From the Document: " Children are especially at risk for health effects from exposure to wildfire smoke and ash, mostly because their lungs are still growing.  Wildfire concerns include the fire itself, the smoke and ash, and the chemicals from materials that have burned, such as furniture.  Smoke can travel hundreds of miles from the source of a fire. Pay attention to local air quality reports during fire season, even if no fire is nearby."
EPA- 452/F-18-006; Environmental Protection Agency- 452/Factsheet-18-006
Government Publishing Office: https://www.gpo.gov/