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

Jefferson Fowles,Tracy Barreau,Nerissa Wu

doi:10.3390/ijerph17062146

Jefferson Fowles, Tracy Barreau + Show 1 more

Open Access

https://doi.org/10.3390/ijerph17062146

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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.

Highlights

E-cigarettes are widely used nationwide [1,2]
The summed contributions of each metal for cancer or combined non-cancer risk at low, high, and average metal concentrations are shown in Tables 3 and 4
5.2 × 10−5 and 3.1 × 10−3 respectively; at the high end of the reported range, cancer risks were estimated at 5.9 × 10−4 for nickel and 3.1 × 10−2 for chromium

Summary

Introduction

The devices come in a variety of designs, with a wide range of possible flavoring agents, carrier solvents, and often nicotine or cannabinoids. In the case of nicotine e-cigarettes, a solvent “carrier liquid” such as glycerin or propylene glycol delivers the flavorings and nicotine. All of these devices employ batteries and metallic heating elements of varying design to aerosolize the liquids. A number of published studies showed that e-cigarette aerosols, e-liquids, and their chemical flavorings can cause respiratory irritation, inflammation, and toxicity to lung and immune cells [4,5,6,7,8,9]. Disruption of lung lipid homeostasis and innate immunity by e-cigarette glycol carrier liquids was reported in

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