Detoxing the Heavy Metal Vape Scare

Jonathan Swift 300 years ago observed that “Falsehood flies, and the Truth comes limping after it; so that when Men come to be undeceiv’d, it is too late; the Jest is over, and the Tale has had its Effect.” (here)  That is the story of e-cigarettes and vaping today. 

Billions of dollars have been transferred from tobacco consumers to companies to the FDA in the form of user fees (here).  The FDA, via the NIH, has transferred hundreds of millions to fund university research on tobacco use and effects, in order to provide a “scientific basis” for FDA regulations (here).  With NIH making no attempt to hide our government’s objective – “a world free of tobacco use” (expressed here) – it is not surprising that much of the funded research and attendant publicity is biased to support the announced policy objective.

In March, anti-vaping researchers published a study claiming that metals in e-cigarette vapor are toxic when inhaled.  While the media headlined the findings “dangerous” and “alarming”, and termed vape products “brain-damaging,” I explained in this blog that the metal doses delivered by e-cigarette liquids in this study are trivial.  I estimated that an e-cigarette user could be exposed to excessive metal levels only by consuming high volumes of vape liquids.  For example, vapers would have to use 15.4 liters (nearly four gallons) of liquid per day to achieve exposure to 2 micrograms of cadmium. (here) 

I worked with Dr. Konstantinos Farsalinos, a prestigious vaping researcher at Greece’s Onassis Cardiac Surgery Center, the University of Patras and the National School of Public Health.  The findings of our risk assessment analysis of the metals study were just published in the journal Inhalation Toxicology (abstract here).

The original study referenced U.S. Environmental Protection Agency safety limits that apply to 24-hour air exposure, or to workers breathing factory air for 8 to 10 hours.  This standard is entirely invalid for e-cigarette analysis, as users do not inhale vapor continuously for such long periods of time. 

Dr. Farsalinos and I applied more realistic federal standards, such as established regulatory safety limits for inhaled medicines.  We calculated total daily exposure to metals by using an average daily vape liquid consumption of 3 to 5 milliliters (e.g., 3 to 5 grams, around 1 teaspoon).

The chart demonstrates that vapers would need to consume impossibly large volumes of liquid in order to exceed the safety limits for almost all metals.  The one exception is nickel, which requires only 17 grams of liquid, but even that is over three times normal daily consumption.

In this case, truth is limping in eight months after widespread false alarms flew about metals in e-cigarette vapor.  The Tale has had its Effect, but in the end, as Shakespeare assures us, truth will out.

Beyond the Headlines, E-Cigarette Vapor Has Only Trace Amounts of Metals

The American media have been obsessed with a new study (here) claiming that “e-cigarettes are a potential source of exposure to toxic metals (chromium, nickel, and lead), and to metals that are toxic when inhaled (manganese and zinc).”

The headlines misrepresent or overdramatize the facts:      

“E-Cig Vapors May Contain Brain-Damaging Toxic Metals, Says New Study” Tech Times

“E-Cigarette Vapor Filled With Dangerous Toxins Like Lead, Study Finds” Newsweek

“E-cigarettes leak toxic metals, study finds” Medical News Today

“Are E-Cigarettes Safe? Alarming Levels Of Metal Found In Its Heating Coils” International Business Times

The research, published in the journal Environmental Health Perspectives, was authored by faculty at Johns Hopkins University, Columbia University, and the Universities of Granada (Spain) and Graz (Austria). 

They reported the metals’ median levels and range (from the 25^th to the 75^th percentile) in 56 e-cigarette devices’ aerosols.  All values are in micrograms (ug, one-millionth of a gram) of metal per kilogram (kg, one thousand grams) of vape aerosol.  For reference, there are 454 grams in a pound. 

The following table shows how much liquid an e-cigarette user must vape per day to exceed either the FDA’s daily exposure limit for inhaled medicines (here), or the CDC’s minimal risk levels (MRLs) for workplace inhalation (here).  I used the upper level (75^th percentile) of the range, so the results below are not underestimates. 

