As the mysterious outbreak of vaping-related illnesses in the U.S. continues to grow, a new study sheds more light on what could be making people sick.
The study, published today (Oct. 2) in The New England Journal of Medicine, concluded that these illnesses are most likely due to toxic chemical fumes produced from vaping, with these fumes directly damaging the smokers' lungs.
This conclusion is based on an analysis of lung biopsies from 17 patients across the U.S.
Some doctors had suspected that the accumulation of fats or oils (known medically as lipids) in patients' lungs had caused these vaping-related illnesses, but the new study found no evidence for this.
"While we can't discount the potential role of lipids, we have not seen anything to suggest this is a problem caused by lipid accumulation in the lungs," study senior author Dr. Brandon Larsen, a surgical pathologist at the Mayo Clinic in Scottsdale, Arizona, said in a statement. "Instead, it seems to be some kind of direct chemical injury, similar to what one might see with exposures to toxic chemical fumes, poisonous gases and toxic agents."
Related: 4 Myths About E-Cigarettes
So far, the outbreak has sickened more than 800 people in 46 states, according to the latest data from the Centers for Disease Control and Prevention (CDC). Among these cases, 12 patients have died.
For the new study, the researchers analyzed patients' lung biopsies under a microscope.
In all cases, the samples showed signs of acute lung injury, including pneumonitis, a type of inflammation of lung tissue that isn't caused by an infection.
According to the authors, their results suggest that patients' vaping-related lung injuries are a form of "chemical pneumonitis," or inflammation of the lungs caused by breathing in chemical fumes.
But it's still unclear what chemicals or contaminants could be causing the illnesses. Last week, the CDC said that THC-containing products may play an important role in these illnesses, with more than three-quarters of patients nationwide reporting use of vaping products containing THC, the active ingredient in marijuana. In the new study, 71% of the patients reported vaping with marijuana or cannabis oil.
Previously, it was reported that a substance known as vitamin E acetate, an oil derived from vitamin E, had been found in some product samples taken from patients. In addition, a recent analysis commissioned by NBC News found another substance, a pesticide called myclobutanil, in 10 THC vaping cartridges obtained from unlicensed dealers. This pesticide can convert into the chemical hydrogen cyanide when burned, NBC News reported.
"This is a public health crisis, and a lot of people are working frantically around the clock to find out what the culprit or culprits could be — and what chemicals may be responsible," Larsen said. "Based on what we have seen in our study, we suspect that most cases involve chemical contaminants, toxic byproducts or other noxious agents within vape liquids."
While the investigation of the outbreak is ongoing, the CDC recommends that people consider refraining from using e-cigarette products, particularly those that contain THC.
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Originally published on Live Science.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.