Effects of Outdoor Tobacco Smoke-Free Policy at Bus Stops on Outdoor Tobacco Smoke Exposure in Seoul

Abstract

The Seoul Metropolitan government implemented an outdoor smoke-free policy at centerline bus stops from December 2011 and began imposing fines for smoking at these bus stops from March 1, 2012. Although significant improvement in indoor air quality due to indoor smoke-free policy has been well documented, impact of outdoor smoke-free policies has not been established. The objectives of this study were to determine the levels of compliance with the outdoor smoke-free policy and to identify the factors associated with outdoor PM2.5 concentrations at the bus stops in Seoul. This study was conducted at 100 bus stops including 50 centerline bus stops (located in the middle of main streets) and 50 roadside bus stops in Seoul, Korea. Smoking was observed and PM2.5 concentrations were measured at the same locations in autumn 2011 and spring 2012. Using real-time aerosol monitor, PM2.5 was measured for 30 minutes at 1-second intervals. Because ambient air pollutants can fluctuate rapidly due to environmental conditions, a peak analysis method was developed to determine the outdoor PM2.5 exposure from cigarette smoke. Using the newly established definition of peak, the peak frequency (number of peaks per hour) and peak concentration were determined at each bus stop. The occurrence of smoking at 100 bus stops in Seoul was observed before and after the implementation of the smoke-free policy. Smoking was observed at 46% and 37% of the 100 bus stops before and after the implementation of the smoke-free policy, respectively. At the centerline bus stops where the policy was applied, smoking occurrence was decreased by 75% after implementation of the smoke-free policy. However, at roadside bus stops where the policy was not applied, smoking was observed at 76% and 70% of the bus stops before and after the policy, respectively. The peak analysis indicated that the PM2.5 peak frequency was significantly associated with the bus stop location, season, occurrence of smoking, and the number of buses servicing a route. The PM2.5 peak concentrations were significantly associated with season, occurrence of smoking, and the number of buses servicing a route. Smoker status was categorized as standing or walking-through, and peak concentrations at bus stops were significantly higher with standing smokers than with walking-through smokers. Higher peak PM2.5 concentrations were recorded when smokers were positioned closer to the monitor. For standing smokers, peak frequency decreased with increasing distance from the monitor, but this effect was not significant. This study found non-compliance with the outdoor smoke-free policy at centerline bus stops in Seoul. More people smoked at roadside bus stops where the policy was not applied. The Smoke-free policy should be applied to both centerline and roadside bus stops to reduce outdoor tobacco smoke exposure at bus stop in Seoul. The PM2.5 peak frequency and peak concentrations were significantly associated with the occurrence of smoking, smoker status, and distance from the smoker to the monitor. Further research using peak analysis is needed to measure smoking-related exposure to fine particulate matter in other outdoor locations.