External Exposure
Equation 6 (radionuclides) and Table 5 present the exposure variables for the external exposure pathway for the residential, industrial, recreational, excavation, and recreational scenarios.
(6)
Table 5. Soil/Sediment External Exposure Parameters
Parameter
Units
Residential
Industrial
Recreational
Excavation
Agricultural
Radionuclide chemical concentration in soil = Csr
pCi/g
Chemical-specific
Chemical-specific
Chemical-specific
Chemical-specific
Chemical-specific
Gamma Shielding Factor = Se
unitless
0.2
(EPA 1991a)
0.2
(EPA 1991a)
0.2
(EPA 1991a)
0.2
(EPA 1991a)
0.2
(EPA 1991a)
Gamma exposure time factor = Te
unitless
1
(EPA 1991a)
8/24
(EPA 1991a)
1/24
(EPA 1991a)
8/24
(EPA 1991a)
1
(EPA 1991a)
Exposure frequency = EF
days/yr
350
(EPA 1989a)
250
(EPA 1991a)
40
(EPA 1992)
20
350
(EPA 1989a)
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 = CF9
yr/days
1/365
1/365
1/365
1/365
1/365