Nutty assumptions produce nutty conclusions



Alarmists of all kinds almost always use straight-line projections from some current trend. But most natural phenomena are not ordered in that way. Below is an example of how a straight-line projection of mortality from radioactivity gives absurd conclusions -- yet it precisely that sort of projection that is generally used by regulators.

The truth is that low to medium doses of ionizing radiation are harmless or even beneficial. It is only high doses that lead to adverse health effects. Google "radiation hormesis" for the relevant facts

Once again reality is not as simple as the theorists imagine


The Union of Concerned Scientists (UCS) All Things Nuclear blog has an analysis of how many deaths occurred at Chernobyl based on linear no threshold view of radiation. So 0.01 milliSieverts (1 milliRem) for each of 6 billion people in the world is calculated to add 4000 deaths from cancer. 0.3 milliSieverts (30 milliRem) for 500 million people in europe is calculated to add 9000 more deaths from cancer.

Using the same analysis (NEI Nuclear Notes) found that, 79,000 and 40,000 would be reasonable estimates of the number of excess cancers and cancer deaths attributable to the flying in the past decade. The numbers increase even more over the 25 years since Chernobyl and would be 200,000 excess cancers and 100,000 excess deaths from commercial aviation over the last 25 years.

As the US EPA (Environmental Protection Agency) explains, exposure to cosmic radiation depends on altitude, latitude, and solar activity, but the EPA estimates that "a typical cross-country flight in a commercial airplane" results in "2 to 5 millirem (mrem)" of dose from radiation.

The statistics from the US Bureau of Transportation Statistics indicate that over 7 billion airline passengers (international and domestic) flew in the US between January 2001 and January 2011. Thus, if we assume a fairly low average value of 3 millirem per passenger, then aviation has resulted in a collective dose of 210,000 passenger-Sv over the past decade.

This is quite a large number already, but Dr. Gronlund did not consider the radiation exposure within just one country. She provided an estimate for the entire world. So we should follow suit.

The US aviation market comprises somewhere between 25 to 30 percent of the entire world's airline passengers (e.g., in 2009, passengers in the US comprised roughly 28% of the airline passengers worldwide, according to IATA statistics). Thus, if we conservatively assume that US passengers comprised 30% of the passengers worldwide during the past decade, then worldwide, the collective dose due to commercial aviation is 700,000 passenger-Sv.

Using Dr. Gronlund's methodology (which was taken from the BEIR VII report), we should assume that "the expected incidence and mortality of solid cancers and leukemia are 0.1135 cancer cases and 0.057 cancer deaths per Sv." Thus, because of radiation exposure due to the airline industry, the expected number of cancer cases is 79,000, of which some 40,000 should result in death.

Note however that, because exposure only increases the probability of developing cancer, we should keep in mind that no given cancer can be attributed to flying. Moreover, because these additional cancers will be distributed among hundreds of millions of people, it is practically impossible to discern them among all the other cancer cases. (About 42% of the general population have cancer at some point in their lives, and about 20% of the population die because of cancer or complications that result from cancer.)

It is somewhat illustrative to compare these numbers to the numbers presented by Dr. Gronlund for the Chernobyl accident: 68,000 cancer cases with 34,000 deaths. Given these numbers, one can scientifically conclude that the airline industry is far more dangerous -- in terms of deaths due to low-dose exposure to radiation -- than old, Soviet-era nuclear reactors.

In light of these numbers, I expect that the UCS will be setting itself up as an "aviation watchdog" any day now.

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