4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone is correlated with 8-hydroxy-2′-deoxyguanosine in humans after exposure to environmental tobacco smoke

► Total NNAL and 8-OHdG in plasma and 8-OHdG in urine were quantified in humans. ► Total NNAL in plasma is a good biomarker for cigarette smoke exposure. ► Total NNAL correlated with 8-OHdG among nonsmokers. ► Oxidative DNA damage is one of major adverse effects induced by ETS exposure.