UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF           

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

December 20, 2007

					

MEMORANDUM

SUBJECT:	Sulfometuron Methyl:  Acute and Chronic Screening-Level
Drinking Water Only Dietary Risk Assessment for the Non-Food/Non-Feed
Use Reregistration Eligibility Decision (RED). DP Barcode: D346139.  PC
Chemical Code: 122001. 

					

FROM:	Wade Britton, MPH, Industrial Hygienist and Risk Assessor

		Reregistration Branch 3

		Health Effects Division (7509P)					

THROUGH:	Sarah Winfield, DESAC Designated Reviewer

		Thurston Morton, DESAC Designated Reviewer

		And

		Catherine Eiden, Branch Chief

		Reregistration Branch 3

		Health Effects Division (7509P)

TO:		Russell Wasem, Chemical Review Manager

		Reregistration Branch 1

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

An unrefined acute and chronic screening-level drinking water only
dietary assessment was conducted for the herbicide sulfometuron methyl
using the Dietary Exposure Evaluation Model DEEM-FCID™, Version 2.03
which use food consumption data from the U.S. Department of
Agriculture’s Continuing Surveys of Food Intakes by Individuals
(CSFII) from 1994-1996 and 1998 to calculate dietary risk.  The present
assessment was undertaken to evaluate the potential for sulfometuron
methyl exposure to humans through drinking water sources only.  This was
done to elucidate the risk levels associated with the proposed
non-food/non-feed uses of this chemical, and to support the human health
risk assessment for the Reregistration Eligibility Decision (RED) for
sulfometuron methyl.   

Characterization of Acute and Chronic Dietary Exposure Results

The present acute and chronic screening-level drinking water dietary
assessment constitutes a conservative evaluation of exposure to
sulfometuron methyl.  It is based on the Environmental Fate and Effects
Division (EFED) determination of Estimated Drinking Water Concentrations
(EDWCs) for exposure (M. Barrett, D334287).  Using the PRZM/EXAMS model,
EFED calculated a peak day (acute) average of 32.4 ppb and a maximum 1
in 10 year annual average (chronic) surface water concentration of 21.8
ppb. The EDWCs include the parent compound, sulfometuron methyl, as well
as the potential water degradates sulfometuron free acid, sulfometuron
pyrimidine amine, sulfometuron sulfonamide, and saccharin.  Ground water
sources were not included, as the EDWCs for this water source are
minimal in comparison to surface water.  Food uses were not incorporated
into this evaluation since only non-food/non-feed uses of sulfometuron
methyl are being supported by the registrant.

Risk estimates were found to be below the 100% acute Reference Dose
(aRfd) and chronic Reference Dose (cRfD) threshold levels of concern for
all population subgroups.  The acute and chronic drinking water exposure
to sulfometuron methyl is estimated to be < 1 % of the RfDs for the
general U.S. population.  For the most highly exposed subgroup, all
infants (< 1 year old), estimated acute dietary exposure is 2.3 % of the
aRfD and chronic dietary exposure is < 1 % of the cRfD.

Cancer Dietary Exposure Results and Characterization

A determination of cancer risk was not performed with DEEM-FCID™ as
part of the screening-level drinking water sulfometuron methyl
assessment, since there are no carcinogenicity studies.  No studies were
required because there are no food or feed tolerances for sulfometuron
methyl.  

I.	Introduction

Dietary risk assessment incorporates both exposure and toxicity of a
given pesticide.  For acute or chronic assessments, the risk is
expressed as a percentage of a maximum acceptable dose (i.e., the dose
which HED has concluded will result in no unreasonable adverse health
effects).  For a drinking water assessment, this dosage is referred to
as the Reference Dose (RfD).  The RfD is equivalent to point of
departure (PoD) (e.g., NOAEL or LOAEL) divided by the necessary
uncertainty or safety factors.  

For acute and non-cancer chronic exposures, HED is concerned when
estimated dietary risk exceeds 100% of the PAD.  HED is generally
concerned when estimated cancer risk exceeds one in one million.
References which discuss the acute and chronic risk assessments in more
detail are available on the EPA/pesticides web site:  “Available
Information on Assessing Exposure from Pesticides, A User’s Guide,”
21-JUN-2000, web link:      HYPERLINK
"http://www.epa.gov/fedrgstr/EPA-PEST/2000/July/Day-12/6061.pdf" 
http://www.epa.gov/fedrgstr/EPA-PEST/2000/July/Day-12/6061.pdf  ; or see
SOP 99.6 (20-AUG-1999).

