The negative impact of second-hand tobacco smoke is well documented. According to the U.S. Centers for Disease Control and Prevention, tobacco smoke contains more than 7,000 chemicals. Hundreds of those chemicals are toxic and 70 are linked to cancer. Each year in the United States 34,000 nonsmokers suffer from premature death from heart disease attributed to second-hand smoke.

Results of a recent study by the University of California, San Francisco, suggest that secondhand marijuana smoke can do as much damage to the heart and blood vessels as secondhand tobacco smoke The researchers found that laboratory rats experienced a 70% reduction in blood vessel function after being exposed to a large amount of marijuana smoke for 30 minutes. This finding is similar to results found with breathing second-hand cigarette smoke.

Another study reported in the Journal of Drug and Alcohol Dependence found that nonsmokers who spent an hour in an unventilated room full of marijuana smoke had “detectable amounts of THC (pot’s active ingredient) in their blood and urine samples afterwards, in some cases enough to test positive for workplace or commercial drug testing programs.“