Secondhand Marijuana Smoke 3 Times Worse Than Tobacco, Study Claims

Marijuana smoke is three times worse for the arterial walls than cigarette smoke, a new study stated Monday. Matthew Springer, a biologist and professor in the division of cardiology at the University of California, San Francisco, claimed while many people think secondhand cigarette smoke was dangerous, passive marijuana smoke had a more adverse effect on health.

“People think cannabis is fine because it’s ‘natural.’ I hear this a lot. I don’t know what it means,” Springer told NPR.

Health officials warned smokers could permanently damage their arteries through constant smoking, which can lead to blood clots, heart attacks, or a stroke.

“We in the public health community have been telling them for decades to avoid inhaling secondhand smoke from tobacco,” Springer added. “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.”

Springer, who was already researching the health effects of secondhand tobacco smoke on rats, decided to run the same tests using marijuana as more and more states are easing up on cannabis laws.

The study was conducted with mice by exposing them to marijuana smoke as well as fume from tobacco. Cigarette smoke was found to affect the expanding of arteries for 30 minutes, while that of marijuana had the blood vessels impaired for 90 minutes.

In the study, Springer mentioned other researchers exploring the possible relationship between marijuana smoke and long-term cancer risk. He pointed out people might think the absence of research on secondhand marijuana might mean it is not an issue.

"People should think of this not as an anti-THC conclusion," Springer said, referencing the active ingredient in marijuana, "but an anti-smoke conclusion."

The active ingredient in marijuana affects brain areas that influence pleasure, memory, thinking, concentration, movement, coordination, and sensory and time perception. According to the Centers for Disease Control and Prevention, smoke from cigarettes contains over 7,000 chemicals. Of these, at least 70 were found to cause cancer.

"We in the public health community have been telling them for decades to avoid inhaling secondhand smoke from tobacco," Springer said. "We have not been telling them to avoid inhaling secondhand smoke from marijuana, and that's not because it's not bad for you — it's because we just haven't known. The experiments haven't been done."