222Rn Alpha Dose to Organs Other than Lung

The alpha dose to cells in tissues or organs other than the lung has been calculated using the solubility coefficients for 222Rn measured in human tissue. The annual alpha dose equivalent from 222Rn and decay products in most tissues is a maximum of 30% of the annual average natural background dose equivalent (1 mSv) for external and internally deposited nuclides (not including the dose equivalent for 222Rn decay products to cells in bronchial airways). The dose to the small population of lymphocytes located in or under the bronchial epithelium is a special case and their annual dose equivalent is essentially the same as that to basal cells in bronchial epithelium (200 mSv) for continuous exposure to 200 Bq.m-3. The significance of this dose is uncertain because the only excess cancer observed in follow-up studies of underground miners with high 222Rn exposure is bronchogenic carcinoma.