Serap Erdal paused at a light pole in Chicago’s Grant Park, took out her phone, and zoomed in on the screen. With skyscrapers towering against a clear blue sky behind her, she focused on her small city map, largely ignoring the bustle of buses, cars, and cyclists around her. She was analyzing the cool summer air.
Mounted on the pole above her was one of Chicago’s new solar-powered air quality monitors. This device, housed in a metallic silver case the size of a tissue box, is part of the largest community air quality monitoring network in the country. Currently, the network comprises 277 air monitors throughout Chicago, gathering air pollution data from every ward and community area, with a particular focus on neighborhoods already facing high pollution burdens.
A bright green dot appeared on Erdal’s phone, and she smiled.
“The air quality index here is 31 right now,” stated Erdal, a professor of environment and occupational health sciences at the University of Illinois Chicago. This reading places the park’s air quality in the Environmental Protection Agency’s safest category, indicating minimal health risk. “With clear skies and a breeze, the air quality is quite consistent across the city,” she noted.
On that June day, nearly all monitors in the city displayed green, except for one on the far South Side, where industrial facilities and freight traffic emit pollutants into nearby Black and Latino neighborhoods. In the future, the monitoring system aims to highlight significant air quality disparities across neighborhoods, even when conditions appear clear and breezy.
Tyler Pasciak LaRiviere / Chicago Sun-Times
The initiative, named Open Air Chicago, launched last fall and is part of a five-year effort to gather hyperlocal air quality data and offer Chicagoans real-time pollution information. The goal is also to aid officials in creating guidelines for permitting, urban planning, and air quality management. The network is now preparing for its first Chicago summer, a period when air pollution typically worsens. During summer, pollutants from vehicles and industries interact with sunlight and heat, creating ground-level ozone, a harmful pollutant and key smog component. As climate change extends and intensifies summers, smog conditions are becoming more prevalent.
The monitoring initiative began after a dispute over Chicago’s plan to move General Iron’s scrap-metal shredding operation from the predominantly white Lincoln Park to the mainly Latino and Black Southeast Side. In 2021, local environmental activists filed a civil rights complaint with the federal Department of Housing and Urban Development, claiming this relocation discriminated against low-income communities of color and harmed their health.
In 2023, the city and community groups reached a settlement that included establishing the community air monitoring network. Chicago officials collaborated with the University of Illinois Chicago to launch it last fall, with a combined expenditure of over $4 million to fund operations until early 2030.
“This air monitoring system is creating an ongoing record of what the air quality is in Chicago,” said Oscar Sanchez, the director of the Southeast Environmental Task Force, one of the groups that successfully filed the civil rights complaint.
Residents of the South and West Sides have had limited means to verify that their air quality is unsafe. Despite having higher rates of respiratory issues, they lacked time-stamped data to connect these health problems with air quality in the region. Sanchez noted that the monitoring system addresses this gap.
“This is Chicago working in good faith,” he said. “We’re here to ensure that there’s publicly available information so people are not gaslit about their experience.”
Each air monitor is situated less than a mile apart. The low-cost devices measure ground-level concentrations of two airborne pollutants: nitrogen dioxide, commonly produced by fossil fuel combustion, and PM2.5, which consists of tiny particles one-twentieth the width of a human hair, capable of entering the bloodstream through the respiratory system. Exposure to these pollutants is associated with childhood asthma and cardiovascular issues. PM2.5 is increasingly identified as the world’s primary environmental health factor, linked to acute mortality and morbidity related to respiratory and cardiovascular conditions.
While air quality has improved over recent decades, it can still reach unhealthy levels in summer when sunlight and warmth react with pollutants to create ground-level ozone. This seasonal smog can further degrade air quality when combined with smoke from more frequent wildfires. Daniel Horton, an assistant professor of Earth and planetary sciences at Northwestern University, said climate change is intensifying these conditions in 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 reliably turns Chicago’s summer skies into a hazy orange. In 2023, smoke from record-setting Canadian wildfires reached Chicago, elevating ground-level ozone levels by nearly 10 percent of the federal pollution limit, according to a study published earlier this year. The study also found that central, western, and southeastern neighborhoods in Chicago were most impacted by ozone.
So far, wildfires have already burned through 2.5 million acres nationwide, nearly doubling the 10-year average for this time of year. The recent increase in wildfires, partly linked to climate change, is reversing the country’s progress in improving air quality, according to a recent study published earlier this month in Science.
Between 2003 and 2015, stricter federal air quality regulations successfully reduced toxic gases that form ozone by approximately 11 percent. However, since 2015, rising ozone levels have reversed about one-third of the nation’s progress toward cleaner air, resulting in an increase of 318 premature deaths annually due to wildfire-related ozone since 2013.
As extreme heat reshapes air pollution in the Midwest and across the country, Horton said the Open Air Chicago network will be able to identify localized pollution hot spots, offering an “unprecedented look at the air quality landscape across the city.”
The local network is expected to build on top of existing data collected by NASA satellites and the EPA’s limited number of regulatory-grade air monitoring sensors, which Horton 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, although less precise, capture over 20,000 data points per day. The sheer volume of data is expected to yield major findings about how air quality changes across the city.
Carl Malings, an assistant research scientist at Morgan State University and NASA Goddard Space Flight Center, said the local data is especially important because, in many cases, satellites are capturing an aerial view that combines the messy interplay of particles and gases throughout the atmosphere’s layers, making it difficult to untangle what’s in the air people breathe near the surface of the Earth.
“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.
Tyler Pasciak LaRiviere / Chicago Sun-Times
Back in downtown Chicago, Erdal said the program is expected to run through 2029. City officials hope to keep the network online even longer. Over the noisy downtown traffic, she said the network is the culmination of two decades of citizen-based research with communities across the city’s West Side and Southeast Side. Previously, she worked on a project to monitor vehicle emissions in several of the city’s majority-Latino neighborhoods, which included helping local environmental justice activists install low-cost PurpleAir sensors.
Now her big 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.”
