DC air stayed in the 'unhealthy' range for hours after Independence Day fireworks
Air quality in Washington, D.C. stayed unhealthy for more than 10 hours after a 40-minute Independence Day fireworks show over the National Mall, with PM2.5 peaking at 212.8 µg/m³ in the Navy Yard at 3 a.m. The pollution lingered near the ground and persisted into late morning and early afternoon, according to AirNow data from the EPA.