Chemical analysis of selected harmful and potentially harmful constituents and in vitro toxicological evaluation of leading flavoured e-cigarette aerosols in the Chinese market

Sample preparation methods for elemental analysis in electronic cigarette aerosols: a critical review

In the last decade, e-cigarettes have been marketed as a less harmful alternative to classical tobacco smoking and are currently being used by millions of people. An e-cigarette consists of an e-liquid and a heating device, generating an aerosol that the user can inhale. Recently, several studies have shown that metals and metalloids, including As, Cd, and Pb, known carcinogens, were present in these aerosols. To ensure the accuracy of dose-toxicity estimations, it is essential to have access to reliable and reproducible methods for estimating the dose in question. Although more standardization methodologies were introduced in the analysis of metal(loid)s from aerosols, a huge divergence in sample preparation can be found in the literature. This work aimed to provide an overview of the sample preparation methods used to quantify these metal(loid)s. Therefore, a literature search was conducted in September 2024, that followed the PRISMA guidelines. Among the 48 articles selected, a wide variability in sample preparation was observed, specifically variations in aerosol generation characteristics and collection techniques. Despite the widespread use of methods as filters and impingers, many studies failed to validate critical steps such as aerosol recovery, blank corrections, and the extent of matrix effects. In addition, poor inorganic methodological practices were often applied, such as excessive use of glass materials for aerosol collection or other sample preparation steps. Therefore, further standardization of methodologies is urgently needed to improve the reliability of metal quantification in e-cigarette aerosols, which could potentially enhance regulatory frameworks and facilitate the routine analysis of e-cigarette emissions.

Method Development and Validation of an Aerosol Sampling Technique for the Analysis of Nicotine in Electronic Cigarette Aerosols

Because of the increasing popularity of e-cigarettes, monitoring the e-cigarette market has become important for national health authorities to guarantee safety and quality. In the EU, the Tobacco Products Directive requires emission studies for e-cigarette products. The absence of industry guidelines for studying these emissions and the lack of proper validation in the literature led us to develop and validate a method using the total error approach for the determination of nicotine in e-cigarette aerosols. A commercial vaping device was used to generate aerosols, which were then collected on Cambridge filter pads and measured for nicotine concentration by UHPLC-DAD after extraction. The method was successfully validated by generating accuracy profiles, which show that the β-expectation tolerance intervals remained below the acceptance limits of ±20%. Within-run repeatability and intermediate precision were considered acceptable since the highest RSD value obtained was below 5%. The method was applied to 15 commercial e-liquids. A complete validation of a method for the analysis of e-cigarette emissions is presented, including several parameters that impact the accuracy and reproducibility. Similar systematic approaches for method development and validation could be used for other e-cigarette emission analysis methods to ensure the reliability of the measurements.

Changes in biomarkers of exposure and withdrawal symptom among Chinese adult smokers after completely or partially switching from combustible cigarettes to an electronic nicotine delivery system

This study assessed changes in biomarkers of exposure (BoE) after 5 days of completely or partially switching to an electronic nicotine delivery system (ENDS) use, compared with continued use of combustible cigarettes and smoking abstinence among Chinese adult smokers. A randomized, open-label, parallel-arm study was conducted among Chinese adult smokers who were naive ENDS users. Forty-six subjects were randomized to 4 study groups (n = 11-12 per group): exclusive ENDS use, dual use of ENDS and cigarettes, exclusive cigarettes use, and smoking abstinence. Subjects were confined in clinic for 5 consecutive days and product use was ad libitum. Nicotine and its metabolites (cotinine and 3-hydroxycotinine), and BoEs (AAMA, CEMA, HEMA, HMPMA, 3-HPMA, SPMA, exhaled CO, and exhaled NO) were measured. Withdrawal symptom was measured using MNWS throughout the 5-day period. Six urine BoEs of volatile organic compounds decreased by 55.1-84.1% in the exclusive ENDS use group, which is similar to the smoking abstinence group (67.2-87.4%). The level of decrease was 56.8-70.4% in the dual use group and 10.7-39.0% in the cigarettes group. Urine total nicotine exposure had a non-significant increase in the exclusive ENDS use group, and plasma nicotine and cotinine showed a trend of increasing day by day. After completely or partially switching to ENDS use among Chinese smokers, exposure to selected toxicants were significantly decreased. The results of this study add to the body of evidence that exposure to toxic substance decreased among smokers after complete or partial switch from combustible cigarettes to ENDS use. As part of transition to experienced ENDS use, this study found that smokers of the initial stage who have no prior ENDS experience may increase nicotine intake after switching to ENDS use.

Critical Review of the Recent Literature on Organic Byproducts in E-Cigarette Aerosol Emissions

We review the literature on laboratory studies quantifying the production of potentially toxic organic byproducts (carbonyls, carbon monoxide, free radicals and some nontargeted compounds) in e-cigarette (EC) aerosol emissions, focusing on the consistency between their experimental design and a realistic usage of the devices, as determined by the power ranges of an optimal regime fulfilling a thermodynamically efficient process of aerosol generation that avoids overheating and "dry puffs". The majority of the reviewed studies failed in various degrees to comply with this consistency criterion or supplied insufficient information to verify it. Consequently, most of the experimental outcomes and risk assessments are either partially or totally unreliable and/or of various degrees of questionable relevance to end users. Studies testing the devices under reasonable approximation to realistic conditions detected levels of all organic byproducts that are either negligible or orders of magnitude lower than in tobacco smoke. Our review reinforces the pressing need to update and improve current laboratory standards by an appropriate selection of testing parameters and the logistical incorporation of end users in the experimental design.