Children exposed to secondhand marijuana smoke have measurable amounts of a metabolite of Δ9-tetrahydrocannabinol, according to results of an investigation published online December 2 in Pediatric Research.
With medical marijuana now legal in 28 states plus the District of Columbia, and recreational use decriminalized in 20 states plus the District of Columbia, childhood exposure could become a public health concern. The effect of secondhand marijuana smoke on children has not been studied, although it contains particulates, toxins, and carcinogens.
Karen Wilson, MD, and colleagues used a new, sensitive analytical method developed by the Centers for Disease Control and Prevention to quantify 11-nor-9-carboxy-(COOH)-THC in the urine of young children exposed to secondhand marijuana smoke. Dr Wilson is the Debra and Leon Black Division Chief of General Pediatrics and vice chair for clinical and translational research, Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York City. The researchers also measured urine cotinine, a metabolite of nicotine.
The investigators sampled urine from 43 healthy babies aged from 1 month to 2 years who were hospitalized in Colorado for bronchiolitis between 2013 and 2015. The parents completed a survey that asked, "Does anyone who lives in your home or who cares for your child smoke marijuana (yes or no)?" Marijuana use is approved for both medicinal and recreational use in Colorado.
Levels of THC and another major active ingredient, cannabidiol, were undetectable in the urine samples. However, COOH-THC was found in 16% of them, ranging from 0.03 to 1.5 ng/ml, with only two children exceeding 1 ng/mL. As expected, these levels were lower than would be seen in the urine of a person directly smoking marijuana.
Exposure did not differ by sex or age (77% of the children were boys, and 52% were younger than 1 year). However, more nonwhite children had COOH-THC in their urine than did white children (44% vs 9%; P = .026). Of children whose parents reported marijuana use or exposure in the home, 75% had detectable COOH-THC; 10% of children whose parents reported no exposure had detectable levels (P < .016).
Urine cotinine levels exceeded 2.0 ng/mL in 23% of the children. The results for cotinine suggest that households that expose children to cigarette smoke may also expose them to marijuana smoke: 56% of children whose cotinine levels exceeded 2.0 ng/mL were positive for COOH-THC, but only 7% of children who had lower cotinine levels (P < .004) were positive for the marijuana metabolite.
The increase in prevalence of detectable COOH-THC after legalization during the studied period, from 10% to 21%, was not significant.
The study demonstrates exposure to secondhand THC among the children, but does not examine health consequences. However, the well-known dangers of exposure to secondhand tobacco smoke (cognitive effects and respiratory illness) suggest that increased exposure to marijuana smoke could pose problems. "In the interim, parents should be cautioned not to smoke marijuana in the presence of their children," the researchers conclude.
"In areas where marijuana use is legal, or common, education is needed to counsel parents on the dangers posed to their children by secondhand smoke," Dr Wilson said in a Mount Sinai news release.
"Parent-reported screening questions in areas where marijuana is legal is a helpful first step. While we do not know yet whether this exposure poses a health risk to children, this study highlights the urgency of further investigation."
Limitations of the study include the use of samples previously collected to assess effects of exposure to secondhand cigarette smoke from parents who consented to future research, which might have selected out some who use the drug. The use of existing samples limited investigation of other factors that might have contributed to marijuana use or the presence of COOH-THC in the children's urine.
The researchers have disclosed no relevant financial relationships.
Pediatr Res. Published online December 2, 2016. Full text