Dangerous Metals in Vaping Put Into Context

Back in February, we covered a Johns Hopkins University study that purported to find dangerous levels of metals in e-cigarette vapor. The study was briefly a fixture in news coverage, as many scary vaping stories are. Reporters covered the Hopkins study uncritically, assuming that the research was legitimate and meaningful.

“Almost 50 percent of aerosol samples had lead concentrations higher than health-based limits defined by the Environmental Protection Agency,” said the Hopkins press release. They noted that “median aerosol concentrations of nickel, chromium and manganese approached or exceeded safe limits.”

However, the authors had expressed the results of their study in terms of environmental exposure. That means they judged the quantities of toxic metals inhaled as though they were being breathed continuously for 24 hours or during an 8-hour workday, rather than calculating risk based on the vapers’ actual daily usage of their devices. Vapers puff their atomizers a few hundred times a day, but we breathe about 17,000 times a day.

Now a paper by Greek cardiologist and vaping researcher Konstantinos Farsalinos and University of Louisville professor of medicine Brad Rodu takes the data from the Hopkins paper and shows how it relates to real-life vaping exposures. Their study was published in the journal Inhalation Toxicology.

Farsalinos and Rodu used three standards for allowable exposure. The first (and preferred) was permissible daily exposure (PDE) for metals in inhaled medicines, defined by the U.S. Department of Health and Human Services. For metals not on the PDE list, the authors used minimum risk level (MRL), a daily exposure limit defined by the Agency for Toxic Substances and Disease Registry, or recommended exposure limit (REL), a CDC measure for workplace exposure.

The authors expressed the results in as the number of grams of e-liquid a vaper would have to consume daily to exceed the exposure limits. (The gram measure aligns fairly closely with milliliters, but since both PG and VG have specific gravities slightly higher than water, the numbers are not exactly the same.)

Using the highest average levels of metals reported in the original study (“75th percentile”) — which would create a nearly worst-case scenario for exposure to metals — the amounts of consumed e-liquid necessary for a vaper to reach dangerous exposure levels are almost all comically high.

For example, to reach the CDC recommended exposure limit for Aluminum (Al), a vaper would need to consume about 1.5 million grams of e-liquid in a day — or more than 3,000 pounds. None of the other metals require that much vaping, but all except one (nickel) would be impossible for a vaper to consume. Cadmium (Cd) wouldn't reach the HHS daily maximum for inhaled medicines until more than 15,000 grams were puffed, and lead (Pb) would require consumption of 135 grams (about five ounces).

Nickel (Ni) is the one metal that has a permissible daily exposure actually within reach for a determined vaper — 17 grams. Farsalinos and Rodu note that although that amount is about three times the average daily e-liquid consumption for vapers, it is possible to vape that much in a day.

Vaping exposures to nickel can probably be reduced or eliminated by avoiding coils that use nickel or nichrome wire. Farsalinos and Rodu note that improved manufacturing standards can reduce metal exposures, even though they’re already lower than acceptable exposure limits.