by adequate storage stability data. The sample storage 

intervals and conditions are presented in Table 4.

The results of the millet crop field trials are summarized in Table 8. Following a single foliar 

broadcast application of the 12.5% WG formulation at 0.0310-0.0314 lb ai/A (0.0347-0.0352 kg 

ai/ha), residues (and per trial averages) of halosulfuron-methyl in/on proso millet forage 

harvested at 0- and 7-day PHIs, respectively, were 2.37-5.81 (2.42-5.04) and 0.0231-0.640 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

Page 19 of 30

(0.0261-0.634) ppm; residues (and per trial averages) in/on hay (36- to 37-day PHIs) and grain 

and straw (51- to 67-day PHIs) were below the LOQ (<0.01 ppm) in/on all samples. 

In the residue decline trial, average residues of halosulfuron-methyl decreased with increasing 

PHIs in forage. Residues in hay, grain, and straw were below the LOQ at all harvest intervals; 

therefore, residue decline could not be assessed. 

Table 8. Summary of Residue Data from Proso Millet Crop Field Trials with Halosulfuron-methyl.

Commodity Total

Rate

lb ai/A

(kg ai/ha)

PHI 

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

PROSO MILLET (proposed use = 0.0313 lb ai/A total application rate; 

PHIs/PGIs = 0 or 7 days (forage) and 37 days (hay)3

Forage 0.0310-0.0314

(0.0347-0.0352)

0 5 2.37 5.81 2.42 5.04 2.76 3.14 1.08

7 5 0.0231 0.640 0.0261 0.634 0.0744 0.179 0.256

Hay 36-37 5 <0.01 <0.01 <0.01 <0.01 0.01 0.01 N/A

Grain 51-67 5 <0.01 <0.01 <0.01 <0.01 0.01 0.01 N/A

Straw 51-67 5 <0.01 <0.01 <0.01 <0.01 0.01 0.01 N/A

1 Except for sample min/max, values reflect per trial averages; n = no. of field trials. For calculation of median, 

mean, and standard deviation, the LOQ (0.01 ppm) was used for any results reported as <LOQ in Table C.3. N/A = 

Not applicable. 

2 LAFT = lowest average field trial; HAFT = highest average field trial.

3 A PHI/PGI of 0 days and 7 days is proposed for millet forage (refer to 860.1200 for additional details); no PHI has 

been proposed for grain and straw.

Conclusions. Pending submission of the deficiencies listed under regulatory recommendations, 

the submitted residue data for proso millet are acceptable. The study reflects the maximum 

proposed use pattern, and the number and locations of the field trials are in accordance with 

OCSPP 860.1500 for proso millet. An acceptable method was used for residue quantitation, and 

the data are supported by adequate storage stability data.

The submitted data for proso millet are sufficient for establishing tolerances for millet 

commodities associated with the proposed use. The data will support tolerances at the LOQ of 

0.01 ppm for proso millet hay, grain, and straw and at 10 ppm for millet, forage. The tolerance 

calculations are presented in Appendix I. 

Provided the petitioner proposes a PHI of 50 days for millet grain and straw and a PHI of 0-day 

for millet forage, the data will support tolerances at the LOQ of 0.01 ppm for proso millet hay, 

grain, and straw and 10 ppm for proso millet forage. 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Pasture and Rangeland Grasses

Gowan Company has submitted field trial data for halosulfuron-methyl on pasture and rangeland 

grasses. Twelve field trials were conducted in the United States during the 2009 growing season 

in the NAFTA Growing Zones 1 (PA; 1 trial), 2 (NC; 1 trial), 4 (LA; 1 trial), 5 (MI, WI, IL, and 

MO; 4 trials), 6 (TX; 1 trial), and 11 (ID and WA; 4 trials). Four trials each were conducted 

using Bermuda grass, bluegrass, and rangeland grass (bromegrass, squirreltail, crested 

wheatgrass). 

Each trial consisted of one untreated plot and one treated plot. At each trial location, the treated 

plots received a single foliar broadcast application of a 12.5% WG formulation of halosulfuronmethyl (Yukon Herbicide) at 0.0622-0.0651 lb ai/A (0.0697-0.0730 kg ai/ha; ~1x the maximum 

proposed seasonal application rate). The 12.5% WG formulation is an MAI formulation that also 

contains 55% dicamba; only data for halosulfuron-methyl are presented herein. All applications 

were made using ground equipment in spray volumes of 10-15 gal/A (94-140 L/ha). An NIS was 

added to the spray mixture for each of the applications for all trials. 

