Antifreeze Chemical in Vapes? AMA Launches Scare Campaign

For many decades, health scares were the purview of environmental NGOs trying to convince voters or politicians to ban some perfectly safe and widely used chemical. Increasingly, however, mainstream medical and scientific institutions are resorting to the same disingenuous tactics activists employ because there’s no evidence to justify the causes they support.

Here’s a recent and especially ridiculous example from the American Medical Association. In a May 30 blog post, the AMA asserted that “e-cigarettes may seem safe to use, but they are not,” then listed a litany of half-truths to justify its prohibitionist stance against safer nicotine products. We’ve refuted most of these claims over the years, though one deserves special consideration because it's particularly misleading.

The antifreeze trope

Recall that when the Environmental Working Group (or any other NGO) wants to scare the public, they select a benign chemical found in a popular product–say, titanium dioxide in Skittles–and exaggerate the risk it poses far beyond absurdity. AMA did the same thing here by hyperventilating about a low-risk food additive used in vapes called propylene glycol (PG). The chemical is Generally Recognized as Safe by the FDA and used in products ranging from ice cream to formulations of pharmaceutical drugs—no doubt including medicines AMA members prescribe for their patients. Importantly, the FDA has authorized 34 nicotine vaping products, most of which likely contain PG. 

Propylene glycol is a colorless, odorless liquid. In vaping devices, it acts as a carrier for nicotine and flavorings and helps mimic the sensation of smoking. When heated, PG vaporizes into an aerosol, forming the vapor that users exhale—without the toxic combustion byproducts of tobacco. The similarity to smoking and the absence of the deadly carcinogens in cigarettes are two of the key features that have made vaping such a powerful and popular harm-reduction tool.

Excluding all this information from its blog post, the AMA asserted that nicotine vapor “contains chemicals such as propylene glycol, which is used in antifreeze, and other chemicals that are known to be toxic if inhaled in certain amounts.” This statement is a masterclass in deception. By linking propylene glycol to antifreeze, the AMA evoked images of deadly poison. But the antifreeze reference is a sleight of hand, as propylene glycol is distinct from ethylene glycol, the highly toxic antifreeze component. 

My colleague Dr. Josh Bloom has helpfully explained the differences between these chemicals previously, but here are the basics. Propylene glycol (C₃H₈O₂) and ethylene glycol (C₂H₆O₂) differ by one carbon and two hydrogen atoms. Ingesting a relatively small dose of EG can be very harmful because the liver converts it into toxic metabolites that can cause severe damage to the kidneys, heart, and brain. In contrast, a puff of PG is all but harmless; I’m inhaling the stuff as I type this sentence. [1] 

But even on AMA’s terms, the antifreeze comparison is asinine because a chemical can be benign in one situation and dangerous in another. A snake bite can kill you, yet the same amount of venom is harmless if swallowed, courtesy of your stomach acid and enzymes. Botulinum neurotoxin is one of the most deadly substance on earth; people also safely inject it into their faces to prevent wrinkles. Such examples are almost limitless, but the point is the same in each case: context is everything when it comes to chemical safety.

What does the evidence show?

The low risk of PG exposure is well documented in the peer-reviewed literature. According to a 2018 report on the toxicity of e-cigarettes from the National Academies of Sciences, Engineering, and Medicine (NASEM):

“PG has long been considered ‘practically non-toxic,’ consistent with FDA's inclusion of PG on the GRAS list. Animal studies, including chronic studies at very high levels, have consistently failed to identify any target organ, or other evidence of toxicity at doses less than several grams per kilogram per day.”

While NASEM observed that many of these studies were conducted years ago and wouldn’t meet the rigorous Good Laboratory Practices (GLP) expected today, the report added that “the large doses used, coupled with the consistent lack of any evidence of organ system effect or reproductive or developmental toxicity, provides strong support for the general lack of toxic effects of PG in humans from dietary or occupational exposures.” A 2021 study–which did adhere to those GLPs–yielded the same result: “the PG exposures were well tolerated and demonstrated minimal physiological, histopathological or molecular changes which is in line with previous studies.”

To illustrate this point about risk, I asked the AMA on X how many cases of PG poisoning have been caused by nicotine vaping, and if that number is greater than the number of smokers who have quit by switching to vaping. They didn’t bother to reply, and that’s probably because this comparison destroys their argument.

While there are a handful of cases in which someone consumed a harmful dose of PG by drinking too much flavored whiskey or injecting nicotine liquid intravenously, there are no examples of people experiencing PG poisoning from the intended use of a vaping product. Meanwhile, FDA data suggests there are more than 18 million US adults who vape, most of whom are former smokers. Moreover, 90 studies representing 29,000 people have failed to detect any serious adverse events from vaping.

Here’s where things stand, then. Smoking continues to kill over 400,000 Americans each year. Nicotine vaping kills no Americans each year. PG in e-cigarettes does not change this risk calculus whatsoever. As a result, the AMA is demonizing a far safer source of nicotine that has helped millions of smokers quit tobacco because, er…antifreeze or something.

Conclusion: A challenge to AMA

If anyone at AMA reads this article, please answer the following question. Among its myriad pharmaceutical applications, propylene glycol is used in some inhalers to treat asthma. Are you prepared to stop recommending these PG-containing medicines because the same ingredient is used to formulate antifreeze? If you can’t or won’t answer the question, then please abandon your double standard and quit prevaricating about vaping.

[1] The standard qualifications apply: I’m an adult former smoker who quit thanks to vaping. Nicotine, in any amount or any form, isn’t meant for children of any age.