Sethoxydim Risk Assessment

Worksheet F03: Consumption of contaminated fruit by a small mammal, acute exposure scenario 
[VegAcERA01]. 
Verbal Description: A 20 g mammal consumes fruit shortly after application of the chemical - i.e. no 
dissipation or degradation is considered.  The contaminated vegetation accounts for 100% of the diet.  Residue 
estimates based on relationships for fruit from Hoerger and Kenaga (1972) summarized in Worksheet A05a. 
Parameters/Assumptions 
Value 
Units 
Source/Reference 
Body weight (W) 
0.020 
kg 
Section 4.2.1 
Allometric coefficients for food consumption in g based on body weight in g 
a 
0.621  
Rodents U.S. EPA/ORD 
1993, p. 3-6
b 
0.584 
Food consumed per day (A): a×(W×1000)
 b
÷1000 
0.003572 
kg 
Application rates (R) 
Central 
0.3 
lb/acre 
APPL.Typ 
Lower 
0.09375 
APPL.Low 
Upper 
0.375 
APPL.Hi 
Residue rates (rr) 
Central 
7 
mg/kg fruit 
HK.FRT2 
per lb/acre
Lower 
7  
HK.FRT2
applied 
Upper 
15 
HK.FRU2 
Concentration in food(C): R × rr 
Central 
2.1 
mg/kg food 
Lower 
0.65625 
Upper 
5.625 
Dose estimates (D): A × C ÷ W 
Central 
3.75e-01 
mg/kg bw 
Lower 
1.17e-01 
Upper 
1.00e+00 
WS-45  

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Worksheet F04a: Consumption of contaminated fruit by a small mammal, chronic exposure scenario at 
application site [VegChSmMam01]. 
Verbal Description: A 20 g mammal consumes contaminated fruit for a 90 day period starting shortly after 
application of the chemical.  Food consumption is estimated from allometric relationships.  The concentration 
of the chemical in fruit at time zero (C
0
) is estimated from the application rate (A), the proportion of drift 
(Drift), and empirical residues rates (rr) summarized in HK.  Because the animal is assumed to inhabit the 
application site, drift is taken as unity - i.e., direct spray.  The foliar halftime (t
50
) is used to estimate the foliar 
decay coefficient (k): k = ln(2)÷t
50
.  The concentration on the vegetation after time t (C
t
) is calculated as C
t
= 
C
0
e
-kt
.  The time-weighted average of the concentration on vegetation (C
TWA
) is calculated as the integral of the 
concentration after time t (C
t
) divided by the duration (t).  The daily dose is calculated as the product of  food 
consumption and the proportion of the diet that is contaminated divided by the body weight. 
Parameters/Assumptions 
Value 
Units 
Duration of exposure (T) 
90 
days 
Body weight (W) 
0.02 
kg 
Allometric coefficients for food consumption in g based on body weight in g 
a 
0.621 
b 
0.584 
Food consumed per day (A): a×(W×1000)
 b
÷1000 
Foliar halftimes (t
½
) 
Application rates (R) 
Residue rates (rr): 
Drift (Drift): 
Decay coefficient (k): ln(2)/t
50 
Central 
0.2310491 
Lower 
0.2310491 
Upper 
0.2310491 
kg 
days 
lb/acre 
mg/kg fruit 
per lb/acre 
applied 
unitless 
day
-1 
Source/Reference 
N/A 
N/A 
U.S. EPA/ORD 1993, p. 3-6 
CHEM.FrT12C 
CHEM.FrT12L 
CHEM.FrT12U 
APPL.Typ 
APPL.Low 
APPL.Hi 
HK.FRT2 
HK.FRT2 
HK.FRU2 
Assume direct spray 
Upper estimate of t
50
 used to 
calculate lower limit of k and 
lower estimate of t
50
 used to 
calculate upper limit of k. 
0.0035718 
Central 
3 
Lower 
3 
Upper 
3 
Central 
0.3 
Lower 
0.09375 
Upper 
0.375 
Central 
7 
Lower 
7 
Upper 
15 
Central 
1 
Lower 
1 
Upper 
1 
WS-46  

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Worksheet F04a (continued): Consumption of contaminated vegetation by a small mammal, chronic exposure 
scenario . 
Initial Concentration on Vegetation (C
0
): : C
0
 = R × rr × Drift 
Central 
2.1 
mg/kg veg. 
Lower 
0.65625 
Upper 
5.625 
Concentration on Vegetation at time T (C
T
): C
T
 = C
0
 e
-kT 
Central 
1.96e-09 
mg/kg veg. 
These values are not used 
directly in calculating the
Lower 
6.11e-10 
dose. 
Upper 
5.24e-09 
Time-weighted Average Concentration on Vegetation (C
TWA
): C
0
 (1 - e
-k T
) ÷ (k T) 
Central 
1.01e-01 
mg/kg veg. 
Lower 
3.16e-02 
Upper 
2.71e-01 
Proportion of Diet Contaminated (Prop)
1
: 
Central 
0.1 
unitless 
See footnote. 
Lower 
0.05 
Upper 
0.2 
Dose estimates (D
Abs
): C
TWA
 × A × Prop ÷ W 
Central 
1.80e-03 
mg/kg/day 
Lower 
2.82e-04 
Upper 
9.66e-03 
1
 Based on data on the shrew (U.S. EPA/ORD 1996, p. 2-214,), the vegetation accounts for about 5% of the diet. 
This is used as the lower limit.  The typical and upper values are judgementally set to account for incidental 
contamination of other contaminated food items such as insects as well as different feeding preferences among 
other small mammals. 
WS-47  

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