Has the mist been peered through? Revisiting the building blocks of human health risk assessment for electronic cigarette use

Electronic cigarettes, battery-powered nicotine delivery devices, have been increasingly used in the past decade. This critical review provides a qualitative research synthesis of the human health risks associated with E-vapor inhalation in the peer-reviewed literature and our own preliminary experimental results. E-cigarettes may be as efficient as traditional cigarettes in nicotine delivery, especially for experienced users, and studies suggest lower emissions of air toxics from E-cigarette vapor and lower second- and third-hand vapor exposures. Some toxic emissions may however surpass those of traditional cigarettes, especially under high voltage vaping conditions. Experimentally, E-vapor/E-liquid exposures reduce cell viability and promote pro-inflammatory cytokine release. User vulnerability to concomitant environmental agent exposures, such as viruses and bacteria, may potentially be increased. While evidence to date suggests that E-cigarettes release fewer toxins and carcinogens compared to...