Variation in Free Radical Yields from U.S. Marketed Cigarettes

Abstract

Free radicals in tobacco smoke are thought to be an important cause of smoking-induced diseases, yet the variation in free radical exposure to smokers from different brands of commercially available cigarettes is unknown. We measured the levels of highly reactive gas-phase and stable particulate-phase radicals in mainstream cigarette smoke by electron paramagnetic resonance (EPR) spectroscopy with and without the spin-trapping agent phenyl-N-tert-butylnitrone (PBN), respectively, in 27 popular US cigarettes and the 3R4F research cigarette, machine-smoked according to the FTC protocol. We find a 12-fold variation in the levels of gas-phase radicals (1.2 to 14 nmol per cigarette) and a 2-fold variation in the amounts of particulate-phase radicals (44 to 96 pmol per cigarette) across the range of cigarette brands. Gas and particulate-phase radicals were highly correlated across brands (ρ = 0.62, p < 0.001). Both radicals were correlated with TPM (gas-phase: ρ = 0.38, p = 0.04; particulate-phase: ρ = 0.44, p = 0.02) and ventilation (gas- and tar-phase: ρ = -0.58, p = 0.001), with ventilation explaining nearly 30% of the variation in radical levels across brands. Overall, our findings of significant brand variation in free radical delivery under standardized machine-smoked conditions suggest that the use of certain brands of cigarettes may be associated with greater levels of oxidative stress in smokers.

Figure 1

Representative EPR spectra for (A) gas-phase PBN radical adducts and (B) particulate-phase radicals for the 3R4F reference cigarette and blank CFP are shown. The concentrations of both gas-phase radicals (C) and particulate-phase radicals (D) are linearly dependent on the number of cigarettes smoked.

Figure 2

Box-plots of free radicals yields comparing brands by cigarette strength and flavor. Box-plots of gas-phase radicals (A) cigarette filter ventilation and (B) cigarette flavor (regular and menthol). Box-plots of particulate-phase (C) filter ventilation and (D) cigarette flavor (regular and menthol). *p ≤ 0.05 between groups.