UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF           

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

December 20, 2007

					

MEMORANDUM

SUBJECT:	Sulfometuron Methyl:  Occupational and Residential Exposure
Assessment for the Reregistration Eligibility Decision (Non-Food).  

					

FROM:	Wade Britton, MPH, Industrial Hygienist

		Reregistration Branch 3

		Health Effects Division (7509P)					

THROUGH:	Catherine Eiden, Branch Chief

		And

		Danette Drew, Chemist

		Reregistration Branch 3

		Health Effects Division (7509P)

TO:		Russell Wasem, Chemical Review Manager

		Reregistration Branch 1

		Special Review and Reregistration Division (SRRD) (7508P)

DP Barcode:  D345025

Pesticide Chemical Code:  122001

ExpoSAC Review Date: 10/11/07; Kelly O’Rourke, Seyed Tadayon

Table of Contents

  TOC \o "1-3" \h \z \u    HYPERLINK \l "_Toc185824932"  Executive
Summary	  PAGEREF _Toc185824932 \h  3  

  HYPERLINK \l "_Toc185824933"  1.0	Occupational Exposure/ Risk
Assessment	  PAGEREF _Toc185824933 \h  4  

  HYPERLINK \l "_Toc185824934"  1.1	Criteria for Conducting Exposure
Assessments	  PAGEREF _Toc185824934 \h  4  

  HYPERLINK \l "_Toc185824935"  1.2 	Toxicological Endpoints	  PAGEREF
_Toc185824935 \h  4  

  HYPERLINK \l "_Toc185824936"  1.3	Incident Report	  PAGEREF
_Toc185824936 \h  5  

  HYPERLINK \l "_Toc185824937"  1.4	Summary of Use Patterns,
Formulations and Application Methods	  PAGEREF _Toc185824937 \h  5  

  HYPERLINK \l "_Toc185824938"  2.0 	Occupational Exposure/ Risks	 
PAGEREF _Toc185824938 \h  6  

  HYPERLINK \l "_Toc185824939"  2.1	Occupational Handler Exposure/Risks	
 PAGEREF _Toc185824939 \h  7  

  HYPERLINK \l "_Toc185824940"  2.1.1	Data and Assumptions for Handler
Exposure Scenarios	  PAGEREF _Toc185824940 \h  8  

  HYPERLINK \l "_Toc185824941"  2.1.2    Sulfometuron Methyl Handler
Exposure Scenarios	  PAGEREF _Toc185824941 \h  10  

  HYPERLINK \l "_Toc185824942"  2.1.3	Sulfometuron methyl Handler
Exposure/Risk Calculations	  PAGEREF _Toc185824942 \h  10  

  HYPERLINK \l "_Toc185824943"  2.1.4	Occupational Handler Exposure/Risk
Estimates	  PAGEREF _Toc185824943 \h  12  

  HYPERLINK \l "_Toc185824944"  2.1.5	Risk Characterization	  PAGEREF
_Toc185824944 \h  14  

  HYPERLINK \l "_Toc185824945"  2.2	Occupational Postapplication
Exposure/Risks	  PAGEREF _Toc185824945 \h  15  

  HYPERLINK \l "_Toc185824946"  3.0	Residential Exposure/Risks	  PAGEREF
_Toc185824946 \h  15  

  HYPERLINK \l "_Toc185824947"  References:	  PAGEREF _Toc185824947 \h 
15  

  HYPERLINK \l "_Toc185824948"  Appendix A: Occupational Handler Unit
Exposure Data	  PAGEREF _Toc185824948 \h  16  

 

Executive Summary

Sulfometuron methyl is a non-selective, sulfonyl urea herbicide.  It is
labeled for commercial pre- and post-emergent applications to manage
annual and perennial broadleaf weeds and grasses in non-agricultural
sites (i.e., forestry, rights of way, industrial sites, and unimproved
turf).  Based upon the 11/28/2006 sulfometuron methyl SMART meeting,
there are no registered uses for sites which could be considered
residential or recreational settings.  While labeled use sites of
sulfometuron methyl include turf (unimproved) and non-crop industrial,
label language prohibits application to these sites in residential and
recreational areas.  According to the OPPIN Database, there are
currently a total of 24 registered products of which 4 are technical or
manufacturing concentrate formulations.  Applications ranging from 0.03
to 0.38 pound of active ingredient (ai) per acre may be made using
ground or aerial equipment. All registered sulfometuron products are
formulated as water dispersable granules (WDGs).    

