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.

 

image\v4ht0204.gif  (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