A new Global Burden of Disease study finds secondhand smoke exposed 2.7 billion people worldwide in 2023. The exposure was linked to one-point-six-six million deaths and 44-point-eight million disability-adjusted life years. Researchers say ischemic heart disease was the leading contributor to health loss, while children accounted for more than 12 percent of the total burden. The study covered 204 countries and territories from 1990 to 2023.