Wednesday, April 13, 2011

I'd Rather Have Nuclear Than Coal

For the first time, Germany's Green Party will control one of the country's state governments, just in time to decide the fate of several nuclear plants temporarily idled in response to the Japanese nuclear mess—the same mess that catapulted the Greens to unfamiliar success in state elections two weeks ago.

Were they to surrender to their inner Al Gore, their answer to the resulting electricity shortage would be for consumers to make do with much higher prices. But Green Party leader Winfried Kretschmann is unlikely to seek immediate return to the political wilderness. Forget the fantasy talk of wind and solar. The choice then is nuclear or coal.

Countries all over the world are making similar choices in light of Japan's disaster, whose severity the government now puts on a par with Chernobyl (even if the radiation releases haven't been remotely comparable). Thanks to Fukushima, officials everywhere will have to reacquaint themselves with one of the great noise-to-signal puzzles of modern science: How much harm does low-level radiation exposure do?

For 60 years, the hunt has been on for handfuls of "excess" cancers in populations subjected to unnatural doses of radiation. The findings have been more politically vexing than scientifically satisfying.

The once-golden Hiroshima and Nagasaki studies, jointly funded by the U.S. and Japanese governments, showed little or no low-dose cancer risk, and even a boost to longevity from low-dose exposure in the form of reduced deaths from "non-cancer" diseases. But the A-bomb studies have had their scientific crown knocked askew in recent decades. One reason is "survivor bias"—having survived not only the bombings but homelessness, hunger and a typhoon in the immediate aftermath, the subjects may be a hardier lot than the Japanese population at large.

Investigations of U.K. infants exposed to X-rays in the womb and workers in U.S. weapons plants gradually began nudging the bomb studies aside in the 1980s, for reasons due partly to legal and regulatory convenience: Their findings seemed to confirm the simple and intuitive "linear, no-threshold" hypothesis, which holds that radiation is always dangerous in direct proportion to dose.

These studies have problems too. British mothers had to guess years after the fact how many X-rays had been taken during pregnancy. A study of workers at the Hanford weapons plant claimed to distinguish between 6% and 7% "excess" cancers out of 2,500 cancers suffered by 35,000 workers.

There are other caveats. In lab experiments, low levels of radiation appear to stimulate the cell's own highly capable repair mechanisms. Studies of radiologists show a heightened cancer rate among those who practiced before the dangers of X-rays were known; later cohorts show no effect from a lifetime of small exposures.

And then there's the "hot particle" problem: The real danger may be long-lasting particles ingested or inhaled, even low-energy particles whose radiation doesn't normally penetrate the skin.

Meeting in Vienna in 1986, experts expressed a hope that Chernobyl would finally resolve the debate. "In 20 to 30 years' time we're going to know whether the linear dose hypothesis [is correct]," predicted one, "at least for leukemia and maybe for lung cancer."

It was not to be. For the record, aside from a serious uptick in curable thyroid cancer among those exposed as children (which faster action at the time would have avoided), a U.N. monitoring project finds "no scientific evidence of increases in overall cancer incidence or mortality rates" among residents of the Chernobyl region. But that hasn't stopped other studies from predicting tens of thousands of "excess" cancer deaths across Europe over many decades based on the same linear, no-threshold modeling that governments everywhere have adopted as a regulatory standard.

All this has direct bearing on Japan, where hot particles especially will be a worry for some time to come. In a linear, no-threshold world, the Japanese government can never call a given level of exposure "safe" even if the additional risk is statistically negligible for the average person. In fact, Japanese politics may be roiled for decades to come by insoluble arguments over small anomalies in the cancer rate and whether a given sufferer is a "victim of Fukushima."

Of course, the galloping irony for the Baden-W├╝rttemberg Greens is that the exact risk model doesn't matter. However you slice it, coal is more dangerous than nuclear.

Start with deaths that aren't the product of statistical imagination: Thousands more die in coal mining accidents each year (especially in China) than have been killed in all nuclear-related accidents since the beginning of time. What's more, coal plants spew toxins like mercury and other metals—along with more radioactive thorium and uranium than a nuclear plant—which are no less amenable to linear, no-threshold thinking. In 2004, the EPA estimated that a new emissions standard then being promoted would, by itself, save 17,000 lives a year.

So the question is a no-brainer for the Baden-W├╝rttemberg Greens. Yep, you guessed it: They can be counted on to shut down the nukes anyway. Their anti-nuke stance is an article of faith not subject to review.

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