Sethoxydim Risk Assessment

Worksheet D04: Consumption of contaminated fruit, chronic exposure scenario [VegChHHRA01]. 
Verbal Description: An individual consumes contaminated fruit for a period of time (t) starting shortly after  
application of the chemical.  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.  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).  
Parameters/Assumptions 
Value 
Units 
Source/Reference 
Halftime on vegetation (t
50
) 
Central 
3 
days 
CHEM.FrT12C  
Lower 
3 
CHEM.FrT12L  
Upper 
3 
CHEM.FrT12U  
Duration of exposure (T) 
90 
days 
N/A  
Amount of fruit consumed per unit body weight(A): Central is also used for lower.  
Central 
0.00168 
kg fruit/kg 
PUBL.FrTC  
bw/day
Lower 
0.00168 
PUBL.FrTL  
Upper 
0.01244 
PUBL.FrTU  
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 per 
WSA05a.FRT2  
lb/acre applied
Lower 
7 
WSA05a.FRT2  
Upper 
15 
WSA05aFRU2  
Drift (Drift)  
Central 
1 
unitless 
Assume direct spray 
Lower 
1 
Upper 
1 
Decay coefficient (k): ln(2)/t
50 
Central 
0.2310491 
day
-1 
Upper estimate of t
50
 used to 
calculate lower limit of k and
Lower 
0.2310491 
lower estimate of t
50
 used to 
Upper 
0.2310491 
calculate upper limit of k. 
WS-29  

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Worksheet D04 (continued): Consumption of contaminated fruit, chronic exposure scenario [VegChHHRA01]. 
Initial Concentration on Vegetation (C
0
): : C
0
 = A × Drift × rr 
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. 
Lower 
6.11e-10 
Upper 
5.24e-09 
Time-weighted Average Concentration on Raw Vegetation (C
TWA
): C
0
 (1 - e
-k T
) ÷ (k T) 
Central 
0.1009887 
mg/kg veg. 
Lower 
0.031559 
Upper 
0.2705053 
Proportion Removed by Washing (
Pwash
): 
Central 
0 
unitless 
Assume that washing is 
Lower 
0 
ineffective. 
Upper 
0 
TWA Concentration on Consumed Vegetation (C
Con
): C
TWA
 × 1-P
Wash 
Central 
1.01e-01 
mg/kg veg. 
Lower 
3.16e-02 
Upper 
2.71e-01 
Dose estimates (D): C
Con
 × A 
Central 
1.70e-04 
mg/kg bw/day 
Lower 
5.30e-05 
Upper 
3.37e-03 
WS-30  

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Worksheet D05: Consumption of contaminated water following an accidental spill, acute exposure scenario 
[DWAcHHRA01]. 
Verbal Description: A young child (2-3 years old) consumes contaminated water shortly after an accidental 
spill of 200 gallons of a field solution into a pond that has an average depth of 1 m and a surface area of 1000 
m
2
 or about one-quarter acre .  No dissipation or degradation is considered. 
Parameters/Assumptions 
Value 
Units 
Source/Reference 
Surface area of pond (SA) 
1000 
m
2 
N/A 
Average depth (DPTH) 
1 
m 
N/A 
Volume of pond in cubic meters (VM) 
1000 
m
3 
N/A 
Volume of pond in Liters (VL) 
1000000 
L 
1 m
3
 = 1,000 L 
Volume of spill (VS) 
200 
gallons 
N/A 
757 
liters 
1 gallon = 3.785 Liters 
Concentrations in field solution (C
Fld  (mg/L)
) 
Central 
3600 
mg/L 
APPL.TypDR × 1000 
Lower 
560 
APPL.LowDR × 1000 
Upper 
9000 
APPL.Hi_DR × 1000 
Concentrations in ambient water (C
Wrt
): C
Fld
 × VS
(Liters)
 ÷ VL) 
Central 
2.7252 
mg/L 
Lower 
0.42392 
Upper 
6.813 
Body weight (W) 
13.3 
kg 
PUBL.BWC 
Amount of water consumed (A) 
Central 
1 
L/day 
PUBL.WCT 
Lower 
0.61 
PUBL.WCL 
Upper 
1.5 
PUBL.WCH 
Dose estimates (D): C
wrt
 × A ÷ W 
Central 
2.05e-01 
mg/kg bw 
Lower 
1.94e-02 
Upper 
7.68e-01 
WS-31  

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