Table 5.2

The Weighted Equivalent Dose to Tissues Other Than the Lung for Continuous Exposure to 1 Bq m-3 of 222Rn in Air

Tissue

mSv y-1 per Bq m-3

Reference

Livera

5.1 × 10-5

Jacobi and Eisfeld (1980)

Kidneysa

5.6 × 10-5

Jacobi and Eisfeld (1980)

Spleena

5.2 × 10-5

Jacobi and Eisfeld (1980)

Red Bone Marrowa

9.6 × 10-5

Jacobi and Eisfeld (1980)

Bone Surfacesa

2.5 × 10-5

Jacobi and Eisfeld (1980)

Soft Tissueb

3.0 × 10-5

Harley and Robbins (1992)

Adipose Tissueb

9.0 × 10-5

Harley and Robbins (1992)

Skinb

50 × 10-5

Harley and Robbins (1992)

Normal Marrowb

6.3 × 10-5

Harley and Robbins (1992)

Adipose Tissue Marrowb

16 × 10-5

Harley and Robbins (1992)

Bone Surfaces (Normal Marrow)b

1.5 × 10-5

Harley and Robbins (1992)

Bone Surfaces (Adipose Tissue Marrow)b

3.0 × 10-5

Harley and Robbins (1992)

T Lymphocytesb,c

0.01

Harley and Robbins (1992)

Alveolar Capillariesb

20 × 10-5

Harley and Robbins (1992)

a Weighted using ICRP (1977) weighing factors.

b Weighted using IRCP (1990) values of Wr and Wt.

c T lymphocytes located in bronchial epithelium.

term) and the dynamic (short-term) components of the exposure. The potentially most important source of short-term exposure is the release of radon from water during showering and the subsequent inhalation of its decay products. The steady-state component has been studied in considerable detail (Fitzgerald and others 1997; Bernhardt and Hess 1996) and is described in chapter 3. Only recently have there been studies of the time-varying exposure. The exposure assessment of waterborne radon includes both its contributions to long-term average indoor radon concentrations and the short-term, perturbed conditions that exist as a result of showering.

Showering Conditions

It is necessary to provide the radon-progeny activity size distribution as a function of time during and after showering. There have been two recent studies of the increments in exposure and dose that arise from showering with radon-laden water (Fitzgerald and others 1997; Bernhardt and Hess 1996).

Exposure conditions are quite different during showering because radon is transferred from water to air with little or no direct release of decay products from the water. As a result, there might be a high local concentration of 222Rn, but it takes time for the decay products to grow into equilibrium concentrations. Because the ingrowth of the activity will occur with an effective half-life of about 30 min, the highest concentrations of decay-product activity occur after the person



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