In 2023, Canada’s worst wildfire season on record produced so much smoke that it spilled across national borders into the United States. At times, a thick haze enveloped much of the U.S. East Coast and triggered “Code Purple” and “Code Maroon” alerts—the most hazardous air quality warning categories—in the Washington, D.C. region.
Chemical traces of 2023 Canadian wildfires detected in Maryland months after smoke subsided
