CINCINNATI — For decades, health experts have warned about the dangers of smoking. While the number of adults lighting up has gone down, experts said about four in 10 children are exposed to secondhand and even thirdhand smoke.

"Secondhand smoke is when you're inhaling cigarette smoke from a lit tobacco product, and thirdhand smoke is the residue that remains in the environment well after the cigarette smoking has ceased," explained Ashley Merianos, a health services researcher at University of Cincinnati.

Merianos said when kids inhale, swallow or touch objects that contain thirdhand smoke, they are at higher risk of asthma, bronchitis and pneumonia. Merianos and her colleagues found that smoke-exposed children had nearly twice the risk of being admitted to the hospital over a one-year period as well as higher rates of emergency room visits, all coming at a cost.

"We found that children exposed to tobacco smoke had an average of almost $120 more per each pediatric emergency department visit compared to unexposed children who do not live with a smoker," detailed Merianos.

Merianos said the research also suggests the need for additional smoke exposure intervention programs, ensuring that adults who want to quit smoking are supported. She said for every 100 adults who try to quit, only seven are successful. Merianos also said it's important they have the resources to rid their homes of thirdhand smoke residue.