Dear Colleagues,

Tobacco smoke contains more than 7,000 chemicals, including hundreds that are toxic and about 70 that can cause cancer. It is a leading cause of preventable death, which accounts for about 10 million deaths annually worldwide. Environmental tobacco smoke (ETS, also called secondhand smoking) has been widely recognized as one of the most important indoor air quality problems. It is a mixture of the smoke emitted by the burning of tobacco products, such as cigarettes, cigars, or pipes, and the smoke exhaled by smokers. Exposure to ETS, classified by the US EPA as a Group A carcinogen, can cause serious health problems, especially for children, seniors, and pregnant women. Recently, it was found that tobacco residues can accumulate on indoor surfaces even after the smokers have left the area for months, which is called thirdhand smoke and which also poses health risks for those who are exposed to it. There is no safe-level of exposure to tobacco smoking. Because of the implementation of Smokefree Indoor Air Laws in public venues in many cities, exposure to tobacco smoking has declined. However, in recent years, a new growing phenomenon, electronic (E-)cigarette vaping has become popular, especially among young adults. E-cigarettes are sometimes called “e-cigs,” “vapes,” “e-hookahs,” “vape pens,” and “electronic nicotine delivery systems” (ENDS). Although e-cigarettes have a very wide variation in terms of device design and component functionality, they typically share basic common features, which include an aerosol generator (heating element), a battery, and a storage tank as a liquid container. Liquid composition can include nicotine, cannabis oils (e.g., THC and/or CBD), solvents, and a variety of flavorants. Its potential health risk is not well understood to date. Many toxic and carcinogenic substances, such as particulate matters (PMs), carbonyls, propylene glycol, glycerol, heavy metals, tobacco-specific nitrosamines, benzene, toluene, ketene, and other volatile organic compounds (VOCs), are reported in aerosols from e-cigarette vaping. Operating conditions (e.g., vaping temperature, device voltage, and wattage) and a user’s pattern (e.g., vaping frequency, puff duration, puff volume, and airflow rate) play important roles in the emissions from the e-cigarette. Various flavors and thermal degradation products add complexity to the emissions. The lack of regulation of e-devices, the constituents of e-liquids, and the potential health risks of the e-cigarette emissions directly on users and indirectly on bystanders from environmental vaping (via vaping’s impact on indoor air quality) need to be addressed. It is important to further evaluate traditional tobacco smoking exposure and alternative e-cigarette vaping exposure to protect public health.

Dr. Ping Wang
Dr. Jiayu Li
Guest Editors

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• tobacco smoking
• e-cigarette vaping
• exposure
• primary emissions
• environmental emissions
• indoor air quality
• risk assessment