The toxicity of vaping

Are e-cigarettes safer than tobacco cigarettes?

Turns out they might be worse, according to researchers from the Johns Hopkins Bloomberg School of Public Health, Baltimore, MD. Significant amounts of toxic metals can leak from some e-cigarette heating coils and be inhaled by users, researchers found. They published their results in Environmental Health Perspectives.

These toxic metals can include unsafe levels of lead, chromium, manganese, and nickel, and chronic inhalation has been linked to lung, liver, immune, cardiovascular, and brain damage, and even some cancers.

Although the Food and Drug Administration has the authority to regulate e-cigarettes, the agency is still pondering how to do so.

“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,” said senior author Ana María Rule, PhD, MHS, assistant scientist, Bloomberg School’s Department of Environmental Health and Engineering.

E-cigarettes contain a metal coil, powered by an electric current, which heats the e-liquids inside to create an aerosol. Inhaling this aerosol, or ‘vaping’ it, is popular among teens, young adults, and former smokers. According to a 2017 survey sponsored by the National Institute on Drug Abuse, one in six 12th-grade students had used an e-cigarette in the previous 30 days.

The popularity of vaping stems from its similarity to smoking, its ability to give users a ‘hit’ of nicotine, and its supposed lack of the extreme health risks inherent in smoking tobacco.

But more and more studies are beginning to show that vaping is not as benign as first believed. For example, studies centered on the e-cigarette liquids show that they contain flavorings and chemicals that may be harmful on a cellular level.

In a previous study, Dr. Rule and colleagues found significant levels of toxic metals in e-liquids exposed to the heating coil in e-cigarettes.

Heavy metal

In the current study, Dr. Rule and fellow researchers included 56 subjects who used e-cigarettes daily. The researchers tested the refilling dispensers from the subjects’ e-cigarette devices for the presence of 15 metals, and found only minimal amounts of metals in the e-liquids in the dispensers. They found much larger amounts of some of the metals in the e-liquids that were exposed to the heating coils, however, indicating that the metals most likely came from the coils.

The metal contamination also carried over to the aerosols produced by heating the e-liquids. For example, the median lead concentration in the aerosols was approximately 15 µg/kg, which is 25 times higher than the median level in the refill dispensers.

Median metal concentrations were higher in the aerosol compared with the dispenser:

• 16.3 vs 10.9 µg/kg, respectively, for aluminum
• 8.38 vs < 0.5 µg/kg for chromium
• 68.4 vs 2.03 µg/kg for nickel
• 14.8 vs 0.476 µg/kg for lead
• 515 vs 13.1 µg/kg for zinc

Nearly half of the aerosol samples had lead concentrations that were higher than the limits set by the Environmental Protection Agency. Median aerosol concentrations of nickel, chromium, and manganese were either near to or exceeding safe limits. The presence of lead, chromium, nickel, and manganese is most problematic because all are toxic upon inhalation.

“These were median levels only,” said Dr. Rule. “The actual levels of these metals varied greatly from sample to sample, and often were much higher than safe limits.”

The researchers surmised that the heating coils are the most likely culprit for contamination, as they consist of nickel, chromium, and other elements. The source of lead contamination is unknown. Also unknown is how the metals move from the coil to the surrounding e-liquid.

“We don’t know yet whether metals are chemically leaching from the coil or vaporizing when it’s heated,” said Dr. Rule.

In an earlier study of the 56 vapers, led by Angela Aherrera, MPH, doctoral student of public health, Bloomberg School, the levels of nickel and chromium in urine and saliva were related to those measured in the aerosol. Their results confirmed that e-cigarette users are indeed exposed to these metals.

Aherrera et al. also found that the metal concentrations contained in the aerosols were higher when users changed coils more frequently, a finding that suggests that fresher coils are more likely to give off metals.

In the present study, Dr. Rule and colleagues also found significant levels of arsenic in the e-liquid refills, in e-liquids in the tank, and in aerosol samples from 10 of the 56 e-cigarette users. The source of the arsenic in the e-liquids is unknown, but demands further investigation.

“We’ve established with this study that there are exposures to these metals, which is the first step, but we need also to determine the actual health effects,” Dr. Rule concluded.

Support for the research was provided by the Maryland State Cigarette Restitution Fund, the Alfonso Martín Escudero Foundation, the American Heart Association Tobacco Regulation and Addiction Center, and the National Institute of Environmental Health Sciences.