Particulate matter (PM2.5) and carbon monoxide from secondhand smoke outside bars and restaurants in downtown Athens, Georgia.

In the study described in this article, the authors' objective was to measure particles < or = 2.5 microm in aerodynamic diameter (PM2.5) and carbon monoxide (CO) in outdoor waiting areas and patios of restaurants and bars in downtown Athens, Georgia, where indoor smoking is banned. The authors also wanted to investigate whether the measured concentrations are directly associated with the number of cigarettes lit in these settings. Real-time PM2.5 and CO were monitored on four summer weekend afternoons/evenings in outdoor waiting areas or patios at five locations in Athens. In addition, smokers and pedestrians present or passing and motorized vehicles passing each sampling location were counted. PM2.5 levels were significantly higher than levels at the control location (all p-values > .001). Carbon monoxide levels outside the restaurant and bar sites did not differ significantly from the control. The results of the authors' study indicate that (1) secondhand smoke (SHS) leads to significant increases in PM2.5 outside of restaurants and bars; and (2) although CO can be used as a proxy for SHS in these outdoor environments, its levels remain relatively low.