UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOX IC SUBST ANCES

MEMORANDUM

DATE: 5/8/2009

SUBJECT: Sulfometuron Methyl: Response to Public Comments for "Phase 3 Amendment of

Sulfometuron Methyl: HED Chapter of the Registration Eligibility Decision (RED)"

PC Code: 12200 I

MRJD No.: NA

Petition No.: NA

Assessment Type: NA

TXRNo.: NA

DP Barcode: 0346177

Registration No.: NA

Regulatory Action: Response to Comments

Reregistration Case No.: NA

CAS No.: 74222 -97-2

FROM:

THROUGH:

TO :

Wade Britton, MPH, Risk Assessor

Risk Assessment Branch V

Health Effects Division (7509P)

Risk

Jack Arthur,

Assessment

Branch

Branch

Chief

V

~.

Health Effects Division (7509 )

Russell Wasem, Chemical Review Manager

Reregistration Branch 1

Special Review & Reregistration Division (7508P)

The Health Effects Division's (HED) Risk Assessment Branch V has addressed public

comments on the human health risk assessment for sulfometuron methyl RED dated

August II , 2008. HED defers to the Environmental Fate and Effects Division (EFED) on

issues identified in the public comments that effect the human health assessment, but

pertain to how EFED calculated concentrations ofsulfometuron methyl's degradates.

HED received public comments from the following groups: DuPont Crop Protection (the

technical registrant), American Forest Management, lnc., Roseburg Resources Company

(Mark Wall and Tim Truax), and an anonymous commenter.

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Comment from DuPont Crop Protection:

Docket ID Number EPA-HQ-OPP-2008-0129-0117, submitted January 9, 2009. 

DuPont proposes the Agency consider surrogate data to inform sulfometuron methyl 

dermal penetration. Due to the absence of a dermal penetration study the Agency 

exposure estimates are driven by a default 100% dermal absorption factor. DuPont’s 

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) ranged from 0.01 to 17.7%. Based on this review, 

DuPont proposed that a penetration value of 10.0% can be conservatively used for the 

assessment of operator exposure. 

HED Response:

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. 

All but one occupational exposure scenario result in MOEs which are not of concern to 

the Agency (at some level of personal protection) using the default estimate for dermal 

absorption. A combined MOE = 90 results for mixing/loading water dispersable 

granulars (WDGs) for aerial application to forestry and non-crop areas. This scenario is 

of concern to the Agency; however, this concern was described as reduced based upon 

conservative inputs (i.e., 100 % dermal absorption) in the risk estimates. 

Comments from Roseburg Resources Company (Mark Wall and Tim Truax) and 

American Forest Management, Inc.:

Roseburg Resources Company (Mark Wall), Docket ID Number EPA-HQ-OPP-2008-

0129-0022, submitted December 31, 2008. 

American Forest Management, Inc., Docket ID Number EPA-HQ-OPP-2008-0129-42 

Roseburg Resources Company (Tim Truax), Docket ID Number EPA-HQ-OPP-2008-

0129-0131, submitted January 9, 2009. 

The following comments and resulting response have been collated due to their similarity 

of topic (i.e., the changes for personal protective equipment (PPE) required due to the 

sulfometuron methyl RED). 

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Mark Wall and Tim Truax of Roseburg Resources Company both commented that the 

proposed PPE rule changes are unnecessary given the “practically non-toxic” status of 

sulfometuron methyl to humans, but are nonetheless not a burden and acceptable as 

presented. 

American Forest Management, Inc. commented that the changes to the proposed PPE 

shown on page 32 appear to be somewhat excessive considering sulfometuron has 

toxicological ratings listed either as a category III or IV rating. The requirement for 

chemical resistant gloves while mixing the concentrated product could be argued, but 

these should not be required for loading or applying a diluted mix with a low pressure 

hand wand. 

HED Response:

The Agency completes occupational handler assessments by using different levels of 

personal protection, or a tiered approach. The lowest tier is represented by the baseline 

scenario (long-sleeved shirt, long pants and no gloves or respiratory protection), followed 

by increasing levels of personal protection represented by personal protective equipment 

(PPE) (e.g., gloves, extra clothing and respirators) and engineering controls (e.g., closed 

cabs and closed loading systems). This approach is always used by the Agency in order 

to be able to define label language using a risk-based approach and not based on generic 

requirements for label language. The minimal level of adequate protection for a chemical 

is generally considered by the Agency to be the most practical option for risk reduction. 

