Harmful and Potentially Harmful Constituents in E-Liquids and Aerosols from Electronic Nicotine Delivery Systems (ENDS).

In 2012, the U.S. Food & Drug Administration (FDA) published an established list of 93 harmful and potentially harmful constituents (HPHCs) targeting four tobacco product types (cigarettes, cigarette tobacco, roll-your-own tobacco, smokeless tobacco). In 2016, the FDA finalized the deeming rule to regulate electronic nicotine delivery systems (ENDS). However, knowledge gaps exist regarding whether certain HPHCs are present in ENDS e-liquids and aerosols. We identified and addressed these gaps by conducting literature searches and then experimentally quantifying HPHCs in the e-liquid and aerosol of 37 ENDS brands based on gaps in the literature. The literature searches identified 66 e-liquid HPHCs and 68 aerosol HPHCs that have limited to no information regarding the quantifiability of these constituents. A contracted ISO 17025 accredited laboratory performed the HPHC quantifications. The availability of validated analytical methods in the contracted laboratory determined the HPHCs included in the study scope (63/66 for e-liquids, 64/68 for aerosols). Combining the results from the quantifications and literature searches, 36 (39%) and 34 (37%) HPHCs were found quantifiable (≥limit of quantification [LOQ]) in ENDS e-liquids and aerosols, respectively, with 25 HPHCs being quantifiable in both matrices. Quantifiability results imply potential HPHC transfers between matrices, leaching from components, or formations from aerosol generation. The study results can inform the scientific basis for manufacturers and regulators regarding regulatory requirements for HPHC reporting. The HPHC quantities can also inform evaluations of the public health impact of ENDS and public communications regarding ENDS health risks.

Harmful and Potentially Harmful Constituents in the Filler and Smoke of Tobacco-Containing Tobacco Products.

The U.S. Food and Drug Administration established a list of 93 harmful and potentially harmful constituents (HPHCs) in tobacco products. While HPHCs are required to be submitted for tobacco products, knowledge gaps exist regarding which tobacco-containing tobacco product (TCTP, i.e., tobacco products that contain tobacco(s) as a component) types (cigarettes, cigars, roll-your-own tobaccos [RYOs], pipe tobaccos [pipes], smokeless tobacco products [STPs], waterpipe tobaccos [waterpipes]) and matrices (filler, smoke) contain which HPHCs. This study identified and addressed such gaps by conducting literature searches and measuring the amount of HPHCs in TCTP types and matrices. First, literature searches, performed for cigarettes, RYOs, and STPs for publications up to 2014 and for cigars, pipes, and waterpipes for publications up to 2016, identified knowledge gaps for the 93 HPHCs (or 119 HPHCs if cresols [o-, m-, p-cresol] are counted as 3 and chlorinated dioxins/furans as 25) across TCTP types and matrices. Then, three ISO 17025 accredited laboratories including two subcontracted laboratories performed the HPHC quantifications. Inclusion of the HPHCs, TCTP types, and matrices in the study scope was also determined by the availability of validated analytical methods in each laboratory. Eleven (9%) HPHCs are quantifiable in all brands for all TCTP types and matrices, 33 (28%) HPHCs are not quantifiable in any brands of any TCTP type and matrix, and 74 (63%) HPHCs are quantifiable only in some brands across TCTP types and matrices examined. Understanding the quantifiability of HPHCs in each TCTP type and matrix can inform the scientific basis for manufacturers regarding the regulatory requirements for reporting HPHCs. The quantity of HPHCs observed can also inform the evaluation of the public health impact of HPHCs and public communications regarding the health risks of tobacco products.

Method Validation Approaches for Analysis of Constituents in ENDS.

