Monday, January 11, 2016

A Slippery Slope

When we read the statistics on deaths involving automobile accidents, we are given the actual count of deaths as compiled by various law enforcement agencies. But when the anti-nuclear zealots tell us about the number of people who died as a result of radiation from exposure to, say, radon, they don't have a single victim they can point to with any degree of certainty. Their "statistical deaths" come from an extrapolation based on the Linear No-Threshold (LNT) theory. Just as with our falling analogy, they correctly note that very high exposures, like falling from very tall buildings, increase the likelihood of death (by cancer, in the case of radiation). Their argument falls apart when they try to extend, or extrapolate, the high-dose exposure to much lower exposures.

For a moment let's jump to an example detailed in a later chapter. Studies of the Japanese indicated that exposure to the equivalent of 100 SXR units (20 rem, if you're ahead of me) in a short time would double the number of leukemia deaths in a population of one million people, from the expected fifty deaths to one-hundred. The LNT extrapolation would predict one-tenth the increase in deaths (in this case, five) if the population were exposed to one-tenth that additional exposure (in this case, 10 SXR units).

Could they point to any bodies? No, they only have their theoretical corpses based on the LNT extrapolation. But in this case, there is actual data that completely contradict the LNT theory's prediction. Not only did the death rate not increase; it actually decreased - by an astounding 40%! To summarize:
Fifty deaths expected in unexposed population
Fifty-five deaths predicted by LNT extrapolation
Only thirty deaths occurred, according to actual data

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Therein lies the crux of the hormesis/LNT controversy: Those who advocate the Linear No-Threshold theory base their belief on the extrapolation of high-level exposure responses down to low levels. But when low-level data are available, they almost always show a bio-positive - or stimulatory - response. It is this response, called hormesis, that we will be discussing in the next chapter.