Chicago’s air map began after a civil rights complaint

After a civil rights complaint argued Chicago’s move of a scrap-metal shredding operation would harm Black and Latino neighborhoods, the city helped launch Open Air Chicago—now the nation’s largest community air monitoring network. With 277 solar-powered monit

On a sunny day in June, Serap Erdal stopped at a light pole in Chicago’s Grant Park, pulled out her phone, and zoomed in on a palm-sized map of the city. Above her, towering skyscrapers cut into a blue sky as buses, cars, and cyclists kept flowing through downtown.

Fixed to the pole above her was one of Chicago’s new solar-powered air quality monitors. The device—encased in a metallic silver shell about the size of a tissue box—was quietly doing its job, sending data to a map meant to make the invisible visible.

“Currently, the air quality index at this location is 31,” Erdal said. The number places the air in the city’s public park in the Environmental Protection Agency’s safest category. meaning it poses little to no risk to public health. Because the day was clear and breezy, she added, concentrations across the city were “quite uniform.”.

But even on that kind of day. the map hinted at what the project was designed to settle: not whether pollution exists. but who has to live with it. Almost all of the city’s monitors showed green. except for one on the far South Side. where legacy industrial facilities and freight traffic pump emissions into nearby Black and Latino neighborhoods. In the coming years. the monitoring system is expected to lay out just how uneven air quality can be across different neighborhoods—sometimes even when the weather looks favorable.

The network behind that map is called Open Air Chicago. It went live last fall as part of a five-year effort to collect hyperlocal air quality data and provide Chicagoans with real-time pollution information. The information is also intended to help officials develop guidance for permitting, urban planning, and air quality control.

As the project heads toward its first Chicago summer—when air pollution typically worsens—it arrives at a moment when the chemistry of smog is becoming harder to outrun. Pollution from cars. heavy vehicles. and industry reacts with sunlight and heat to form ground-level ozone. described as a harmful pollutant and the key ingredient in smog. With climate change making summers longer and hotter, conditions for smog formation are also becoming more common.

Open Air Chicago’s origins trace to a different fight—one rooted in where pollution was allowed to be located.

In 2021, local environmental activists filed a civil rights complaint with the federal Department of Housing and Urban Development. The complaint challenged the city’s decision to relocate General Iron’s scrap-metal shredding operation from Lincoln Park—described as a mostly white neighborhood—to the predominantly Latino and Black Southeast Side. The activists argued that the move discriminated against low-income communities of color and harmed their health.

The city and the community groups reached a settlement in 2023. That settlement included launching the community air monitoring network. Chicago officials partnered with the University of Illinois Chicago to launch the system last fall at a combined cost of over $4 million to cover operations through the beginning of 2030.

Oscar Sanchez, the director of the Southeast Environmental Task Force and one of the groups that filed the civil rights complaint, framed the point of the network in plain terms. “This air monitoring system is creating an ongoing record of what the air quality is in Chicago.”

For South and West Side residents, the gap before Open Air Chicago was not only pollution risk, but verification. Sanchez said people had limited ways to corroborate that their air was unsafe. even as they experienced higher rates of respiratory issues. They often lacked time-stamped data needed to connect health outcomes to regional air quality.

The monitoring system, he said, changes that. “This is Chicago working in good faith,” Sanchez said. “We’re here to ensure that there’s publicly available information so people are not gaslit about their experience.”

Open Air Chicago now has 277 air monitors across Chicago, collecting air pollution data from every ward and community area. The network includes an increased concentration in already-overburdened neighborhoods. Each air monitor sits less than a mile from the next.

The equipment measures ground concentrations of two airborne pollutants: nitrogen dioxide. typically formed by the combustion of fossil fuels. and PM2.5. PM2.5 consists of small particles just one-twentieth the width of a single human hair. capable of passing through a person’s respiratory system and entering the bloodstream. Exposure to both pollutants is linked to childhood asthma and cardiovascular issues. and PM2.5 is increasingly singled out as a leading environmental health-determining factor. associated with acute mortality and morbidity for respiratory and cardiovascular health outcomes.

