When Jailene Ochoa’s family moved in 2017 from suburban Cicero to Gage Park in Chicago’s Southwest side, she could feel a difference in the air.
“You can smell the air, obviously, and it smells like you’re breathing in something dirty,” she said.
But Ochoa, an economics major at Roosevelt University, said she doesn’t have the same problem on her school’s campus in the Loop.
“It’s nine miles that I travel. You see such a difference,” she said. “And then when you’re further to the North Side, those people do have environmental issues, but it’s such a significant difference.”
While environmental catastrophes like Canada’s wildfires this year made Chicago’s air the worst air in the world for a few hours, everyday air pollution remains a constant health threat in some parts of the city–especially industrial corridors. Chicago’s communities of color are consistently impacted by air pollution at higher rates, contributing to racial disparities in health risks.
A 2025 zoning and land use assessment from Chicago’s Metropolitan Planning Council found that Chicagoans of Latin descent face elevated air pollution; an estimated 50 percent of the population living in areas with the most air pollution from fine particulate matter are Latino, compared to only 30 percent of the city’s overall population.
These findings are consistent with a 2022 investigation conducted by the Department of Housing and Urban Development (HUD). In a letter sent to the city, the department said it found Chicago had a “broader policy of constraining industrial and other polluting land uses to majority Black and Hispanic areas and relocating polluting facilities from predominantly White areas.”
To avoid having millions in federal funding withheld, the city entered a voluntary compliance agreement with HUD and three environmental groups. The agreement outlined steps for the city to take to address environmental inequities, including enhanced monitoring of neighborhood-level air pollution.
To meet the agreement requirements, the city is installing 277 Clarity air sensors around the city. In August HUD announced it would no longer track the city’s compliance with the agreement, but officials are installing the network anyway.
Locations for the sensors are being selected in collaboration with environmental groups, some of whom are also putting up their own PurpleAir sensors. Despite some tensions over how the Clarity sensors will be used, advocates hope the influx of detailed air quality information will lead to meaningful change.
So far, the city has installed 189 of the air sensors it plans to use in the system. The solar-powered Clarity Node-S sensors are being placed on city light posts and can measure nitrogen dioxide and fine particulate matter, or PM 2.5. While the city technically meets EPA standards for PM 2.5, the American Lung Association’s most recent State of the Air report determined the Chicago metropolitan area was 13th worst in the nation for long-term PM 2.5 exposure.
Transportation is a key source of particulate matter pollution in Chicago. Vehicles transporting materials to and from manufacturing facilities contribute additional PM 2.5 to what’s emitted from the facilities themselves.
Medium and heavy-duty road vehicles are a particular problem. Despite being only 7% of road-traveling vehicles in Illinois, these trucks and buses account for nearly 60% of all PM 2.5 pollution emitted from on-road vehicles.
It’s not just cars, though. A quarter of all freight trains in the U.S. pass through the Chicago metropolitan area. Ochoa sees their effects firsthand.
“Right near my house, I have the train tracks. It’s not the CTA, it’s the cargo ones. And also by my house there’s the cargo trucks. They’re on the roads and all this diesel, you could just smell it. It’s terrible,” she said.
Freight cars sit in a Norfolk Southern intermodal facility in Chicago on August 20, 2025. Hundreds of thousands of freight trains pass through the city annually.
However, manufacturers aren’t randomly scattered throughout the city. Zoning policies, or rules that govern land use in the city, constrain them to industrial corridors. Unsurprisingly, these areas have higher average levels of cumulative pollution.
They also have an outsized presence in Black and Latino neighborhoods. According to research by the Metropolitan Planning Council, in areas where most Black and Latino Chicagoans live, 23% and 29% of the land is zoned for manufacturing, respectively. For comparison, 6% of land is zoned for manufacturing in places with the highest concentrations of white Chicagoans.
“Sometimes I can’t help but look around and I’m not jealous, but kind of annoyed, maybe a little bit angry, because there’s such a huge difference,” Ochoa said. “It feels like it’s because there’s more money, there’s not as many people of color there.”
There were already eight air monitors placed around the city before the start of the new system. These monitors, maintained by the state and federal Environmental Protection Agency and the Cook County Department of Environment and Sustainability, assess air quality around the city for fine particulate matter and other pollutants.
However, Victoria Lang, a Ph.D. candidate in Northwestern University’s Department of Earth, Environmental and Planetary Sciences who studies air pollution, said the eight sensors can’t capture hyper-specific differences in Chicago’s air.
