UNITED STA TES ENV IRONMENTAL PROTECTION AGENCY

WASHI NGTON, D.C. 20460

OFFICE OF

PREVENTION. PESTICIDES AND

TOXIC SUBSTANCES

MEMORAND UM

DATE: 12/02/2009

SUBJECT: Sulfometuron Methyl: Amendment to the "1-IED Chapter of the Reregistration

Eligibility Decision Document (RED) (D346064)"

PC Code: 12200 I

MRID No.: NA

Petition No.: NA

Assessment Type: Amendment

T XR No.: NA

DP Barcode: D346 192

Registration No .: NA

Regulatory Action: Risk Assessment

Reregistration Case No.: NA

CAS No.: 74222-97 -2

FROM:

THROUGH:

TO:

R

Wa

isk

de B

Assess

ritton

ment

, Industri

Branch

al H

V

ygienist ~~J

Healt h Effects Division (7509P) .

Ja

Ri

ck A

sk Assess

rthur, Br

ment

anch

Branch

Chief

V

~~

Health Effects Division (750 P)

Russell Wasem

Risk Management and Implementation Branch I

Pesticide Re-evaluation Division (7508P)

The purpose of this document is to amend the memorandum, "HED Chapter of the Reregistration

Eligibility Decision Document (RED) (D346064)," based upon changes in the maximum single

application rates for forestry. rights-of-way and non-crop area uses. The rate changes were

proposed due to the comments received from various stakeholders from both the commercial

forestry industry. and the railroad industry which expressed concernabout the measures,

including application parameters and buffer zones, intended to mitigate potential ecological risk

to non-target organisms (endangered and non-endangered plant species). Commenters noted that

Pagel of5
Page 2 of 5 

some of the measures required in the RED would make it difficult or dangerous to use 

sulfometuron methyl in a commercial forestry or railroad rights-of-way settings. During the 

comment period, EPA met with representatives from the National Alliance of Forestry Owners 

(NAFO) and the National Council for Air and Stream Improvement (NCASI) to discuss elements 

of the Agency’s risk assessment including application methods (such as equipment and practices) 

and application rates relevant to forestry uses. Following the comment period, the technical 

registrant, DuPont, also proposed reduced application rates and modified application 

requirements. Based upon the application rate changes proposed, the updated maximum single 

application rate for all forestry applications have been reduced from 0.38 to 0.19 lb ai/acre and 

rights-of-way (non-crop areas) from 0.38 to 0.28 lb ai/ acre. 

HED has reassessed the forestry and rights-of-way (non-crop areas) use sites with the reduced 

application rates. Based upon the updated assessment of short- and intermediate-term combined 

dermal and inhalation occupational exposure/risk from the use of sulfometuron methyl, all 

forestry uses and all except one rights-of-way exposure scenarios (mixing/loading/applying 

liquids with a low pressure handwand) are not of concern to the Agency (i.e., an MOE ≥ 100) at 

baseline level of personal protective equipment (PPE). The exposure scenario 

mixing/loading/applying liquids with a low pressure handwand results in an MOE = 97 at 

baseline level of PPE and an MOE = 21,000 with the addition of chemical resistant gloves. A 

summary of risk calculations performed for occupational sulfometuron methyl forestry and 

rights-of-way uses at baseline PPE is presented below in Table 1; a summary of calculations for 

the occupational uses with additional PPE (single layer plus gloves) is presented in Table 2. 

Table 1. Sulfometuron Methyl MOEs Attributable to Short- and Intermediate-term Combined Dermal 

and Inhalation Occupational Exposure (Baseline PPE)a

No. Scenario Target App. Rateb 

(lb ai/acre) 

Area 

Treated 

(acres) 

Dermalc

MOEs 

Inhalationd

MOEs

Combinede

MOEs 

Mixer/Loaders 

1 

WDGs: Aerial 

Equipment 

(Fixed Wing and 

Helicopter) 

Forestry (Hardwoods, 

Conifers) 0.19 1200 120 10500 120 

2 

WDGs: 

Groundboom 

Equipment 

Forestry (Hardwoods, 

Conifers), Non-Crop 

Areas 

0.19 200 730 63000 720 

3 

WDGs: Rightsof-Way 

Equipment 

Rights-of-Way, NonCrop Areas 0.28 25 4200 360000 4100 

Applicators 

4 

Liquids: Aerial 

Applications 

(Fixed Wing and 

Helicopter) 

Forestry (Hardwoods, 

Conifers) 0.19 1200 1600 120000 1600 
Page 3 of 5 

Table 1. Sulfometuron Methyl MOEs Attributable to Short- and Intermediate-term Combined Dermal 

and Inhalation Occupational Exposure (Baseline PPE)a

No. Scenario Target App. Rateb 

(lb ai/acre) 

Area 

Treated 

(acres) 

Dermalc

MOEs 

Inhalationd

MOEs

Combinede

MOEs 

5 

Liquids: 

