A new study using "five types of real-time airborne particle monitoring devices" indicates that people who stand near and downwind from smokers in outdoor settings may be exposed to levels of combustion products similar to those seen indoors, except that the pollutants disappear as soon as the smoking stops. The levels measured by air monitors that were upwind or more than two meters away, by contrast, "approached zero." Since the researchers conclude that "it is possible for OTS [outdoor tobacco smoke] to present a nuisance or hazard under certain conditions of wind and smoker proximity," the study no doubt will be cited by supporters of outdoor smoking bans. But as Michael Siegel notes, the study could just as well be cited by opponents of such bans, since it shows that exposure to outdoor tobacco smoke is negligible unless you're planted right near (and downwind from) a smoker. From this Siegel concludes that outdoor smoking bans are justified only in locations where people may be stuck close to smokers, such as in stadium seating (although it seems like segregation of smokers would also work in such settings). He proposes this criterion for deciding whether a smoking ban is reasonable: "Are nonsmokers easily able to avoid the smoke by moving away from smokers?"

While I agree with Siegel that sweeping outdoor smoking bans, such as the one in Calabasas, California, are hard to justify, at least many of the locations they cover (sidewalks and streets, for example) are public property, which means the government has to pick some rule, whether it bans smoking in certain places, bans it entirely, or permits it everywhere. On private property, by contrast, there is no need for the government to get involved, since the smoke is confined to a particular location that no one is forced to enter. The concentration of tobacco smoke may be higher in a bar or restaurant than it is on a city street, but it is easily avoidable. By Siegel's standard, then, indoor smoking bans on private property (which he supports) are harder to justify than outdoor bans.