Effect of pyrolysis temperature on the mutagenicity of tobacco smoke condensate

Tobacco smoke aerosols with fewer mutagens in the particulate fraction may present reduced risk to the smoker. The objective of this study was to test the hypothesis that the temperature at which tobacco is pyrolyzed or combu sted can affect the mutagenicity of the particulate fraction of the smoke a erosol. Tobacco smoke aerosol was generated under precisely controlled temp erature conditions from 250 to 550 degreesC by heating compressed tobacco t ablets in air. The tobacco aerosols generated had a cigarette smoke-like ap pearance and aroma, The tobacco smoke aerosol was passed through a Cambridg e filter pad to collect the particulate fraction, termed the smoke condensa te. Although condensates of tobacco smoke and whole cigarette mainstream sm oke share many of the same chemical components, there are physical and chem ical differences between the two complex mixtures. The condensates from smo ke aerosols prepared at different temperatures were assayed in the Ames Sal monella microsome test with metabolic activation by rat liver S9 using test er strains TA98 and TA100. Tobacco smoke condensates were not detectably mu tagenic in strain TA98 when the tobacco smoke aerosol was generated at temp eratures below 400 degreesC. Above 400 degreesC, condensates were mutagenic in strain TA98. Similarly, condensates prepared from tobacco smoke aerosol s generated at temperatures below 475 degreesC were not detectably mutageni c in strain TA100. In contrast, tobacco tablets heated to temperatures of 4 75 degreesC or greater generated smoke aerosol that was detectably mutageni c as measured in TA100. Therefore, heating and pyrolyzing tobacco at temper atures below those found in tobacco burning cigarettes reduces the mutageni city of the smoke condensate. Highly mutagenic heterocyclic amines derived from the pyrolysis of tobacco leaf protein may be important contributors to the high temperature production of tobacco smoke Ames Salmonella mutagens. The relevance of these findings regarding cancer risk in humans is difficu lt to assess because of the lack of a direct correlation between mutagenici ty in the Ames Salmonella test and carcinogenicity. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.