Jose Luis Salas has lived in Pacoima for 26 years. On certain windless days, he can see smoke hanging visibly in the streets. When he exercises outdoors, he struggles to breathe. The problem is no longer invisible to him, but until recently, it was largely invisible to the world outside his neighborhood.
Pacoima, a densely packed community of more than 81,000 people in Los Angeles's northeast San Fernando Valley, sits in what amounts to a pollution trap. Hemmed in by Interstate 5, Highway 118, and Interstate 210, the neighborhood also hosts a regional airport, auto-dismantlers, landfills, factories, and a rail line cutting through the middle. The California environmental protection agency has designated it one of the state's most environmentally burdened communities. Nearly 9% of residents have asthma.
Yet for years, the closest official air quality monitor used for regulatory purposes was miles away, capturing almost nothing about what residents actually breathed at street level.
That dynamic is shifting. Pacoima Beautiful, a local environmental group founded in 1996 by five mothers concerned about industrial pollution near their children's school route, is now running a hyperlocal air quality monitoring program that transforms what was invisible into data.
In 2025, the organization installed six Aeroqual sensors across the neighborhood. These white boxes, about the size of a shoebox and covered with wires and instruments, sit on house rooftops, business buildings, and playgrounds. They measure PM2.5, PM10, ozone, nitrogen dioxide, temperature, and humidity. Every few minutes, their readings stream to a public dashboard. The results confirm what residents suspected: the air quality in Pacoima is routinely worse than in neighborhoods just miles away.
The monitoring effort extends beyond stationary sensors. From 2020 to 2025, Pacoima Beautiful ran a summer program called Air Ambassadors, where residents clipped palm-sized AirBeam monitors to their clothing and walked their neighborhoods, logging real-time air quality snapshots tied to specific locations. The organization also deployed Purple Air monitors on community buildings and homes starting in 2019.
Amanda Ortega, a Los Angeles USD teacher, participated in the Air Ambassadors program in summer 2025. She walked the paths her students take to school, watching the air quality readings spike and dip. She noticed the worst pollution clustered in lower-income neighborhoods. When she approached San Fernando Road near the freeway, the numbers stopped her in her tracks. "I thought: Whoa. This is bad," she said. Many of her students have asthma.
The sensors reveal a grim reality. Pacoima sees more than 500 trucks passing through each day, along with more than 100,000 cars on each freeway. A 2023 study by California State University, Northridge students tallied more than 200 trucks in just the first two and a half hours of the morning. These vehicles release diesel exhaust, particulates, and volatile compounds that increase the risk of asthma, respiratory disease, and heart issues, particularly for older residents and young children.
Salas, whose house hosts one of the Aeroqual sensors, says the data has shifted his concern. The highest pollution readings he sees cluster near the freeway areas where heavy trucks carrying materials rumble constantly. "Those freeways are right inside the city of Pacoima," he noted.
The power of this hyperlocal data extends beyond awareness. In Sonoma County during the 2020 wildfires, researchers compared air quality readings from the EPA's official AirNow system with data from 359 PurpleAir monitors. They discovered that a widespread belief about safety at night was false. Nighttime air quality was sometimes worse than daytime. Armed with this evidence, farmworkers could make informed decisions about when to work in the fields. Two major wineries subsequently guaranteed hazard pay whenever air quality from wildfire smoke reached unhealthy levels.
Michael Mendez, a UC Irvine professor who led that research, grew up in Pacoima. He watched his friends and relatives struggle with respiratory diseases and asthma. "The town is a bowl that traps in hazardous pollutants," he said. He also pointed out that even California's air quality system, often considered a national leader, relies on an antiquated network that captures only certain pollutants. Official monitors focus on smog precursors and PM2.5 but miss heavy metals and volatile organic compounds, especially important after wildfires.
As the climate warms, air quality is expected to worsen. Los Angeles is predicted to experience an average of 22 extreme heat days annually by 2050, compared to six per year between 1980 and 2000. Heat traps polluted air in place, concentrating it near the ground where people breathe.
Pacoima Beautiful is now advocating for a broader network of official AQI sensors across the entire northeast San Fernando Valley. The organization recognizes that data in the hands of residents becomes a tool for advocacy. "They can come to the city saying: Look at our levels. Our levels are much higher than everywhere else. Do something about it," said Paloma Giottonini, an urban planning professor at California State University, Northridge.
The organization has also pursued other climate projects simultaneously. The city has covered more than 700,000 square feet of roads, school playgrounds, and parking lots with reflective, light-colored epoxy coatings designed to lower street temperatures. A 2020 study found such coatings decreased pavement temperatures by up to 10 degrees Fahrenheit. Residents have planted edible fruits and vegetables on a sidewalk garden that once suffered from illegal dumping.
For communities like Pacoima, low-cost sensors are reshaping who can access environmental data and who can act on it. In Washington state's Methow Valley, where steep geography traps seasonal wildfire smoke near the ground, a network of 35 PurpleAir sensors now monitors air quality across approximately 180 miles. Residents check the air like the weather, aware that hazardous conditions could arrive at any moment.
"Sensors are incredible for making previously invisible places visible," said Liz Walker, a University of Washington professor and air quality consultant who helped build that network. "You have an actual record of the air quality numbers that matches up with a health standard established by a federal agency."
Back in Pacoima, Salas watches his sensor transmit its readings to the world. The box on the side of his house is no longer just his problem anymore. It is documentation, evidence, and a voice for a neighborhood that has struggled to be heard.
Author James Rodriguez: "Community-grade sensors are transforming environmental justice from a moral argument into a mathematical one, and that data matters far more than any politician's empty promise."
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