UNIT ED STA TES EN V IRON MENT AL PR OTECTION A GENCY W ASHI NGTON, D .C

. 20460 OFF ICE OF PREVENTION

. PESTIC IDES AND TOX I C S U BSTAN CES

M E MORA ND UM

DAT E: 12 /02/2009

SU BJECT: Sulfometuron Methyl: Amendment to t he "1-IED Ch apt e r o f the Reregi strati on E ligibility Deci sion Doc ume nt (RE D) (D 346064)"

P C C ode: 1 2200 I MRID N o.: NA Petition N o.: NA A sse ssment T ype: Amendmen t T XR N o.: NA DP Barcode: D 346 192 Registration No .: NA Regulatory Action: Risk A ssess ment Reregi stration C ase No. : NA CAS No .: 74 222-97 -2

F ROM :

TH ROU GH:

TO : Wa de B ritton
, In dustri a l H ygienist

# ~~ R

i sk As sess ment Bran ch V 

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H ealt h E ffects D ivision (7 509P)

.

Ja ck A rthur, Br anch C hi ef

# ~~ Ri sk Assess ment Branch V Health E ffects Di vi sion (750 P )

Ru ssell W asem Ri sk M an ag em e n t and Im plementat ion B ran ch I Pes ticide R e-evaluation Di vision (7508 P)

The purpose of thi s document is t o ame nd the m emorandum, " HED Chapter o f the Re registration E

lig i bi l ity D eci s ion Doc ument (RE D) ( D346064), " based upon ch anges i n th e maximum si ngle applica tion rat e s fo r fores try. ri ghts-of-way and n on-crop ar ea uses . The ra te chang es we re p roposed du e t o th e com ment s r eceived from va rious stake holders f rom bot h th e co mmercial f ores t ry i ndustry. and th e r ailroad i ndustry w hich ex pre sse d co ncern abo ut th e m e asure s, including app li cation p aramete r s and b uffer zo ne s, int ended to m itigate po ten tia l e co logi cal r isk t o n on - target orga nism s (e ndangered a nd n on -e ndang ered plant s pecies). Commenters noted th at

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### Page 2 of 5 some of the measures required in the RED w ould 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 fro m the National Alliance of Forestry Owners (NAFO) and the National Council for Air and Str eam Improvement (NCASI) to discuss elements of the Agency’s risk assessment including applic ation methods (such as equipment and practices) and application rates relevant to forestry us es. Following the comment period, the technical registrant, DuPont, also proposed reduced application rates and m odified 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) fr om 0.38 to 0.28 lb ai/ acre.

HED has reassessed the forestry and rights-of-w ay (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-w ay exposure scenarios (mixing/loading/applying liquids with a low pressure handwand) are no t of concern to the Agency (i.e., an MOE ≥ 100) at baseline level of personal protective e quipment (PPE). The exposure scenario mixing/loading/applying liquids with a low pr essure handwand results in an MOE = 97 at baseline level of PPE and an MOE = 21,000 with th e addition of chemical resistant gloves. A summary of risk calculations performed for occupational sulf ometuron 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. Rate b (lb ai/acre) Area Treated (acres) 

### Dermal c 

### MOEs Inhalation d MOEs Combined e 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. Rate b (lb ai/acre) Area Treated (acres) 

### Dermal c 

### MOEs Inhalation d MOEs Combined e 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. Rate a (lb ai/acre) Area Treated (acres) 

### Dermal b 

### MOEs Inhalation c MOEs Combined d 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 th e conduct of the 21-day dermal study for sulfometuron methyl, it was deemed unsuitable for endpoint selecti on. In lieu of a route-sp ecific 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 conf ident 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 t oxicity study in rabbits shows an LD 50 

### > 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 ac tual dermal absorption, would result in risk estimates which are not of concern for all scenar ios, 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 sulfom eturon methyl, Dupont Cr op Protection proposed that the Agency consider surrogate data to in form 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 Du Pont sulfonylureas (i.e., bensulfuron methyl, nicosulfuron, tribenuron methyl, ri msulfuron, thifensulfuron methyl and triflusulfuron methyl). In the memorandum, “Sulfometuron Methyl: Re sponse to Public Comments for “Phase 3 Amendment of Sulfometuron Methyl: HED Chapte r 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 an d HED considers it speculative at this time to use data from these other sulfonylur eas as surrogate data to estab lish a dermal absorption factor. Therefore, in the absence of actual data w ith sulfometuron methyl, HED uses the more conservative default estimate of 100% dermal absorption.” HED conti nues 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 protectiv e equipment was either reduced to baseline level, or further reduced with the addition chemical resistant glov es. HED does not anticip ate that a requirement for chemical resistant glove use for mixing/lo ading/applying liquids with a low pressure handwand to rights-of-way (non-crop areas) woul d present increased difficulty or danger for

### Page 5 of 5 those individuals handling sulfometuron methyl.