| Summary: | In this narrative review, we highlight the challenges of comparing emissions from
different tobacco products under controlled laboratory settings (using smoking/
vaping machines). We focus on tobacco products that generate inhalable smoke or
aerosol, such as cigarettes, cigars, hookah, electronic cigarettes, and heated tobacco
products. We discuss challenges associated with sample generation including
variability of smoking/vaping machines, lack of standardized adaptors that connect
smoking/vaping machines to different tobacco products, puffing protocols that are
not representative of actual use, and sample generation session length (minutes
or number of puffs) that depends on product characteristics. We also discuss the
challenges of physically characterizing and trapping emissions from products with
different aerosol characteristics. Challenges to analytical method development
are also covered, highlighting matrix effects, order of magnitude differences in
analyte levels, and the necessity of tailored quality control/quality assurance
measures. The review highlights two approaches in selecting emissions to monitor
across products, one focusing on toxicants that were detected and quantified with
optimized methods for combustible cigarettes, and the other looking for productspecific
toxicants using non-targeted analysis. The challenges of data reporting
and statistical analysis that allow meaningful comparison across products are also
discussed. We end the review by highlighting that even if the technical challenges
are overcome, emission comparison may obscure the absolute exposure from novel
products if we only focus on relative exposure compared to combustible products.
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