States with legal recreational marijuana access had around seven fewer cases of EVALI per million population than medical marijuana and prohibition states.

Those living in legal recreational marijuana markets were less likely to acquire e-cigarette– or vaping–associated lung injury (EVALI) than those where adult-use cannabis access was illegal, reports a new study published this week. Though scientists haven’t yet confirmed the definitive cause behind EVALI, the majority of analysis indicates the illness is tied to marijuana vaping products purchased on the black market.

According to the study published in the JAMA Network Open, legal “recreational marijuana states had among the lowest EVALI rates of all states.” 

Nearly 3,000 people suffered from EVALI, resulting in 60 deaths, according to Centers for Disease Control and Prevention (CDC) data in February 2020. Vitamin E acetate is strongly associated as a culprit behind EVALI, and is typically used as a thickening agent by black market distributors. A small study published in February found vitamin E deposits in the lung tissue in 48 out of 51 EVALI patients.

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This new research dug deeper into this belief black markets played a significant role in the EVALI outbreak, which caused a significant drop in vaping sales at the time. Researchers compared confirmed cases from the CDC database against the prevalence of e-cigarette consumption using 2017 estimates from the Behavioral Risk Factor Surveillance System.

“The data suggest that EVALI cases were concentrated in states where consumers do not have legal access to recreational marijuana dispensaries,” researchers wrote. “This association was not driven by state-level differences in e-cigarette use, and EVALI case rates were not associated with state-level prevalence of e-cigarette use. One possible inference from our results is that the presence of legal markets for marijuana has helped mitigate or may be protective against EVALI.”

Cross-sectional study finds states with legal recreational marijuana had fewer cases of e-cig/vaping associated lung injury #EVALI. @aaronecarroll @ajhollingsworth @AshleyCBradford @coady_wing #VisualAbstract https://t.co/9dXGchag16 pic.twitter.com/nIoeV7v39b

— JAMA Network Open (@JAMANetworkOpen) April 7, 2020

Legal adult-use marijuana states had an average of 1.7 EVALI cases per million population, while medical marijuana states saw 8.8 EVALI cases per million — slightly more than prohibition states, which had 8.1 EVALI cases per million population.

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“The reason for this association is not yet clear,” researchers concluded. “It is possible that in recreational states, people tend to purchase marijuana products at legal dispensaries, which may be less likely to sell the contaminated products that are thought to cause EVALI.”