Groundboom 

Applications 

Forestry (Hardwoods, 

Conifers) 0.19 200 3500 65000 3300 

6 

Liquids: Rightsof-Way 

Applications 

Rights-of-Way, NonCrop Areas 0.28 25 210 70000 210 

Flaggers 

7 

Liquids: Aerial 

Sprays (Fixed 

Wing and 

Helicopter) 

Forestry (Hardwoods, 

Conifers) 0.19 350 2500 79000 2400 

Mixer/Loader/Applicators 

8 

Liquids: Low 

Pressure 

Handwand 

Rights-of-Way, NonCrop Areas 0.28 1 97 320000 97 

a Baseline = Long pants, long-sleeved shirt, no gloves 

b Application rate based upon maximum labeled value. 

 c Dermal MOE = Dermal NOAEL (27.5 mg/kg/day)/ ( Dermal Daily Dose [Reference W.Britton, 345025]) 

 d Inhalation MOE = Inhalation NOAEL (27.5 mg/kg/day) / ( Inhalation Daily Dose [Reference W.Britton, 

345025]) 

 e Combined MOE = 1/((1/Dermal MOE)+(1/Inhalation MOE)) 

Table 2. Sulfometuron Methyl MOEs Attributable to Short- and Intermediate-term Combined Dermal

 and Inhalation Occupational Exposure (Additional PPE) 

No. Scenario Target App. Ratea 

(lb ai/acre) 

Area 

Treated 

(acres) 

Dermalb

MOEs 

Inhalationc

MOEs

Combinedd

MOEs 

Mixer/Loader/Applicators - Single Layer with Gloves Level of PPE

8 

Liquids: Low 

Pressure 

Handwand 

Rights-of-Way, NonCrop Areas 0.28 1 22000 320000 21000 

 a Application rate based upon maximum labeled value. 

 b Dermal MOE = Dermal NOAEL (27.5 mg/kg/day)/ ( Dermal Daily Dose [Reference W.Britton, 345025]) 

 c Inhalation MOE = Inhalation NOAEL (27.5 mg/kg/day) / ( Inhalation Daily Dose [Reference W.Britton, 

345025]) 

 d Combined MOE = 1/((1/Dermal MOE)+(1/Inhalation MOE)) 
Page 4 of 5 

Risk Characterziation 

Due to a number of deficiencies identified in the conduct of the 21-day dermal study for sulfometuron 

methyl, it was deemed unsuitable for endpoint selection. In lieu of a route-specific study, the endpoint 

from the chronic oral toxicity study in dogs was used to estimate the potential for risk from dermal 

exposure to sulfometuron methyl. The Agency is confident that the use of the chronic oral study results 

in a health protective risk assessment for the following reasons: 

• Although the 21-day dermal study had significant flaws, no toxicity was observed at 2000 

mg/kg/day following 21 days of dosing; 

• The results of the acute dermal toxicity study in rabbits shows an LD50 > 2000 mg/kg [Toxicity 

Category III]); and 

• Dermal risks, which drive handler risks, were calculated assuming 100% dermal absorption due 

to lack of acceptable dermal absorption data. Assuming even a slightly lower dermal absorption 

of 90%, which is still likely to exceed the actual dermal absorption, would result in risk 

estimates which are not of concern for all scenarios, assuming some level of personal protective 

equipment is employed. 

The exposure scenario mixing/loading/applying liquids with a low pressure handwand to rights-of-way 

(non-crop areas) results in the lowest combined MOE = 97 at baseline level of personal protection. 

While this exposure scenario is of potential concern, this concern is significantly reduced because of the 

use of the conservative inputs described above. 

Under the public comment period for sulfometuron methyl, Dupont Crop Protection proposed 

that the Agency consider surrogate data to inform sulfometuron methyl dermal penetration. 

Dupont recommended a dermal penetration value of 10% based upon review of in vitro and in 

vivo dermal penetration values for other DuPont sulfonylureas (i.e., bensulfuron methyl, 

nicosulfuron, tribenuron methyl, rimsulfuron, thifensulfuron methyl and triflusulfuron methyl). 

In the memorandum, “Sulfometuron Methyl: Response to Public Comments for “Phase 3 

Amendment of Sulfometuron Methyl: HED Chapter of the Registration Eligibility Decision 

(RED) (W. Britton, D346177),” HED responded that, “HED reviewed the data on the 

sulfonylurea chemicals provided in Table 1 of the DuPont’s submission. However, no actual 

data with sulfometuron methyl were provided and HED considers it speculative at this time to 

use data from these other sulfonylureas as surrogate data to establish a dermal absorption factor. 

Therefore, in the absence of actual data with sulfometuron methyl, HED uses the more 

conservative default estimate of 100% dermal absorption.” HED continues to support this 

determination. 

Due to the reduction of the application rates for forestry and rights-of-way and despite 

conservative assumptions inputs/assumptions regarding dermal exposure for sulfometuron 

methyl, required personal protective equipment was either reduced to baseline level, or further 

reduced with the addition chemical resistant gloves. HED does not anticipate that a requirement 

for chemical resistant glove use for mixing/loading/applying liquids with a low pressure 

handwand to rights-of-way (non-crop areas) would present increased difficulty or danger for 
Page 5 of 5 

those individuals handling sulfometuron methyl.