II.	Residue Information

There are no proposed tolerances and percent crop treated information
relevant to this action for consideration.  Sulfometuron methyl is a
non-food/non-feed use chemical with no current or proposed usages which
could lead to dietary exposures from raw agricultural commodities and/or
processed foods.  It is registered for management of annual and
perennial broadleaf weeds and grasses in non-agricultural sites (i.e.,
forestry, rights of way, industrial sites, and unimproved turf).  As a
result, FQPA requirements are not applicable to the current action
pursuant to this RED.  Because FQPA guidelines do not apply in this
instance, screening-level drinking water only risk calculations are
therefore expressed as RfDs rather than population adjusted doses
(PADs).  Consequently, there are no dietary risk assessments being made
reflecting food consumption for sulfometuron methyl given the fact that
it is a non-food/non-feed use active ingredient.                        
     

III. 	Drinking Water Data

The drinking water residues used in the dietary risk assessment were
provided by the Environmental Fate and Effects Division (EFED) in the
following memorandum: “Tier I Sulfometuron Methyl Drinking Water
Assessment for Reregistration Eligibility Decision Document” (M.
Barrett, D334287, 10/31/07) and incorporated directly into this dietary
assessment.  This assessment relied solely on modeling analyses to
calculate both surface and ground water EDWCs for exposure.  A number of
degradates were identified and these have been added to the parent
compound sulfometuron methyl.  The drinking water assessment, therefore,
models the parent compound sulfometuron methyl as well as degradates. 
It is conservative in its approach and is unlikely to underestimate the
concentration of sulfometuron methyl in drinking water. The highest
ground and surface water (acute) EDWCs relevant to the maximum supported
use rate of sulfometuron methyl were 1.1 and 32.4 ppb, respectively. 
The highest ground and surface water (chronic) EDWCs relevant to the
maximum supported use rate of sulfometuron methyl were 1.1 and 21.8 ppb,
respectively. Accordingly, the larger values of 32.4 (acute) and 21.8
(chronic) ppb were used in the present acute and chronic screening-level
drinking water dietary assessments.             

IV.	DEEM-FCID™ Program and Consumption Information

Sulfometuron methyl acute and chronic dietary exposure assessments
(drinking water only) were conducted using the Dietary Exposure
Evaluation Model software with the Food Commodity Intake Database
DEEM-FCID™,Version 2.03 which incorporates consumption data from
USDA’s Continuing Surveys of Food Intakes by Individuals (CSFII),
1994-1996 and 1998.  The 1994-96, 98 data are based on the reported
consumption of more than 20,000 individuals over two non-consecutive
survey days.  Foods “as consumed” (e.g., apple pie) are linked to
EPA-defined food commodities (e.g. apples, peeled fruit - cooked; fresh
or N/S; baked; or wheat flour - cooked; fresh or N/S, baked) using
publicly available recipe translation files developed jointly by
USDA/ARS and EPA.  For chronic exposure assessment, consumption data are
averaged for the entire U.S. population and within population subgroups,
but for acute exposure assessment are retained as individual consumption
events.  Based on analysis of the 1994-96, 98 CSFII consumption data,
which took into account dietary patterns and survey respondents, HED
concluded that it is most appropriate to report risk for the following
population subgroups: the general U.S. population, all infants (<1 year
old), children 1-2, children 3-5, children 6-12, youth 13-19, adults
20-49, females 13-49, and adults 50+ years old.

For chronic dietary exposure assessment, an estimate of the residue
level in each food or food-form (e.g., orange or orange juice) on the
food commodity residue list is multiplied by the average daily
consumption estimate for that food/food form to produce a residue intake
estimate.  The resulting residue intake estimate for each food/food form
is summed with the residue intake estimates for all other food/food
forms on the commodity residue list to arrive at the total average
estimated exposure.  Exposure is expressed in mg/kg body weight/day and
as a percent of the cPAD.  This procedure is performed for each
population subgroup.

For acute exposure assessments, individual one-day food consumption data
are used on an individual-by-individual basis.  The reported consumption
amounts of each food item can be multiplied by a residue point estimate
and summed to obtain a total daily pesticide exposure for a
deterministic exposure assessment, or “matched” in multiple random
pairings with residue values and then summed in a probabilistic
assessment.  The resulting distribution of exposures is expressed as a
percentage of the aPAD on both a user (i.e., only those who reported
eating relevant commodities/food forms) and a per-capita (i.e., those
who reported eating the relevant commodities as well as those who did
not) basis.  In accordance with HED policy, per capita exposure and risk
are reported for all tiers of analysis.  However, for tiers 1 and 2, any
significant differences in user vs. per capita exposure and risk are
specifically identified and noted in the risk assessment.

