The city of Philadelphia recently installed over 70 new air quality monitors and a public dashboard that displays hourly air quality readings as part of a new citywide health initiative.
The Breathe Philly project adds to the 10 existing monitoring stations in the city, providing residents with real-time access to an array of air quality metrics. Under the new system, all city residents will be within 1.5 miles of a sensor, which Penn researchers say has significant implications for their research and the Philadelphia community as a whole.
According to a Philadelphia Department of Public Health spokesperson, the initiative is designed to help residents, especially those with chronic conditions like asthma, make “informed decisions” to protect their health.
“The Breathe Philly network gives Philadelphians the information they need to decide if now is a good time to head to the park or if they should take extra precautions,” the spokesperson wrote.
They added that the existing monitors only provided an “overall sense” of the city’s air quality, which is less useful on a day-to-day basis.
“The Health Department has been monitoring air quality in Philadelphia for decades,” the statement read. “For most of the history of that effort, monitoring has taken place at EPA-located monitors that have favored placement in areas that have lots of pollution, like next to highways or in industrial areas.”
Only monitoring air quality at federally mandated locations posed challenges for researchers such as Penn lecturer Thomas McKeon and Perelman School of Medicine professor Wei-Ting Hwang.
“How [the monitors] are distributed across the state is not for health assessments, but for compliance with the Clean Air Act,” McKeon said in an interview with The Daily Pennsylvanian. “When I look for air quality information or any public health data, there are more optimal places to have air monitors.”
Hwang explained that the new monitors will serve as “preliminary data” for her research, which focuses on the effects of environmental exposure on lung cancer.
“One of the limitations I run into often is that I don’t have very granular data to really zoom in on the health outcome data,” Hwang told the DP. “So when I do a clustering or hotspot analysis … I don't have enough data to actually pinpoint a smaller area. Now I may have it.”
The project — which the City of Philadelphia described as a “first-in-the-nation” initiative — comes after a 2025 American Lung Association report gave the city “a failing grade for pollution levels.”
McKeon — who studies how lifelong exposure to environmental hazards affects cancer risk — attributed this poor air quality to several factors, including urbanization and industrial activity in the area.
“We generally found that along the I-95, the zip codes along those areas between Delaware and Philadelphia had higher risk and higher exposure to lung carcinogens,” McKeon said.
The Breathe Philly sensors measure two “common” pollutants, nitrogen dioxide and particulate matter 2.5 micrometers or less in diameter.
“PM2.5 is a particularly good starting point because of its size,” Medical School professor and Director of the Center of Excellence in Environmental Toxicology Trevor Penning told the DP. “It can go deep into the lung and penetrate the alveoli, which are the air sacs, and can actually transit into systemic circulation.”
He explained that PM2.5 contains a “carbonaceous core,” which can attach to other compounds.
“What we’re really concerned about are the volatile organic compounds — compounds like benzene, acrolein, butadiene — which will evaporate unless collected appropriately,” he added.
Penning hopes that eventually, location-dependent air quality can be integrated into electronic health records and act as a “flag” for clinicians to follow up with certain patient groups, such as children with asthma.
According to a press release, the City Health Department will also use the data collected by the program to help “identify localized pollution patterns, inform enforcement actions, and shape evidence-based environmental policies.”
“As we build a database of information from throughout the city, we'll be able to see smaller, long-term differences between neighborhoods and can work to investigate why those differences persist and potentially address them through regulation,” a Philadelphia Department of Public Health spokesperson wrote.
