A Little Radiation May be Good for You by Jeremy Whitlock The Chalk River Branch of the Canadian Nuclear Society (CNS) opened its 2001-02 public speaker season on Thursday, November 8. The guest speaker was Philippe Duport, Director of the International Centre for Low-Dose Radiation Research (University of Ottawa), speaking on "Radiation and Cancer at Low Doses, Put into Perspective". Dr. Duport is the former head of the Health and Environmental Effects Research Section of the Canadian Nuclear Safety Commission. In 1996 he left that position to establish the ICLDRR within the University of Ottawa's Institute for the Environment. He receives funding from the DOE, Japan, France, the mining company COGEMA, and was given start-up funding by the Canadian Nuclear Society. Dr. Duport began by introducing the basics of the low-dose radiation research problem. At issue is the health effect of background (environmental) levels of radiation, 88% of which come from natural sources and the remainder from man-made sources (mostly medical tests). He described how radiation is both natural and abundant in the environment, and how exposures vary widely depending on geography and lifestyle. Some locations see background levels up to 30 times the Canadian average, which is four times the annual limit for atomic workers. Dr. Duport's point, however, was that life on this planet evolved in this radiation-filled environment (actually 5-7 times higher at that time), and consequently developed powerful repair mechanisms that protect against it. Therefore, although environmental radiation can theoretically cause cancer, it is a weak carcinogen by comparison with other agents. Simply by breathing, the human metabolism inflicts 10 millions times the amount of DNA damage, than that caused by radiation exposure. This onslaught from the environment, along with genetic disposition, leads to 30% of the population contracting cancer (and 25% dying from it). Dr. Duport's mission is to find out what fraction of that 30% figure is caused by low-dose radiation, and his suggestion to his CNS audience was: probably little to none. Dr. Duport showed many graphs that attempt to quantify this relationship. As expected, in all cases cancer risk decreases as radiation exposure decreases. The surprising part is that risk seems to go to zero long before the dose does. In other words, some data suggests that a threshold exists, below which radiation not only doesn't cause cancer, but may be beneficial in the fight against it. Dr. Duport's data calls on sources around the globe, and includes a study by Ron Mitchel, of AECL, which suggests a significant extension of lifespan for mice exposed to low-dose radiation. Dr. Duport concluded by asking if we are doing more harm than good, in our drive to reduce radiation exposure as low as possible. Several questions were asked by the audience, including whether data existed that contradicted Duport's conclusions. Duport responded that this data does exist, but is not as statistically significant.