Cancer and Non-Cancer Risk Concerns from Metals in Electronic Cigarette Liquids and Aerosols

Abstract

We evaluated metal concentrations in e-liquids and e-aerosols from eight studies and estimated the range of corresponding cancer and non-cancer risks. Chromium and nickel were the leading contributors to cancer risk, with minor contributions from cadmium, lead, and arsenic. The increased cancer risks, assuming exposure to 2 mL/day, ranged from 5.7 to 30,000 additional cancers in a million e-cigarette users. The average cancer risk was 3 in 1000. Cancer risks in the mid to upper end of these ranges exceed acceptable levels. The hazard quotient (HQ) approach was used to evaluate non-cancer risks. Hazard quotients exceeding 1.0 indicate the possibility for non-cancer adverse health effects. Estimated exposures at the maximum reported concentrations of nickel, chromium, and manganese resulted in HQ values of 161, 1.1, and 1.0, respectively, with additional contributions from lead. The average concentration of nickel resulted in an HQ value of 14. We conclude from these studies that exposure to metals in e-cigarette liquids and aerosols may pose a significant cancer and non-cancer health risk at the mid and upper end of the reported ranges. The device design and heating elements appear to be the main source of metals in e-aerosols. The large range of metals within and across e-cigarette brands indicate the need for improvements in product design, enforced product safety regulations and manufacturing quality control. Implementation of such measures could reduce metal exposure in e-cigarette users.

Vaping cartridge heating element compositions and evidence of high temperatures

“…Except for Au, these metals are consistent with those reported in previous nicotine device liquids and heated aerosol measurements [ 12 – 16 ]. These metals represent a potential chronic health risk when inhaled, though estimated risks have exceeded health limits mostly under high temperature or high usage scenarios [ 24 , 25 ].…”

Design features and elemental/metal analysis of the atomizers in pod-style electronic cigarettes

“…The metals in EC products have not yet been directly linked to these illnesses, and such linkage may be challenging to demonstrate given the high variability in metal transfer to EC aerosols from different products and the variations in user topography [ 43 ], which also affects metal concentrations in aerosols [ 44 ]. A recent risk assessment study based on published concentrations of metals in EC products concluded that nickel and chromium are high enough in EC liquids and aerosol to present a cancer risk and that nickel, chromium, and manganese may also present non-cancer health risks [ 45 ]. In addition, human urine samples from EC users had higher concentrations of zinc than those from nonsmokers, and zinc concentration was positively correlated with increased DNA oxidation, suggesting a potential increased risk for disease in the EC user group [ 46 ].…”

Evidence From the Scientific Assessment of Electronic Cigarettes and Their Role in Tobacco Harm Reduction

“…High-powered and open-system devices are likely to have higher metal content in aerosol than closed systems ( 130), but none of the metal content is likely to generate significant adverse health effects (131). FOWLES et al (132) concluded in a review that metals in vapour could constitute a health risk to EC users but that high product standards can minimize exposure and reduced health risks associated with metals in EC aerosol.…”