Maximum Levels of Metals in E-Cigarette Vapors, and Amount of Liquid Used Daily to Exceed FDA Maximum Levels for Inhaled Medicines And/Or CDC Minimal Risk Levels (MRLs)
Metal	Maximum Vapor Level (ug/kg)	Daily FDA Maximum or CDC MRL* (ug)	Volume of Vaping Liquid Exceeding FDA Max or CDC MRL*
Aluminum	22.2	NA	--
Cadmium	0.13	2	15.4 LITERS
		0.136*	1.1 LITER*
Chromium	43.9	3	68 milliliters
Copper	51.0	30	588 milliliters
Iron	23.6	NA	--
Manganese	9.56	4.08*	427 milliliters*
Nickel	289	5	17.3 milliliters
Lead	37.1	5	135 milliliters
		30*	808 milliliters*
Antimony	1.93	20	10.4 LITERS
Tin	19.4	60	3.1 LITERS
Zinc	809	NA	--

NA, not available

One thing is crystal clear: an e-cig user could be exposed to excessive metal levels only by consuming high volumes of vape liquids.  For example, vapers would have to use 15.4 liters (nearly four gallons) of liquid per day to achieve exposure to 2 micrograms of cadmium. 

Nickel is an outlier because at a high 75^th percentile value (289 ug/kg), the exposure limit is 17 milliliters (the typical vaper uses 10 milliliters or less daily).  However, the median value for nickel in all samples was much lower (6 ug/kg), meaning that users could consume 800 milliliters before reaching the recommended exposure limit.

The authors emphasize that some of these metals, notably cadmium, chromium, nickel and lead, are toxic.  However, they fail to mention that toxicity is proportional to dose and duration.  The metal doses delivered by e-cigarette liquids in this study are trivial.

Note: Thanks to Dr. Konstantinos Farsalinos, a researcher at the Onassis Cardiac Surgery Center,

the University of Patras and the National School of Public Health in Greece, for his expert assistance with this entry.

Trace Metals in E-Cigarettes: No Cause for Concern

I have discussed a study reporting that smokeless tobacco contains trace levels of several metals, including cadmium, arsenic, nickel, chromium and lead (here).  Now researchers at the University of California, Riverside, report that the aerosol from an undisclosed e-cigarette contained numerous metals.

The study, whose lead author is Monique Williams, appears in PLoS One (here). It notes, “A total of 22 elements were identified in EC [electronic cigarette] aerosol, and three of these elements (lead, nickel, and chromium) appear on the FDA's ‘harmful and potentially harmful chemicals’ list.  Lead and chromium concentrations in EC aerosols were within the range of conventional cigarettes, while nickel was about 2–100 times higher in concentration in EC aerosol than in Marlboro brand cigarettes.”

The article implies that e-cigarettes are the source of inhaled toxic metals.  But, as pointed out previously by Boston University’s Michael Siegel (here), the amount of metals delivered to e-cigarette users is lower than the daily exposures permitted by the authoritative US Pharmacopeial Convention (USP) for inhalable medications.

Williams and colleagues reported that 10 aerosol puffs, the equivalent of one cigarette, contained 0.017 micrograms (ug, one-millionth of a gram) of lead.  This means that a pack-a-day equivalent (200 puffs) contains 0.34 ug of lead.  According to the USP (here), it is permissible for an inhaled medication to deliver up to 5 ug of lead per day to a 50 kilogram (~ 100 pound) person. 

The same holds true for nickel, chromium and copper.  For nickel, Williams reported the pack-a-day e-cigarette level at 0.1 ug, while the USP allows 1.5 ug per day in inhaled medicines.  For chromium, Williams reported that e-cigarettes deliver 0.14 ug, while the USP allows 25 ug in inhaled medicines.  For copper, the Williams-reported level is 4.06 ug; the USP allows 100 ug.  

Tin is another metal Williams reported in e-cigarette vapor, at 0.74 ug per 200 puffs. The CDC reports (here) that the average U.S. daily intake of tin by inhalation is 3 ug.  

To be clear, the problem with the Williams study is not that it reported trace concentrations of metals in e-cigarette vapor.  That is useful information.  The problem with this study, as with most works of this kind in the past 20 years, is that it was published without context.  As the above quote shows, e-cigarettes were compared to traditional cigarettes without any reference to exposure from other inhalation settings and/or products.  

Such demonization of e-cigarettes is inappropriate, and authors and journal editors share culpability.  Greater effort should be made to avoid bias in reporting of scientific data, particularly when public health is at stake.