Standing in a mosh pit at a concert near people smoking marijuana may pose a danger to your health more than secondhand tobacco smoke, researchers at the University of California San Francisco said.   They found the effects on the heart are similar to being around cigarette smoke but last three times longer.

>> Read more trending stories

Just one minute of exposure to marijuana smoke can restrict blood flow, increasing the risk of a heart attack and other cardiovascular problems.

UCSF's Matthew Springer said the public tends to underestimate the risks.

"The biggest reason that people believe marijuana secondhand smoke is harmless is because the public health community hasn't had direct evidence of its harmful effects like it does with tobacco," Springer said.

The scientists came to their conclusions after exposing rats to marijuana smoke.

Twenty-five states now allow some form of marijuana use.