Effect of temperature and atmosphere on the mutagenicity and cytotoxicity of smoke condensate in tobacco pyrolysis
Total particulate matter (TPM) generated by the combustion of tobacco leaves shows in vitro biological activities. Tobacco leaves are subjected to a wide range of temperatures and oxygen concentrations during cigarette smoking. It is known that the mutagenicity of the TPM varies according to the pyrolysis temperature, but the influence of the pyrolysis condition on the cytotoxicity is less known. To develop an understanding of the mutagenicity and cytotoxicity of the TPM, we investigated the relationship between the activities and the pyrolysis conditions. Two types of tobacco leaf (Burley and flue-cured) were individually pyrolyzed using an infrared image furnace under the following conditions: pyrolysis temperatures (350-800°C) in 100% N2 and pyrolysis atmospheres (0-20% of O2in N2) at 800°C. The pyrolyzed products were assayed by Salmonella mutagenicity testing using TA98 with metabolic activation and neutral red uptake cytotoxicity testing. The mutagenicity and the cytotoxicity which were calculated on a TPM basis increased with increasing temperature and reached a plateau around 500°C. The variability of the mutagenicity is more extreme than that of the cytotoxicity. When calculated on a nicotine-free dry particulate matter (NFDPM) basis, the variability of the mutagenicity shown on a TPM basis was still observed. In contrast, the cytotoxicity did not have much variability. Moreover, the pyrolyzed products showed decreases in both activities on a TPM and NFDPM basis with increasing oxygen concentration in the atmosphere. The results revealed that not only the mutagenicity but also the cytotoxicity were affected by the temperature and atmosphere in tobacco pyrolysis. Further investigation including chemical analysis may provide the information to understand the relationship between the biological activity and the constituents in the TPM.