According to a new study released by the American Medical Association, second-hand pot smoke could be up to 66% more damaging to your blood vessels than tobacco.

The study, released Thursday, tested rats who were exposed to second-hand tobacco and pot smoke.

In the rats exposed to marijuana, researchers found their blood vessels were less efficient in carrying blood through arteries for up to 90 minutes after exposure, compared to only 30 minutes in those exposed to second-hand tobacco smoke.

According to a statement from the AMA:

“While the effect is temporary for both cigarette and marijuana smoke, these temporary problems can turn into long-term problems if exposures occur often enough and may increase the chances of developing hardened and clogged arteries,” said Matthew Springer, Ph.D., study senior author and professor of medicine at the University of California, San Francisco’s Division of Cardiology."

Rats were used for the study for their close similarity to humans, and their response to smoke (pot and tobacco) is virtually the same.

Researchers and the AMA say there's a mistaken idea that exposure to second-hand or even primary pot smoke is benign, and this study appears to refute that idea. For years, says the AMA, we've been telling people to avoid second-hand tobacco smoke, but not pot because until now there haven't been thorough enough studies done on it's effects.