Is a little radiation good for you?

An ongoing debate considers whether low levels of exposure to radiation may have beneficial effects. It had been assumed that there is a linear relationship between radiation risk and dose – the more radiation a person is exposed to, the greater the harm. This assumption arises from a probabilistic model of the risks of radiation: the greater the probability of a collision of a gamma ray photon with a DNA molecule, the greater the risk of harm. However, some researchers have suggested that the reality of the risk-to-dose relationship is more complex. Data from British nuclear industry workers suggest modest doses of radiation (10-50 mSv per year) may lead to lower incidences of leukaemia and cancer than found in the general population. In addition, an analysis of cases of cancer has found that the incidence of the disease was lower in areas with higher radon concentrations (over 10 mSv per year) in comparison to areas with lower levels of radon (less than 2 mSv per year). Studies of survivors of the nuclear bombs dropped on Hiroshima and Nagasaki revealed that victims of the blasts who received modest doses of radiation lived, on average, four years longer than the general population. One suggested mechanism to explain this unexpected effect is that exposure to low levels of radiation may induce changes in the immune system. For example, a study found that the number of antibodies produced by mice rose by a factor of five when exposed to doses of radiation up to 200 mSv per day. Such claims are controversial and more recent studies of radiation workers report that even small increments in dose led to increased incidences of cancer.