Governments must also work to present a clear narrative about the health implications of accidents such as Chernobyl and Fukushima For heroic plant workers exposed to extreme radiation doses and for those still suffering from Chernobyl's legacy of thyroid cancer -the risks are all too clear. But it is harder to pin down more subtle health effects. There are hints that low-level exposure can raise the risk of cardiovascular disease, breast cancer and other conditions, consistent with the idea that there is no safe threshold for radiation exposure. To clarify the situation, the world needs studies of large numbers of people exposed to very low doses of radiation-and Chernobyl can provide those. Funding such research is vital for those affected by Chernobyl's radiation, but it should also answer some of the questions over the future of nuclear People legitimately ask whether the low levels of radioactivity now drifting across Japan are safe The current best answer is ' probably!. a better response would be to find out, before another 25 years pasGovernments must also work to present a clear narrative about the health implications of accidents such as Chernobyl and Fukushima. For heroic plant workers exposed to extreme radiation doses — and for those still suffering from Chernobyl's legacy of thyroid cancer — the risks are all too clear. But it is harder to pin down more subtle health effects. There are hints that low-level exposure can raise the risk of cardiovascular disease, breast cancer and other conditions, consistent with the idea that there is no safe threshold for radiation exposure. To clarify the situation, the world needs studies of large numbers of people exposed to very low doses of radiation — and Chernobyl can provide those. Funding such research is vital for those affected by Chernobyl's radiation, but it should also answer some of the questions over the future of nuclear power. People legitimately ask whether the low levels of radioactivity now drifting across Japan are safe. The current best answer is 'probably'. A better response would be to find out, before another 25 years pass