Overview and summary remarks

The non-scientific community believes that there is such a thing as safety and that this should be an attainable goal in any technology. People are poor intuitive judges of risks. If the first inducer of mutation to be discovered had been mustard gas rather than ionizing radiation, we probably would not be as concerned about radiation. Radiation is a relatively poor mutagen; it is a good recombinogen but poor compared to ultraviolet and may chemicals for the production of point mutagens. The issue of threshold doses has not been resolved; when one allows for the existence of repair, one opens the possibility that repair-proficient cells could have a dose-response curve with a zero slope at very low doses. Another issue concerns mutagen burden, particularly when comparing radiation with chemicals. Exposure to ionizing radiation may be a very minor component of the total mutagen burden to which we are all exposed. There can exist both synergistic and antagonistic interactions among mutagens. We should not forget the role of metabolism in genetic responses. The responses of cells to mutagens of all kinds are much more complex biochemically than one would imagine on the basis of the simple notion of DNA damage and its error-free or error-prone repair. (L.L.)