A New Look at Radicals in Cigarette Smoke

Radicals in cigarette smoke have been proposed to contribute to the harm caused by cigarette smoking. For the first time, using HPLC and high-resolution mass spectrometry analysis of stable radical adducts, we have identified specific radical species in cigarette smoke:  7 acyl and 11 alkylaminocarbonyl radicals. Their combined abundance measured in fresh whole smoke from a single 2R4F cigarette is ∼225 nmol (1.4 × 10¹⁷ radicals). The fiberglass Cambridge filter pad conventionally employed to separate the gas phase from mainstream smoke was found to reduce the apparent yield of these radicals, introducing artifacts of measurement. The long-accepted steady-state mechanism for the formation of carbon-centered radicals in cigarette smoke involving NO₂ chemistry cannot account for these newly identified radicals, and it does not in general appear to be a major source of carbon-centered radicals in fresh mainstream cigarette smoke. Consequently, we suggest that the precise nature of radicals in cigarette smoke warrants reexamination.