DEEM-FCID™ modeling software.           

V.	Toxicological Information

To carry out the acute and chronic screening-level drinking water
dietary assessments, a toxicological profile was assembled to identify
the possible hazards for exposure.  All information specific to the
toxicity characteristics of sulfometuron methyl are presented in the
risk assessment for the sulfometuron methyl RED (D346064, W. Britton,
et. al., in preparation).  The acute and chronic endpoint for drinking
water exposure was selected from the toxicity study results.  Using
these data, a No Observed Adverse Effect Level (NOAEL) of 27.5 mg/kg/day
was selected and an aRfD and cRfD of 0.275 mg/kg/day were determined. 
The LOAEL is based on hemolytic anemia in both sexes and decreased
body-weight gain in males (0-4 weeks).

For the acute and chronic exposure scenarios, the standard 100 fold
uncertainty factor (UF) was applied to account for inter-species
extrapolation and intra-species variation.  As previously noted, a
cancer risk evaluation is not included in this screening-level drinking
water assessment.  In addition, FQPA guidelines do not apply given the
fact that sulfometuron methyl is a non-food/non-feed use active
ingredient.  To provide an overview of this toxicological profile, a
summary of the doses and endpoints selected for the drinking water
exposure scenarios which were performed are provided in Table 1.  

Table 1.  Summary of Toxicological Doses and Endpoints for the  

 Screening-Level Drinking Water Risk Assessment of Sulfometuron Methyl

Exposure

Scenario	

POD	Hazard and Exposure Based FQPA Safety Factor	Study and Toxicological
Effects

Acute Dietary

All populations	NOAEL= 27.5 mg/kg/day

UF = 100

Chronic RfD = NOAEL

                              UF

= 0.275 mg/kg/day	The FQPA SF is not applicable to this risk
determination since sulfometuron methyl is a non-food/non-feed use
chemical.	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.  

Chronic Dietary

All populations



	Cancer (dermal, inhalation)	Not available for assessment.

Point of Departure (PoD) = A data point or an estimated point that is
derived from observed dose-response data and  used to mark the beginning
of extrapolation to determine risk associated with lower environmentally
relevant human exposures.  NOAEL = no observed adverse effect level. 
LOAEL = lowest observed adverse effect level.  UF = uncertainty factor.
RfD = reference dose.  FQPA = Food Quality Protection Act.  SF = Safety
Factor

VI.	Results/Discussion 

For acute and chronic assessments, HED is concerned when dietary risk
exceeds 100% of the RfD.  The DEEM-FCID™ analysis estimates the
exposure of the U.S. population and its various subgroups.  The results
reported in Tables 2 and 3 are for the general U.S. Population, all
infants (<1 year old), children 1-2, children 3-5, children 6-12, youth
13-19, females 13-49, adults 20-49, and adults 50+ years.

Results for Acute Dietary Exposure Analysis

An acute dietary risk analysis was conducted with the DEEM-FCID™ model
to form a conservative evaluation of exposure for sulfometuron methyl. 
The acute analysis yielded estimates well below the 100% of the aRfD
threshold exposure level of concern for the US population and each
population subgroup.  For the US Population, acute dietary risk was
calculated at < 1 % of the aRfD with an exposure level of 0.0017
mg/kg/day.  For the subgroup with the highest esimated exposure, all
infants less than 1 year old, acute dietary risk occupied 2.3 % of the
aRfD with an exposure of 0.0064 mg/kg/day.  An overview summarizing the
results of the acute dietary assessment with the population subgroup
having the highest exposure being noted in bold is presented in Table 2.

Table 2.  Summary of Screening Level Drinking Water Exposure and Risk
for Sulfometuron Methyl



Population Subgroup	Acute Dietary1

	Dietary Exposure (95th percentile) (mg/kg/day)	%aRfD

General U.S. Population	0.001690	< 1

All Infants (< 1 year old)	0.006372	2.3

Children 1-2 years old	0.002652	< 1

Children 3-5 years old	0.002422	< 1

Children 6-12 years old	0.001686	< 1

Youth 13-19 years old	0.001371	< 1

Adults 20-49 years old	0.001566	< 1

Adults 50+ years old	0.001414	< 1

Females 13-49 years old	0.001575	< 1

1 Acute dietary analysis based on a 0.275 mg/kg/day aRfD.

  

