Colleagues:
I wish to comment on the recent discussions about DNA damage/repair and hormesis.Most biological explanations for radiation hormesis have been based on cellular phenomena such as adaptive responsiveness, and other repair mechanisms. Hormesis proponents have argued that cells undergo extensive oxidative damage during normal metabolism and are able to repair such damage. Ionizing radiation is believed to stimulate repair thus further reducing the number of damaging oxidative species conferring overall benefit to the cell. Although these cellular phenomena are well known, it is unclear how they relate to an overall benefit to the body as reflected in reduction in cancer incidence/mortality. Cancer is a multifactorial disease; although DNA changes must occur in critical target cells to initiate cancer, the overall probability of occurrence of disease depends on numerous host and other environmental factors that may be independent of the initiating event in the target cell(s). Thus, macromolecular changes in cells may tell us little about the overall risk of disease.
Regards,
Ken
Kenneth L. Mossman
Professor and Director
Office of Radiation Safety
Arizona State University
Tempe, AZ 85287-3501
Voice: 480.965.0584/6190
Fax: 480.965.6609
Cellular: 602.769.2371
E-mail: ken.mossman@asu.edu