Attached Smoking Room Is a Source of PM2.5 in Adjacent Nonsmoking Areas

The smoking ban is not working in some entertainment venues in China. PM2.5 pollution induced by cigarette smoking in these places is still unknown. In this study, we took mahjong clubs as target places, monitored the real-time PM2.5 concentration, and recorded on-site inspection information to investigate the PM2.5 pollution characteristics induced by cigarette smoking. In occupied and smoking rooms, the geomean and median values of PM2.5 concentration were 276 and 347 μg/m3. The number of smoking persons in room is the dominant factor to enhance PM2.5 levels. For each additional person smoking in the room, PM2.5 increased by 32% (95% CI: 31%, 33%). Regarding adjacent nonsmoking rooms, PM2.5 increased due to the air penetration from smoking rooms and the increase trend usually had a lag time of 20 minutes. The geomean values of PM2.5 concentrations were 109 μg/m3 in the nonsmoking and occupied rooms and 148 μg/m3 in the vacant rooms. To close the door of the room is the most effective measure to alleviate the PM2.5 penetration. The geomean values of 24-hour and annual average excess exposure concentration if spending 5 hours/day and 2 days/week in mahjong club were 32.1 and 9.2 μg/m3, respectively; both exceeded the World Health Organization’s air quality guidelines, 15 and 5 μg/m3, respectively. Our results revealed severe PM2.5 pollution and exposure risk by cigarette smoking in entertainment venues, as well as the penetration effect on adjacent nonsmoking areas. The smoking bans should be strictly enforced in entertainment venues, and the setting of smoking areas in indoor public places should be scientific to avoid diffusion into nonsmoking areas.