The cancerogenic pollution by non-ionizing radiations is limited to the case of solar ultraviolet, whose activity at ground level may be increased as a consequence of the stratospheric depletion of ozone, itself produced by certain chemical pollutants: nitrogen oxydes from supersonic aircrafts, freon. 2. As regards ionizing radiations, the discussion is focused on the fundamental problem of the "threshold", aand on the means by which one may obtain some quantitative data related to carcinogenesis by small radiation doses in Man. A new concept, that of a "practical threshold" is proposed. 3. One discusses a theory which links radiocancerogenesis, as well as chemical cancerogenesis, to errors produced in the repair of lesions in the DNA. 4. One presents and discusses the "rads-equivalent" project for chemical mutagens and cancerogens.
