In November, eight more states legalized marijuana, either for medical reasons or adult recreational use. Legal or not, many Americans smoke pot. Some do so around young children. But emerging research suggests secondhand pot smoke might affect kids' health.
While parents may believe using pot is safer and more natural than smoking tobacco, experts say secondhand smoke from pot might be just as hazardous for children's developing bodies and minds.
In a study released in December in the journal Pediatric Research, babies and toddlers in Colorado showed traces of THC, the psychoactive ingredient in marijuana, in their urine. Researchers studied 43 children who were hospitalized between 2013 and 2015 for a lower respiratory infection called bronchiolitis. Of the children, who were all between 1 month and 2 years old, 16 percent had been exposed to marijuana smoke. Those children were also more likely to have been exposed to tobacco smoke.
At the time of data collection, study author Dr. Karen Wilson, division chief of general pediatrics at Mount Sinai Hospital in New York City, was an associate professor of pediatrics as the University of Colorado School of Medicine and Children's Hospital Colorado. Her group had been studying the risks of secondhand tobacco smoke in children when they saw signs of a cultural shift.
"As we were asking the families whether their children were exposed to tobacco smoke, more and more of them started to say, 'Oh, no, we don't smoke tobacco -- we only smoke marijuana because that's natural,'" Wilson says.
With growing legalization, including the opening of Colorado's recreational pot stores in 2014, the researchers recognized that secondhand marijuana smoke exposure among kids was likely to become even more of a problem. "Although," Wilson notes, "I have to say that the exposure seems to have been pretty significant even before legalization, based on our own anecdotal evidence and also based on the study that we did."
The study does not demonstrate whether pot smoke contributed to kids' infections, if it's better or worse than tobacco smoke or what happens when you combine the two, Wilson points out.
It's already clear that secondhand tobacco smoke is harmful to health. According to the Centers for Disease Control and Prevention, secondhand smoke in kids causes ear infections; more frequent and severe asthma attacks; respiratory symptoms such as sneezing, coughing and shortness of breath; bronchitis; pneumonia and a higher risk for sudden infant death syndrome.
The new study findings are cause for concern, says Dr. Seth Ammerman, a clinical professor of pediatrics and adolescent medicine at Stanford University. "We do know that anything you burn isn't good to breathe in," he says. "Anything you burn creates smoke, which then contains tar and other toxic chemicals. So I'm not surprised that marijuana smoke would have a similar process to tobacco smoke." The effect would likely be greater for a child who has allergies or asthma since a sensitive airway is more prone to inflammation, he says. Ammerman notes that marijuana dispensaries offer vaporizers, which help eliminate smoke-related toxins.
The notion that marijuana is natural and therefore safe is "misleading," says Ammerman, who works with the American Academy of Pediatrics' committee on substance abuse. "Cyanide comes from a plant, as an example," he says. "There are many deadly poisons that also come from plants."
Much remains to be discovered. A typical marijuana plant has at least several hundred cannabinoids, Ammerman says. Other than THC and a few others, he says, little is known about most of these active ingredients. It's possible that one may benefit kids with intractable seizures, he says, while other yet-unknown effects may be good or not so good. Research continues.
In a November 2014 study, laboratory rats experienced a 70 percent drop in their blood vessel function after a short period of exposure to secondhand pot smoke, according to University of California--San Francisco researchers. Impaired blood vessel function, a known effect of secondhand tobacco smoke, puts people at risk for heart disease. However, results from animal research don't necessarily translate to humans, and much more research is needed.
A May 2015 study with 19 participants showed how nearby nonsmokers feel the effects of pot smoke, basically getting buzzed themselves. Researchers from the Johns Hopkins University showed that exposure under certain conditions, like spending an hour in an unvented room with people smoking pot, could reduce memory and coordination in nonsmokers and give them a mild sense of intoxication -- and a positive drug test in some cases.
Parenting and Pot
With marijuana legal in Colorado, Wilson says, some pregnant women may be misinformed that marijuana is safe and can help them with their morning sickness. In fact, doctors advise against smoking anything, including pot, while pregnant. "Definitely, marijuana during pregnancy is to be avoided," Ammerman says. "Studies are emerging that it could have negative developmental consequences in the newborn and the infant."
That advice holds after the child is born. "We would recommend that you not smoke in the same house as a child," Wilson says. If you insist on smoking, she adds, wait until the child is not present. "And just make sure you're protecting your child from the marijuana smoke in the same way you would want to protect your child from tobacco smoke."
Long after traditional cigarettes are extinguished, they leave thirdhand smoke in their wake. Heavy smoking emits toxic contaminants that coats surfaces such as curtains, furniture and car interiors. Research suggests thirdhand tobacco smoke might be harmful to kids, and the next question is what the effects of thirdhand marijuana smoke could be.
Parenting and pot-smoking issues extend beyond secondhand smoke. "I worry sometimes about parenting, let alone this toxic exposure," Ammerman says. "Because you can get too high ... and you're probably not at your best parenting at that moment." And by smoking pot around preteens and older teens, he says, parents send a message of approval through their actions.
Edible products containing marijuana pose a different hazard. Portion-size restrictions, better labeling and safer packaging are helpful, Wilson says; still, parents must be cautious about having edible marijuana in the house. "Obviously, it's a poisoning risk," she says. "And if they are going to keep it in the home, keep it under lock and key, even if it's child-safe packaging. Because a child in the presence of a brownie can do a lot of different stuff."
Lisa Esposito is a Patient Advice reporter at U.S. News. She covers health conditions, drawing on experience as an RN in oncology and other areas and as a research coordinator at the National Institutes of Health. Esposito previously reported on health care with Gannett, and she received her journalism master's degree at Georgetown University. You can follow her on Twitter, connect with her on LinkedIn or email her at email@example.com.