Now let's look at the Klepeis study:
1) average OTS concentrations measured … during visits to outdoor patios that were enclosed by fences or walls … were 50% and 43% higher, respectively, than those observed in more open areas. … (Page 10)
2) We observed a clear reduction in OTS levels as the distance from a tobacco source increased. Generally, average levels within 0.5 m from a single cigarette source were quite high and comparable to indoor levels, and OTS levels at distances greater than 1 or 2m were much lower. (Page 12)
3) At distances larger than 2 m, levels near single cigarettes were generally close to background. … [If] one spends time downwind from a smoker, then moving to a distance of more than 2m can reduce the likelihood of experiencing elevated particle exposure due to OTS. (Page 14)
Again, the data confirm common sense. The more open the space and the farther away you are, the lower your smoke exposure. To get the kind of exposure you'd suffer indoors, you have to stand within two feet of the smoker. Move seven feet away, and you're "close to background," i.e., breathing normal air. I recommend greater distance than that, just to be safe. But you don't need to ban smoking throughout Central Park.
Repace offers additional arguments for outdoor smoking bans. He points out that "there are millions of asthmatics in this country" and says outdoor smoke levels can be "high enough to trigger an asthmatic attack in susceptible persons." He also contends that "most nonsmokers find SHS to be a nuisance. Just as noise and dog droppings are regulated in public spaces, governments have the right and the obligation to protect the susceptible from the stupid."
If you want to argue for parkwide smoking bans based on asthma or on an analogy to noise pollution, go ahead and make that case. But let's not cloud that debate by invoking the general harm of secondhand smoke. Studies of secondhand smoke have indeed moved outdoors. Their findings support restrictions on lighting up within a few feet of other people. But they don't warrant more than that.