US health officials announced a breakthrough on Friday about the mysterious outbreak of limestone disease, saying they have a "very strong culprit."
The same chemical was found in fluid taken from the lungs of 29 patients across the country, according to Centers for Disease Control and Prevention. The compound – Vitamin E Acetate – was previously found in liquid from electronic cigarettes and other vaporizing devices used by many patients.
But for the first time they found a common suspect in the damaged lungs of patients, officials said.
"We're in a better place when it comes to one very strong culprit," said Dr. Anne Schuchat of the CDC.
Agency officials warn that they cannot rule out all other toxic substances, and animal studies can clearly show that vitamin E acetate causes visible lung damage.
Over 2,000 Americans who have died have fallen ill since March, including many teenagers and young adults, and at least 40 have died. Most cases occurred in August and September, but new cases are still being reported.
Vitamin E Acetate has recently been used as a thickener in a vaporizing fluid, especially in black cartridge cartridges. While vitamin E is safe as a vitamin tablet or for use on the skin, inhaling its oil droplets can be harmful. It's sticky and stays in your lungs – Dr. Jim Pirkle from CDC compared him to honey.
Many people who fell ill claimed to have evaporated THC containing liquids, a high induction part of marijuana, and many said they got them from friends or bought on the black market.
E-cigarettes and other vaping devices heat the liquid to the inhaled vapor. Most products contain nicotine, but THC vaporization is becoming more common.
Pirkle said thickeners such as Vitamin E Acetate are unlikely to be routinely added to nicotine fluids, which must be more watery during vaping.
Juul Labs, producer of the best-selling e-cigarette brand, issued a statement after the CDC announcement, noting that its nicotine products do not contain THC or any vitamin E compounds.
Symptoms of vaping disease include breathing problems, chest pain, fatigue and vomiting. Imaging tests show lung injuries, and doctors can't find infection or other causes.
About two months ago, New York turned their attention to vitamin E acetate when a state public health laboratory discovered it in samples of vaporizing products from sick patients. In some cases, it accounted for more than half the fluid in the cartridges.
The chemical also appeared in tests in other laboratories, including the US Food and Drug Administration laboratory in Cincinnati, which found vitamin E acetate in half of more than 400 THC samples.
In the latest test, the CDC used fluid taken from the lungs of 29 patients in 10 states, including two dead. Laboratory staff were looking for a number of substances found in various vaping devices, including nicotine, THC and other cannabis ingredients, vegetable oils, mineral oil and cutting agents used on the black market.
It was an exhaustive list of over 1,000, said Pirkle, who oversees the agency's analytical laboratories.
The only substance that appeared in all 29 was vitamin E acetate.
"For me, what they found and what they didn't find is important," said Scott Becker, head of the Public Health Laboratories Association. "It was the only thing they found."
Robert Strongin of Portland State University, who studied e-cigarettes, welcomed the CDC report, but warned that this does not mean that other ingredients in vaping products are safe. "They can still cause long-term damage," he said.
Pirkle from CDC said animal testing is now a priority and can produce results over the course of the year.
"We really need animal testing to determine cause and effect," he said.