Results of Chronic Dietary Exposure Analysis

DEEM-FCID™ model to form a conservative evaluation of exposure for
sulfometuron methyl.  The chronic analysis yielded risk estimates well
below the 100% of the cRfD threshold level of concern for each
population subgroup.  For the US Population subgroup, chronic dietary
risk was calculated at < 1 % of the cRfD with an exposure level of
0.00046 mg/kg/day.  For the subgroup with the highest calculated
exposure, all infants less than 1 year old, chronic dietary risk
occupied < 1 % of the cRfD with an exposure of 0.0015 mg/kg/day.  An
overview summarizing the results of the chronic dietary assessment with
the population subgroup having the highest exposure being noted in bold
is presented in Table 3.

Table 3.  Summary of Screening Level Drinking Water Exposure and Risk
for Sulfometuron Methyl.



Population Subgroup	Chronic Dietary1

	Dietary Exposure  (99th percentile) (mg/kg/day)	%cRfD

General U.S. Population	0.000460	< 1

All Infants (< 1 year old)	0.001508	< 1

Children 1-2 years old	0.000683	< 1

Children 3-5 years old	0.000639	< 1

Children 6-12 years old	0.000441	< 1

Youth 13-19 years old	0.000332	< 1

Adults 20-49 years old	0.000429	< 1

Adults 50+ years old	0.000452	< 1

Females 13-49 years old	0.000428	< 1

1 Chronic dietary analysis based on a 0.275 mg/kg/day cRfD.

VII.	Characterization of Inputs/Outputs

DEEM-FCID™ analysis does not underestimate risk from exposure to
sulfometuron methyl for the general U.S. population and all its
subgroups.

VIII.	Conclusions

The conservative acute and chronic screening-level drinking water
dietary assessments made with DEEM-FCID™ indicates that exposures to
sulfometuron methyl are below HED’s level of concern.  The analysis
utilizes a survey-based consumption distribution together with an
upper-bound residue value for drinking water.  The acute and chronic
dietary exposure to sulfometuron methyl is estimated to be < 1 % for the
general U.S. population.  For the most highly exposed subgroup, all
infants (< 1 year old), the acute and chronic risk estimates are also
below HED’s level of concern.  For this subgroup, the resulting acute
dietary exposure is 2.3 % of the aRfD and chronic dietary exposures is <
1 % of the cRfD.  Therefore, HED does not believe that the
non-food/non-feed use of sulfometuron methyl could result in
unacceptable risk through the potential exposure from drinking water
sources.   

IX.		List of Attachments

1.	Attachment 1: Acute Drinking Water Assessment Input File

2.	Attachment 2: Acute Drinking Water Assessment Results File

3.	Attachment 3: Chronic Drinking Water Assessment Input File

4.	Attachment 4: Chronic Drinking Water Assessment Results File

Attachment 1

U.S. Environmental Protection Agency                                
Ver. 2.02

DEEM-FCID Acute analysis for SULFOMETURON METHYL

Analysis Date 12-14-2007             Residue file dated:
12-14-2007/13:36:56/8

Reference dose: aRfD = 0.275 mg/kg bw/day  NOEL = 27.5 mg/kg bw/day

Comment: Acute drinking water only (PRZM-EXAMS parent + metabolites)

------------------------------------------------------------------------
--------

  EPA    Crop                                   Def Res     Adj.Factors 
 Comment

  Code    Grp  Food Name                         (ppm)       #1    #2   

-------- ---- -------------------------------  ----------  ------ ------
 -------

86010000 O    Water, direct, all sources         0.032350   1.000  1.000

86020000 O    Water, indirect, all sources       0.032350   1.000  1.000

Attachment 2

U.S. Environmental Protection Agency                                 
Ver. 2.02

DEEM-FCID ACUTE Analysis for SULFOMETURON METHYL                
(1994-98 data)

					                 Adjustment factor #2 NOT used.

Analysis Date: 12-14-2007/13:39:53    Residue file dated:
12-14-2007/13:36:56/8

NOEL (Acute) =  27.500000 mg/kg body-wt/day

Daily totals for food and foodform consumption used.

