Secondhand marijuana smoke more dangerous than tobacco – study

© Cathal McNaughton
With an increasing number of states legalizing medicinal and recreational marijuana, a new study has found that exposure to secondhand marijuana smoke is more damaging to blood vessels than breathing secondhand tobacco smoke.

The study revealed that the blood flow in the arteries of rats that had inhaled secondhand marijuana smoke for one minute was less efficient for at least 90 minutes. Under a similar test for secondhand tobacco smoke, blood vessel impairment lasted only 30 minutes.

“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, PhD, the study’s senior author and a professor of medicine at the University of California, San Francisco’s Division of Cardiology, in a released statement.

Researchers also found that merely burning the plant material appears to cause impaired blood vessels, unlike chemicals like nicotine and tetrahydrocannabinol.

Researchers say the arteries of rats and humans are similar in how they respond to secondhand tobacco smoke.

The study on the health consequences of exposure to secondhand smoke from cannabis comes as three more states – California, Maine and Nevada – are due to vote on ballot initiatives on whether to legalize recreational marijuana this November.

ABC News reported that one in six Americans now live in states where cannabis is legal.

“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.”

The study was published in the Journal of the American Heart Association.