The Sciences

How Many People Died (or Will Die) From Chernobyl? And, Population Risk vs. Individual Risk

The IntersectionBy Chris MooneyApr 12, 2011 1:23 PM


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Aware of the big debate over this question, I wanted to dig into the topic with David Brenner of Columbia on Point of Inquiry. The exchange on this, which gets into the reasons why people disagree about the magnitude of the disaster, begins around minute 13:30 and runs on for more than 5 minutes. I want to call attention to one part of the exchange in particular (stream here). After Dr. Brenner explained why there are such wildly varying estimates (from 6,000 to as high as nearly 1 million) for the Chernobyl death toll--it all has to do with whether you multiply very minimal radiation doses by the very vast populations that did get at least some tiny exposure to radiation from Chernobyl--I asked the following:

Chris Mooney: The World Health Organization studied Chernobyl, and they put a low end estimate on the number of deaths, so they were ruling out, essentially, these extremely low doses to extremely large numbers. Was that a valid thing to do? Dr. David Brenner: "Valid" is a tricky word. Was it an appropriate thing to do? That's a hard question. The best science that we have, I would suggest, cannot rule out the possibility that we should really include everybody who was exposed to extremely low doses. And if you do that, you end up with quite large population cancer burdens. That being said, that doesn't mean that the individual risk to anybody was high. The distinction here is between individual risk--the risk that any one person gets from a tiny dose of radiation--and population risk, the risk to a whole population, the number of cancers that might be produced in a whole population. They're different concepts. Population risk involves individual risk and the number of people exposed. Individual risk is just individual risk. Trying to make that distinction--it's an absolutely critical distinction, and it's one that gets lost in the flurry of debate. Chris Mooney: But it's even trickier than that, because it both implies that, "Hey, I'm in California, and something happened in Japan, so I individually don't need to worry very much," but at the same time, it gives ammo to those who will say later, well, it killed this ungodly number of people--which will scare people in the future. Dr. David Brenner: Indeed, you've hit the nail very much on the head. But it is fair that one should look at risk from both of these aspects. It's important to know what people's individual risks are, but it's also important to understand what the consequences for a very large population would be.

As you can maybe tell, I really don't like the idea of these vast populations of unidentifiable victims. It bothers me. It doesn't sound right. However, Brenner explains why we can't rule it out, and his explanation is very cogent. As a result of this, I'm now way more skeptical of George Monbiot. He's treating the WHO study as if it is the right answer, but this issue of low dose exposures to very large numbers, while maddening and tricky, cannot be dismissed at this point. I'm not taking the side of his opponent, either; I'm not sure we dash to the extreme high end estimate either, but clearly, this topic requires caution. Again, you can stream the latest Point of Inquiry episodehere.

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