Dos and don’ts in the design of indoor air quality studies on smoke-free products
Indoor air quality (IAQ) studies on smoke-free products (SFPs), such as electrically heated tobacco products (EHTPs) and e-vapour products (EVPs), have demonstrated substantial reduction of environmental emissions relative to cigarette smoking. IAQ studies on these products include measurement of common airborne markers (carbonyls, volatile organic compounds, particulate matter, and CO) together with specific tracers such as nicotine. Indoor environments are typically free of these specific tracers. However, depending on the ambient pollution levels in building surroundings, emissions from interior materials, and human occupancy and activities, indoor environments naturally contain certain levels of the general markers. Accordingly, assessment of environmental aerosols emitted by SFPs requires evaluation of all these confounding pollution sources. In addition, control measures should be taken to ensure compliance of the study participants with the experimental protocol. The results of previous studies have shown that prolonged human presence and activities indoors lead to an increase in the levels of several airborne constituents. This has reinforced the necessity for specific experimental requirements for IAQ assessment of SFPs. Thus, simply using “empty room air” as a background is insufficient; it is essential to use “room air” obtained in the presence of the same number of panelists doing the same activities as those during the sessions with SFPs. When experiments with SFPs are run in real-life conditions (restaurant, bars, etc.), careful monitoring of activities during measurement (drinking, cooking, and serving hot food) and levels of constituents in outdoor air is obligatory for proper interpretation of the results. Furthermore, the consumption of SFPs should be verified, for example, by weighing the EVPs before and after use or by measuring the nicotine content in EHTP filters. Finally, the levels of aerosol retention by the individual panelists should be assessed.