There are currently few studies focused on air pollution resulting from outdoor smoking activity. The handful of studies that have been completed are uniform in their assessment that exposure to outdoor tobacco smoke can sometimes rival exposure to secondhand smoke occurring indoors. As one moves closer to an outdoor smoker and spends more time downwind from the smoker, one's exposure goes up. Of course, as the number of outdoor smokers increases, one's risk of exposure also increases.

A recent study by Klepeis et al. (2007)¹³ shows that thin streams, or plumes, of tobacco smoke near an outdoor smoker can reach levels over 1000 μg/m³. For reference: On what the USEPA considers a relatively clean day, background air pollution levels are under 20 μg/m³. Visit the following link to learn more about this study: http://tobaccosmoke.org/outdoor-tobacco-smoke.

If one were to spend time outdoors near multiple smokers over a day, say as a worker at an outdoor pub or as a child accompanying a smoker, it would be possible to receive an outdoor exposure to particles that exceeds the current USEPA health-based standard for PM-2.5, which is currently 35 μg/m³. By sitting at an outdoor table for an hour with a smoker, who consumes 2 cigarettes over the hour, one could be exposed to a level of PM-2.5 greater than that caused by being in a smoky tavern for an hour.