Characterization of exposure to and associated acute effects of outdoor secondhand smoke following indoor smoking bans in Athens, Georgia
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Objectives: (1) To investigate whether particulate matter (PM2.5) and carbon monoxide (CO) outside establishments are directly associated with secondhand smoke (SHS); (2) to characterize systemic exposure of non-smokers to outdoor SHS using biomarkers, salivary cotinine and urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL); and (3) to assess the utility of urinary Clara cell protein (CC16) as a biomarker of SHS-induced lung epithelial permeability. Methods: Real-time PM2.5 and CO were monitored in outdoor patios at five locations, two restaurants, two bars, and a control site. Number of smokers and patrons at and vehicles passing each location were counted. The effects of these variables on PM2.5 and CO were estimated through linear mixed effects models. Further, twenty-eight non-smokers were assigned to outdoor patios of a restaurant and a bar and an open-air location with no smokers (control) on three weekend days in a crossover study. Saliva and urine samples were collected before, post-3 h visits, and next-morning, and analyzed for salivary cotinine and total NNAL and CC16 in urine. CC16 was measured in post-100 mL urine from males. Number of lit cigarettes was counted per sampling occasion. Changes in biomarkers were analyzed across locations and with cigarette count, respectively. CC16 analyses were stratified by gender. Results: Smoker count had a significant positive effect on log(CO) (p=0.032) and log(PM2.5) (p<0.001). The vehicle effect was non-significant. Also, significant increases in salivary cotinine were measured post- and next-morning following visits outside the bar and restaurant compared to the control (p<0.001). Next-day–pre-exposure NNAL differences were significantly higher following visits outside the bar and restaurant compared to the control (p=0.005). A tendency of increasing post:pre-exposure ratios of urinary CC16 with increasing SHS was observed among females. Cigarette count had a significant effect on post-:pre-exposure urinary CC16 among females (p=0.048). Urinary CC16 in males were several times higher indicative of post-renal CC16 contamination. Conclusion: PM2.5 outside establishments where smoking is allowed is proportional to number of cigarettes smoked. Also, non-smokers exposed to outdoor SHS are exposed systemically to components of SHS and these levels may be associated to increased lung epithelial permeability. However, urinary CC16 applicability in males needs futher study.