In recent years, the paradigm of the tobacco industry has been changing with the development of heated tobacco products (HTPs) that have a similar taste to cigarettes but significantly reduce the amount of smoke components. The purpose of this study was to compare the in vitro toxicity of HTPs with that of combustible cigarettes.

We used two kinds of HTPs which have different design characteristics such as heating temperature and method, and a 3R4F reference cigarette. The mainstream smoke/aerosol were generated under the Health Canada (HC) smoking regime and both total particulate matter (TPM) and gas vapour phase (GVP) were collected for toxicity assessment. Bacterial reverse mutation assay (Ames test) and the NRU cytotoxicity assay, which are widely used in the tobacco industry, were conducted to evaluate their in vitro toxicity.

In the Ames test, TPMs obtained from 3R4F was mutagenic in TA98, 100, 1537 in the presence of S9 mix whereas TPMs obtained from HTPs were not mutagenic under any of the conditions tested, although the highest obtainable concentration in the vehicle, 5 mg/plate was treated. In the NRU cytotoxicity test, TPM and GVP from HTPs showed more than 90 % reduction in cytotoxicity as compared to those from 3R4F and the order of cytotoxic potential was: 3R4F >> HTP-A > HTP-B.

However, in the case of HTPs, the EC₅₀ values could not be determined since HTPs did not show enough cytotoxicity to calculate them. Therefore further studies are needed to develop reliable in vitro assays for HTPs.

As a result, our data confirm that the toxicity of the heated tobacco product was significantly lower than that of conventional cigarettes and reduced the risk potential.