Second Hand Cannabis Smoke

Measuring indoor fine particle concentrations, emission rates, and decay rates from cannabis use in a residence


-60 experiments comparing indoor PM2.5 from secondhand marijuana & tobacco smoke.

-The marijuana joint’s emission rate was 3.5 times that of the tobacco cigarette.

-All the cannabis sources had PM2.5 emission rates greater than tobacco cigarettes.

-The order of cannabis emission rates was joint, bong, glass pipe, and vaping pen.

-The vaping pen’s mean decay rate exceeded the other sources’ mean decay rates.


Secondhand bong smoke is worse than that from tobacco.

The fine particulate matter in cannabis smoke from bongs is at least four times greater and more dangerous


Conclusion: Metabolites of marijuana smoke can be
detected in children; in this cohort, 16% were exposed.
Detectable COOH-THC is more common in children with
tobacco smoke exposure. More research is needed to assess
the health impacts of marijuana smoke exposure on children
and inform public health policy.

Wilson KM, et al. Detecting biomarkers of secondhand marijuana smoke in young children. 2017;81(4):589-592. Doi:10.1038/pr.2016.261


Approximately half of the children who qualified for our study had biological evidence of exposure to marijuana. Researchers in studies such as this provide valuable data on secondhand exposure to children from parents using tobacco and marijuana and can inform public health policies to reduce harm.

Wilson KM, et al. Marijuana and tobacco coexposure in hospitalized children. 2018;142(6):1-7. Pediatrics. e20180820

Conclusions: One minute of exposure to marijuana SHS substantially impairs endothelial function in rats for at least 90 minutes, considerably longer than comparable impairment by tobacco SHS. Impairment of FMD does not require cannabinoids, nicotine, or rolling paper smoke. Our findings in rats suggest that SHS can exert similar adverse cardiovascular effects regardless of whether it is from tobacco or marijuana.

Wang X, et al. One minute of marijuana secondhand smoke exposure substantially impairs vascular endothelial function. 2016;5:e003858 doi:10.1161/J Am Heart Assoc.116.003858 

Second-hand marijuana smoke is not benign.

Here are three important facts from these articles for your consideration.     

  1. One out of six or 16% of children under 2 years of age, hospitalized with bronchiolitis in Colorado between 2013-2015, were found to have marijuana products in their blood, indicating prior exposure to the drug. 
  2. Approximately 50% of hospitalized Colorado children whose parents were in a smoke cessation program also showed biologic evidence of exposure to marijuana.  
  3. In animals, only one minute of exposure to secondhand marijuana smoke substantially harms vascular function for at least 90 minutes, suggesting that secondhand marijuana smoke can harm the heart and blood vessels just as we know secondhand tobacco smoke contributes to heart attacks and peripheral vascular disease.