The Effects of Thirdhand Vape Residue from Nicotine and Non-Nicotine Vapes on Cells: A Systematic Review

Rationale: Vapes are increasingly popular, however, their clouds leave a residue on surfaces, referred to as thirdhand smoke. Recent studies have reported the detrimental cellular impacts of thirdhand smoke. However, research on thirdhand vape residue exposure is relatively new and understudied. Objectives: This review aims to evaluate the current literature associated with the impact of thirdhand vape residue from nicotine and non-nicotine vapes on cells, compared to unexposed controls. Methods: A systematic search was performed in PubMed (Medline), Embase, Web of Science, Scopus, and Google databases to identify relevant studies. Two independent reviewers screened articles using the inclusion criteria of controlled experimental studies on human and animal in vitro and in vivo models which investigate thirdhand vape residue as the exposure variable and cell concepts. Studies were assessed for bias through tools specialised for animal studies. Data were extracted and synthesised in accordance with PRISMA guidelines. Results: Of 139 articles retrieved, three are included in this review, focusing on mice cell models only, one of which investigates non-nicotine vapes. No studies on human cell models that fit the criteria were found. Mice were directly exposed to vape-infused materials from which their cells were extracted and evaluated, finding that exposure to thirdhand nicotine vape residue damages mice cells. The effects of non-nicotine vapes are inconclusive. Conclusions: Thirdhand nicotine vape residue contributes to changes in some cells in mouse models but not others. Data available to date provide no convincing evidence of likely significant harm to humans. Further investigation is warranted to confirm or deny this impression.