Samples of lung fluid from 29 lung injury patients in 10 states all contained the same chemical, the Centers for Disease Control and Prevention said today. The discovery is a huge step forward for the ongoing investigation into the severe and mysterious lung injuries that have affected e-cigarette users across the country.

The chemical, called vitamin E acetate is now considered a “chemical of concern” by the CDC, which is investigating the outbreak. As of November 5th, 2019, 39 people have died of the injury, and 2,051 cases are being investigated.

when vitamin E acetate is inhaled, it may interfere with normal lung functioning

The agency says that vitamin E acetate is an oily substance found in a ton of typical household items, including foods, supplements, and even skin creams.

According to the CDC’s website, “Vitamin E acetate usually does not cause harm when ingested as a vitamin supplement or applied to the skin. However, previous research suggests when vitamin E acetate is inhaled, it may interfere with normal lung functioning.”

The oil might be great for skincare, but when heated up, it can act almost like a grease, chemistry professor Michelle Francl told The Washington Post in September. As you might imagine, breathing in vaporized grease could seriously affect the lungs, though researchers are still trying to figure out the exact mechanism that’s causing the lung damage.

Investigators believe that the substance has been added to e-cigarette products as a thickener, and is particularly attractive to people manufacturing illicit products because it resembles tetrahydrocannabinol (THC) oil. THC is the substance in marijuana that provides a high.

Vitamin E acetate was previously linked to the injuries in early September

Vitamin E acetate was previously linked to the injuries in early September, when some state agencies identified the substance in samples of vaping products that had been used by people who later came down with the disease. But finding it in products wasn’t the same as finding it in the patients themselves.

In this case, researchers looked at fluid taken from the lungs of patients suffering from the injury, and found vitamin E acetate in every single sample. THC was found in 82 percent of the lung fluid samples, and nicotine was found in 62 percent of the samples, suggesting that the vast majority of patients were vaping THC products, and that many were using both nicotine and THC products.

The CDC looked for other additives in the samples, including mineral oils and plant oils, but didn’t find anything to cause concern.

Today’s discovery does not mean that the investigation is over, or that vitamin E acetate is the only cause of the injuries. Other chemicals could have also played a role in the ongoing outbreak. The CDC’s work — and an accompanying Food and Drug Administration investigation into the outbreak of injuries — continues. The agency continues to recommend that people not use THC vaping products, particularly ones that were obtained online, or from family or friends.