In a study conducted by researchers at the Johns Hopkins Bloomberg School of Public Health, it was determined that there are high levels of toxic metals in the liquid that creates the aerosol in e-cigarettes. Users inhale the aerosol when they vape.

It is believed that the study is the first to scrutinize a cross section of metals in multiple e-cigarette brands. The liquid in five brands of first generation e-cigarettes was analyzed for chromium, cadmium, manganese, lead and nickel. The liquid is the element of e-cigarettes that is heated and then used to deliver ingredients, including nicotine and flavors, to the user. The liquid is contained in a cartridge that is in close contact with the heating coil in first generation e-cigarettes. The study results showed that all five heavy metals were present in all five brands, although the levels of each were different by brand. When inhaled, these metals can all be carcinogenic or toxic. The researchers believe that the main source of the metals is the coil that heats the liquid. This process creates the aerosol, which is often mistakenly referred to as vapor. The study did not examine whether metals are present in the e-cigarette aerosol or not.

Ana María Rule, PhD, MHS, an assistant scientist in the Bloomberg School’s Department of Environmental Health and Engineering was the study leader. She noted that although it is not known if the levels found are dangerous, their presence is worrying as it could mean that the metals end up in the aerosol and these would then be inhaled by e-cigarette users. The metals in e-cigarette coils are toxic when inhaled. As the coils heat the liquid that creates the aerosol, it is perhaps a good idea that regulators look into alternative materials that could be used to manufacture e-cigarette heating coils.

Although the Food and Drug Administration (FDA) started regulating e-cigarettes last year, no warnings have yet been issued. For current smokers who switch over to electronic cigarettes completely, e-cigarettes may be less harmful than cigarettes. Since e-cigarettes might not be completely safe and might be habit forming, a serious worry is the appeal of e-cigarettes to young people who have not smoked before. Emerging research shows that nicotine can adversely affect the developing adolescent brain, whether it is inhaled though traditional cigarettes or e-cigarettes.

E-cigarette use among high school students increased by 900 percent between 2011 and 2015. The then U.S. Surgeon General Vivek Murthy, last fall described e-cigarette use by young people as a serious concern.

The researchers chose five leading brands of so-called first generation e-cigarettes for their study. First generation e-cigarettes are also called ‘cig a likes’ because they look like traditional cigarettes. Newer ones resemble small cassette recorders with a mouthpiece and the liquid is added from a dispenser before use. In first generation e-cigs however, the liquid is stored in the cartridge together with the coil. This increases the liquid’s exposure to the coil even while heating is not taking place. The five brands used in the study are sold online as well as across the United States in convenience stores, gas stations and big box retail stores. Three of the brands held 71 percent of total market share in 2015. If a brand was available in more than one flavor, the researchers used one flavor only for consistency’s sake.

The team extracted samples of the liquid to test the liquid for metal levels. The liquid had not been heated by the coil before it was extracted. The liquid contains a mixture of glycerin, propylene glycol, nicotine and flavorings. As the volume of liquid is vastly different from brand to brand, the team measured the concentrations of metals in micrograms per liter.

The five metals that were checked for were present in all five brands. Nickel is considered the most serious carcinogen when inhaled. The concentration of cadmium was substantially lower than the other metals across all brands, while the concentrations of the different metals varied considerably among the brands. One brand had the highest concentrations of all five metals. In that brand, the concentration of nickel was 22,600 micrograms per liter, which is 400 times that of the brand with the lowest concentration of nickel. In that same brand, the concentration of manganese was 690 micrograms per liter, which translates to 240 times that of the lowest concentration in another brand.

Rule noted that it was remarkable to discover the varying degrees by which the metals were present in the liquid. She added that this suggests that the FDA should consider not only regulating the ingredients found in e-cigarette liquids, but also the the quality control of e-cigarette devices. Currently, FDA regulations require e-cigarette makers to submit information about ingredients that are potentially harmful, including four of the five metals analyzed in this study – chromium, cadmium, nickel and lead, as well as an ingredient list. The FDA has not yet issued proposed regulations on e-cigarette labeling. The researchers believe that in addition to the coil, some of the potentially harmful metals may come from the manufacturing process, or other components of the e-cigarette device.

The full peer reviewed study was published in the journal Environmental Research.