After months of searching, the United States’ Centers for Disease Control and Prevention finally have an explanation for the thousands of cases of vaping-related lung injury across the country. The culprit appears to be a thick, gooey additive that made its debut on the vape black market in 2019 — vitamin E acetate.

An analysis published last week in the New England Journal of Medicine found that vitamin E acetate was present in 48 out of 51 lung tissue samples from people with vaping-related lung injury (now called EVALI). Vitamin E acetate is typically found in topical ointments and skin products. It was never intended to be used in a vape cartridge, but the analysis shows that it often was, and to great consequence.

"We can conclude that… the explosive outbreak of cases of EVALI can be attributed to exposure to THC-containing vaping products that also contained Vitamin E acetate."

There are currently 2,506 cases of EVALI in the US, according to the most-recent case count from the CDC. EVALI often begins with respiratory symptoms, including a cough or shortness of breath, and stomach discomfort, which can make it easy to confuse for another illness, like the flu. Unlike the flu, EVALI, is far more dangerous and has caused 54 deaths in 2019 so far.

The theory that vitamin E acetate may be responsible for EVALI isn’t new. In September 2019, a New York State investigation into local cases of EVALI found traces of the substance in black-market THC vape cartridges (brands Dank Vapes and Chronic Carts, to be exact). The new analysis offers more conclusive evidence: The data spans 16 states and highlights the tight ties between THC cartridges and vitamin E acetate — 47 of the 51 patients analyzed had traces of THC in their lungs.

"I started seeing oil that looked ‘clean’ on the black market about two months ago."

Anne Schuchat, CDC principal deputy director, told reporters at a press conference Friday vitamin E may not be the only additive of concern in vape cartridges, but the agency is confident that it is at the center of this outbreak:

“Given all of these findings, including today’s study, we can conclude that what I call the explosive outbreak of cases of EVALI can be attributed to exposure to THC-containing vaping products that also contained Vitamin E acetate,” she said.

How did Vitamin E acetate end up in vape cartridges?

The paper doesn’t speculate how vitamin E ended up in those vape cartridges. Evidence from Minnesota, where vape cartridges from 2018 did not contain vitamin E acetate, but those from 2019 did, suggests it’s likely fairly recent addition to the market, Schuchat said.

In September this year, Inverse reported that vitamin E acetate was a popular black market scam used to thicken THC oil that is added to a vape cartridge.

A Dank Vape box. New York State's investigation detected Vitamin E acetate in Dank Vapes and Chronic Carts cartridges found in the state. NYDOH

“The black market started to see that we looked for ‘thick’ oil, so they developed a thickener with zero regard for safety,” @dankbustersofficial, a watchdog Instagram account told Inverse at the time.

“I started seeing oil that looked ‘clean’ on the black market about two months ago.”

The account has since been deleted.

Pure THC oil is expensive. Black market dealers often cut THC oil with vitamin E, allowing them to sell their products for a fraction of the price and in higher quantities. In fact, an entire sub-market for vitamin E-based thickeners had emerged online to meet demand, Inverse reported earlier this year.

One of these sellers was Andrew Jones, the founder of Mr. Extractor and Connoisseur Concentrates, two Oregon-based companies, and the creator of Clear Cut, a vitamin-E based thickener. In September, Jones told Inverse that he and other manufacturers believed the vitamin E acetate was safe, though it had never been approved for use in vaporizers.

“Each company in the industry received the vitamin E acetate, be it through one of the 50 companies selling it under their own brand name — Final Cut, Uber Thick, Thickener Extra — and also did their internal due diligence. We all came to the same conclusion, that the product was suitable for use,” he said.

Clear Cut, a Vitamin E-based thickener that was used in THC vapes, before we knew anything about its safety. dankbustersofficial

Vitamin E acetate isn’t illegal. The US Food and Drug Administration approved it for use in food, but it has never been approved for use in a vape cartridge. The legal grey area enabled sellers, like Mr. Extractor, to make the call themselves — and regulators were left playing catch up.

Now, regulators appear to be closing in on the online market that has allowed illegal vape cartridges and untested additives to thrive. The CDC notified states that do regulate THC vapes to test for vitamin E acetate, Schuchat said.

Meanwhile, the FDA and DEA “seized” 44 websites that sold unregulated THC vape cartridges. The agencies are focusing on investigating online supply chains, and are “not pursuing any enforcement actions associated with personal use of any vaping products,” according to a statement released Friday to coincide with the new research.

Does your THC vape product have vitamin E acetate in it?

The CDC released lists of black market THC vape brands linked to EVALI (Dank Vapes is the most common). But buyers beware: Unregulated THC vape products will almost certainly not list vitamin E acetate as an ingredient on the box. The boxes are often mass-produced and shipped to sellers with the ingredients already printed on the side.

Vitamin E acetate is most prominently found in black market, unregulated vape cartridges — though this report doesn’t link Vitamin E acetates to any brands in particular. Previous CDC reports have closed in on a few brands that also have tight ties to EVALI including Dank Vapes, Smart Cart, and Rove. Rove is a legal brand, but it is often counterfeited by illegal dealers who buy similar packaging and sell their own products.

The good news is that the current EVALI outbreak appears to be slowing, suggesting that sellers and buyers may be practicing caution, Schuchat said. Regardless, the CDC recommends that people steer clear of all THC vape products, just in case.