Detroit Tops Global Pollution Ranking After July 4 Fireworks

Detroit briefly became the world’s most polluted major city on the morning of July 5 after Fourth of July fireworks pushed its air quality index to a peak of 192, according to IQAir.

The Swiss air monitoring firm said fireworks smoke pushed up fine particulate matter, known as PM2.5, across much of the country overnight. Readings were high by the morning of July 5 in areas stretching from Southern California to the Eastern Seaboard.

Chicago, Minneapolis and Washington, D.C., also ranked among the world’s most polluted major cities that morning, IQAir said.

The worst conditions were in southeastern Michigan. Calm overnight weather allowed smoke to build up over metropolitan Detroit, where the company’s maps showed Unhealthy air stretching from the Ann Arbor area through Detroit and into eastern suburbs.

Los Angeles had some of the most widespread problems, according to the company. Much of the metro area recorded moderate air quality, but numerous hotspots—clustered mostly in central portions of the region—reached unhealthy, very unhealthy, and even hazardous levels.

Washington, D.C., hit a peak AQI of 161 late on July 4, an IQAir report shows. The worst pollution in the District appeared around Capitol Hill, Kingman Island and communities extending toward Cheverly, where readings reached Hazardous levels.

Thousands of simultaneous displays can foul the air across entire metro regions. — IQAir

Air quality improved steadily after sunrise on July 5 as the smoke cleared, IQAir said. Thousands of simultaneous displays can foul the air across entire metro regions, the company said. Millions of people breathe the result well after the shows end.

Wildfire smoke, which can linger for days, even weeks, is not the same as fireworks pollution, the company said. Fireworks are typically set off after sunset, by which time the atmosphere has stabilized and smoke is likely to stay near the ground. Previous national IQAir research showed that PM2.5 tends to peak late on Independence Day and dissipate after sunrise.