Marijuana use among parents with children in the home is increasing, while rates of cigarette smoking among this group of parents are declining, a new study finds.

Researchers found past-month marijuana use among parents with children in the home increased from 4.9 percent in 2002 to 6.8 percent in 2015, while cigarette smoking declined from 27.6 percent to 20.2 percent. Among cigarette-smoking parents, marijuana use increased from 11 percent in 2002 to 17.4 percent in 2015, HealthDay reports. The study also found an increase in marijuana use among parents who don’t smoke tobacco—from 2 percent to 4 percent.

“As we are removing cigarette smoke — and that’s a major public policy achievement — that success will be attenuated by increasing exposure to secondhand marijuana smoke,” said lead researcher Renee Goodwin of the City University of New York. “The kids who are already exposed to one thing, they’re more likely to be exposed to both. It’s even worse for them.”