Hazard Concerns

The dermal and inhalation endpoints were selected from a chronic oral
study in dogs (1983, MRID No.: 129051) since the 21-day dermal rabbit
study was determined to be insufficient to assess dermal exposures due
to a number of deficiencies and no route specific study was available
for inhalation toxicity. With chronic oral exposure, signs of hemolytic
anemia were observed in dogs and body weight effects were seen beginning
on week 4 (and persisting throughout the entire study) of repeated
exposure.  Although no hematological or clinical chemistry assessments
are available at the 4-week interval, the decreases in body weight gain
noted beginning on the fourth week of the study provide an appropriate
endpoint for short-term risk assessment.  Since the hematological
effects noted at the end of the study occurred at the same dose level as
the body weight gain decrements seen beginning on the fourth week of
exposure, this study and endpoints are also appropriate to assess
potential intermediate- and long-term risks due to sulfometuron methyl
exposure. 

Occupational Handler Exposure/Risk

Short- (up to 30 days) and intermediate-term (30 days to 6 months)
dermal and inhalation exposures/risks were calculated for occupational
handlers of sulfometuron methyl for different exposure scenarios. 
Long-term handler exposures (greater than 6 months) are not expected to
occur.  All but one of the occupational handler short- and
intermediate-term scenarios assessed (dermal and inhalation combined)
resulted in risk estimates (MOEs) ≥ 100 at some level of personal
protection and, therefore, are not of concern.  The exposure scenario
mixing/loading WDGs for aerial application to forestry and non-crop
areas results in a combined MOE = 90 at the maximum level of personal
protection (double layer with gloves) and, therefore, is of potential
concern.  However, this concern is significantly reduced because of the
use of conservative inputs in the risk estimates (e.g., 100% dermal
absorption).

Occupational Postapplication Exposure/Risk

An occupational postapplication assessment of exposure to sulfometuron
methyl was not performed. Since sulfometuron methyl is a non-selective
herbicide used in non-agricultural areas, HED has determined that
contact with previously treated areas is likely to be insignificant.  

Residential Handler and Postapplication Exposure/Risk 

Residential exposure/risk (handler and postapplication) was not assessed
since label instructions do not allow applications of sulfometuron
methyl to residential or recreational settings.   

Occupational Exposure/ Risk Assessment

Criteria for Conducting Exposure Assessments

An occupational and/or residential exposure assessment is required for
an active ingredient if (1) certain toxicological criteria are triggered
and (2) there is a potential for exposure to handlers during use or to
persons entering treated sites after application is complete. 
Sulfometuron methyl meets the first criterion based upon the potential
for exposure to occupational handlers of sulfometuron methyl.  

	1.2 	Toxicological Endpoints

The toxicology database for sulfometuron methyl is limited, but
sufficient to provide screening level endpoints for this
non-food/non-feed pesticide.  Sulfometuron methyl is not acutely toxic. 
The acute oral LD50 in rats is > 5 g/kg (Toxicity Category IV), the
acute dermal LD50 is > 2 g/kg (Toxicity Category III), and the acute
inhalation LC50 > 5.0 mg/L (Toxicity Category IV).  Sulfometuron methyl
shows minimal eye irritation and minimal skin irritation, but is not
considered a dermal irritant or dermal sensitizer.  The acute toxicity
for sulfometuron methyl is presented in Table 1.  The toxicological
endpoints used to complete the occupational exposure assessment are
summarized in Table 2.  

