Worst wildfire smoke days in recent U.S. history 2006-2023
The worst wildfire smoke day in the United States in recent years was June 7, 2023. On this day, the average American was exposed to 27.5 micrograms per cubic meter (μg/m³) of fine particulate matter (PM2.5) carried within the plumes of smoke. This was mainly due to large forest fires in Canada that spread south into the U.S.
PM2.5 is a fine air pollutant that can be inhaled deep into the lungs and bloodstream, causing a range of health effects, including asthma and heart disease.