20 occupational exposure scenarios were identified based on the types of equipment and 

techniques that can potentially be used to make sulfometuron methyl applications. Of the 

20 exposure scenarios assessed, 2 (mixing/loading aerial equipment with WDGs and 

mixing/loading/applying liquid with low pressure handwand) resulted in a risk of concern 

at baseline level and, therefore, required an increase (or tiered) level of personal 

protection to equal or exceed the Agency’s level of concern (LOC). 

The exposure data, toxicological endpoints, and other factors which were used to estimate 

occupational exposure/risk represent the best sources of data available to the Agency. 

Maximum application rates were derived directly from sulfometuron methyl labels. 

Exposure factors (e.g., body weight, amount treated per day, protection factors, etc.) are 

all standard values that have been used by the Agency for several years and are derived 

from peer reviewed sources whenever possible. The unit exposure values (UEs) used are 

the best available estimates of exposure. 

The toxicological database for sulfometuron methyl was considered sufficient to provide 

information to conduct a screening level assessment for the occupational exposure 

scenarios identified. The acute toxicity profile (i.e., 6-pack) was not used to for the 

purposes of risk assessment and/or ORE mitigation, rather dermal and inhalation toxicity 

endpoints were used to quantify risk were selected from a chronic dog feeding study. 

Therefore, the required increase in personal protection (chemical resistant gloves) was 

based upon the endpoints selected from the chronic study, not the acute toxicity profile of 

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sulfometuron methyl. A dermal absorption factor of 100% was assumed since no data 

were provided. A full description of the algorithms and inputs used by the Agency to 

assess occupational handler exposure is described in the document, “Sulfometuron 

Methyl: Occupational and Residential Exposure Assessment for the Reregistration 

Eligibility Decision (Non-Food)” (W. Britton, D345025, 12/20/2007). 

Comment from Anonymous: 

Docket ID Number EPA-HQ-OPP-2008-0129-0038, no submission date provided, 

received January 6, 2009. 

An anonymous commenter stated that the Agency’s statements regarding personal 

protective equipment have no merit. The formulation of an extruded pellet or a dry 

flowable formulation. Chemical resistant gloves are most important with liquid or 

emulsifiable concentrate formulations. The proposed label changes are regarding liquid 

formulation. I feel the product label already meets the safety and personal protective 

equipment. 

HED Response: 

The Agency uses a concept known as unit exposure (UE) as the basis for the scenarios 

used to assess occupational worker exposures to pesticides. UEs numerically represent 

the exposures one would receive related to mixing/loading or an application. The 

Agency has developed a series of UEs that are unique for each scenario typically 

considered in our assessments (i.e., there are different unit exposures for different types 

of application equipment, job functions, and levels of protection). The UE concept has 

been established in scientific literature and also through various exposure monitoring 

guidelines published by the Agency and international organizations such as Health 

Canada and OECD (Organization for Economic Cooperation and Development). 

The unit exposure values used to assess occupational exposure for varying scenarios of 

sulfometuron methyl use were based on surrogate exposure data from Pesticide Handlers 

Exposure Database (PHED) Version 1.1. PHED was developed by the Agency to 

provide the best available information on occupational handler exposures. It is a software 

system consisting of two parts – a database of measured exposure values for workers 

involved in the handling of pesticides under actual field conditions and a set of computer 

algorithms used to subset and statistically summarize the selected data. Mixer/loader 

sulfometuron methyl exposure scenarios were estimated using PHED data specific to dry 

flowable (DF) products since this formulation is most similar to WDGs; however, all 

other tasks (i.e., applicators, flaggers, and mixer/loader/applicators) were assessed with 

PHED data specific to liquid products since the WDGs are mixed into and applied as a 

liquid. 

Using the UE values from PHED specific to dry flowable formulations and incorporating 

the tiered approach for estimating exposure and risk described in the previous response, 

the Agency determined that double layer (i.e., coveralls over a single layer of clothing) 

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and chemical resistant gloves are required for mixing/loading for aerial equipment with 

WDGs (e.g., an MOE = 64 without gloves and an MOE = 90 results with the addition of 

gloves). Employing the same method of risk quantification/estimation, the Agency 

determined that single layer of clothing and gloves are required for 

mixing/loading/applying liquids with a low pressure handwand. 

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