Samples of forage were harvested at normal crop maturity (6-inch to early boot stage) at a 0-day 

PHI and again at a 6- to 7-day PHI. Hay samples were harvested at a 23- to 37-day PHI; hay was 

dried in the field for 1-9 days prior to collection. To assess residue decline, additional samples 

were harvested from one trial at PHIs of 3 and 14 days for forage and at PHIs of 25, 38, and 47 

days for hay. 

Samples were analyzed for residues of halosulfuron-methyl using the tolerance enforcement 

method, and the study is supported by adequate storage stability data. The sample storage 

intervals and conditions are presented in Table 4.

The results of the grass field trials are summarized in Table 9. Following a single foliar 

broadcast application of the 12.5% WG formulation at 0.0622-0.0651 lb ai/A (0.0697-0.0730 kg 

ai/ha), residues (and per trial averages) of halosulfuron-methyl in/on grass forage harvested at 0-

and 6- to 7-day PHIs, respectively, were 3.06-11.2 (3.24-11.0) and 0.0252-4.89 (0.0269-4.57) 

ppm; residues (and per trial averages) in/on hay (23- to 37-day PHIs) were <0.01-0.389 (<0.01-

0.384) ppm. HED notes that the highest residues in hay (average 0.384 ppm) were observed in 

samples collected from Trial 01 at a 23-day PHI; average residues in samples from the remaining 

trials (PHIs of 31-37 days) were <0.01-0.0473 ppm.

In the residue decline trial, average residues of halosulfuron-methyl decreased with increasing 

PHIs in grass forage and hay.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Table 9. Summary of Residue Data from Pasture and Rangeland Grass Crop Field Trials with 

Halosulfuron-methyl.

Commodity Total

Rate

lb ai/A

(kg ai/ha)

PHI 

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

PASTURE AND RANGELAND GRASSES (proposed use = 0.0625 lb ai/A total application rate;

PHIs/PGIs = 0 or 14 days (forage) and 37 days (hay)3

Grass forage 0.0622-0.0651

(0.0697-0.0730)

0 12 3.06 11.2 3.24 11.0 6.52 6.66 2.69

6-7 12 0.0252 4.89 0.0269 4.57 0.972 1.46 1.50

Grass hay 23-37 12 <0.01 0.389 <0.01 0.384 0.0329 0.0702 0.109

1 Except for sample min/max, values reflect per trial averages; n = no. of field trials. For calculation of median, 

mean, and standard deviation, the LOQ (0.01 ppm) was used for any results reported as <LOQ in Table C.3. 

2 LAFT = lowest average field trial; HAFT = highest average field trial. 

3

Per OCSPP 860.1000 Table 1, a 0-day PHI/PGI is required for grass forage. 

Conclusions. The submitted residue data for pasture and rangeland grasses are acceptable. The 

study reflects the maximum proposed use pattern for pasture and rangeland grasses, and the 

number and locations of the field trials are in accordance with OCSPP 860.1500 for crop group 

17, grass forage, fodder, and hay. An acceptable method was used for residue quantitation, and 

the data are supported by adequate storage stability data.

HED notes that the petitioner has proposed 0- and 14-day PHI/PHIs for forage; however, per 

Table 1 in OCSPP 860.1000, a 0-day PHI/PGI is required for grass forage. Therefore, the 

tolerance for grass forage must be based on the 0-day data. 

The submitted data for grasses are sufficient for establishing tolerances for grass commodities 

associated with the proposed use. The available field trial data will support tolerances of 20 ppm 

for grass forage and 0.50 ppm for grass hay. The tolerance calculations are presented in 

Appendix I.

860.1520 Processed Food and Feed

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

860.1650 Submittal of Analytical Reference Standards

An analytical standard is currently available in the EPA National Pesticide Standards Repository 

for halosulfuron-methyl (expiration 4/21/2014) and the metabolite chlorosulfonamide acid 

(expiration 6/21/2016); however, a standard is not available for the rearrangement ester (RRE; 1-

H-pyrazole-4-carboxylic acid, 3-chloro-5-[(4,6-dimethoxy-2-pyrimidinyl)amino]-1-methyl, 

methyl ester) (personal communication with Theresa Cole, ACB, 3/6/2012). A standard for the 

RRE of halosulfuron-methyl is required in support of the tolerance enforcement method for plant 

commodities. The analytical reference standard of the RRE must be supplied and supplies 

replenished as requested by the Repository. 

