July 4 fireworks caused brief but hazardous air pollution in Milwaukee

The fireworks that lit up Milwaukee's skies Thursday night also produced air pollution that soared to hazardous levels in some neighborhoods.

Data collected by MKE FreshAir Collective, a nonprofit air quality monitoring organization that operates 19 air quality sensors around the city, show the exponential rise of the local air quality index, which measures pollutant levels, during the July 4 festivities.

Any number over 300 is deemed to be hazardous, surpassing "unhealthy" and "very unhealthy" levels and posing risks to everyone breathing it in. Last summer, when Canadian wildfire smoke blanketed Wisconsin, air quality indexes of 329 and 393 gave the cities of Brookfield and Waukesha, respectively, some of the worst air quality in the world.

Late Thursday night, the sensor in Milwaukee's Amani neighborhood measured an air quality index of 472, said Langston Verdin, founder and co-executive director of MKE FreshAir Collective. Multiple sensors across the city were reporting hazardous or very unhealthy air, including in the Near West Side, Franklin Heights, Silver Spring and Rufus King neighborhoods.

Unlike the wildfire smoke, which lingered for days, the air pollution caused by firework displays largely dissipated by Friday morning.

"The dust settles," Verdin said. "But it settles somewhere ... it's settling in our neighborhoods."

The brilliant colors that delight audiences during fireworks shows come from powdered metallic salts added to the explosive shells, according to the Wisconsin Department of Natural Resources. Copper produces the color blue, strontium produces the color red, powdered magnesium creates bright white flashes, and so on. In addition to the metals, fireworks produce smoke, which contains fine particles also known as PM2.5 that can be especially hard on the lungs.

Children, older adults and people with cardiac or respiratory conditions, like asthma, are most susceptible to health impacts from short-term exposures like fireworks smoke, according to the DNR.

Thursday night's air pollution was pretty typical for July 4 in Milwaukee, Verdin said. And this isn't a unique phenomenon. Detroit and Los Angeles, where wind and weather conditions caused the pollution to linger, had among the worst air quality in the country Friday morning following holiday celebrations.

Verdin believes personal fireworks displays, not city or county-sanctioned ones that crowds gather to watch, drove the spikes in air pollution. Sensors in some neighborhoods were recording air quality index spikes as early as 7 p.m. He said this style of fireworks became more common during the pandemic.

"We have this new culture of neighbor trying to one-up neighbor with their fireworks displays," Verdin said. "As a negative side effect, you're putting these dangerous pollutants in the air.

The DNR also notes that personal fireworks can produce more pollution because they concentrate smoke at the ground level, in contrast to sanctioned shows, which can usually shoot the fireworks higher and allow the smoke to clear before it reaches the ground.

To keep yourself safe this weekend and at future celebrations, Verdin recommended sticking to sanctioned fireworks shows, and if that's not possible, wearing a mask if you think your health may be affected. People in areas with lots of neighborhood fireworks should close their windows during that time, he added.

Though the fireworks-related hazardous air is temporary, Verdin said it's still a concern, particularly in a city where air pollution isn't experienced equally. A 2022 analysis from the environmental advocacy group Clean Wisconsin found that Wisconsin residents of color were exposed to 26% more dangerous particulate matter than the state average. That disparity was greatest in Milwaukee, where historic redlining policies pushed communities of color into more industrial areas of the city.

Madeline Heim is a Report for America corps reporter who writes about environmental issues in the Mississippi River watershed and across Wisconsin. Contact her at 920-996-7266 or mheim@gannett.com.