Chemical and Heavy Metal Analysis of E-liquids and E-liquid Emissions Under Different Vaping Conditions

Abstract

Electronic cigarettes (e-cigarettes) have rapidly gained popularity recently, especially in younger adults. Evidence to date suggests that e-cigarettes are safer than conventional cigarettes but are not harmless. E-cigarettes use e-liquids to aerosolise the general ingredients including propylene glycol, vegetable glycerine, nicotine and flavourings. New toxic compounds can be formed after aerosolising the e-liquid. This project evaluated the chemical composition, including heavy metal analysis, in NZ-made e-liquids with various formulations and resulting aerosol condensates under different vaping conditions. Vaping conditions included ISO 20769:2018 standard conditions, lower and higher power settings of 10W and 80W, and a longer puff duration of 5 seconds. The chemical analysis of nicotine, flavourings, and degradation products was performed using Headspace Solid-Phase Microextraction Gas Chromatography-Mass Spectrometry (HS-SPME GC-MS). Results demonstrated 142 flavourings, nicotine and two nicotine-related degradation products called nicotyrine and myosmine. Trace elements of nicotine appeared in e-liquids that claimed to be nicotine-free, and trace elements of flavourings were present in products labelled as flavourless. High temperatures in e-cigarettes have been found to degrade components into toxic chemicals. One of the flavouring-related degradations, formaldehyde in condensates was not detected via GC-MS but was detected through preliminary High-Performance Liquid Chromatography. The heavy metal analysis of twenty-two elements was performed using Inductively Coupled Plasma Mass Spectrometry. The e-liquids contained eighteen metals at dangerous levels that exceeded the occupational health standard limitation. Metal present in highest concentration was silicon which made up 98.9% of total metal content. After aerosolisation, increases in several metals were found such as Fe, Zn and Cr at the highest concentrations. Increased device power setting and puff duration led to elevated coil temperatures and oxygen supply, resulting in more toxicants with higher concentrations in e-liquid emissions, including nicotine, nicotyrine, myosmine, and heavy metals. Assessment of the literature to link chemicals found with negative health implications was conducted. Many of the chemicals detected in this study have been linked with adverse health consequences, especially to lung function and the respiratory system as a whole. This body of work provided the first characterisation of the chemical composition of NZ-made e-liquids and a foundation for regulating these products.