Jerry Cuttler, Ph.D. Nuclear Sciences and Engineering, past president of Canadian Nuclear Society. William Hannum, Ph.D. retired Argonne National Laboratory, (reactor physics and safety, former Deputy Director General of the OECD Nuclear Energy Agency, Paris, France): Current EPA regulations are based on the linear no-threshold (LNT) dose-response model. These regulations have long been considered to be conservative, and it is widely recognized that they are excessively restrictive. There is emerging evidence that the effects of low or even moderate levels of ionizing radiation are in fact beneficial. Researchers are now postulating that rather than being a simple cause of additional cell damage, the principal effect of low-level radiation is to stimulate the body’s natural defense mechanisms — for instance, against cancer cells. To see discussion on this article go to the search box on this website and enter "Hayden LNT".