Change in indoor particle levels after a smoking ban in Minnesota bars and restaurants.

BACKGROUND: Smoking bans in bars and restaurants have been shown to improve worker health and reduce hospital admissions for acute myocardial infarction. Several studies have also reported improved indoor air quality, although these studies generally used single visits before and after a ban for a convenience sample of venues. PURPOSE: The primary objective of this study was to provide detailed time-of-day and day-of-week secondhand smoke-exposure data for representative bars and restaurants in Minnesota. METHODS: This study improved on previous approaches by using a statistically representative sample of three venue types (drinking places, limited-service restaurants, and full-service restaurants), conducting repeat visits to the same venue prior to the ban, and matching the day of week and time of day for the before- and after-ban monitoring. The repeat visits included laser photometer fine particulate (PM2.5) concentration measurements, lit cigarette counts, and customer counts for 19 drinking places, eight limited-service restaurants, and 35 full-service restaurants in the Minneapolis/St. Paul metropolitan area. The more rigorous design of this study provides improved confidence in the findings and reduces the likelihood of systematic bias. RESULTS: The median reduction in PM2.5 was greater than 95% for all three venue types. Examination of data from repeated visits shows that making only one pre-ban visit to each venue would greatly increase the range of computed percentage reductions and lower the statistical power of pre-post tests. Variations in PM2.5 concentrations were found based on time of day and day of week when monitoring occurred. CONCLUSIONS: These comprehensive measurements confirm that smoking bans provide significant reductions in SHS constituents, protecting customers and workers from PM2.5 in bars and restaurants.