A hidden wildfire pollutant causes thousands of excess deaths per year, satellite data shows

When you think of air pollution from wildfires, you probably picture the thick plumes of smoke and ash that waft into the atmosphere during a blaze. And if you've lived in an area that’s been enveloped by these emissions, you know to stay inside or wear a mask when the light tints red and gets hazy. But this thick cloud isn't the only component of wildfire smoke that carries a health risk. Now, new research based on satellite data helps quantify the impact of an "invisible" wildfire pollutant: ground-level ozone. It would appear the yearly human cost of this hidden consequence lies in the thousands. Over the past few decades, climate change — primarily driven by human activities like burning coal — has turned wildfire smoke from an occasional, regional-specific concern to a major source of air pollution in the U.S. Since the 1990s, the area burned by wildfires in the country each year has roughly doubled . This means the amount of pollution released by these fires is on the rise, too. Researchers have therefore been scrambling to quantify what risk all that smoke poses for human health. So far, however, most of these efforts have focused on fine particulate matter, or PM2.5. This is made up of tiny bits of ash, dust, carbon or other material less than 2.5 microns across that get released into the air from fires or other sources, like industrial emissions. …