Significant amounts of lead and other toxic metals leak from some heating coils in e-cigarettes and contaminate aerosols that the user inhales, a new study suggests.
A number of the 56 e-cigarette devices used in the research generated aerosols with potentially unsafe levels of lead, chromium, manganese, and/or nickel, scientists found.
“…these heating coils, as currently made, seem to be leaking toxic metals, which then get into the aerosols that vapers inhale…”
Chronic inhalation of these metals is linked to lung, liver, immune, cardiovascular and brain damage, and cancers.
The Food and Drug Administration has authority to regulate e-cigarettes, but is still considering how to do so, the researchers say. The finding that e-cigarettes can expose users—known as vapers—to what may be harmful levels of toxic metals could make this issue a focus of future FDA rules.
“It’s important for the FDA, the e-cigarette companies and vapers themselves to know that these heating coils, as currently made, seem to be leaking toxic metals, which then get into the aerosols that vapers inhale,” says senior researcher Ana María Rule, assistant scientist in environmental health and engineering in Johns Hopkins University’s Bloomberg School of Public Health.
What is vaping and how does it work?
In e-cigarettes, electric current passes through a metal coil to heat nicotine-containing “e-liquids,” creating an aerosol—a mix including vaporized e-liquid and tiny liquid droplets. Vaping—inhaling this aerosol as if it were cigarette smoke—is popular especially among teens, young adults, and former smokers. A 2017 survey of 8th-, 10th-, and 12th-grade students, sponsored by the National Institute on Drug Abuse, found that about one in six had used e-cigarettes in the previous 30 days.
Vaping is popular in part because it provides a nicotine “hit” and the look and feel of tobacco smoking, but without some of smoking’s extreme health risks. Evidence that vaping is not entirely safe continues, however, to accumulate. Recent studies found that e-cigarette liquids contain flavorings and other chemicals that harm cells in standard toxicology tests.
Rule and her colleagues, including lead author Pablo Olmedo, a postdoctoral researcher at the Johns Hopkins University’s Bloomberg School at the time of the study, recruited 56 daily e-cigarette users from vaping conventions and e-cigarette shops around Baltimore in autumn 2015. Working with participants’ devices, the scientists tested for 15 metals in e-liquids in the refilling dispensers, e-liquids in coil-containing e-cigarette tanks, and in generated aerosols.
They found minimal metal in e-liquids within refilling dispensers, but much larger amounts in e-liquids that had been exposed to heating coils within e-cigarette tanks. The difference indicated that the metals almost certainly had come from the coils, the researchers say. Most important, the scientists showed that the metal contamination carried over to the aerosols produced by heating the e-liquids.
Hazardous to inhale
Of the metals significantly present in the aerosols, lead, chromium, nickel, and manganese were of most concern, as all are toxic when inhaled. Median lead concentration in the aerosols, for example, was more than 25 times greater than the median level in the refill dispensers. Almost 50 percent of aerosol samples had lead concentrations higher than health-based limits defined by the Environmental Protection Agency. Similarly, median aerosol concentrations of nickel, chromium, and manganese approached or exceeded safe limits.
“These were median levels only,” Rule says. “The actual levels of these metals varied greatly from sample to sample, and often were much higher than safe limits.”
E-cigarette heating coils typically are made of nickel, chromium, and a few other elements, making them the most obvious sources of metal contamination, although the source of lead remains a mystery. Precisely how metals get from the coils into e-liquid is another mystery.
“We don’t know yet whether metals are chemically leaching from the coil or vaporizing when it’s heated,” Rule says. In an earlier study of the 56 vapers, levels of nickel and chromium in urine and saliva related to those measured in the aerosol, confirming that e-cigarette users are exposed to these metals.
Aerosol metal concentrations tended to be higher for e-cigarettes with more frequently changed coils, suggesting that fresher coils shed metals more readily.
The researchers also detected significant levels of arsenic, a metal-like element that can be highly toxic, in refill e-liquid and in the corresponding tank e-liquid and aerosol samples from 10 of the 56 vapers. How arsenic got into these e-liquids is yet another mystery. Rule’s team plans further studies.