A new study from the Mayo Clinic weakened a popular theory about the cause of the vaping illness. Now what?

Ever since news broke of the vaping illness outbreak, scientists have rushed to solve what caused it. More than 800 cases have been reported with at least 12 people dying from vaping. Vitamin E acetate was an early culprit by the New York Department of Health, among others. Last week the Centers for Disease Control and Prevention said their latest findings “suggest THC products play a role in the outbreak.”

While a number of the illnesses have been tied to the cannabis black market, “THC products” don’t provide specific answers to the cause. A group of Mayo Clinic researchers may provide a stronger suspect in the illness. In what these scientists have called a first, the Mayo Clinic analyzed 17 tissue samples from lungs of patients who suffered from the vaping illness, including two fatalities.

As published in the New England Journal of Medicine, the scientists said the samples compared to tissue damage following exposure to toxic chemicals. Previous studies suggested the vaping illness represented exogenous lipoid pneumonia, but none of the Mayo Clinic’s cases had such findings.

“What we see with these vaping cases is a kind of severe chemical injury that I’ve never seen before in a tobacco smoker or a traditional marijuana smoker,” study co-author Dr. Brandon Larsen said. “I think we’ve only seen the tip of the iceberg.”

It’s important to note that analysis of 17 biopsies can’t stand in for more than 800 cases nationwide. While the study’s authors believe the illness is caused by “a form of airway-centered chemical pneumonitis from one or more inhaled toxic substances,” whatever “the agents responsible remain unknown.” The study remains significant because it poked holes in a popular theory that vaping fatty oils, including flavoring agents, was the cause behind the outbreak.

“Investigators believe, but have not yet confirmed, that one or more of the additives used in the underground manufacturing process has led to a toxic product when inhaled,” the Marijuana Policy Project wrote.

The lingering mystery behind the vaping illness has led some states to place a temporary ban on all vaping products. But this could cause more problems than it solves.

“Regulating cannabis use is effective public policy, and we strongly urge states to regulate — not ban — vapor products,” the MPP wrote.​ “Bans will simply make a difficult situation more dangerous by driving more consumers away from regulated businesses and toward illicit sources.”