https://techcrunch.com/2019/11/08/vape-lung-breakthrough-suggests-lethal-culprit-in-thc-products-could-be-vitamin-e-acetate/

Official word has come down from federal authorities on one potential cause of the mystery illness affecting vape users: Vitamin E acetate, a chemical found in some vaping products that has been demonstrated to linger in the lungs long afterwards. The finding has been called a “breakthrough” but is far from the last word on the situation.

Sadly, the condition has already claimed the lives of at least 39 people, and more than 2,000 cases have been reported collectively from every state but Alaska. At present the only advice offered has been to stop vaping altogether.