  

Table 1.	Acute Toxicity Profile – Sulfometuron Methyl1

Guideline No.	Study Type	MRID(s)	Results	Toxicity Category

870.1100	Acute oral - rat	43089201	LD50 = > 5000 mg/kg	IV

870.1200	Acute dermal [species]	43089202	LD50 = > 2000 mg/kg 	III

870.1300	Acute inhalation – rat	43089203	LC50 = > 5 mg/L	IV

870.2400	Acute eye irritation [species]	00071412	Minimal Irritant	III

870.2500	Acute dermal irritation [species]	41672808	Not a Dermal
Irritant	IV*

870.2600	Skin sensitization [species]	43089204	Not a Dermal Sensitizer
N/A

1 All studies were conducted on technical grade Sulfometuron methyl, of
at least 98.8%, purity.

* Minimal  skin irritation was noted in the acute dermal toxicity study 
(MRID 43089202) and an older dermal dermal irritation study of a 75%
formulation (MRID 00071411)

Table 2.  Summary of Toxicological Doses and Endpoints for Sulfometuron
Methyl for Use in Occupational Human Health Risk Assessments

Exposure/

Scenario	Point of Departure	Uncertainty Factors	Level of Concern for
Risk Assessment	Study and Toxicological Effects



Dermal and Inhalation Short- (1-30 days)  and Intermediate-Term (1-6
months)

(no residential uses)	NOAEL= 27.5 mg/kg/day	UFA=10x

UFH=10x	MOE = 100	Chronic 1-year dog study

LOAEL = 148.5 mg/kg/day based on decreases in body weight in males
(beginning on the fourth week of exposure and persisted throughout),
hemolytic anemia and a slight increase in alkaline phosphatase in males
and females

Cancer (oral, dermal, inhalation)	No data available for assessment

UF = uncertainty factor.  UFA = extrapolation from animal to human
(intraspecies).  UFH = potential variation in sensitivity among members
of the human population (interspecies).  MOE = margin of exposure. 

	1.3	Incident Report

The incident report was incomplete at the time of document submission
(please see R.H. Allen, M. Hawkins & H. Allender, D343943).

	1.4	Summary of Use Patterns, Formulations and Application Methods

Sulfometuron methyl is a nonselective herbicide labeled for pre- and
post-emergent applications to manage annual and perennial grasses and
broadleaf weeds.  All sulfometuron methyl products are formulated as WDG
(ranging from 18 to 75% ai) and are directed to the target via liquid
spray applications via aerial or ground application methods.  Registered
uses of sulfometuron methyl include:

forestry (conifers, hardwoods, hybrid poplar plantations);

non-crop industrial sites (public, private, and military lands,
rights-of-way, under asphalt and concrete);

turf (unimproved); and

non-crop habitat restoration sites.

Mode of Action and Targets Controlled

Sufometuron methyl acts by inhibiting acetolactate synthase (ALS), an
enzyme that catalyzes the biosynthesis of three branched-chain amino
acids (valine, leucine, and isoleucine), all of which are essential for
plant growth.  

Formulation Types and Percent Active Ingredient

A listing of registered sulfometuron methyl products are summarized
below in Table 3.  All products are formulated as WDGs.  

Table 3.  End-Use Product Formulations and EPA Reg. Number

Formulation Type	Number of Products	EPA Registration Number (Percent
Active Ingredient)

WDG	20	352-401 (75%), 352-408 (75%), 352-601 (75%), 352-603 (63.2%),
352-620 (56.3%), 352-621 (50%), 352-622 (56.3%), 352-626 (68.6%),
352-645 (50%), 352-647 (56.3%), 352-712 (18%), 352-725 (18%), 66330-326
(75%), 53883-164 (75%), 74477-7 (75%), 74477-11 (56.3%), 79676-16 (75%),
81927-5 (56.3%), 81959-2 (75%), 81959-15 (56.3%) 

Technical/ Manufacturing Product	4	352-554 (97.6%), 66330-322 (99%),
74477-3 (99%), 81959-1 (99%)





Application Rates, Timing and Frequency of Applications

Application rates of sulfometuron methyl range from 0.03 to 0.38 pound
of active ingredient (ai) per acre. Control is generally for a full
season or longer with only one required application per year; however,
in some situations (i.e., weed escapes) a second application may be
made, but the total applied annually should not exceed the maximum
application rate. 

