Incidental Soil/Sediment Ingestion
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)