General Considerations of the Choice of Dose Limits, Averaging Areas and Weighting Factors for the Skin in the Light of Revised Skin Cancer Risk Figures and Experimental Data on Non-stochastic Effects

Summary

In recent years considerable clinical and experimental data have become available which can form the basis of a better understanding of the response of skin to radiation exposure and should lead to improved radiological protection criteria. Recent biological data from man and pig on the non-stochastic effects following exposure with a range of β-emitters are combined with recent epidemiological analyses of skin cancer risks in man to form a basis for suggested improved protection criteria for the skin following whole- or partial-body skin exposures. Specific consideration is given to the choice of an organ weighting factor for the evaluation of effective dose-equivalent. Since the stochastic and non-stochastic end-points involve different cell types, which reside at different depths in the skin, the design of an ideal physical dosemeter may depend on the proportion of the body skin that is exposed and the penetrating power of the radiation. Possible choices of design parameters for skin dosemeters are discussed. The limitation of skin exposure from small radioactive sources (‘hot particles’) is an important practical problem, which is addressed for the first time using animal data. Dose limitation on the basis of an average dose to an area of skin in the vicinity of the particle or on the basis of number of β-particles emitted could be used. Animal data, for several energies and sizes of β-emitting sources, indicate that limitation of the average dose to 1 Gy (average dose to 1 cm² of skin at a depth between 100 and 150 μm) should prevent the occurrence of transient acute ulceration from small sources with dimensions of less than about 1 mm.