Children in households where cannabis smoking occurred were significantly more likely to have detectable levels of tetrahydrocannabinol equivalents in their urine, according to a recent cross-sectional study.

Using deidentified data collected from Project Fresh Air, investigators analyzed 275 children younger than 14 years (mean age = 3.6 years, 52.4% male) residing in households in San Diego County, California, where at least one adult was a tobacco smoker. The participants included in the study identified as 48.0% Hispanic, 18.9% White, and 13.8% Black participants. The investigators analyzed baseline data from a randomized clinical trial aimed at reducing particulate matter levels in homes.

Parents or guardians reported cannabis smoking within the home over the past 7 days, and the investigators measured urinary tetrahydrocannabinol (THC) and its metabolites, including 11-hydroxy–delta-9–THC and 11-nor-9-carboxy–delta-9–THC. Biomarker levels were summed as total THC equivalents (TTE) to quantify exposure.

According to the study, published in JAMA Network Open, 27.3% of participants (n = 75) had detectable urinary cannabinoids. The investigators also determined that children in households with reported in-home cannabis smoking had five times the risk of detectable urinary THC compared with children in households without cannabis smoking (odds ratio [OR] = 5.0, 95% confidence interval [CI] = 2.4–10.4).

Each additional daily cannabis smoking event increased the risk of detectable THC by 2.5 times (OR = 2.5, 95% CI = 1.6–3.9). Although children exposed to more daily cannabis smoking events showed higher TTE levels (35.68% increase per event), the increase was not statistically significant (95% CI = −7.12% to 98.21%).

"As young children spend most of their time at home, reducing in-home cannabis smoking could substantially reduce their exposure to the toxic and carcinogenic chemicals found in cannabis smoke," wrote lead study author Osika Tripathi, PhD, of the School of Public Health at San Diego State University, and colleagues.

While the investigators established a strong association between in-home cannabis smoking and child THC exposure, the study was observational in nature and could not establish causation. Additionally, environmental factors such as ventilation and co-exposure to tobacco smoke were adjusted for but may have influenced results.

The authors reported no conflicts of interest concerning the study.