“If you look within a city block, PM might actually change five to eight times,” Lang said. “We don’t have data sets that can capture that very localized hot spots.”
“The Chicago Air Sensor Network is a public infrastructure investment to increase the concentration of air sensors throughout the city,” the city said in an email statement. “When operational, it will provide neighborhood-level air quality data to the public, supplementing the air monitoring data that is currently accessible on AirNow.gov from federal-grade monitoring systems.”
A Clarity air sensor attached to a lightpole in Chicago assesses the air for PM 2.5 pollution on August 23, 2025.
Pilsen Environmental Rights and Reform Organization, or PERRO, is one of the groups working with the city to determine where the sensors will be placed. Citlalli Trujillo, the president of PERRO’s board, said her experience working with the city was largely positive.
“They were very open to hearing our feedback and thoughts and took very thorough notes about our reasonings for selecting each sensor site,” she said.
To determine a sensor’s location, the PERRO representatives were given three options on a street where it could go. After reviewing maps with information about traffic, historic PM 2.5 emissions and nearby vulnerable populations like children and the elderly, the PERRO ranked the three choices for each spot.
“It was a little disappointing that we couldn’t select the locations in the neighborhood based off our knowledge of the neighborhood,” Trujillo said. “But they’ve used their own data and scientific requirements to place these sensors in a grid that evenly distributes these sensors . . . of course they’re more qualified to do that.”
Trujillo said city officials made it clear that the new system could be used for informational purposes, but not regulatory ones. While special care is being taken to ensure that the sensors are installed in the most scientifically rigorous manner possible, the Clarity sensors aren’t the same as the EPA sensors, which are considered the gold standard in air monitoring.
The Clarity system can’t be used to bring legal action against a polluting business, but it can still inform policy. The HUD agreement that prompted its installation says the data it generates can be used to improve enforcement of environmental regulations, develop policies to address air pollution and inform the placement of regulatory monitors.
Jocelyn Vazquez, the community science organizer at the Little Village Environmental Justice Organization (LVEJO) said she hopes the data will inspire city interventions like emergency alerts or increased health resources for schools.
“Something that I hope to see from the city with this network is that, regardless of the fact that it’s not for regulatory purposes, that they’ll still use the data to push us forward, to move us in a better direction,” Trujillo said.
An N4EJ representative holds an example PurpleAir outdoor monitor at an informational table on August 8, 2025. The organization is currently recruiting volunteers to host the monitors at or near their homes.
Anthony Moser, a founding member of environmental group Neighbors for Environmental Justice (N4EJ), had a different perspective.
“The city knows that [air pollution is] a problem,” he said. “More data is only the solution if the problem is not knowing what’s happening.”
In addition to collaborating with the city, N4EJ plans to install a set of indoor and outdoor PurpleAir sensors in September to close any gaps the Clarity system might miss. This effort is part of a study coordinated by the University of Illinois in Chicago’s school of public health. PERRO and four other environmental community groups also received funding to put up their own PurpleAir sensors, and are in the process of recruiting hosts for them.
Lang said additional data from these smaller networks will complement the city’s monitoring. No pollution detection technology is perfect, and having multiple layers of data can help researchers identify areas where different sensors agree – or disagree – pollution is worse.
While installing more local air sensors will add more data for experts to work with and better understand air quality in the neighborhood, Moser said that’s not the point for N4EJ.
“Our goal is to use this as a tool of community engagement, to help people understand that something which is invisible, but around them all the time, is still very real and very tangible in some ways, and that it has serious impacts on them,” he said.
Vazquez said she’s thinking about using some portable air sensors LVEJO has in combination with the PurpleAir sensors to zero in on sources of particulate matter pollution. LVEJO sometimes conducts mobile air monitoring with these sensors during regular cleanups at Douglass Park.
Moser said community engagement efforts can create change by helping people understand why industry exists where it does in Chicago. This information, he said, would empower people to advocate for themselves.
“It isn’t an accident,” he said. “It is a series of choices, and those choices could be different.”
Though the Clarity system is still incomplete, it’s already sparking change. Sonia Monet Saxon, N4EJ’s air monitoring program lead, said meetings with the city inspired collaborations with PERRO and LVEJO to unpack pollution problems unique to the Southwest Side.
“We’re building ways to work together that didn’t exist in the past,” they said. “And that alone is very meaningful and powerful.”