Brain and Body

Sick Kids in Colorado Are Testing Positive for THC, Flagging Concern over Secondhand Marijuana Smoke

May 4, 2016 | Kelly Tatera

Marijuana joint, smoke
Photo credit: Chmee2/wikimedia (CC by SA 3.0)

The research on the effects of secondhand marijuana smoke is lacking.

Scientists at the University of Colorado School of Medicine just released research that raises concerns about secondhand marijuana smoke in the recreational-marijuana-approved state — traces of THC were found in one in six infants and toddlers admitted to a Colorado hospital for coughing, wheezing, and other symptoms of bronchiolitis.

In the study, the researchers looked at previously healthy children between one month and two years old who were admitted to the Children’s Hospital Colorado (CHC) between January 2013 and April 2014 with cases of bronchiolitis — an inflammatory lung infection in infants and young children.

Then, the parents of the children were recruited and asked to complete questionnaires about their child’s health, demographics, exposure to tobacco smoke, and whether anyone in the home smoked marijuana. Marijuana became legal in Colorado on January 1, 2014.

SEE ALSO: Starting Age for Marijuana Use May Have Important Implications for the Brain

After identifying the children who had been exposed to marijuana smokers in their homes, they found that 16 percent of their urine samples showed traces of metabolites of THC (tetrahydrocannabinol — the psychoactive component of marijuana). Further, the results showed that more of the children were THC-positive after weed had been legalized in the state — jumping up to 21 percent from the previous 10 percent. Non-white children were more likely to be exposed than white children, the researchers also noted.

"Our study demonstrates that, as with secondhand tobacco smoke, children can be exposed to the chemicals in marijuana when it is smoked by someone nearby," lead researcher Dr. Karen Wilson, associate professor of pediatrics at the University of Colorado School of Medicine and section head at CHC, said in a press release.

According to a 2014 study by researchers at the University of California, San Francisco, secondhand marijuana smoke may damage the blood vessels as much as secondhand cigarette smoke.

In fact, blood vessel function in the lab rats used in the study dropped 70 percent after just 30 minutes of exposure to secondhand marijuana smoke.

“If you’re hanging out in a room where people are smoking a lot of marijuana, you may be harming your blood vessels,” senior author Matthew Springer, cardiovascular researcher at UCSF, said in a press statement. “There’s no reason to think marijuana smoke is better than tobacco smoke.”

However, the research on secondhand marijuana smoke is still lacking, and the above-mentioned study only dealt with adults. Studying its effects on infants and children is something that future research will need to tackle.

“As marijuana becomes more available and acceptable, we need to learn more about how this may affect children's health and development,” said Dr. Wilson. In the meantime, she advises that "marijuana should never be smoked in the presence of children."

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