Study evaluates second-hand marijuana smoke exposure among children

In a study designed to evaluate second-hand marijuana smoke exposure among children--a topic that scientists have not yet widely addressed--researchers at the Icahn School of Medicine at Mount Sinai found that nearly half of children whose parents smoked marijuana showed evidence of second-hand marijuana smoke exposure. The study appears in the December issue of Pediatrics.

"While the effects of tobacco smoke have been studied extensively, we are still learning about marijuana exposure. What we found in this study is that secondhand marijuana smoke does get into the lungs and little bodies of young children," says Karen Wilson, MD, MPH, Debra and Leon Black Division Chief of General Pediatrics, and Vice-Chair for Clinical and Translational Research for the Jack and Lucy Clark Department of Pediatrics at the Icahn School of Medicine at Mount Sinai. Dr. Wilson also chairs the American Academy of Pediatrics Tobacco Consortium and is an investigator with the Julius B. Richmond Center of Excellence.

The study is a secondary analysis of data and samples collected as part of a larger study to test the efficacy of a tobacco smoking cessation program for parents of children who had been hospitalized in Colorado. The cohort consisted of parents who reported being current tobacco cigarette smokers, with some who also reported using marijuana. The research took place after recreational marijuana use had become legal in Colorado. The medical use of marijuana is legal in 33 states while 10 states to date have legalized recreational use.

Among the parents studied, smoking was the most common form of marijuana use (30.1 percent), followed by edibles (14.5 percent) and vaporizers (9.6 percent). This finding is consistent with national trends pointing to smoked marijuana as the most common form of consumption.

Testing of urinary marijuana biomarkers was conducted by the U.S. Centers for Disease Control and Prevention (CDC). Researchers at the CDC discovered that 46 percent of the children had detectable levels of the marijuana metabolite tetrahydrocannabinol carboxylic acid (COOH-THC). In addition, 11 percent of children had detectable levels of tetrahydrocannabinol (THC), the primary psychoactive constituent in marijuana. THC is considered a reliable indicator of both recent and active exposure, and a higher level of exposure overall. "These are worrisome results, suggesting nearly half of the children of parents who smoke marijuana are getting exposed and 11 percent are exposed to a much greater degree," says Dr. Wilson.

Although most parents reported that no one ever smoked marijuana inside their homes (84.0 percent), 7.4 percent reported marijuana smoking in the home daily. When asked what happened if someone wanted to smoke marijuana in the home while the children were present, 51.8 percent reported that there was no smoking when children were home, 21.7 percent stepped outside, and 9.6 percent smoked in another room or another floor.

One-third (33.3 percent) of children whose parents stepped outside to smoke tested positive for COOH-THC. "Stepping outside might sound like a good idea, but the evidence we collected suggests that kids are still getting exposed through second-hand or possibly third-hand smoke exposure," says Dr. Wilson.

Third-hand smoke is the residue that lingers after a cigarette has been extinguished. "We know that third-hand smoke--smoke that lingers in our hair, our clothes, even our skin--results in biological exposure that we can detect. What remains unclear is the extent and consequence of this mechanism of exposure," says Dr. Wilson.

"Our findings suggest that smoking in the home, even in a different room, results in exposure to children. The more we understand second-hand and third-hand smoke exposure, the better we can protect children in the home in states where marijuana is legal," says Dr. Wilson.

The study points out that tobacco and marijuana smoke contain similar harmful chemicals, with a large body of research data on the former and little on the latter. According to a 2006 Report of the Surgeon General, second-hand exposure to tobacco smoke causes an increased risk of sudden infant death syndrome, acute respiratory infections, middle ear disease, and more severe and frequent asthma attacks in infants and children.

Although most states with legal marijuana use restrict its use in public indoor and outdoor spaces, they do not have any restrictions on combustible marijuana use in the presence of children.