CBS Local — As the government continues to crack down on tobacco products, more and more states are easing up on marijuana laws. One biologist is now saying those policies are misguided after finding that secondhand smoke from marijuana users may be just as deadly as cigarette smoke.

According to Matthew Springer, a professor at the University of California, San Francisco, marijuana smoke is three times worse for the arterial walls than cigarette smoke. In a study conducted with mice, secondhand smoke from tobacco was found to hinder the expanding of arteries for 30 minutes before the body recovers. Mice exposed to marijuana smoke had their arteries impaired for 90 minutes before returning to normal.

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“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 warn that smokers could permanently damage their arteries through constant smoking, which can lead to blood clots, heart attacks, or a stroke.

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“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.”

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According to the CDC, smoke from cigarettes contains over 7,000 chemicals; at least 70 of which have been found to cause cancer. Although the CDC’s report also focused on tobacco-based smoke, the agency wrote that “there is no risk-free level of exposure to secondhand smoke.”