While air quality has improved in recent decades, summer still brings a familiar threat. The seasonal smog described in Chicago’s air chemistry can worsen when it mixes with smoke from increasingly frequent wildfires.

Daniel Horton. an assistant professor of Earth and planetary sciences at Northwestern University. pointed to climate change as a factor that is tightening the grip of these conditions across the Midwest. “We also have to deal with the consequences of increased frequency and intensity of wildfires,” Horton said. “That’s a problem that doesn’t necessarily occur in our backyards. but when the wind blows in the right direction. we suffer the consequences in the Midwest.”.

Wildfire smoke, in other words, doesn’t ask permission. In 2023. smoke from record-setting Canadian wildfires reached Chicago and raised ground-level ozone levels by nearly 10 percent of the federal pollution limit. according to a study published earlier this year. The study found central, western, and southeastern neighborhoods in Chicago were most impacted by ozone.

Wildfires are burning at a scale that is reshaping air quality trends nationwide. So far, wildfires have already burned through 2.5 million acres nationwide—nearly double the 10-year average for this time of year. A recent study published earlier this month in Science reported that this surge in wildfires. tied in part to climate change. is reversing steady progress toward improving air quality. The study found that between 2003 and 2015. stricter federal air quality rules cut down the toxic gases that form ozone by approximately 11 percent. Since 2015. however. rising ozone levels have undone about a third of the nation’s headway toward cleaner air. translating to an increase of 318 premature deaths per year from wildfire-related ozone since 2013.

Back in downtown Chicago, Erdal talked about what Open Air Chicago can do as those summer conditions arrive. The network is expected to run through 2029, and city officials hope to keep it online even longer. For her. the project is also a culmination of two decades of citizen-based research with communities across the city’s West Side and Southeast Side.

Previously, Erdal worked on a project to monitor vehicle emissions in several majority-Latino neighborhoods. That work included helping local environmental justice activists install low-cost PurpleAir sensors.

Now. she said. her goal is that the data collected over the next five years can help craft a roadmap for city officials and community leaders to cut down Chicagoans’ exposure to unsafe air. “We hope we’ll strengthen the network in the future,” Erdal said. “Measuring more pollutants and providing more data to the public.”.

The promise of the system is tied to what it can reveal—especially when other measurement tools struggle to separate what’s happening near the surface from what’s happening overhead. Horton described the network as an add-on to existing data collected by NASA satellites and the Environmental Protection Agency’s limited number of regulatory-grade air monitoring sensors. called the “gold standard.” While the EPA’s more sophisticated monitoring devices provide precise measurements of pollutants like PM2.5 and nitrogen dioxide. they are also more expensive to maintain. Chicago’s low-cost sensors, though less precise, are able to capture over 20,000 data points per day. The sheer volume of information is expected to produce major findings about how air quality shifts across the city.

Carl Malings. an assistant research scientist at Morgan State University and NASA Goddard Space Flight Center. described a key challenge of satellite observations. He said satellites can capture an aerial view that combines the interplay of particles and gases throughout the atmosphere’s layers. making it difficult to untangle what’s actually in the air people breathe near the surface.

“If you see a smoke plume from satellite data in the absence of other information, it could be hard to say, Is that smoke actually reaching down to the surface, where it’s impacting air quality and people’s health, or is it rising a little bit above the surface and passing overhead?” Malings said.

All of these pieces—the civil rights complaint, the settlement, the monitors clustered in overburdened neighborhoods, and the technical limits of older data—connect back to the same need: time-stamped, neighborhood-scale evidence.

On the phone in Erdal’s hand, the map flashed green. The air at that exact spot looked safe. But elsewhere in Chicago, a single point on the same map showed the city’s uneven reality—one that Open Air Chicago was built to measure, track, and, eventually, use.

Open Air Chicago air quality monitoring civil rights complaint Chicago PM2.5 nitrogen dioxide ozone ground-level ozone smog wildfire smoke EPA PurpleAir University of Illinois Chicago