Application Methods

Applications of sulfometuron methyl can be made aerially (helicopter and
fixed-wing airplane) or by ground (high and low pressure handwand,
groundboom, and rights-of-way sprayer).  Low pressure handwand
applications are typical for selective foliar applications (applied to
target vegetation), while aerial, groundboom, and rights-of-way
applications are specific to wide-area, broadcast treatments.

2.0 	Occupational Exposure/ Risks

It has been determined there is a potential for exposure in occupational
scenarios from handling sulfometuron methyl products during the
application process (i.e., mixer/loaders, applicators, flaggers, and
mixer/loader/applicators).  A risk assessment has been completed for the
occupational handling of sulfometuron methyl; however, an occupational
postapplication assessment of exposure to sulfometuron methyl was not
performed.  Since sulfometuron methyl is a non-selective herbicide used
in non-agricultural areas, HED has determined that contact with
previously treated areas is likely to be insignificant.  

2.1	Occupational Handler Exposure/Risks 

The Agency uses the term “handlers” to describe those individuals
who are involved in the pesticide application process.  The Agency
believes that there are distinct tasks related to applications and that
exposures can vary depending on the specifics of each task.    SEQ
CHAPTER \h \r 1 Job requirements (e.g., the amount of chemical to be
used in an application), the kinds of equipment used, and the target
being treated can cause exposure levels to differ in a manner specific
to each application event.

The first step in the handler risk assessment process is to identify the
kinds of individuals that are likely to be exposed to sulfometuron
methyl during the application process.  In order to do this in a
consistent manner, HED has developed a series of general descriptions
for tasks that are associated with pesticide applications.  Tasks
associated with occupational pesticide use (i.e., for “handlers”)
can generally be categorized using one of the following terms:

Mixers and/or Loaders:  these individuals perform tasks in preparation
for an application.  

Applicators: these individuals operate application equipment during the
release of a pesticide product into the environment. 

Flaggers: these individuals guide aerial applicators during the release
of a pesticide product onto an intended target.

Mixer/Loader/Applicators: these individuals are involved in the entire
pesticide application process (i.e., they do all job functions related
to a pesticide application event).  

Next, assessors must understand how exposures to sulfometuron methyl
occur (i.e., frequency and duration) and how the patterns of these
occurrences can cause the effects of the chemical to differ (referred to
as dose response).  Wherever possible, use and usage data determine the
appropriateness of certain types of risk assessments.  Other parameters
are also defined from use and usage data such as application rates and
application frequency.  HED always completes non-cancer risk assessments
using maximum application rates for each scenario because what is
possible under the label (the legal means of controlling pesticide use)
must be evaluated in order to ensure there are no concerns for each
specific use.

  

HED believes that occupational sulfometuron methyl exposures can occur
over a single day or up to weeks at a time for many use-patterns and
intermittent exposures over several weeks are also anticipated.  Custom
or commercial applicators may apply sulfometuron methyl over a period of
weeks completing applications for a number of different clients.  HED
classifies exposures up to 30 days as short-term and exposures greater
than 30 days up to several months (6) as intermediate-term.  Based upon
the use pattern of sulfometuron methyl, HED anticipates both short- and
intermediate-term occupational exposure.  Long-term handler exposures
(greater than 6 months) are not expected to occur.  The dermal and
inhalation endpoint selected for sulfometuron methyl is for short- and
intermediate-term durations of exposure.  

