At about 8 p.m. on the Fourth of July last year, air pollution levels across Chicago started to climb. Just a few hours later, as Chicagoans watched brightly colored fireworks explode in the sky, the city reached a level of air pollution more than four times the hourly average of a normal summer evening.
The hours between 9 p.m. and midnight on July 4, 2021, ranked as the most intensely polluted hours the city experienced at any point over the past year, according to an analysis of data on Chicago’s air quality. The new analysis is part of an ongoing project by MuckRock, WBEZ and the Sun-Times.
