Detecting biomarkers of secondhand marijuana smoke in young children

The impact of secondhand marijuana smoke exposure on children is unknown. New methods allow detection of secondhand marijuana smoke in children. We studied children ages 1 mo to 2 y hospitalized with bronchiolitis in Colorado from 2013 to 2015. Parents completed a survey, and urine samples were analyzed for cotinine using LC/MS/MS (limits of detection 0.03 ng/ml) and marijuana metabolites including COOH-THC (limits of detection 0.015 ng/ml). A total of 43 subjects had urine samples available for analysis. Most (77%) of the subjects were male, and 52% were less than 1 y of age. COOH-THC was detectable in 16% of the samples analyzed (THC+); the range in COOH-THC concentration was 0.03–1.5 ng/ml. Two subjects had levels >1 ng/ml. Exposure did not differ by gender or age. Non-white children had more exposure than white children (44 vs. 9%; P 2.0 ng/ml were THC+, compared with 7% of those with lower cotinine (P < 0.01). 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.