The reference standards should be sent to the Analytical Chemistry Lab, which is located at Fort 

Meade, Maryland. They can be sent to the attention of either Theresa Cole or Thuy Nguyen at 
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

Page 22 of 30

the address listed below. The full 9-digit zip code is mandatory or the mail will be returned to 

the registrant.

USEPA

National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

701 Mapes Road

Fort George G. Meade, MD 20755-5350

The letter of transmittal should include the assay of the standards, names of the analytical 

methods used, a statement of principal impurities, purification procedures employed, storage 

requirements, and special precautions for safe handling. Replacement of standards may be 

required periodically if supplies are exhausted or if decomposition occurs during storage. 

Material Safety Data Sheets (MSDSs) must accompany all analytical standards as specified by 

Occupational Safety and Health Administration (OSHA) in 29 CFR 1910.1200.

860.1850 and 860.1900 Confined/Field Accumulation in Rotational Crops

DP# 225273, G.J. Herndon, 10/29/1998

Metabolism Committee decision, G. Herndon, 5/21/1996

DP# 192510, G. Kramer, 8/30/1993

DP#s 188144 and 188814, G. Herndon, 3/11/1993

Acceptable confined rotational and limited field rotational crop studies were previously 

submitted. The results of both studies indicate that metabolites containing the pyrazole moiety 

may accumulate in harvested crops planted at intervals greater than one year. The confined 

rotational crop study, conducted at 0.19 lb ai/A, indicated that no measurable residues of 

halosulfuron-methyl were detected in any rotational crop commodities of wheat, soybean, radish 

and lettuce at any plantback interval (30, 120, and 360 days after treatment). The limited field 

rotational crop study, conducted at 0.22 lb ai/A in a split (preplant + postemergence) application, 

with rotated crops of winter wheat, spring wheat, soybean, sugar beet, and leaf lettuce indicated 

that no measurable residues of halosulfuron-methyl were detected in any field rotational crop 

samples, except in one spring wheat forage sample at 0.090 ppm (364-day plantback interval).

HED previously concluded that the residue of concern in rotational crops is halosulfuron-methyl. 

Based on the absence of the parent compound in the confined studies and in the limited field 

rotational crop studies, with the exception of one forage sample, HED previously concluded that 

rotational crop tolerances and restrictions are not required for halosulfuron-methyl.

Conclusion. The proposed uses on proso millet and rice will not alter HED’s earlier assessment 

regarding the potential for inadvertent residues in rotatable crops addressed in this registration 

action. No additional data are required. 

860.1550 Proposed Tolerances

Tolerances are established under §180.479(a)(2) for residues of halosulfuron-methyl in/on plant 

commodities, to be determined by measuring only halosulfuron-methyl. The proposed tolerance 

expression is consistent with the established tolerances.
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Adequate field trial data reflecting the proposed use patterns are available for purposes of 

establishing tolerances for proso millet for all commodities except millet forage, and for grass 

forage and hay. 

Residues in/on proso millet hay, grain, and straw were below the LOQ; the available data will 

support tolerances at the LOQ of 0.01 ppm for these commodities. These tolerances are in 

agreement with the proposed tolerances for grain and straw; however, the proposed tolerance for 

hay was 0.02 ppm. The difference in the proposed and recommended tolerances for millet hay 

are due to the petitioner having used residue values below the LOQ and the NAFTA tolerance 

calculation procedures in determining the hay tolerance. 

Residues of halosulfuron-methyl were quantifiable in/on proso millet forage, grass forage, and 

grass hay; therefore, the OECD tolerance calculation procedures were utilized in determining 

appropriate tolerance levels for these commodities. The tolerance calculations are presented in 

Appendix I. Using the OECD tolerance calculation procedures, the recommended tolerances are: 

10 ppm (0-day PHI) and 1.5 ppm (7-day PHI) for millet forage, 20 ppm for grass forage and 0.5 

ppm for grass hay. HED recommends a tolerance of 10 ppm for millet forage based on residue 

data using 0-day PHI. The proposed tolerances are too low for grass forage and too high for 

grass hay. The differences in the proposed and recommended tolerances for these commodities 

are due to the petitioner having used the NAFTA tolerance calculation procedures in determining 

the proposed tolerances.

