PT - JOURNAL ARTICLE AU - Georg E Matt AU - Penelope J E Quintana AU - Eunha Hoh AU - Joy M Zakarian AU - Zohir Chowdhury AU - Melbourne F Hovell AU - Peyton Jacob AU - Kayo Watanabe AU - Teaba S Theweny AU - Victoria Flores AU - Anh Nguyen AU - Narinder Dhaliwal AU - Gary Hayward TI - A Casino goes smoke free: a longitudinal study of secondhand and thirdhand smoke pollution and exposure AID - 10.1136/tobaccocontrol-2017-054052 DP - 2018 Feb 09 TA - Tobacco Control PG - tobaccocontrol-2017-054052 4099 - http://tobaccocontrol.bmj.com/content/early/2018/02/09/tobaccocontrol-2017-054052.short 4100 - http://tobaccocontrol.bmj.com/content/early/2018/02/09/tobaccocontrol-2017-054052.full AB - Background Secondhand smoke (SHS) in US casinos is common, but little is known about the residue of tobacco smoke pollutants left behind in dust and on surfaces, commonly referred to as thirdhand smoke (THS). We examined SHS and THS pollution and exposure before and during a casino smoking ban and after smoking resumed.Methods A casino was visited nine times over a 15-month period to collect dust, surface and air samples in eight locations. Finger wipe and urine samples were collected from non-smoking confederates before and after a 4-hour casino visit. Samples were analysed for markers of SHS and THS pollution and exposure.Results Exceptionally high levels of THS were found in dust and on surfaces. Although the smoking ban led to immediate improvements in air quality, surface nicotine levels were unchanged and remained very high for the first month of the smoking ban. Surface nicotine decreased by 90% after 1 month (P<0.01), but nicotine and tobacco-specific nitrosamines in dust decreased more slowly, declining by 90% only after 3 months (P<0.01). Exposure was significantly reduced after the ban, but the benefits of the ban were reversed after smoking resumed.Conclusions Long-term smoking in a casino creates deep THS reservoirs that persist for months after a smoking ban. A complete smoking ban immediately improves air quality and significantly reduces exposure to SHS and THS. However, THS reservoirs contribute to continued low-level exposure to toxicants. To accelerate the effect of smoking bans, remediation efforts should address specific THS reservoirs, which may require intensive cleaning as well as replacement of carpets, furniture and building materials.