A review of constituents identified in e-cigarette liquids and aerosols

Abstract

INTRODUCTION Identification of chemicals present in e-liquids and aerosols is a vital first step in assessing the human health effects of e-cigarettes. We aim to identify the qualitative and quantitative constituents present in e-cigarette liquids and aerosols. METHODS A comprehensive search of scientific databases included literature up to July 2020. A total of 28 articles met inclusion criteria; 18 articles assessed e-liquid constituents and 15 articles assessed aerosol constituents. Of these, 5 assessed constituents present in both mediums. We included English-language publications that examine qualitative and/or quantitative constituents in e-cigarette liquids and aerosols. RESULTS In total, articles identified 60 compounds in e-liquids and 47 compounds in aerosols. A total of 22 compounds were identified in both e-liquids and aerosols. These are: acenaphthylene, acetaldehyde, acetol, antimony, benzaldehyde, benzene, chromium, copper, diacetyl, formaldehyde, glycerol, lead, limonene, naphthalene, nickel, nicotine, nicotine-N'-oxides, 4-(methylnitrosamino)-1-(3pyridyl)-1-butanone (NNK), N-Nitrosonornicotine (NNN), propylene glycol, toluene, and vegetable glycerin. Some of the identified chemicals have been labeled as harmful, toxic, or cancerous through human, animal, and cell line studies. A variety of laboratory methods were used for analyses, which made reported levels less consistent. CONCLUSIONS E-liquids and aerosols contain a variety of chemicals with potential health effects from inhaling them. Further, secondhand health effects are unknown because of limited understanding of the dose of exposure by nonusers. Identification of constituents in e-cigarettes is the first step to determine their risks to humans and support evidence-based regulations and health policies.

Nose-only Exposure to Cherry and Tobacco Flavored E-cigarettes Induced Lung Inflammation in Mice in a Sex-dependent Manner

“…To determine the potential inhalation effects of flavoring chemicals added into e-liquids, we determined the concentration of five distinct flavoring chemicals (maltol, ethyl maltol, benzaldehyde, methyl salicylate, and hexyl acetate), but the presence of other flavorants are still under investigation. Prior literature also indicates that these compounds have an abundant and widespread presence in market-available e-liquids (Eshraghian and Al-Delaimy 2021; Krusemann et al 2020; Tierney et al 2016). While quantification of flavorants are important, a recently published study showcases the inherent variability in lung deposition of flavoring chemicals as a function of inhalation modality: in “lung inhalers” nearly 100% retention of flavorants was observed, but lower retention was observed for “mouth inhalers” (Khachatoorian et al 2022).…”

Cigarette Smoke Extract, but Not Electronic Cigarette Aerosol Extract, Inhibits Monoamine Oxidase in vitro and Produces Greater Acute Aversive/Anhedonic Effects Than Nicotine Alone on Intracranial Self-Stimulation in Rats

“…self-administration model is also needed to clarify the relevance of our findings to tobacco product consumption. Finally, given the considerable differences in constituent profiles between brands of cigarettes and ECs (e.g., Jain et al, 2019 ; Eshraghian and Al-Delaimy, 2021 ), evaluating the effects of extracts of other products is needed to better understand the generality of the current findings.…”

“…For example, at a 1.0 mg/kg nicotine dose, EC extract contained ≈0.5% PG whereas the EC liquids contained ≈1.0–3.0% PG depending on the product. This difference in PG levels may reflect our use of an EC aerosol extract rather than an EC liquid and/or our use of a different product, as both of these factors could influence constituent levels (e.g., Eshraghian and Al-Delaimy, 2021 ). Regardless, the PG levels in EC extract may have been insufficient to attenuate the ICSS threshold-elevating effects of high nicotine doses.…”

Review of industry reports on EU priority tobacco additives part A: Main outcomes and conclusions

“…Given that the primary source of diacetyl in MSS is pyrolysis, potential regulation of diacetyl as an additive may be complemented or replaced by regulation of additives that promote diacetyl generation. Although diacetyl is rarely added to cigarettes anymore, it is still frequently used in other tobacco products (based on Dutch EU-CEG data retrieved in 2021) and e-liquids 67 . We, therefore, recommend that the effects of the application of diacetyl in these products should be carefully evaluated.…”