Still fresh from victories over both cigarettes and the second-hand smoke they emit, many public health advocates have turned their attention to new supposed hazards: e-cigarette “vapor” and “third-hand” smoke. While the previous campaigns to prevent smoking have had positive results, the latest ones smack of hubris and overreach. In fact, the new focus on what you might call public health “micro-aggressions” does at least as much harm as good.

There’s no scientific doubt that cigarettes and the smoke they emit present a real public health hazard. The surgeon general’s most recent report on smoking links it to more than 20 million deaths since the mid-1960s and maladies ranging from lung cancer to sexual dysfunction. The Centers for Disease Control and Prevention report that cigarette smoke contains over 7,000 chemicals, 70 of them strongly linked to cancer. The Institute of Medicine concludes that persistent second-hand smoke exposure increases the risk of heart disease by 25 to 30 percent.

While it may well clash with many concepts of personal autonomy and private property rights, the public health rationale for both discouraging smoking and banning it in public places is strong. As a result of tobacco-control efforts, the percentage of adults who smoke has declined from more than 40 percent when the first stern public health warnings were issued in the mid-1960s to a bit less than 20 percent today (the decline seems to have stopped in recent years, however). In addition, the near-universal ban on smoking in workplaces and indoor public gathering spots has largely ended involuntary exposure to secondhand smoke.

If third-hand smoke or e-cig vapor caused the same ills, another campaign might be warranted. But they probably don’t.

Third-hand smoke refers to the contamination that may linger in a place after people smoke there. Determining its actual risks, however, presents a research challenge. If a home, car or public space gets saturated with cigarette smoke, anyone who enters it regularly is going to be exposed to second-hand smoke. If there’s a huge amount of third-hand smoke in a place, it’s highly likely to be because at least one regular occupant is a smoker. Studies about third-hand smoke show that there are some harmful contaminants that linger (although in minute quantities). Still, it’s hardly clear that there’s enough to be harmful. One report in the journal Tobacco Control, for example, found that the difference in environmental nicotine in smokers’ and nonsmokers’ homes wasn’t statistically significant.

Other research has a clear political agenda. As Boston University public health researcher Michael Siegel has pointed out, one recent report on the dangers of third-hand smoke done by a team at the University of California, Riverside announced its conclusions before the research began—hardly a model of scientific impartiality. That report, in turn, got covered in the media with headlines like “Study: Third-hand Smoke Exposure as Deadly as Smoking.”

And that’s a problem. Whatever the harms of third-hand smoke—and nobody has proven that they’re zero—their harm to public health overall is tiny in a country that already bans almost all indoor smoking in public places. Any effort to protect people from the dangers of third-hand smoke will almost by definition mean going into quintessentially private spaces and regulating private behaviors.

If efforts against third-hand smoke are intrusive and have a questionable basis in research, efforts to demonize e-cigarette vapor may prove downright harmful. Unlike the campaign against third-hand smoke, which is mostly an academic one for now, the anti-e-cigarette effort has shown legislative success. New York, Los Angeles, Chicago and Philadelphia have already passed municipal bans on “vaping” in public that treat the products as if they were cigarettes. But the rationale for conflating e-cigarettes and tobacco cigarettes is weak. The main ingredient in e-cigarette aerosol (other than water vapor) is propylene glycol, which is also a common propellant in asthma inhalers, and its toxicological category is “generally recognized as safe,” according to the FDA. An October 2012 study published in the journal Inhalation Toxicology found that, for all byproducts measured, e-cigarettes produced very small exposures relative to tobacco cigarettes. Common sense, as well as the great bulk of existing research, suggests that e-cigarettes and their vapor present essentially no risk to bystanders.

This isn’t to suggest that e-cigarettes are safe. They contain nicotine, a very addictive stimulant that, like all stimulants, has the potential to cause heart problems. The fact that they’re quite addictive and may have long-term risks nobody has discovered (they’ve been on the market for less than a decade) is good reason to keep them away from children and out of schools, daycare centers and medical facilities. Although not perfect, newly issued FDA regulations, which would ban sales to minors nationally, take a much more sensible approach to e-cig regulation than most localities have to date.

But, whatever their dangers, e-cigarettes aren’t the same as cigarettes. People who use them instead of tobacco cigarettes can expect at least some of the same health benefits as those who quit smoking. And nothing suggests that their vapor is anything like second-hand smoke. Indeed, almost all research indicates the opposite.

The preponderance of the evidence indicates that both third-hand smoke and e-cigarette vapor are the chemical equivalent of dirty looks. They may well be unpleasant or offensive to some people. But the public health case against them appears weak to nonexistent. Public policy would do well simply to leave them alone.

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