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Stanford University School of Medicine

What about secondhand marijuana smoke? Stanford Medicine expert weighs in

In 1995, California became the first state in the country to enact laws protecting people from exposure to secondhand cigarette smoke in public spaces. Those laws have been linked to broad public health benefits, including lower rates of heart attacks, as well as some of the lowest levels of tobacco use in the country.

But now, the state is facing a big change in the landscape of secondhand smoke as it implements the legalization of recreational marijuana. That raises a looming, unanswered question: Will the law treat secondhand tobacco and marijuana smoke equally?

Scientific evidence suggests they should, according to Bonnie Halpern-Felsher, PhD, a Stanford adolescent medicine expert who studies teens' attitudes toward marijuana. With two colleagues at the University of California, San Francisco, Halpern-Felsher has written an editorial in JAMA Internal Medicine that urges policymakers to protect the public from the harmful effects of secondhand marijuana smoke, which they note is already recognized as a human carcinogen by the California Environmental Protection Agency and has been shown in animal and human research to have negative effects on heart health.

In part, they write:

The evidence that secondhand marijuana smoke is dangerous to health is more limited than the evidence that secondhand tobacco smoke is. Yet there is already at least as much evidence concerning marijuana risk as there was for secondhand tobacco smoke in the late 1970s, when the clean indoor air movement started to gain steam. In particular, it is known that the cardiovascular effects of secondhand smoke are more important in terms of population impact than cancer, that these effects occur quickly, and that marijuana smoke may be worse than tobacco smoke.

But the public may now see marijuana smoke as less harmful than tobacco smoke, they write, concluding that, "Stressing the right of all to breathe clean air should also be at the core of educational and legislative efforts to reinforce the marijuana smoke-free norm for everyone."

Previously: Stanford doctor weighs in on marijuana marketing debate, Is marijuana safe for teens? American Academy of Pediatrics says no and The health effects of legalizing marijuana: A Q&A with a Stanford drug policy specialist
Image by Олег Жилко

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