2.1.1	Data and Assumptions for Handler Exposure Scenarios  TC \l3 "2.1.1
Data and Assumptions For Handler Exposure Scenarios 

Assumptions for Handler Exposure Scenarios  TC \l4 "2.1.1.1	Assumptions
for Handler Exposure Scenarios 

A series of assumptions and exposure factors served as the basis for
completing the occupational handler risk assessments.  The assumptions
and factors used in the risk calculations include:

HED has patterned this risk assessment on a series of likely
representative scenarios that are believed by HED to represent the vast
majority of sulfometuron methyl uses;

Average body weight of an adult handler is 70 kg because the toxicity
endpoint values used for the assessments are appropriate for average
adult body weight representing the general population;

For non-cancer assessments, HED assumes the maximum application rates
allowed by labels in its risk assessments;

Since no dermal absorption data are available, a default 100% absorption
factor is assumed;

The average occupational workday is assumed to be 8 hours; and 

The daily areas treated were defined for each handler scenario (in
appropriate units) by determining the amount that can be reasonably
treated in a single day (e.g. acres, square feet, or gallons per day).
The assumptions for daily areas treated are taken from the HED ExpoSAC
SOP #9: Standard Values for Daily Acres Treated in Agriculture which was
completed on July 5, 2000.  

Aerial Applications for Forestry – 1200 acres

Groundboom Applications – 200 acres

Flaggers – 350 acres

Right-of-Way Sprayer –  25 acres (based upon 1000 gallons/day, as
specified by SOP #9, and a labeled rate of 40 gallons/acre)

Low Pressure Handwand Sprayer – 1 acre (based upon 40 gallons/day, as
specified by SOP #9, and a labeled rate of 40 gallons/acre)

Data for Handler Exposure Scenarios  TC \l4 "2.1.1.2	Exposure Data for
Handler Exposure Scenarios 

No chemical specific information was available for sulfometuron methyl
handler exposure assessments.  All analyses were completed using
acceptable surrogate exposure data for the scenario in question.

HED uses a concept known as unit exposure as the basis for the scenarios
used to assess handler exposures to pesticides.  Unit exposures
numerically represent the exposures one would receive related to an
application.  They are generally presented as mg active ingredient
exposure/pounds of handled (mg ai/lb).  HED has developed different unit
exposures for different types of application equipment; job functions;
and levels of protection.  The unit exposure concept has been
established in the scientific literature and also through various
exposure monitoring guidelines published by the U.S. EPA and
international organizations such as Health Canada and OECD (Organization
for Economic Cooperation and Development).  All unit exposure values
used to assess occupational handler exposure/risk are presented in
Appendix A at the end of this document.  

Pesticide Handler Exposure Database (PHED) Version 1.1 (August 1998): 

PHED was designed by a task force of representatives from the US EPA,
Health Canada, the California Department of Pesticide Regulation, and
member companies of the American Crop Protection Association.  PHED 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.  Currently, the database
contains values for over 1,700 monitored individuals (i.e., records). 
The distribution of exposure values for each body part (e.g., chest,
upper arm) is categorized as normal, lognormal, or “other” (i.e.,
neither normal nor lognormal).  A central tendency value is then
selected from the distribution of the exposure values for each body
part.  These values are the arithmetic mean for normal distributions,
the geometric mean for lognormal distributions, and the median for all
“other” distributions.  Once selected, the central tendency values
for each body part are composited into a “best fit” exposure value
representing the entire body.

The unit exposure values calculated by PHED generally ranges from the
geometric mean to the median of the selected data set.  To add
consistency and quality control to the values produced from this system,
the PHED Task Force has evaluated all data within the system and has
developed a set of grading criteria to characterize the quality of the
original study data.  The assessment of data quality is based upon the
number of observations and the available quality control data.  While
data from PHED provide the best available information on handler
exposures, it should be noted that some aspects of the included studies
(e.g., duration, acres treated, pounds of active ingredient handled) may
not accurately represent labeled uses in all cases.  HED has developed a
series of tables of standard unit exposures for many occupational
scenarios that can be used to ensure consistency in exposure
assessments.

Review of Human Research

This risk assessment relies in part on data from studies in which adult
human subjects were intentionally exposed to a pesticide or other
chemical.  The studies which compose PHED were determined to require a
review of their ethical conduct, have received that review and have been
determined to be ethical.

