As a major threat to global health, particulate air pollution has a great possibility of affecting bone metabolism. However, the results of limited studies examining the association between particulate air pollution and bone mineral density (BMD) as well as incident osteoporosis (OP) are conflicting, and the role of physical activity in the association above remains to be further studied. We evaluated the relationship between long-term exposure to Black Carbon (BC) and Particulate Matter (PM) (including PM