Lung damage from blackmarket vapes was less common in states with legal pot, study finds

States that legalized marijuana may have avoided the worst outcomes from a respiratory disease outbreak tied to unregulated cannabis vaping products, a federally funded study found.

In late 2019 and early 2020, a vaping-related lung disease called EVALI led to 68 deaths and nearly 3,000 hospitalizations in the United States. The Centers for Disease Control and Prevention later linked the ailment to a Vitamin E acetate found in blackmarket THC vape concentrates.

The new study published in the journal Drug and Alcohol Dependence and reported on by online news site Marijuana Moment found that the frequency of EVALI cases was lower in states where cannabis is legal for adults or where users of medical pot are allowed to grow their own.



The United States’ 2019 outbreak of e-cigarette or vaping-associated lung injuries (EVALI) was linked to an additive most common in informally-sourced vaporizable marijuana concentrates. This study estimates how states’ recreational and medical marijuana policies related to their 2019 EVALI incidence and residents’ likelihood of vaping as their primary mode of marijuana use.


Multivariable negative binomial regressions estimated associations between states’ total 2019 EVALI cases and marijuana policies: recreational legalization, medical legalization only, and whether medical-only policies allowed home cultivation, prohibited combustible use, or had operational dispensaries. Logistic regressions used survey data from the Behavioral Risk Factor Surveillance System’s 2016–2019 marijuana supplements to assess how these policies related to past-30-day marijuana users’ selection of vaping as their primary mode of use.


EVALI incidence was 42% lower in recreational marijuana states (95%CI=0.339,0.993), versus a positive but statistically insignificant association with medical legalization alone. Adjusting for policy attributes revealed heterogeneity: among medical-marijuana-only states, EVALI incidences were > 60% lower where laws allowed home cultivation (aIRR=0.374; 95%CI=0.196, 0.715). Similarly, among past-30-day marijuana users, odds of vaping as one’s primary mode of use were > 40% lower in medical-only states where home cultivation was allowed versus prohibited (aOR=0.588; 95%CI=0.365,0.946).

Marijuana policy attributes linked to lower EVALI incidences were also associated with reduced likelihoods of vaping as one’s primary mode of use. As additives in informally-sourced vaping concentrates could drive future EVALI cases, marijuana policy design should account for effects on mode of use in licit and illicit markets, to limit the scope of future outbreaks.

Meanwhile, states with the highest number of EVALI cases tended to be those with blanket bans on pot use or prohibitions on medical cannabis patients cultivating their own.

The study concludes that the harm from the blackmarket vaping products was lessened in states where weed users could obtain legal, regulated alternatives.

“Simply put, if the public can obtain products legally from reputable sources, there is less demand for illicit products,” the report states.

Cannabis remains illegal under Texas law, except for those suffering from medical conditions including cancer and PTSD. During the time covered under the study, however, the Lone Star State’s medical weed laws were even more strict.

It’s unclear from the analysis how Texas’ prohibition played into its number of EVALI cases. There’s no data from Texas to indicate how many of its cases required hospitalization during the study period, the authors note.