What caused the deaths linked to e-cigarettes / vaping products in the USA?

In 2019, an outbreak of serious lung injuries in the USA, known as EVALI (e-cigarette, or vaping, product use-associated lung injury), resulted in thousands of hospitalisations and 68 confirmed deaths.

The outbreak was primarily linked to THC-containing vaping products, particularly those obtained from informal sources such as friends, family or dealers. Vitamin E acetate, an additive used in some THC-containing vaping products, was strongly linked to the outbreak and was identified by the US Centers for Disease Control and Prevention (CDC) as playing a major role.

However, the CDC noted that there was not sufficient evidence to rule out the contribution of other chemicals in some cases.