Secondhand marijuana smoke may be just as dangerous as secondhand tobacco smoke, according to a new study.

“Smoke is smoke,” Matthew Springer, author of the study and an associate professor of medicine at University of California San Francisco, told CBS. “Both tobacco and marijuana smoke impair blood vessel function similarly. People should avoid both, and governments who are protecting people against secondhand smoke exposure should include marijuana in those rules.”

In the study, laboratory rats were exposed to secondhand marijuana smoke for 30 minutes. Researchers then used a high-resolution ultrasound to measure their blood vessel function. They found that function was reduced by 70 percent, a rate similar to the effect of secondhand tobacco smoke.

According to CBS, “Reduced blood vessel function can increase a person’s risk of developing hardened arteries, which could lead to a heart attack.”

“Marijuana for a long time was viewed as a relatively innocuous drug, but a lot of that came from a lack of information,” Dr. Stephen Thornton, a toxicologist at the University of Kansas Hospital, told CBS. “Now, as more and more people are using it, we’re finding more and more detrimental effects. People just need to be cautious.”

Cully Stimson, manager of The Heritage Foundation’s National Security Law Program, said, “Smoking anything is bad for you.  Everyone knows that secondhand cigarette smoke is bad for you.  Pot pushers want people to believe that the law of chemistry and physics cease to exist when applied to pot.  That simply is not the case.  Today’s marijuana is a dangerous substance, much more so than alcohol.  It is a Schedule I controlled dangerous substance for good reason, and must remain so.”

CBS notes that “because the study findings were presented at a medical meeting they should be viewed as preliminary until published in a peer-reviewed journal.”