From here -
http://www.nature.com/nature/journal/v440/n7087/full/440982a.html
Twenty years after the worst nuclear accident in history, arguments over the death toll of Chernobyl are as politically charged as ever, reports Mark Peplow.
No more than 4,000 people are likely to die as a result of Chernobyl. That was the conclusion released by the United Nations and the governments of Ukraine, Belarus and Russia in September last year, in the most comprehensive assessment of the accident so far.
But despite promising "definitive" answers the report, based on two decades of research, has done little to resolve the debate over Chernobyl's impact. The estimate drew howls of protest from environmental groups, which accused the UN's Chernobyl Forum of a whitewash. And scientists whose work is cited in the report are concerned about how their figures were presented, pointing out that the true cost of the disaster will not be known for decades to come, if ever.
Chernobyl's runaway nuclear reaction in 1986 was triggered by a faulty safety test, and exacerbated by a design flaw that caused a catastrophic temperature rise in the reactor core. This caused about 6.7 tonnes of radioactive material to spread for hundreds of kilometres around the site. Two of the most significant elements in the chemical cocktail were iodine and caesium, and the most devastating effects were seen within a few tens of kilometres of the reactor, in the region where Ukraine, Belarus and Russia meet.
In the confusion that followed, local families continued to graze and milk their cattle on contaminated land. Many predicted that the accident would cause hundreds of thousands of cancers.
Cooking the books?
The forum reports that the fallout has since caused about 4,000 cases of thyroid cancer, mainly in children and adolescents. But just 15 of these patients have died. Along with highly exposed rescue workers who brought the reactor inferno under control, 62 deaths have been attributed directly to the accident so far.
The report also says that there has been no significant increase so far in the incidence of other cancers. In total, it said, "up to 4,000 people" may ultimately die as a direct result of the disaster — much lower than previous estimates.
That conclusion upsets many. "The report gave a completely misleading view of the health consequences of the accident," says Ed Lyman, a nuclear-power expert with the Union of Concerned Scientists in Washington DC.
The argument stems from uncertainty about the health effects of low doses of radiation. Evidence from survivors of the atomic bombs dropped on Nagasaki and Hiroshima has allowed researchers to predict the effects of high doses. But as the exposure drops, so does the understanding of its impact. Last year, a working group of the US National Research Council concluded that even tiny amounts of radiation cannot be considered safe.
In contrast, the forum based its headline figure on just the 600,000 people exposed to the most radiation, predicting that roughly 4,000 of them will die as a result. The full report acknowledges that, of 6.8 million others living further from the explosion who received a much lower dose, Chernobyl will kill another 5,000 — more than doubling the projected death toll. But this is not mentioned in the report's 50-page summary or the accompanying press release.
The figures come from a study published in 1996 by Elisabeth Cardis of the International Agency for Research on Cancer in Lyon, France. "I was very shocked that they were quoting figures we had found ten years ago," says Cardis. "I didn't expect the numbers to be picked up and used in a press release without qualification."
Even the forum's chair, Burton Bennett, former head of the Radiation Effects Research Foundation in Hiroshima, Japan, says caveats about the figures should have been clearer. But he points out that the extra 6.8 million people were, on average, exposed to a radiation dose of just 7 millisieverts — little more than the natural background delivers in a year in most parts of the world.
Melissa Fleming, a press officer working at the International Atomic Energy Agency in Vienna, who helped coordinate the report's publicity, says the scientists involved checked the press material. But she admits a decision was made to focus on the lower 4,000 figure, partly as a reaction to the inflated estimates of past decades. "I was sick of seeing wild figures being reported by reputable organizations that were attributed to the UN," she says. "It was a bold action to put out a new figure that was much less than conventional wisdom." The figure has been removed from the final summary, however, published this month.
