A new study says 16 percent of children hospitalized in Colorado for an inflammation of the lungs tested positive for exposure to marijuana.

Researchers looked at children between one month and two years old who were admitted to Children’s Hospital Colorado in 2013 and 2014 with bronchiolitis.

Tests found one in six had traces of THC, the psychoactive component of marijuana.

“I think that we need to pay more attention to the impact of that second-hand smoke, not only on children, but also on people who are living in adjacent apartments to somebody who may be smoking marijuana," said Dr. Karen Wilson of the University of Colorado School of Medicine. She led the study.

Wilson says the findings suggest secondhand marijuana smoke may be a rising child health issue as recreational marijuana becomes legalized elsewhere in the U.S.

She says more study is needed.