Pre-clinical research funded by the National Institute on Drug Abuse (NIDA) suggests that secondhand marijuana smoke may cause longer lasting cardiovascular harm than secondhand tobacco smoke.
In this study, rats were exposed to secondhand marijuana or tobacco smoke at moderate to high levels (equivalent to secondhand tobacco exposure in restaurants that allow smoking). Blood vessel function was tested before and after exposure by measuring flow-mediated dilation (FMD), which is the extent to which arteries enlarge in response to increased blood flow. Dysfunctional FMD indicates potential cardiovascular impairment, since proper FMD ensures there is sufficient blood flow through the heart and rest of the body. The researchers found that just one minute of exposure to secondhand marijuana smoke produced FMD impairment that lasted for at least 90 minutes. In contrast, impairment from one minute of secondhand tobacco exposure was recovered within 30 minutes.
More research is needed to determine levels of secondhand marijuana exposure under different real world situations. Such research would better inform policy discussions on marijuana use in enclosed public spaces.
For a copy of the abstract, "One minute of marijuana secondhand smoke exposure substantially impairs vascular endothelial function," published in the Journal of the American Heart Association, go to https://www.ahajournals.org/doi/10.1161/JAHA.116.003858.
To learn more about the health effects of marijuana, go to: www.drugabuse.gov/publications/research-reports/marijuana/.