Radon and thoron associated dose to the basal layer of the skin

The radon related alpha-particle annual dose equivalent to the basal layer of the epidermis has been calculated theoretically and is estimated as 2.5 (range 1.7 to 17) mSv y-1, for the exposed, uncovered skin of the face and neck, at the UK average domestic radon exposure of 20 Bq m-3. The thoron-related annual dose equivalent is estimated as 0.3 (range 0 to 1.9) mSv y-1 at the equilibrium equivalent concentration of 0.3 Bq m-3 estimated for UK exposures. Considerably lower dose equivalents are received by regions of the skin which are habitually covered in clothing. The wide range in the dose estimates reflects the wide range in quoted plateout rates for radon and thoron daughters, and uncertainties in the magnitude of the electrostatic charge of the individual. To improve the dose estimates experimental measurements are needed of radon and thoron daughter deposition on the skin surface in situations corresponding to domestic exposure.