Second-hand marijuana smoke may damage blood vessels

Breathing second-hand marijuana smoke could damage your heart and blood vessels as much as second-hand cigarette smoke, according to a new study.
In the study, blood vessel function in lab rats dropped 70 per cent after 30 minutes of exposure to secondhand marijuana smoke.
Even when the marijuana contained no tetrahydrocannabinol (THC) - a compound in marijuana that produces intoxication - blood vessel function was still impaired.
Reduced blood vessel function may raise the chances of developing atherosclerosis and could lead to a heart attack.
Atherosclerosis is the disease process that causes plaque build-up in the arteries which narrows them and restricts blood flow.

"Most people know secondhand cigarette smoke is bad, but many don't realise that secondhand marijuana smoke may also be harmful," said Matthew Springer, senior author of the study, from the University of California, San Francisco.

Marijuana and tobacco smoke are chemically and physically alike, aside from their active ingredients.
The drop in blood vessel function from THC-free marijuana suggests that the compound is not responsible for the effect. Similarly, this study confirms that nicotine is not required for smoke to interfere with blood vessel function.
In the study, researchers used a modified cigarette smoking machine to expose rats to marijuana smoke. A high-resolution ultrasound machine measured how well the main leg artery functioned.

Researchers recorded blood vessel dilation before smoke exposure and 10 minutes and 40 minutes after smoke exposure.
They also conducted separate tests with THC-free marijuana and plain air. There was no difference in blood vessel function when the rats were exposed to plain air.
In previous tobacco studies, blood vessel function tended to go back to normal within 30 minutes of exposure.
However, in the marijuana study, blood vessel function did not return to normal when measured 40 minutes after exposure.
"If you are hanging out in a room where people are smoking a lot of marijuana, you may be harming your blood vessels. There is no reason to think marijuana smoke is better than tobacco smoke. Avoid them both," Springer said.