2.1.2    Sulfometuron Methyl Handler Exposure Scenarios  TC \l3 "2.1.2
Imazapyr Handler Exposure Scenarios 

Exposure to pesticide handlers is likely during the occupational use of
sulfometuron methyl based on the types of equipment and techniques that
can potentially be used.  The quantitative exposure/risk assessment
developed for occupational handlers is based on the following scenarios.
 Sulfometuron methyl dermal and inhalation exposure was estimated using
PHED data.  Mixer/loader 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. 

	Mixer/Loaders:

	(1) WDG: Aerial (Fixed Wing Airplane and Helicopter)

(2) WDG: Groundboom

(3) WDG: Right-of-Way Applications

	

Applicators:

	(4) Liquid: Aerial Applications (Fixed Wing Airplane and Helicopter)

(5) Liquid: Groundboom Applications

(6) Liquid: Rights of Way Applications

	Flaggers:

	(7) Flagging for Aerial Sprays

	Mixer/Loader/Applicators:	

	(8) Liquid: Low Pressure Handwand Sprayer

	

Sulfometuron methyl Handler Exposure/Risk Calculations

The daily exposure is the product of the amount of active ingredient
(ai) handled per day and a unit exposure value. The amount of ai handled
per day is the product of the application rate and the area treated. 
For example, if 0.188 lb ai/acre of sulfometuron methyl were applied to
1200 acres in one day, the amount of sulfometuron methyl handled that
day would be 226 lbs.  The unit exposure value is the amount of exposure
that results from handling a given amount of active ingredient by a
certain method while using certain PPE.  For example, the dermal unit
exposure value for open mixing and loading of granulars (WDG) with
baseline PPE is 0.066 mg per pound of ai handled.  In this example, the
daily exposure would be 226 lbs ai handled multiplied by 0.066 mg unit
exposure per pound of ai handled which equals 15 mg per day.  The daily
absorbed dose (mg/kg body weight) is calculated from the exposure by
multiplying the exposure by an absorption factor (1.0) and dividing the
result by the body weight (70 kg).  In this example the absorbed daily
dose (ADD) would be (15 mg/day *1.0)/70 kg which would equal 0.21
mg/kg/day.  The MOE is calculated by dividing the endpoint for the
appropriate pathway (inhalation endpoint is a NOAEL = 27.5 mg/kg/day) by
the ADD.  For this example, the resulting MOE = 130 (rounded to 2
significant figures).

Daily dermal exposure is calculated:

Daily dermal exposure = Unit exposure x Application rate x Area Treated 

          (mg/day)                     (mg/lb ai)         ( lb ai/acre) 
       (acres/day)

Where:

Unit exposure = 	normalized exposure value (mg exposure per pound ai
handled) derived from PHED surrogate exposure data (Appendix A);

Application rate = 	normalized application rate based on a logical unit
treatment such as acres, a maximum value is generally used (lb ai/acre);
and

Area treated = 		normalized application area such as acres/day.

Daily inhalation unit exposure values were calculated for inclusion into
the PHED surrogate exposure tables and presented as (μg/lb ai) based on
a human inhalation rate of 29 L/minute and an 8-hour working day.

Daily inhalation exposure is calculated:

Daily inhalation exposure =   [Unit exposure x Application rate x Area
Treated] / Conversion Factor

    (μg/kg/day)	        (lb ai/acre)	       (acres/day)	 (1 mg/1000
μg)

Where:

Unit exposure = 		normalized exposure value (μg/lb ai handled) derived
from PHED;

Application rate = 	same as for dermal exposure (lb ai/acre); and

Daily treatment = 	same as for dermal exposure (acres/day).

Absorbed daily dermal and inhalation doses are then calculated by
adjusting for dermal and inhalation absorption and normalizing by body
weight. A body weight of 70 kg (average body weight) was used because
the effects observed in the toxicology study were not gender specific.

