(1)The incidental ingestion of soil is a potentially significant source of exposure. Equation 1(non-radionuclides), Equation 2 (radionuclides), and Table 2 present the exposure variables for the soil/sediment ingestion pathway for the residential, industrial, recreational, and agricultural scenarios. The potential for exposure to children is greater due to behavioral patterns present during childhood. The higher value for children, under the non-industrial scenarios, are based on fecal tracer studies and account for the ingestion of both indoor and outdoor dust.
(1)
(2)
Table 2. Soil/Sediment Ingestion Parameters
|
Parameter |
Units |
Residential |
Industrial |
Recreational |
Excavation |
Agricultural |
|
Non-radionuclide chemical concentration in soil = Csn |
mg/kg |
Chemical-specific |
Chemical-specific |
Chemical-specific |
Chemical-specific |
Chemical-specific |
|
Radionuclide chemical concentration in soil = Csr |
pCi/g |
Chemical-specific |
Chemical-specific |
Chemical-specific |
Chemical-specific |
Chemical-specific |
|
Conversion factor = CF1 |
kg/mg |
10-6 |
10-6 |
10-6 |
10-6 |
10-6 |
|
Exposure frequency = EF |
days/yr |
350 (EPA 1989a) |
250 (EPA 1991a) |
40 (EPA 1992) |
20 |
350 (EPA 1989a) |
|
Fraction ingested = FI |
unitless |
1 |
1 |
1 |
1 |
1 |
|
Exposure duration = ED |
years |
24 (adult) 6 (child) (EPA 1989a) |
25 (adult) (EPA 1991a) |
24 (adult) 6 (child) (EPA 1989a) |
1
|
24 (adult) 6 (child) (EPA 1989a) |
|
Conversion factor = CF8 |
g/mg |
10-3 |
10-3 |
10-3 |
10-3 |
10-3 |
|
Ingestion rate of soil = IR |
mg/d |
100 (adult) 200 (child) (EPA 1989a) |
200 (adult) (EPA 1989a) |
100 (adult) 200 (child) (EPA 1989a) |
480 (construction worker) (EPA 1991b) |
100 (adult) 200 (child) (EPA 1989a) |
|
Body weight = BW |
kg |
70 (adult) 15 (child) (EPA 1991a) |
70 (adult) (EPA 1991a) |
70 (adult) 15 (child) (EPA 1991a) |
70 (adult) (EPA 1991a) |
70 (adult) 15 (child) (EPA 1991a) |
|
Conversion Factor == CF2 |
days/yr |
365 |
365 |
365 |
365 |
365 |
|
Lifetime = LT |
years |
70 (EPA 1989a) |
70 (EPA 1989a) |
70 (EPA 1989a) |
70 (EPA 1989a) |
70 (EPA 1989a) |
|
Averaging time = AT |
years |
LT (carcinogen) ED (noncarcinogen) |
LT (carcinogen) ED (noncarcinogen) |
LT (carcinogen) ED (noncarcinogen) |
LT (carcinogen) ED (noncarcinogen) |
LT (carcinogen) ED (noncarcinogen) |