Sethoxydim Risk Assessment

EXPOSURE ASSESSMENTS FOR TERRESTRIAL SPECIES  
Worksheet F01: Direct spray of small mammal assuming first order absorption kinetics [DDFOAEco01].  
Verbal Description: A mammal of a specified body weight is directly sprayed over one half of the body surface 
as the chemical is being applied.  An empirical relationship between body weight and surface area is used to 
estimate the surface area of the animal.  The absorbed dose over the first day – i.e., a 24 hour period –  is 
estimated using the assumption of first-order dermal absorption. 
Parameter/Assumption 
Value 
Units 
Source/Reference 
Period of exposure (T) 
24 
hour 
N/A 
Body weight (W) 
0.020 
kg 
Section 4.2.1. 
Exposed surface area (A) 
m
2
=0.11 × BW(kg)
0.65 
U.S. EPA/ORD 1993, eq. 3-22, p. 
3-14 
0.0086509 
m
2 
86.51 
cm
2 
10,000 cm
2
 /m
2 
Application rate in lbs/acre (R
lbs
) 
Central 
0.3 
lb/acre 
APPL.TYP 
Lower 
0.09375 
APPL.LOW 
Upper 
0.375 
APPL.HI 
Conversion Factor (CF) for lb/acre to 
0.01121 
Const.LBAC_MGCM 
mg/cm
2 
Application rate in mg/cm
2
 (R
mg
):  R
lbs
 × CF 
Central 
0.003363 
lb/acre 
Lower 
0.0010509 
Upper 
0.0042038 
First-order dermal absorption rate (k) 
Central 
0.00110 
hour
-1 
DERM.AbsC 
Lower 
0.000470 
DERM.AbsL 
Upper 
0.00250 
DERM.AbsU 
Amount deposited on animal (Amnt): 0.5 × A × R
mg 
Central 
0.14547 
mg 
Lower 
0.045458 
Upper 
0.18183 
Proportion absorbed over period T (Prop): 1-e
-k T 
Central 
0.02605 
unitless 
Lower 
0.011217 
Upper 
0.05824 
Estimated Absorbed Doses (D): Amnt × Prop ÷ W 
Central 
1.90e-01 
mg/kg 
Lower 
2.55e-02 
Upper 
5.29e-01 
WS-42  

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Worksheet F02a: Direct spray of small mammal assuming 100% absorption over the first 24 hour period 
[DDEco01]. 
Verbal Description: A 20 g mammal is directly sprayed over one half of the body surface as the chemical is 
being applied.  The deposited dose is assumed to be completely absorbed during the first day.  An empirical 
relationship between body weight and surface area is used to estimate the surface area of the animal. 
Parameter/Assumption 
Value 
Units 
Source/Reference  
Period of exposure (T) 
24 
hour 
N/A  
Body weight (W) 
0.020 
kg 
Section 4.2.1.  
Exposed surface area 
m
2
=0.011 × BW(g)
0.65 
U.S. EPA/ORD 1993, eq. 3-22, p.  
3-14 
0.0086509 
m
2
 (SA) 
86.51 
cm
2 
m
2
 = 10,000 cm
2 
Application rate in lbs/acre (R
lbs
) 
Central 
0.3 
lb/acre 
APPL.TYP 
Lower 
0.09375 
APPL.LOW 
Upper 
0.375 
APPL.HI 
Conversion Factor (CF) for lb/acre to 
0.01121 
Const.LBAC_MGCM 
mg/cm
2 
Application rate in mg/cm
2
 (R
mg
):  R
lbs
 × CF 
Central 
0.003363 
mg/cm
2 
Lower 
0.0010509 
Upper 
0.0042038 
Amount deposited on animal (Amnt): 0.5 × SA × R
mg 
Central 
0.14547 
mg 
Lower 
0.045458 
Upper 
0.18183 
Estimated Absorbed Doses (D
Abs
):  Amnt ÷ W 
Central 
7.27e+00 
mg/kg 
Lower 
2.27e+00 
Upper 
9.09e+00 
WS-43  

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Worksheet F02b: Direct spray of bee assuming 100% absorption over the first 24 hour period [DDEco02]. 
Verbal Description: A honeybee is directly sprayed over one half of the body surface as the chemical is being 
applied.  The deposited dose is assumed to be completely absorbed during the first day.  An empirical 
relationship between body weight and surface area is used to estimate the surface area of the animal. 
Parameter/Assumption 
Value 
Units 
Source/Reference 
Period of exposure (T) 
24 
hour 
N/A 
Body weight (W) 
0.000093 
kg 
Section 4.2.1. 
Exposed surface area (SA) 
cm
2
=1110×BW(kg)
0.65 
Boxenbaum and D’Souza 1990 
2.6597260 
cm
2 
Application rate (R
lbs
) 
Central 
0.3 
lb/acre 
APPL.TYP 
Lower 
0.09375 
APPL.LOW 
Upper 
0.375 
APPL.HI 
Conversion Factor (CF) for lb/acre to 
0.01121 
Const.LBAC_MGCM 
mg/cm
2 
Application rate in mg/cm
2
 (R
mg
):  R
lbs
 × CF 
Central 
0.003363 
mg/cm
2 
Lower 
0.0010509 
Upper 
0.0042038 
Amount deposited on animal (Amnt): 0.5 × SA × R
mg 
Central 
0.00447 
mg 
Lower 
0.001398 
Upper 
0.00559 
Estimated Absorbed Doses (D
Abs
):  Amnt ÷ W 
Central 
4.81e+01 
mg/kg 
Lower 
1.50e+01 
Upper 
6.01e+01 
WS-44  

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