Run Comment: "Acute drinking water only (PRZM-EXAMS parent +
metabolites)"

========================================================================
=======

Summary calculations (per capita):

      95th Percentile             99th Percentile             99.9th
Percentile

 Exposure  % aRfD     MOE    Exposure  % aRfD     MOE    Exposure  %
aRfD     MOE  

---------- ------- -------- ---------- ------- -------- ----------
------- --------

U.S. Population:

  0.001690    0.61   16272    0.003174    1.15    8663    0.006351   
2.31    4330  

All infants:

  0.006372    2.32    4316    0.009134    3.32    3010    0.016362   
5.95    1680  

Children 1-2 yrs:

  0.002652    0.96   10370    0.004428    1.61    6210    0.006440   
2.34    4270  

Children 3-5 yrs:

  0.002422    0.88   11352    0.003797    1.38    7243    0.006197   
2.25    4437  

Children 6-12 yrs:

  0.001686    0.61   16307    0.002804    1.02    9807    0.003829   
1.39    7181  

Youth 13-19 yrs:

  0.001371    0.50   20058    0.002307    0.84   11922    0.004149   
1.51    6628  

Adults 20-49 yrs:

  0.001566    0.57   17563    0.002622    0.95   10488    0.004743   
1.72    5798  

Adults 50+ yrs:

  0.001414    0.51   19449    0.002022    0.74   13600    0.003279   
1.19    8386  

Females 13-49 yrs:

  0.001575    0.57   17464    0.002534    0.92   10851    0.004494   
1.63    6119

Attachment 3

U.S. Environmental Protection Agency                                
Ver. 2.00

DEEM-FCID Chronic analysis for SULFOMETURON METHYL               
1994-98 data

                                                           Adjust. #2
NOT used

Analysis Date 10-29-2007             Residue file dated:
10-29-2007/10:53:27/8

Reference dose (RfD) = 0.275 mg/kg bw/day

Comment:Chronic drinking water only (PRZM-EXAMS parent + metabolites)

------------------------------------------------------------------------
--------

Food Crop                                       Residue      
Adj.Factors      Comment

EPA Code  Grp  Food Name                          (ppm)       

                                                             #1        
#2 

-------- ---- -------------------------------   ---------- ------    
------   -------

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U.S. Environmental Protection Agency                                
Ver. 2.00

DEEM-FCID Chronic analysis for SULFOMETURON METHYL              (1994-98
data)

                                                 Adjustment factor #2
NOT used.

Analysis Date 10-29-2007/10:58:39     Residue file dated:
10-29-2007/10:53:27/8

Reference dose (RfD, Chronic) = .275 mg/kg bw/day

COMMENT 1: Chronic drinking water only (PRZM-EXAMS parent + metabolites)

========================================================================
=======

                    Total exposure by population subgroup

------------------------------------------------------------------------
-------

                                                    Total Exposure

                                        
-----------------------------------

          Population                         mg/kg             Percent
of   

           Subgroup                       body wt/day             Rfd   
   

--------------------------------------   -------------      
---------------

U.S. Population (total)                     0.000460                
0.2%

U.S. Population (spring season)             0.000456                
0.2%

U.S. Population (summer season)             0.000494                
0.2%

U.S. Population (autumn season)             0.000445                
0.2%

U.S. Population (winter season)             0.000445                
0.2%

Northeast region                            0.000420                
0.2%

Midwest region                              0.000465                
0.2%

Southern region                             0.000437                
0.2%

Western region                              0.000527                
0.2%

Hispanics                                   0.000522                
0.2%

Non-hispanic whites                         0.000449                
0.2%

Non-hispanic blacks                         0.000437                
0.2%

Non-hisp/non-white/non-black                0.000564                
0.2%

All infants (< 1 year)                      0.001508                
0.5%

Nursing infants                             0.000559                
0.2%

Non-nursing infants                         0.001868                
0.7%

Children 1-6  yrs                           0.000643                
0.2%

Children 7-12 yrs                           0.000418                
0.2%

Females 13-19 (not preg or nursing)         0.000324                
0.1%

Females 20+ (not preg or nursing)           0.000459                
0.2%

Females 13-50 yrs                           0.000445                
0.2%

Females 13+ (preg/not nursing)              0.000447                
0.2%

Females 13+ (nursing)                       0.000637                
0.2%

Males 13-19 yrs                             0.000338                
0.1%

Males 20+ yrs                               0.000412                
0.1%

Seniors 55+                                 0.000452                
0.2%

Children 1-2 yrs                            0.000683                
0.2%

Children 3-5 yrs                            0.000639                
0.2%

Children 6-12 yrs                           0.000441                
0.2%

Youth 13-19 yrs                             0.000332                
0.1%

Adults 20-49 yrs                            0.000429                
0.2%

Adults 50+ yrs                              0.000452                
0.2%

Females 13-49 yrs                           0.000428                
0.2%

------------------------------------------------------------------------
-------

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