Cigarette smoke is a major exogenous source of free radicals, and the resulting oxidative stress is one of the major causes of smoking-caused diseases. Yet, many of the factors that impact free radical delivery from cigarettes remain unclear. In this study, we machine-smoked cigarettes and measured the levels of gas- and particulate-phase radicals by electron paramagnetic resonance (EPR) spectroscopy using standardized smoking regimens (International Organization of Standardization (ISO) and Canadian Intense (CI)), puffing parameters, and tobacco blends. Radical delivery per cigarette was significantly greater in both gas (4-fold) and particulate (6-fold) phases when cigarettes were smoked under the CI protocol compared to the ISO protocol. Total puff volume per cigarette was the major factor with radical production being proportional to total volume, regardless of whether volume differences were achieved by changes in individual puff volume or puff frequency. Changing puff shape (bell vs sharp vs square) or puff duration (1-5 s), without changing volume, had no effect on radical yields. Tobacco variety did have a significant impact on free radical production, with gas-phase radicals highest in reconstituted > burley > oriental > bright tobacco and particulate-phase radicals highest in burley > bright > oriental > reconstituted tobacco. Our findings show that modifiable cigarette design features and measurable user smoking behaviors are key factors determining free radical exposure in smokers.
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