ADD is calculated:

Absorbed daily dermal/inhalation dose = (Daily dermal/inhalation
exposure x abs factor) /body weight 		(mg/kg/day) 				(mg/day) 	        
  (unitless)	        (kg)

[Note: an absorption factor of 1.0 was used for dermal and inhalation
exposures.]

The level of concern for occupational handlers is defined by an MOE =
100. Exposure scenarios with estimated risk (MOEs) greater the level of
concern (i.e., an MOE ≥ 100) do not indicate a risk of concern for the
occupational population.

MOEs are calculated for each individual pathway (dermal, inhalation)
using the MOE formula:

MOE (unitless) =   NOAEL / ADD

Combined MOEs (dermal and inhalation) were calculated for sulfometuron
methyl because common toxicity endpoints were used to calculate dermal
and inhalation risks.  The dermal and inhalation MOEs were combined
using the formula below:

                                 

Combined MOE      =                              
    1                         __

          (1/Dermal MOE ) + (1/Inhalation MOE)

Occupational Handler Exposure/Risk Estimates

sessed (dermal and inhalation combined) resulted in risk estimates
(MOEs) ≥ 100 at some level of personal protection and, therefore, are
not of concern.  The exposure scenario mixing/loading of WDGs for aerial
application to forestry and non-crop areas results in a combined MOE =
90 at the maximum level of personal protection (double layer with
gloves) and, therefore, is of potential concern.  A summary of risk
calculations performed for occupational sulfometuron methyl handlers at
baseline PPE is presented below in Table 4; a summary of calculations
for occupational sulfometuron methyl handlers with additional PPE is
presented in Table 5. (as mentioned previously, unit exposure values are
provided in Appendix A).

Table 4.  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	InhalationdMOEs	

Combinede MOEs



Mixer/Loaders

1	WDGs: Aerial Equipment (Fixed Wing and Helicopter)	Forestry
(Hardwoods, Conifers), Non-Crop Areas (Public, Private, Military Lands)
0.38	1200	65	5600	64



Turf (Unimproved)	0.19

130	11000	130



Non-Crop Land Restoration	0.09

260	22000	260

2	WDGs: Groundboom Equipment	Forestry (Hardwoods, Conifers), Non-Crop
Areas	0.38	200	390	33000	380



Turf (Unimproved)	0.19

780	66000	770



Non-Crop Land Restoration	0.09

1500	130000	1500

3	WDGs:  Rights-of-Way Equipment	Rights-of-Way, Non-Crop Areas	0.38	25
3100	270000	3100



Turf (Unimproved)	0.19

6200	530000	6100



Non-Crop Land Restoration	0.09

12000	1100000	12000

Applicators

4	Liquids: Aerial Applications (Fixed Wing and Helicopter)	Forestry
(Hardwoods, Conifers), Non-Crop Areas 	0.38	1200	900	63000	840



Turf (Unimproved)	0.19

1700	130000	1700



Non-Crop Land Restoration	0.09

3400	250000	3400

5	Liquids: Groundboom Applications	Forestry (Hardwoods, Conifers),
Non-Crop Areas	0.38	200	1800	35000	1700



Turf (Unimproved)	0.19

3700	70000	3500



Non-Crop Land Restoration	0.09

7300	140000	7000

6	Liquids: Rights-of-Way Applications	Rights-of-Way, Non-Crop Areas	0.38
25	160	53000	160



Turf (Unimproved)	0.19

320	110000	310



Non-Crop Land Restoration	0.09

630	210000	630

Flaggers

7	Liquids: Aerial Sprays (Fixed Wing and Helicopter)	Forestry
(Hardwoods, Conifers), Non-Crop Areas 	0.38	350	1300	42000	1300



Turf (Unimproved)	0.19

2700	84000	2600



Non-Crop Land Restoration	0.09

5300	170000	5200

Mixer/Loader/Applicators

8	Liquids: Low Pressure Handwand	Non-Crop Areas	0.38	1	51	170000	51



Turf (Unimproved)	0.19

100	340000	100



Non-Crop Land Restoration	0.09

210	680000	210

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

 and Inhalation Occupational Exposure (Required Additional PPE)

