Tuesday, March 20, 2012

Radiation Hormesis

Petr Beckmann used to argue that the linear hypothesis regarding radiation wasn't just off, its sign was often wrong as low level radiation could actually be beneficial. (He used the term hormesis to describe the more general phenomenon.) An article in the WSJ cites more evidence for this view:
In the early 1980s, a Taiwan steel company accidentally mixed some highly radioactive cobalt-60 into a batch of steel rebar. The radioactive rods were then used in the construction of 1,700 apartments. As a result, people living in these buildings were subject to radiation up to 30 times the normal amount received from the natural background.

When dismayed officials discovered this enormous error 15 years later, they surveyed past and present apartment dwellers expecting to find an epidemic of cancer. Normal incidence would have predicted 160 cancers among the 10,000 residents. To their astonishment, the researchers discovered only five cases of cancer—97% lower than the anticipated amount. Birth defects were also 94% below the anticipated rate. These findings were published in the Journal of American Physicians and Surgeons in 2004. As one researcher phrased it, exposure to high levels of background radiation had apparently bestowed upon residents "an effective immunity from cancer."
The article also does a good job of showing why the linear hypothesis doesn't gibe with our more general experience:
The real problem, however, may be in the public's overestimation of the danger posed by small exposures to radiation. In order to avoid any possible charge of negligence, regulatory bodies around the world have adopted what is called a "linear-no-threshold" or "no safe dose" standard for radiation safety.

This says, quite simply, that because huge doses of radiation—the kind you might get from standing in the same room with a spent fuel rod—can cause illness or cancer, we must assume that even the smallest doses will have the same effect on a smaller scale. It's exactly the same as saying that because jumping off a 10-story building will break every bone in your body, stepping off a one-foot curb will also cause some minor damage.
I hope that someday soon science will prevail over fear mongering in the energy arena...

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