OBJECTIVE: We assessed how many peer-reviewed publications reporting chemical quantities and/or yields from electronic nicotine delivery systems (ENDS) have included adequate method validation characteristics in the publication for appropriate interpretation of data quality for informing tobacco regulatory science. METHODS: We searched 5 databases (Web of Knowledge, PubMed, SciFinder, Embase, EBSCOhost) for ENDS publications between January 2007 and September 2018. Of the 283 publications screened, 173 publications were relevant for analysis. We identified the publications that report a certain degree of control in data quality, ie, the publications that report marginally validated methods (MVMs). MVMs refer to the methods that: (1) report 3 or more International Conference on Harmonisation (ICH) method validation characteristics, (2) state the method was validated, (3) cite their own previous publication(s) that report MVMs, or (4) use a method within the accreditation scope of an accredited laboratory. RESULTS: Overall, 97 publications (56%) report MVMs in their studies. This percentage also reflects the publication distribution for the majority of the 28 chemicals measured by MVMs. CONCLUSIONS: This study highlights the need for reporting sufficient validation characteristics following appropriate guidance to ensure the accuracy and reliability of the published analytical data for proper data interpretations that may support policy.

Chemical evaluation of electronic cigarettes.

OBJECTIVE: To review the available evidence evaluating the chemicals in refill solutions, cartridges, aerosols and environmental emissions of electronic cigarettes (e-cigarettes). METHODS: Systematic literature searches were conducted to identify research related to e-cigarettes and chemistry using 5 reference databases and 11 search terms. The search date range was January 2007 to September 2013. The search yielded 36 articles, of which 29 were deemed relevant for analysis. RESULTS: The levels of nicotine, tobacco-specific nitrosamines (TSNAs), aldehydes, metals, volatile organic compounds (VOCs), flavours, solvent carriers and tobacco alkaloids in e-cigarette refill solutions, cartridges, aerosols and environmental emissions vary considerably. The delivery of nicotine and the release of TSNAs, aldehydes and metals are not consistent across products. Furthermore, the nicotine level listed on the labels of e-cigarette cartridges and refill solutions is often significantly different from measured values. Phenolic compounds, polycyclic aromatic hydrocarbons and drugs have also been reported in e-cigarette refill solutions, cartridges and aerosols. Varying results in particle size distributions of particular matter emissions from e-cigarettes across studies have been observed. Methods applied for the generation and chemical analyses of aerosols differ across studies. Performance characteristics of e-cigarette devices also vary across and within brands. CONCLUSIONS: Additional studies based on knowledge of e-cigarette user behaviours and scientifically validated aerosol generation and chemical analysis methods would be helpful in generating reliable measures of chemical quantities. This would allow comparisons of e-cigarette aerosol and traditional smoke constituent levels and would inform an evaluation of the toxicity potential of e-cigarettes.

Fluorescent detection of lipid peroxidation derived protein adducts upon in-vitro cigarette smoke exposure.

Oxidative stress in biological systems can result in radical-induced lipid peroxidation (LPO), which can lead to the production of secondary reactive by-products such as 4-hydroxy-2-nonenal (HNE), malondialdehyde (MDA), acrolein, and acetaldehyde. These deleterious compounds are known to react with and concomitantly modify nucleophilic amino acid residues on proteins. Oxidative stress induced by cigarette smoke (CS) has been put forth as a major mechanism for tobacco-induced pathologies. At present, there are few reliable biomarkers for measuring the extent of oxidatively-induced damage resulting from CS exposure in vivo. This study has utilized a previously reported CS exposure system to expose cultured cells in-vitro to whole CS and determine the extent of LPO resulting from CS exposure by quantifying the increase in HNE within the exposure media versus controls via gas chromatography mass spectrometry. Additionally, we obtained protein enriched cell lysate post-CS exposures and measured the fluorescent signal obtained via direct injection fluorescent analysis at 375 nm ex./415 nm em. This study determined that the fluorescent signal intensity was directly proportional to the quantity increase of HNE in CS exposed media. It further tested this correlation by performing HNE titration addition experiments to cultured cells and Western blot analysis on proteins obtained from cell lysates. Finally, the fluorescent signal increase from authentic BSA solutions incubated with increasing concentrations of HNE was measured. It is proposed that the fluorescent signal observed from the protein lysate of CS exposed cultured cells corresponds to the extent of biological damage resulting from secondary reactive by-products formed from LPO induced via CS exposure and represented by HNE. The fluorescent signals increased in intensity upon increasing CS dose up to 20 min and remained elevated over 24 h after cessation of CS exposure.