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.
- secondhand smoke
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Contributors ND and GH initiated the study. GEM, PJEQ, and MFH designed the study. PJEQ, EH, ZC, GEM and JMZ designed field sampling protocols. JMZ and GEM designed the personal interviews. JMZ managed data collection, managed data entry, cleaning and archiving. EH and PJ designed and supervised laboratory analyses conducted by KW, with assistance from TST. TST, ND and VF collected samples on site. AN compiled PM data. GEM prepared the data analysis plan and conducted the statistical analyses. GEM, PJEQ, EH, ZC, MFH, and JMZ provided input on analysis and interpretation of data. All authors contributed to the editing of the manuscript drafts, and GEM prepared the final manuscript.
Funding This research was supported by funds from the California Tobacco-Related Disease Research Program of the University of California, grant number 22RT-0139 and 23PT-0013, and from the National Center for Research Resources, S10 RR026437, for laboratory resources at the University of California, San Francisco.
Competing interests None declared.
Patient consent Not required.
Ethics approval This study was conducted with the approval of the San Diego State University Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
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