Study finds significant exposure of second-hand children to cannabis from smoking at home, highlighting the need for preventive measures and stricter policies to protect their health.
Study: Secondhand cannabis smoke exposure among children. Image credit: ThamKC/Shutterstock.com
In a recent study published in JAMA Network Opena research team from the United States investigated the relationship between cannabis smoking at home and secondhand exposure among children using urine biomarkers.
They evaluated how cannabis use at home affects levels of Δ9-tetrahydrocannabinol (THC) and its metabolites in children. Their goal was to quantify exposure and highlight the need to take preventive measures to protect children’s health.
Background
Cannabis use, mainly through smoking, emits harmful chemicals, including carcinogens and fine particles, which can negatively affect respiratory and cardiovascular health.
Secondhand cannabis smoke (SHCS) is a combination of direct emissions and exhaled smoke, and evidence suggests that it may contribute to adverse health effects.
Children, being more vulnerable to environmental pollutants, are at greater risk when exposed to SHCS. Existing studies have linked cannabis use by healthcare professionals to respiratory illnesses in children. However, most have focused on indirect measures or single biomarkers, limiting understanding of the extent and effects of such exposure.
Despite the increasing use of cannabis, particularly in households with children, research on SHCS and its effects remains limited.
This lack of data reflects the need to use objective measures, such as urinary biomarkers, to investigate how exposure to SHCS affects children and to inform policies and interventions aimed at reducing the potential health risks of this vulnerable population.
About the study
In the present cross-sectional study, researchers used data obtained from Project Fresh Air, focusing on households with children under 14 years of age and resident smokers in San Diego County. They combined data from air particle monitoring with parent reports of cannabis use at home to assess children’s exposure to SHCS.
Urine samples from 275 children were analyzed for THC and its metabolites, including 11-hydroxy-THC and 11-nor-9-carboxy-THC, which serve as biomarkers of cannabis exposure.
These biomarkers were measured using advanced mass spectrometry methods and the researchers summed all molecular equivalents to determine total THC equivalents (TTE).
To estimate cannabis smoking at home, the study used a residual use approach, which combined self-reported cannabis use and air particle data and adjusted for other sources such as cigarette smoke and household activities that produce particles. The researchers also identified daily non-specific smoking events through air particle counts that exceeded a specified threshold and quantified their association with reported cannabis use.
In addition, they collected data on air nicotine dosimeters and household demographic factors, including ventilation practices, income, and parental education.
The study used logistic regression to assess the probability of detectable TTE based on home cannabis use. Instead, linear regression was performed to quantify exposure among children using detectable biomarkers.
Important findings
The results showed that children who lived in homes where cannabis was smoked indoors had significantly higher exposure to secondhand cannabis smoke, as evidenced by detectable THC biomarkers in their urine.
Among the 275 children included in the study, 27.3% had detectable levels of cannabinoids in their urine. Additionally, households that reported cannabis use at home were five times more likely to have detectable levels of TTE compared to those with no reported cannabis use.
Furthermore, for each additional daily event of cannabis smoking, the probability of detectable urinary TTE in children was found to increase by a factor of 2.5.
Among children who showed detectable urinary cannabinoid levels, higher frequencies of reported cannabis smoking events were associated with greater TTE levels, although this increase was not statistically significant.
The researchers observed that children under the age of six showed similar exposure patterns, indicating an increased risk for younger age groups who spend more time indoors.
Although non-specific smoking events recorded by air particulate monitors contributed to the exposure data, self-reported cannabis smoking at home provided a more direct association with urinary biomarker detection.
Furthermore, sensitivity analyzes confirmed the reliability of these findings across multiple measures of smoking events.
This study highlighted the impact of cannabis use in the home on children’s exposure to SHCS, with detectable biomarkers serving as critical indicators of exposure levels. These results also highlighted the importance of implementing preventive measures to minimize indoor cannabis smoking, particularly in households with young children.
conclusions
Overall, the findings demonstrated a significant association between cannabis smoking at home and increased secondhand exposure in children, as indicated by urinary THC biomarkers.
The study suggested that reducing indoor cannabis use could significantly reduce children’s exposure to harmful chemicals found in cannabis smoke. The team also believes that further research is needed to investigate the long-term health effects of such exposure and to develop policies that protect children from environmental risks associated with cannabis use.
Journal Reference:
Tripathi, O., Humberto, P., Sosnoff, C., Matt, GE, Penelope, Shi, Y., Liles, S., Wang, L., Caron, KT, Oneill, J., Nguyen, B., Blount, BC, & Bellettiere, J. (2025). Secondhand cannabis smoke exposure among children. JAMA Network Open8(1), e2455963–e2455963. doi:10.1001/jamanetworkopen.2024.55963.