In conjunction with the proposed uses on proso millet and grasses, HED has updated the dietary 

burden calculations for ruminants and has concluded that tolerances at 0.05 ppm are needed for 

residues of halosulfuron-methyl in the milk, muscle and fat of cattle, goats, horses, and sheep. 

The petitioner must propose a tolerance of 0.05 ppm for these livestock commodities. The 

available feeding study data indicate that the established tolerances of 0.1 ppm for the meat 

byproducts of cattle, goat, horse, and sheep are too low and should be increased to 1.0 ppm. 

There are no Codex, Canadian, or Mexican maximum residue limits (MRLs) established for 

residues of halosulfuron-methyl in/on crop or livestock commodities. An International Residue 

Limit (IRL) form is appended to this Summary Document as Appendix II.

Tolerances related to this action are summarized in Table 10. 

Table 10. Tolerance Summary for Halosulfuron-Methyl.

Commodity Proposed/Existing

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Comments; Correct Commodity 

Definition

Millet, proso, forage 7.0 10 The data supports a tolerance of 10 ppm 

with a 0-day PHI/PGI.

Millet, proso, hay 0.02 0.01

Millet, proso, grain 0.01 0.01

Millet, proso, straw 0.01 0.01
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Table 10. Tolerance Summary for Halosulfuron-Methyl.

Commodity Proposed/Existing

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Comments; Correct Commodity 

Definition

Grass forage, fodder, and 

hay, Crop group 17 forage

17 20 Grass, forage, fodder, and hay, group 17, 

forage

Grass forage, fodder, and 

hay, Crop group 17 hay

0.90 0.5 Grass, forage, fodder, and hay, group 17, 

hay

Additional Livestock Commodity Tolerances That Need to be Proposed/Established

Cattle, meat byproducts 0.1 1.0

Goat, meat byproducts 0.1 1.0

Horse, meat byproducts 0.1 1.0

Sheep, meat byproducts 0.1 1.0

Additional Livestock Commodity Tolerances That Need to be Proposed/Established

Cattle, fat None 0.05

Cattle, meat None 0.05

Goat, fat None 0.05

Goat, meat None 0.05

Horse, fat None 0.05

Horse, meat None 0.05

Milk None 0.05

Sheep, fat None 0.05

Sheep, meat None 0.05

Attachments: 

Appendix I: Tolerance Assessment Calculations

Appendix II: International Residue Limits
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Appendix I

Tolerance Assessment Calculations

The OECD tolerance calculation procedures (March 2011 version) were used for calculating 

recommended tolerances for proso millet (forage) and pasture and rangeland grasses (forage and 

hay). The statistical goal of the OECD tolerance calculation procedures is to produce an MRL 

proposal in the region of the 95th percentile of the underlying residues distribution. The average 

residue values used to calculate the tolerances are provided in Table I-1. 

Table I-1. Residue data used to calculate tolerances for halosulfuron-methyl.

Regulator: EPA

Chemical: Halosulfuron-methyl

Crop: Proso Millet, Forage Grass, Forage Grass, Hay

PHI: 0 days 7 days 0 days 37 days

App. Rate: 0.031 lb ai/A 0.0625 lb ai/A

Submitter: Gowan Gowan

MRID Citation: 48583601 48583602

Halosulfuron-methyl Residues (ppm)

5.04 0.634 8.94 0.384

2.50 0.0662 4.09 0.0433

2.76 0.0935 3.24 0.01*

2.99 0.0744 11.0 0.0184

2.42 0.0261 10.1 0.0443

6.57 0.01*

4.11 0.0348

9.63 0.183

3.75 0.01*

5.47 0.0309

6.53 0.0265

6.50 0.0473

*censored values

Proso Millet

The dataset used to establish a tolerance for halosulfuron-methyl on proso millet forage consisted 

of field trial data on proso millet at application rates of 0.0310-0.0314 lb ai/A, with a 0-day PHI

and a 7-day PHI. The field trial application rates and PHIs are within 25% of the maximum label 

application rate and minimum label PHI, respectively. The average residue values used to 

calculate the tolerances are provided in Table I-1. Residues of halosulfuron-methyl were 

quantifiable (LOQ = 0.01 ppm) in/on all samples of forage (0- and 7-day PHI). Using the OECD 

tolerance calculation procedures, the recommended tolerance is 10 ppm (0-day PHI).
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Halosulfuron-methyl

Proso Millet, Forage

USA

0.031 lb ai/A, 0-day PHI

Total number of data (n) 5

Percentage of censored data 0%

Number of non-censored data 5

Lowest residue 2.420

Highest residue 5.040

Median residue 2.760

Mean 3.142

Standard deviation (SD) 1.085

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 5.040

- Mean + 4 SD 7.480

- CF x 3 Mean 9.426

Unrounded MRL 9.426

Rounded MRL 10

High uncertainty of MRL estimate.

