Emissions of Free Radicals, Carbonyls, and Nicotine from the NIDA Standardized Research Electronic Cigarette and Comparison to Similar Commercial Devices.

E-cigarettes (e-cigs) are a diverse and continuously evolving group of products with four generations currently in the market. The National Institute on Drug Abuse (NIDA) standardized research e-cigarette (SREC) is intended to provide researchers with a consistent e-cig device with known characteristics. Thus, we conducted laboratory-based characterizations of oxidants and nicotine in aerosols produced from SREC and other closed-system, breath-activated, commercially available e-cigs (Blu and Vuse). We hypothesized that oxidant and nicotine production will be significantly affected in all devices by changes in puffing parameters. All e-cigs were machine vaped and the aerosols generated were examined for nicotine, carbonyls, and free-radicals while varying the puff-volumes and puff-durations to reflect typical human usage. The data were normalized on a per puff, per gram aerosol, and per milligram nicotine basis. We found that aerosol production generally increased with increasing puff-duration and puff-volume in all e-cigs tested. Increased puff-duration and puff-volume increased nicotine delivery for Blu and Vuse but not the SREC. We report, for the first time, reactive free-radicals in aerosols from all closed-system e-cigs tested, albeit at levels lower than cigarette smoke. Formaldehyde, acetaldehyde, acetone, and propionaldehyde were detected in the aerosols of all tested e-cigs. Carbonyl and free radical production is affected by puff-duration and puff volume. Overall, SREC was more efficient at aerosol and nicotine production than both Blu and Vuse. In terms of carbonyl and free radical levels, SREC delivered lower or similar levels to both other devices.