No surprise: Smoking is bad for your health. But even people who never touch a cigarette can be harmed by cigarette smoke. They merely have to inhale the airborne pollutants exhaled by a smoker. That so-called secondhand smoke can linger in the air for days. Teens who can’t avoid breathing it in may develop coughing and trouble breathing. But even those who don’t may still suffer, a new study finds. And that’s not the worst of it. Another study found that in teens exposed to that smoke for years, far more serious lung disease may develop.

Some 9.6 million U.S. teens and preteens are exposed to secondhand smoke, which can aggravate asthma. That’s a lung disease that can make it hard to breathe. Most secondhand-smoke studies focus on teens with asthma. But Ashley Merianos, a tobacco researcher at the University of Cincinnati in Ohio, wondered if this pollution might hurt other kids, too. To find out, her team decided to look at overall sickness rates in these kids. They also tracked their school attendance rates.

The researchers used data from a national survey known as PATH. (It stands for Population Assessment of Tobacco and Health.) Every year since 2011, the U.S. Department of Health and Human Services has surveyed people 12 and up about the effects of tobacco on their health. Its findings help guide government policies to protect public health.

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