Smoking bans and Kyoto

Another Bjørn Stærk logroll: This time about "passive smoking." Legislation went into effect June 1st that prohibits smoking in bars, restaurants, etc., out of consideration for employees and others whose health might be affected by secondhand smoke.

Bjørn's point - which he stresses in the discussion thread - is not to argue whether there should be a smoking ban, but whether the government can use "dodgy science" to justify it. He points to numerous studies that show only weak evidence that second hand smoke is dangerous to your health. And then there are sites that denounce the second hand smoke issue as a fraud.

You will run into a similar debate if you are interested in CO2 emissions and the greenhouse effect. Opponents of the Kyoto accord point out that the evidence to link global warming to increasing CO2 emissions is not strong enough to be warrant the expense of dealing with it in a hurry. Supporters of the accord point out that it's hardly worth the risk waiting to find out. The Day After Tomorrow paints the dangerous scenario of taking that risk. Curiously, a similar argument came into play about Saddam's weapons of mass destruction: the only definitive proof, we were told, would be a mushroom cloud.

How strong must the evidence be before authorities should act? It all depends, as always. It depends on the magnitude and prevalence of the adverse event we're concerned about; it depends on the cost and effectiveness of preventing the event; and it depends on the level of confidence we can have in these two measures.

In this case, we know the type of damage tobacco smoke can cause: increased prevalence of cancer, pulmonary disease, and coronary disease, at least. We know that these illnesses often are expensive to treat and all too often lethal.

We don't fully know the effects of secondary smoke, though. Bjørn points to a number of studies that indicate that the incidence of such diseases increases by 20% to as much as 80%. But this statistic is not particularly helpful. After all, most of us will eventually die of a heart attack or cancer, and the exact causality of these illnesses is hard to figure out. The statistic also doesn't say whether we're more likely to get a particular illness at all, or whether we're more likely to get it sooner.

And we don't know anything about how much smoke has what effect. Someone who spent all his days and nights in a place where people constantly smoke probably inhales as much smoke as a firsthand smoker and incurs the same risks. Someone who catches a whiff of tobacco smoke on the street is unlikely to increase her risk at all.

(This is a good illustration of why it is so difficult to design public health research projects, by the way. The Framingham Heart Study is one of the most ambitious longitudinal studies ever conducted, and its core findings are still disputed. For decades, tobacco companies argued that there was only inconclusive evidence to link smoking to disease. This is because the scientific method doesn't allow us to make definitive positive assertions. Merely showing that there is a positive correlation between smoking and heart disease does not prove causality.)

So we can say this much: all else being equal, a person who is exposed to more tobacco smoke is more likely to get sick than the person who is exposed to less. This holds true whether the exposure is first- or second hand.

For some, this is enough. Since there are no benefits to second-hand smoke, they would argue, why quibble over the exact numbers? Why should we tolerate that non-smokers increase their mortality rate by 30%, or even 10% without any benefit to show for it? And when there is compelling anecdotal evidence to support smoking bans, it could be argued that authorities that allow second hand smoke are outright reckless.

Others argue that there has to be a stronger burden of proof: authorities can't rely on tenuous and anecdotal evidence to regulate what is fundamentally private behavior.

This brings us back to Kyoto. The Bush administration has, like so-called "smokers' rights advocates" argued that there is insufficient evidence to support the hypothesis that CO2 emissions damage the environment in general or cause global warming in particular, and if they do, what the extent of the damage is. Kyoto supporters argue, why take the risk when there is so much at stake? We should reduce CO2 emissions just in case.

The big difference between Kyoto and smoking is that reducing CO2 emissions is costly in the short term (e.g., 10-50 years), banning smoking in public places really isn't.

And smoking isn't private behavior, the way chewing tobacco (or even snorting cocaine) would be. The argument against smoking in public places has nothing to do with the damage smokers choose to do to themselves - it has to do with weighing the convenience of smokers against the convenience of non-smokers. Non-smokers suffer at best inconvenience and at worst health risks because smokers feel they have the "right" to indulge in a habit that is costly, smelly, and dangerous.

Comments

[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 (http://www.tidsskriftet.no/pls/lts/pa_lt.visSeksjon?vp_SEKS_ID=897244) 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 - http://www.foxnews.com/story/0,2933,100318,00.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.