Children who breathe second-hand cigarette smoke face an increased risk of lung cancer, even if they never smoke, according to a new study.

The research, which involved 624 people in Maryland suffering from lung cancer and an independent control group of 348 healthy individuals, found that the likelihood that a person who had been exposed to second-hand smoke during childhood had contracted lung cancer was more than twice that of a person who had not. Researchers interviewed the participants about their histories of exposure to second-hand cigarette smoke.