No.	Scenario	Target	App. Ratea

(lb ai/acre)	Area Treated (acres)	Dermalb MOEs	InhalationcMOEs	

Combinedd MOEs



Mixer/Loaders - Double Layer with Gloves Level of PPE

1	WDGs: Aerial Equipment (Fixed Wing and Helicopter)	Forestry
(Hardwoods, Conifers), Non-Crop Areas (Public, Private, Military Lands)
0.38	1200	91	5600	90

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

8	Liquids: Low Pressure Handwand	Non-Crop Areas	0.38	1	12000	170000
12000

	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))

2.1.5	Risk Characterization

The occupational handler dermal exposure scenario is the only scenario
for which significant risks were estimated for some uses; other risk
assessments completed (e.g., chronic and acute drinking water) were not
of concern.  Due to a number of deficiencies identified in the conduct
of the 21-day dermal study, 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 of WDGs for aerial application to
forestry and non-crop areas results in the lowest combined MOE = 90 at
the maximum level of personal protection (double layer with gloves). 
While this exposure scenario is of potential concern, this concern is
significantly reduced because of the use of the conservative inputs
described above.

2.2	Occupational Postapplication Exposure/Risks  TC \l2 "2.2
Occupational Postapplication Exposures and Risks 

HED uses the term “postapplication” to describe exposures to
individuals that occur as a result of being in an environment that has
been previously treated with a pesticide (also referred to as reentry
exposure).  HED believes that there are distinct job functions or tasks
related to the kinds of activities that occur in previously treated
areas.  Job requirements (e.g., the kinds of jobs to cultivate a crop),
the nature of the crop or target that was treated and how the chemical
residues degrade in the environment can cause exposure levels to differ
over time.  

An assessment of occupational postapplication exposure to sulfometuron
methyl was not performed. Since sulfometuron methyl is a non-selective
herbicide used in non-agricultural areas, HED has determined that
contact with previously treated areas is likely to be insignificant.  

3.0	Residential Exposure/Risks

Residential exposure/risk (handler and postapplication) was not assessed
since label instructions do not allow applications of sulfometuron
methyl to residential or recreational settings.   

  

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References:

US EPA. 1998a. "PHED Surrogate Exposure Guide. Estimate of Worker
Exposure from the Pesticide Handlers Exposure Database," Version 1.1. 
Science Advisory Council for Exposure, Office of Pesticide Programs.
U.S. Environmental Protection Agency. Washington, DC.  August, 1998. 

US EPA, 2000.  "Science Advisory Council for Exposure, Policy #: 9.
Standard Values for Daily Acres Treated in Agriculture."  Science
Advisory Council for Exposure, Office of Pesticide Programs, U. S.
Environmental Protection Agency, Washington, DC.  July, 2000.

Appendix A: Occupational Handler Unit Exposure Data

Table A.  Exposure Data Used for Occupational Handler/Applicator Risk
Assessment (PHED Data)

Exposure Scenarios	Baseline Dermal (Single Layer Gloves) 

(mg/ lb ai)	Baseline Inhalation (No Respirator) 

(µg/ lb ai)	Dermal – Additional PPE  (mg/ lb ai)

Mixer Loader Unit Exposure Values

WDGs: Aerial Equipment	0.066	0.77	0.047 

(Double Layer with Gloves)

WDGs: Groundboom Equipment

	NA

WDGs: Rights of Way Equipment



	Applicator Unit Exposure Values

Liquids: Aerial Applications (Fixed Wing)	0.005	0.068	NA

Liquids: Groundboom Applications (Open Cab)	0.014	0.74	NA

Liquids: Rights of Way Equipment	1.3	3.9	NA

Flagger Unit Exposure Values

Liquids: Aerial Sprays	0.011	0.35	NA

Mixer/Loader/Applicator Unit Exposure Values

Liquids: Low Pressure Handwand	100	30	0.43 

(Single Layer with Gloves)



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