Stanford University Sep 18 2025 Wildfires burning across Canada and the Western United States are spewing smoke over millions of Americans – the latest examples of ashy haze becoming a regular experience, with health impacts far greater than scientists previously estimated.  Although wildfires have long been part of life in the Western U.S., warmer, drier conditions are fueling bigger blazes that occur more often and for longer. Smoke from these blazes is spreading farther and lingering longer