Comparison of toxic pyrogenic compounds derived from conventional cigarettes and heated tobacco products

Heated tobacco products (HTPs) have gained popularity as alternatives to conventional cigarettes (CCs). Nevertheless, assessing their health hazards remains challenging owing to variations in individual smoking habits. Thus, this study aimed to identify toxic compounds from simulated smoking conditions and evaluate their toxicity in humans. Tobacco leaves (TL) and reconstituted tobacco leaves (RTL), sourced from the CCs and HTPs, were used as model feedstocks. Thermogravimetric analysis revealed that RTL contained higher nicotine and glycerol levels but lower carbohydrate content than TL. The smoking mechanisms of both tobacco samples were found to be governed by pyrolysis under different temperatures (TL: 200-800 °C and RTL: 350 °C). In TL pyrolysis, the toxic compound formations are influenced by the temperature. Nicotine was dominant at ≤ 400 °C, whereas temperatures ≥ 400 °C led to increased formation of toxic compounds, particularly carcinogens. In contrast, RTL pyrolysis at 350 °C generated fewer carcinogens because controlled heating inhibited thermolysis of the lignocellulosic components. To assess carcinogenicity, peak intensities of TL and RTL-derived carcinogens were normalized using nicotine as an addiction factor. Relative carcinogenicity of RTL was reduced by more than two folds compared with that of TL. This comparative assessment suggests that HTP smoking may reduce exposure to carcinogenic compounds compared to CC smoking, although additional clinical factors should be considered for more accurate assessment of the associated health risks.