[Small dataset]
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Halosulfuron-methyl

Proso Millet, Forage

USA

0.031 lb ai/A, 7-day PHI

Total number of data (n) 5

Percentage of censored data 0%

Number of non-censored data 5

Lowest residue 0.026

Highest residue 0.634

Median residue 0.074

Mean 0.179

Standard deviation (SD) 0.256

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 0.634

- Mean + 4 SD 1.201

- CF x 3 Mean 0.537

Unrounded MRL 1.201

Rounded MRL 1.5

High uncertainty of MRL estimate.

[Small dataset]
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Pasture and Rangeland Grasses

The dataset used to establish a tolerance for halosulfuron-methyl on pasture and rangeland 

grasses consisted of field trial data on pasture and rangeland grasses at application rates of 

0.0622-0.0651 lb ai/A, with a 0- day PHI for forage and 23-37-day PHIs for hay. The field trial 

application rates and PHIs are within 25% of the maximum label application rate and minimum 

label PHI, respectively, with the exception that the PHI for hay at one trial (23 days at Trial -01) 

differed from the target PHI of 37 days by >25%. The average residue values used to calculate 

the tolerances are provided in Table I-1. Residues of halosulfuron-methyl were quantifiable 

(LOQ = 0.01 ppm) in/on all forage samples and in/on samples from 9 of 12 hay sites. Using the 

OECD tolerance calculation procedures, the recommended tolerances are 20 ppm for grass, 

forage and 0.50 ppm for grass, hay.

Halosulfuron-methyl

Grass, Forage

USA

0.0625 lb ai/A, 0-day PHI

Total number of data (n) 12

Percentage of censored data 0%

Number of non-censored data 12

Lowest residue 3.240

Highest residue 11.000

Median residue 6.515

Mean 6.661

Standard deviation (SD) 2.687

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 11.000

- Mean + 4 SD 17.409

- CF x 3 Mean 19.983

Unrounded MRL 19.983

Rounded MRL 20
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Halosulfuron-methyl

Grass, Hay

USA

0.0625 lb ai/A, 37-day PHI

Total number of data (n) 12

Percentage of censored data 25%

Number of non-censored data 9

Lowest residue 0.010

Highest residue 0.384

Median residue 0.033

Mean 0.070

Standard deviation (SD) 0.109

Correction factor for censoring (CF) 0.833

Proposed MRL estimate

- Highest residue 0.384

- Mean + 4 SD 0.507

- CF x 3 Mean 0.176

Unrounded MRL 0.507

Rounded MRL 0.5
Halosulfuron-methyl Summary of Analytical Chemistry and Residue Data DP# 393948

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Appendix II

International Residue Limits

Halosulfuron-methyl (128721; 02/29/2012)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex3

40 CFR 180.479

Plant: Halosulfuron-methyl, methyl 5-[(4,6-

dimethoxy-2-

pyrimidiny)amino]carbonylaminosulfonyl]-3-

chloro-1-methyl-1H-pyrazole-4-carboxylate

Livestock: Halosulfuron-methyl residues containing 

the 3-chlorosulfonamide (3-CSA) moiety, expressed 

as the stoichiometric equivalent of halosulfuronmethyl

None None

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

US Canada Mexico2 Codex3

Millet, proso, forage 10

Millet, proso, hay 0.01

Millet, proso, grain 0.01

Millet, proso, straw 0.01

Grass, forage, fodder, and hay, 

group 17, forage

20

Grass, forage, fodder, and hay, 

group 17, hay

0.5

Cattle, meat byproducts 1.0

Goat, meat byproducts 1.0

Horse, meat byproducts 1.0

Sheep, meat byproducts 1.0

Cattle, fat 0.05

Cattle, meat 0.05

Goat, fat 0.05

Goat, meat 0.05

Horse, fat 0.05

Horse, meat 0.05

Milk 0.05

Sheep, fat 0.05

Sheep, meat 0.05

Completed: M. Negussie; 06/21/2012

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.

3 * = 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.