[Thoughts on carcinogenic pollution caused by ionizing radiation]

The pollution phenomenon groups the effects of small doses of radiation on large populations. These effects on Man are not directly accessible. One must: a) consider some epidemiological statistics (cosmic radiation at high altitudes; radioactivity from granitic surroundings); b) extrapolate from datas obtained with high doses; c) extrapolate from datas obtained with low doses in micro-organisms or mammalian cells in vitro. The interpolation scheme of Abrahamson et al. is so available for mutagenicity. The question of a threshold remains theoretical, although radiation-induced carcinogenesis often displays a dose-effects curve with a well market threshold. A new concept, that of a "practical threshold" is developped, which may be of great usefulness. The main genetic considerations are listed upon which the present international admissible doses are based. Finally, in order to establish quantitative comparisons between chemical and radiation carcinogenic pollution, the concept of "rad equivalents" for the main chemical mutagens is stressed.