A new study finds a majority of parents who smoke expose their children to tobacco smoke in their cars. Many of these parents have smoke-free policies at home, CBS News reports.

According to the Centers for Disease Control and Prevention, there is no risk-free level of exposure to secondhand smoke. In children, secondhand smoke causes many health problems, including severe asthma attacks, respiratory infections, ear infections, and sudden infant death syndrome.

The study included 795 parents who were smokers. More than 70 percent said someone had smoked in their car in the previous three months. Of the 562 parents who allowed smoking in their car, 48 percent said they smoked in the car when their children were present. The researchers found while most parents strictly enforced a smoke-free policy at home, only 24 percent had a similar policy for their cars.

“Workplaces, restaurants, homes and even bars are mostly smoke-free, but cars have been forgotten,” lead researcher Emara Nabi-Burza of Massachusetts General Hospital said in a news release. “Smoking in cars is not safe for motorists and nonsmokers – especially children, who have no way to avoid tobacco smoke exposure in their parent’s car. Now that we know the magnitude of the problem, pediatricians and the public can act to help these children.”

The study appears in the journal Pediatrics.