In our study, the detection of vitamin E acetate in BAL fluid in most of the patients with EVALI provides evidence that e-cigarette, or vaping, products can deliver vitamin E acetate to respiratory epithelial-lining fluid, the presumed site of injury in the lung. In this convenience sample, the finding that 48 of 51 patients with lung injury had vitamin E acetate in their BAL fluid is noteworthy. By contrast, vitamin E acetate was not detected in any BAL fluid collected from 99 healthy participants, including 18 e-cigarette users. In addition, the absence of other toxicants (plant oils, medium-chain triglyceride oil, coconut oil, petroleum distillates, and diluent terpenes) in BAL fluids from nearly all patients with EVALI provides evidence against the role of any of these toxicants as a primary cause of EVALI. Whether limonene or coconut oil (found in the BAL fluid of 1 patient each) may have some toxicologic effect is unclear.

Vitamin E acetate was not detected in the BAL fluid obtained from three patients with probable EVALI. Since EVALI is a diagnosis of exclusion for which there is no confirmatory diagnostic test, we could not confirm case status for these three patients. The EVALI case definition is intentionally sensitive, which raises the likelihood that a patient’s illness could be misattributed to EVALI. The alternative diagnoses that are listed in Table 4 could reasonably explain the lung injury in these patients. Of note, the two patients who were successfully interviewed by public health officials denied vaping THC products. Reliable information on the time interval from the last use of an e-cigarette product until bronchoscopy is not available, so we cannot assess the likelihood that vitamin E acetate may have already been cleared from the lung in these patients. The detection of vitamin E acetate and other oils can be impaired by inadequate mixing of BAL fluid. Because BAL fluid was collected and processed in the local hospital setting according to its own protocols, we could not confirm that samples were adequately mixed. Patient 2 (as described in Table 4) reported the daily use of flavored nicotine products and had positive results for limonene (which is found in flavored nicotine solutions) in BAL fluid. Whether limonene has a toxicologic effect is unclear.22,23

Vitamin E acetate is commonly used as a dietary supplement and in skin creams. It is common in multivitamins and is enzymatically cleaved to vitamin E during absorption.24,25 Although the ingestion and dermal application of vitamin E acetate have not generally been associated with adverse health effects, the safety of inhaling vitamin E acetate has received little attention. Vitamin E acetate is the ester of vitamin E (α-tocopherol) and acetic acid. The structure shows a long aliphatic tail that can penetrate a layer of surfactant to align the molecule in parallel with phospholipids26 (Fig. S1). Phosphatidylcholines undergo transition from a gel to a liquid crystalline phase when exposed to increasing amounts of tocopherols, such as vitamin E acetate.26,27 Transitioning to a liquid crystalline phase25 would cause the surfactant to lose its ability to maintain the surface tension that is necessary to support respiration in the lung,26,28,29 thus providing a possible mechanism by which vitamin E acetate could cause respiratory dysfunction.

Another potential harmful effect of vitamin E acetate that may contribute to lung injury occurs when it is heated in e-cigarette products. Heating vitamin E acetate in these devices may create ketene by splitting off the acetate group from some or all of the vitamin E acetate.30 Ketene is a reactive compound that has the potential to be a lung irritant, depending on concentration. The CDC is currently examining ways to quantify ketene and its effects in BAL fluid.

Data that have been reported to date indicate that vitamin E acetate in the supply of THC-containing products and use among patients with EVALI aligns with the timing of the 2019 EVALI outbreak. In Minnesota, 10 of 10 products seized by law enforcement during 2018, before the EVALI outbreak, did not contain vitamin E acetate, whereas 20 of 20 THC-containing products seized by law enforcement during September 2019, at the peak of the outbreak, contained vitamin E acetate.31 This finding is consistent with laboratory measurements and trade websites, which suggests that the addition of vitamin E acetate to product fluid began to appear in the illicit market in late 2018 or early 2019 and gained popularity in 2019.

Pure THC oil has a viscosity like that of vitamin E acetate. Cutting THC oil with vitamin E acetate has been reported to be common in the illicit market.9-11 The FDA reports that most case-associated THC product fluids contain vitamin E acetate, at an average concentration of 50% by weight, ranging from 23 to 88%.8 By contrast, the FDA detected no vitamin E acetate in 197 case-associated nicotine products analyzed to date. The viscosity of vitamin E acetate makes it undesirable as an additive to nicotine solutions; the propylene glycol and vegetable glycerin in nicotine solutions create a fluid with a much lower viscosity than that of vitamin E acetate.

Additional studies (including studies in animals) are in progress to examine the respiratory effects of inhaling aerosolized vitamin E acetate and will provide information on whether vitamin E acetate in isolation causes lung injury.32 Research analyzing the aerosol and gases generated by case-associated product fluids is ongoing.

This study has several limitations. First, it is possible that vitamin E acetate may be a marker for exposure to alternative toxicants. Such an alternative toxicant would need to meet at least three criteria: correlate with the presence of vitamin E acetate in BAL fluid, be in widespread use across the United States, and have been added to THC product fluids in 2019 or substantially increased in concentration in 2019 to match the timing of the outbreak. We have not been able to identify a toxicant that meets these three requirements but continue to study this possibility. Second, the contribution to injury of aerosol constituents formed from the heating of vitamin E acetate, especially at higher voltages, requires further examination. Until aerosolized constituents are better characterized, it is possible that one or more of them could act alone or synergistically with other compounds such as vitamin E acetate to increase the risk of EVALI. Third, sample collection was performed as part of routine clinical care and thus was not standardized. Fourth, the timing and burden of exposure to the potential toxicants in relation to the BAL sample acquisition could not be assessed. Finally, this study reports data for case patients and healthy comparators from an independent cross-sectional study, which limits insights because samples were collected at a single point in time, and the possibility of unknown confounding remains.

Vitamin E acetate may play a role in EVALI, a conclusion supported by the high detection rate of vitamin E acetate in BAL fluid from case patients who live in 16 states across the United States and the absence of vitamin E acetate in samples obtained from a healthy comparison group, by the absence of other priority toxicants in nearly all BAL fluid samples from case patients, by a biologically plausible mechanism for lung injury associated with vitamin E acetate, and by the temporal alignment between EVALI and the use of vitamin E acetate in the illicit marketplace. Results from studies in animals can provide information on whether exposure to vitamin E acetate alone can directly cause the lung injury seen in patients with EVALI.