The risk of breathing second-hand smoke from cigarettes is well-documented, but the dangers from breathing second-hand marijuana smoke are not, until now.
A new study from a researcher at the University of California, San Francisco School of Medicine found exposure to second-hand marijuana smoke is three times more dangerous than exposure to tobacco smoke.
Matthew Springer, a professor at UC San Francisco tested blood flow in rats after they were subjected to second-hand marijuana and cigarette smoke. He found arteries in the rats were constricted for about 30 minutes when exposed to cigarettes and for 90 minutes when exposed to marijuana smoke, before returning to normal.
Springer concluded "that SHS (second-hand smoke) can exert similar adverse cardiovascular effects regardless of whether it is from tobacco or marijuana."
"People think cannabis is fine because it's 'natural.' I hear this a lot. I don't know what it means," Springer said in an interview with NPR.
"We in the public health community have been telling them for decades to avoid inhaling second-hand smoke from tobacco," Springer said. "We have not been telling them to avoid inhaling secondhand smoke from marijuana … it's because we just haven't known. The experiments haven't been done."
Cigarette smoking is the greatest preventable cause of premature death in the United States, according to the National Institutes of Health. It can lead to heart disease, stokes, heart attacks and blood clots. Cigarette smoking is responsible for 87 percent of lung cancer deaths and at least 30 percent of all cancer deaths every year, the NIH reported.
Springer's study findings take on greater importance as more states around the country consider decriminalizing marijuana.
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