Introduction:
The aim of this study was to quantify levels of carcinogenic tobacco specific nitrosamines (TSNAs) in human volunteers transitioning from tobacco use to electronic cigarettes (EC). ECs have increased in popularity, with consumers using ECs to aid with smoking cessation, reduce cigarette consumption, or to minimise withdrawal symptoms when smoking but not vaping is prohibited. There has been little investigation into the long term health impacts of ECs, but they are generally considered less toxic than conventional tobacco cigarettes. This is due to the absence or decreased levels of harmful chemicals commonly found in tobacco cigarettes. However, some studies have shown the presence of traces of TSNAs in e-liquid, and the endogenous nitrosation of nicotine to TSNAs in nicotine replacement therapies (NRT). These TSNAs include NNK, NNN, and NNAL, which are potent oesophageal and pulmonary carcinogens. Therefore, inhalation of these compounds may provide an added risk to the use of ECs, when compared to other NRT products.

Methods:
Biofluids have been analysed for TSNAs in the urine and saliva of heavy smokers (>10 cigarettes/day) who quit and transition to EC use for 28 days. A solid phase extraction method using TSNA specific molecular imprinted polymers was used to concentrate samples, which were subsequently analysed using UHPLC-ESI-HRMS.

Results:
Analysis of longitudinal urine and saliva samples (n=13) has shown a decrease in TSNA levels over the period of transition from tobacco use to EC only use.

Conclusions:
The findings are consistent with the notion that substituting conventional cigarettes with ECs significantly lowers exposure to carcinogenic TSNAs. Further work is needed to determine whether TSNAs present in urine and saliva represent continued low level exposure to TSNAs as contaminants in EC or markers of nitrosation.

Funding:
This work is funded by Horizon 2020, and Public Health England