Early studies of the impact of second hand smoke often found a statistically significant impact on heart attack rates. Or perhaps I should say, "Early published studies"; I have no idea what early unpublished studies found.
When faced with this sort of evidence, scientists will try to replicate the results with much larger data sets, accounting for omitted variables. And that's exactly what occurred. Here's Slate.com:
Contradictory research continued to come in. A clever study led by researchers at RAND Corp. in 2010 tested the possibility that the large reductions identified in small communities were due to chance. They assembled a massive data set that allowed them to essentially replicate studies like those in Helena, Pueblo, and Bowling Green, but on an unprecedented scale. Whereas those studies had compared just one small community to another, the RAND paper compared all possible pairings of communities affected by smoking bans to all possible controls, for a total of more than 15,000 pairings. They stratified results by age in case there were differential effects on the young, working age adults, or the elderly. And in an improvement on most other studies, they also controlled for existing trends in the rate of heart attacks.
The study found no statistically significant decrease in heart attacks among any age group. The data also suggested that fluctuations in heart attack rates were common, indicating that comparisons of small communities would frequently turn up dramatic reductions due purely to chance; large increases in heart attacks happened about as often. This explained the headline-grabbing dramatic results in places like Helena or Monroe County that eluded replication in larger jurisdictions. The conclusion of the study was blunt: "We find no evidence that legislated U.S. smoking bans were associated with short-term reductions in hospital admissions for acute myocardial infarction or other diseases in the elderly, children or working age adults."
I was directed to this article by Steve Winkler, who made this comment:
Slate explores the implications of the junk science used to ban smoking on grounds of secondhand dangers. I believe we are in an age of rising puritanism. Tobacco is the drug in the cross hairs. It is low brow. Interestingly alcohol and marijuana are higher and rising status. Once again, mood affiliation and out-group shaming guides public policy.
Let's assume that despite the RAND study, we conclude that second hand smoke has some negative health effects (which seems plausible in my view.) In that case, what would be the appropriate public policy toward second hand smoke?
It turns out that it entirely depends on the location of the second hand smoke. According to the Coase Theorem, externalities do not call for government regulation unless it is too costly to privately negotiate an efficient solution.
In the case of indoor smoke, it is almost never costly to negotiate the optimal solution. That's because in most cases the optimal policy toward indoor smoking will be the policy that maximizes the value of the property. Thus a restaurant owner will have an incentive to set a smoking policy that maximizes the value of her business. Ditto for the owners of office buildings, apartments and airplanes.
Actual public policies toward second hand smoke are almost nothing like what the science would suggestion. Conservatives are often criticized for rejecting the scientific consensus on climate change. I believe the criticism is justified. But those conservatives are only rejecting a single scientific hypothesis. Second hand smoking regulations are far harder to justify, as they represent a rejection of two very different types of science:
1. The science of how to establish statistical significance when there is publication bias in favor of rejecting the null hypothesis.
2. The science of the Coase Theorem, and particularly its implications for public policy.
Many people claim that some conservatives reject the science of global warming because they are not comfortable with the policy responses proposed by people on the other side. I prefer not to attack motives, but if that is your view, shouldn't you also be asking how many progressives reject the science of second hand smoke, and also the science of when to use government regulations, solely because they don't like the policy implications of those two types of science?
PS. I try not to let my political views influence my views on scientific questions. I was serious when I said that I believe second hand smoke does have some negative health effects. As an anecdote, my grandfather died of emphysema. He was a nonsmoker who worked in an office filled with smokers. It seems plausible to me that all of that second hand smoke was a problem for a guy who (like me) had bad lungs. Yet I oppose government regulation of smoking for Coase Theorem reasons. On the other hand, I support a carbon tax, as the transactions costs of a Coasian negotiated solution are prohibitive.