One Minute of Secondhand Pot Smoke Could Damage Blood Vessels, Study Says

Inhaling secondhand marijuana smoke for just one minute may impair blood vessels, a new study suggested.

According to a new research from the American Heart Association, blood vessel functions are three times less likely to recover after only a minute of inhaling secondhand marijuana smoke, compared with a minute of breathing secondhand tobacco smoke.

"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," Matthew Springer, professor of medicine at the University of California, San Francisco's Division of Cardiology and senior author of the study, said in a press release.

In the study, which was published in the open access Journal of the American Heart Association/American Stroke Association, the researchers examined blood vessel functions in rats before and after exposure to similar levels of secondhand marijuana smoke and secondhand tobacco smoke.

After inhaling marijuana smoke, researchers found that the rats' arteries carried blood less efficiently for at least 90 minutes, while similar levels of exposure to secondhand tobacco smoke caused damage in blood vessel functions that recovered only within 30 minutes.

The researchers also found that it was not the chemicals in marijuana - such as tetrahydrocannabinol (THC) - that cause blood vessel impairment, but rather the mere burning of the plant material.

"There is widespread belief that, unlike tobacco smoke, marijuana smoke is benign," Springer said.

"We in public health have been telling the public to avoid secondhand tobacco smoke for years, but we don't tell them to avoid secondhand marijuana smoke, because until now we haven't had evidence that it can be harmful."

While the study involved animal subjects, the researchers noted that it is likely to have the same effect on human blood vessels.

According to the researchers, the legalization of the drug in a number of states either for recreational or medicinal purposes could lead to more cases of exposure to secondhand marijuana smoke.

As such, the researchers emphasize the importance of understanding the possible health implications of secondhand marijuana smoke.