Effects of smoking regimens and test material format on the cytotoxicity of mainstream cigarette smoke

The purpose of this study was to evaluate the effects of test material format and smoking regimens on comparative toxicity testing of cigarette smoke. Total particulate matter (TPM) or whole smoke (WS) generated from three test cigarettes under International Organization for Standardization (ISO) or Health Canada Intensive (HCI) regimens were assessed for cytotoxicity using the neutral red uptake (NRU) cytotoxicity assay. Under both ISO and HCI regimens, the relative differences of cytotoxicity among the test cigarettes indicated by the EC50 values in WS were significantly higher than those in TPM. For TPM testing, cytotoxicity was decreased going from ISO regimen to HCI regimen, consistent with the reported reductions of toxicant output on a per unit of TPM basis under the HCI regimen. For WS, cytotoxicity increased for the two lower TPM cigarettes, and decreased for the higher TPM cigarette going from HCI regimen to ISO regimen. Results from this study demonstrated WS should be the preferable test material format for smoke toxicity testing whenever possible. Intensive smoking regimens, such as HCI, are less likely to underestimate smoke toxicant intakes by smokers, and should be included in the comparative toxicological testing strategy.