Monday, December 04, 2006

"The tobacco industry: proudly seeming a little sillier every time you read something about us."


Eric said...

While, Mike, I will not contest your argument about the silliness of the tobacco lobby, and I in no way mean to defend them, I do believe that Mr. Proctor, the writer of the op-ed piece you reference, is twisting some information in order to grind his ax. He has taken a couple of scientific facts and completely misused them - manipulating his numbers in a How to Lie with Statistics-type fashion.

To wit:

"A fraction of a trillionth of a curie...may not sound like much, but remember that we’re talking about a powerful radionuclide disgorging alpha a much higher rate even than the plutonium used in the bomb dropped on Nagasaki. Polonium 210 has a half life of about 138 days, making it thousands of times more radioactive than the nuclear fuels used in early atomic bombs."

I have three problems with the previous statement:
1) The radioactivity of a material is independent of half-life. Radioactivity, measured as a decay rate, expressed in Curies (Ci) or Becquerels (Bq), is an instantaneous property of a radioactive substance, a measure of the number radioactive decays per time. There is no direct correlation between the radioactivity of a substance and the biological effects of this radioactivity on soft tissue. What is dependent on half-life and can be used to determine biological effects is the total dose received, measured in Grays (Gy) or Rads. An even more accurate measure when determining biological effects is the dose equivalent, measured in Rem or Sieverts (Sv), which converts the dose, using an empirically-determined quality factor (20 for alpha, 10 for neutrons, 1 for beta/gamma), to a meaningful number for determining the biological damage done by the radiation.
2) I am at a loss as to how Polonium-210 having a half-life of 138 days has anything to do with anything. Uranium-235, a common fissile material used in early nuclear weapons, has a half-life of roughly 700 million years. Granted, U-235 is a neutron-emitter and not an alpha-emitter like Po-210, and alpha particles are more harmful when their precursors are inhaled/ingested than are neutrons (though only by a factor of two), but to say that 0.04 pCi of one substance is any more or less radioactive than 0.04 pCi of any other substance is just flat wrong. Yes, Po-210 is extremely radioactive and a gram of Po-210 is undoubtedly more radioactive than a gram of most other radioactive substances (I could look up some examples, but I'm not going to - I will give him the benefit of the doubt that this is correct), but correlating this with the half-life is completely nonsensical.
3) The radioactivity of the fuel of a nuclear weapon is completely irrelevant to Mr. Proctor's argument. The fuel is well-shielded in the innards of the weapon (n.b.: effective shielding for neutron-emitters is lead, water, or some polycarbonates; a sheet of paper or a few feet of distance is effective for alphas). The radiation damage done by a nuclear weapon is the result of the radioactivity of the fission products and their daughters, many of which are alpha-emitters, not that of the fuel itself.

If .04 picocuries of polonium are inhaled with every cigarette, about a quarter of a curie of one of the world’s most radioactive poisons is inhaled along with the tar, nicotine and cyanide of all the world’s cigarettes smoked each year. Pack-and-a-half smokers are dosed to the tune of about 300 chest X-rays.

True. But who cares about the total radioactivity inhaled by everyone in the world? The final sentence is the only somewhat-logical part of this entire argument, though it is still not entirely logical. The dose received by a medical x-ray is significantly worse than the same dose received over a few hours or even a few minutes; acute doses are much more damaging than are chronic doses. Mr. Proctor isn't comparing apples and oranges - he's comparing apples and Yugos. Sure they might both be red and sure they might both kill you if they come at you too fast, but they're not quite the same thing.

Mike said...

I can say with a fair amount of authority that Robert Proctor is unlikely to have intentionally manipulated anything in order to "grind his ax." But your point is well-taken. And given what you do for a living, I'm hardly in a position to disagree with you.

Instead, I'll just reiterate how much I appreciate your comment, as it is the most substantive thing ever written on this particular blog. So bravo for that.