Review and comparative analysis of the particulate matter generated in conventional cigarettes and heated tobacco products - mainstream and environmental emissions

Abstract

This study aims to revise and compare published data devoted to the identification, characterization, and quantification of suspended particulate matter (PM) in the smoke from combustible cigarettes or the aerosol from heat-not-burn products (HNBP), analyzing mainstream and indoor scenarios. It has been motivated by the difficulty of a proper comparison from the published data, mostly due to the very different experimental conditions used in each published study, often not even clearly indicated. Despite the difficulty in a straightforward comparison, important differences in the particulate matter present in the smoke from combustible cigarettes and the aerosols from HNBPs have been confirmed. In general, the concentration of particulate matter in the aerosol emitted by HNBPs is much lower than in cigarette smoke. However, in the mainstream, ultrafine particulate matter has been isolated both with combustible cigarettes and HNBPs, and the TPM collected is in the same range, around 50 mg/stick, slightly higher for HNBPs. The indoor concentration of PM usually ranges from 100-500 μg/m3 for combustible cigarettes, 1-2 orders of magnitude higher than the present in background air (1.3-14.7 μg/m3), whereas for HNBPs ranges from 1.4-15.5 μg/m3, which is similar to the background. Indoors, the number of particles generated from cigarette smoking is much larger than those from the use of HNPBs in a factor 3-6. Nevertheless, the mean particle sizes and particulate composition are among the main differences between cigarette smoke and HNBP aerosols. The mean particle sizes are larger in the smoke from combustible cigarettes and contain black carbon particles (soot), whereas the particulate matter from HNPB presents a smaller size, is predominantly liquid-based, and is much more volatile.

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