LAUSR

In the current study, electron paramagnetic resonance (EPR) spectroscopy was employed to measure environmentally persistent free radicals (EPFRs) in total particulate matter (TPM) of mainstream and sidestream TPM of conventional cigarette and TPM of e-cigarettes. Comparable concentration of EPFRs was detected in both sidestream (8.05 ±1.32) x104pmol/g and mainstream TPM (7.41 ± 0.85) x 104pmol/g of conventional cigarettes. TPM exposure to air resulted in long lived oxygen centered, secondary radicals with EPR g value of 2.0041 for mainstream and 2.0044 for sidestream. Surprisingly, despite no combustion process, the TPM from e-cigarettes (menthol flavor of NJOY and V2 brands) also contain EPFRs with g value of 2.0031 - 2.0033, characteristic of carbon centered radicals, while radical signal in vanilla flavor of V2 brand was remarkably similar to semiquinones in cigarette smoke with higher g value (2.0063). The radical concentration in e-cigarettes was much lower as compared to tobacco TPM. Though the production of ROS generated by e-cigarette is comparatively lower than ROS generated by conventional cigarettes, EPFRs in e-cigarettes appear to be more potent than in tobacco TPM in respect to hydroxyl radical generation yield per unit EPFR. EPFRs in e-cigarettes TPM may be a potential source of health impacts.