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Bjørn stærk

Remember that when you talk about risk increases of 30% or 10%, those numbers aren't too small because a 30% increase in risk for lung cancer isn't bad, but because you can't feel confident that there's more than an accidental correlation here. There more I look into this, the more I find confirmation that a risk increase of less than 100% (RR less than 2.0) is generally considered too low to be meaningful, because of the uncertainty of the methods used. This is statistics, not science, and there are many traps to fall into.

For instance, one report mentioned here ( was based on a comparison between Adventists and other Americans, and assumed that because Adventists are little exposed to passive smoking, any difference in lung cancer occurences could be attributed to that. Is that science? It's not even good statistics.

Leif Knutsen, New York

If you want convincing scientific evidence, you need to have convincing study design. That's very difficult when it comes to longitudinal research where you a) can't control the subjects' behavior; and b) all kinds of other variables come into play. This was difficult to do even when researching "active" smoking - people underreported how much they smoked, they picked it up and dropped it, and they often had other behaviors that could have adversely affected their health. In other words, there won't be totally convincing evidence for quite a while (though the Helena, Montana story is pretty compelling) - authorities shouldn't oversell what they have, but "pro-smoking" advocates should understand that just because something hasn't been proven doesn't mean it's been disproven, either.

It only stands to reason that tobacco smoke is dangerous to inhale one way or the other, but so are any number of gases and particles in our environment. My point was that you can accept varying levels of evidence depending on your tolerance for risk. Health authorities - and public opinion - feel that "as little as possible" is the right risk level.

Bjørn Stærk

Leif: "but "pro-smoking" advocates should understand that just because something hasn't been proven doesn't mean it's been disproven, either."

But that's just not relevant. You're arguing a kind of knowledge from ignorance - since we _can't_ know that passive smoking is dangerous, we have to act as if it were. But if we can't know, then we don't know, and what we believe but don't know is faith. For smoking, we do know. For passive smoking, it seems we don't.

There are levels of ignorance, of course. Epidemiology did not prove that the many hundred percent increases in risk of lung cancer for smokers were _caused_ by smoke, (only that they were strongly correlated), but it gave us a reasonable suspicion to act on, as well as to base scientific research on. Epidemiology has not given us that reasonable suspicion for passive smoking. To base laws on meaningless numbers is to base laws on faith.

Helena, Montana -,2933,100318,00.html

Leif Knutsen, New York

But let me state two premises for the discussion here:

1) Passive smoking in some amount (unclear how much) is dangerous. Someone who lived all his life in a smokefilled room will end up inhaling the equivalent of several cigarettes a day. Yes, we don't know when the level goes to "hazardous to your health," but it's reasonable to believe that no cigarette smoke is healthier than any cigarette smoke.

2) The critique of the Montana experience or other studies basically says that the data doesn't convincingly support the conclusion. That doesn't mean that the conclusion is incorrect, only that the critics aren't convinced. Of course, this kind of criticism is valuable and essential to scientific inquiry, but it is more valuable when you have to make a tough cost/benefit trade-off.

These two support the decision to ban smoking. I'd contend that this kind of logic is too complex to put into a PR program, and that authorities have instead chosen to overstate the evidence. As a matter of principle, this is bad policy. As a practical matter, there was probably no other way.

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