Imagine a city in which the air we breathe was a subject of continued scrutiny, the way we think about weather or traffic today. You’d wake up, check the air quality, and know that your city was taking steps to keep it clean and breathable, even for those among us suffering from asthma or other chronic lung diseases. Eventually, we’d look to the culprits of air pollution—smog, industrial waste, car exhaust—and work to cut them down, for all our sake. What would that mean?

Jefferson University pulmonary specialist Gregory Kane has some ideas: There might be lower subway rates during high-risk days, to cut down on traffic pollution; school district-wide calls to keep students with asthma inside; alerts to environmental authorities when local industry is releasing pollutants into the air. Even what Kane, chair of Jefferson’s Department of Medicine, calls a “big hairy audacious goal:” A city of the future where traffic is limited because of bad air quality, like what happens already in Beijing.

Philadelphia, where some 22 percent of children suffer from asthma, is the third most challenging city to live in with the disease, according to the Asthma and Allergy Foundation of America. With some 35,000 Philly students with asthma, it is the most common reason for chronic absenteeism here and around the country, with the Environmental Protection Agency estimating 13 million asthma-related missed days every year. For adults, asthma flareups can mean missed work—and the paycheck that goes with it—expensive hospital visits, a series of piled-on health problems.

The reasons for Philly’s high rate are many, including old housing stock in (especially) poor neighborhoods which often contain triggers, poor access to health care, and rampant air pollution. These are all solvable problems. First, though, we need to understand them in more detail.

That’s what the city of Louisville, Kentucky, undertook a few years ago with AIRLouisville, a research project with medical device startup Propeller Health to track the incidences of asthma attacks among residents. That data, gathered over 30 months, gave the city an intimate look at when, where and who asthma attacks struck most. It started the city on a path to cleaning its air, to make a more livable city for everyone. And it revealed some information that could be relevant outside of Louisville, in cities across the country.

The project started with Propeller, which was founded in 2010 by David Van Sickle, a former medical anthropologist who had worked at the Centers for Disease Control and Prevention where he was continuously frustrated by the lack of progress on reducing asthma and its flareups, despite the effective medications on the market. Propeller, which launched in 2012, is a small smart device attached to an inhaler that tracks how often patients take daily prescribed medications and/or the rescue medications they take during an attack.

Philadelphia, where some 22 percent of children suffer from asthma, is the third most challenging city to live in with the disease. With some 35,000 Philly students with asthma, it is the most common reason for chronic absenteeism here and around the country.

Through an app accessible from a digital device, Propeller then merges the data with about 30 different environmental layers—weather, land use, climate—to understand where and when patients are having flareups, how well they are following their daily regimens, and when there are spikes in symptoms. In most cases, that information is available to both patients and doctors, so they can adjust lifestyles and medications as needed.

Propeller, based in Madison, Wisconsin, has since partnered with insurance companies, clinics, pharmaceutical companies and providers to get to as many patients as possible. Though there are other sensors out there—Vice President of Research Meredith Barrett says all inhalers will soon be connected to some sort of tracker—Propeller is largest in terms of users and commercial footprint.

Among its earliest partnerships, Propeller started working with Louisville—one of the worst cities in which to have asthma or chronic obstructive pulmonary disease (COPD)—as part of an effort by Mayor Greg Fischer, to solve the riddle of the city’s air quality. “He wanted to reposition Louisville as innovative, forward-thinking midsized city that is a good place for families and businesses,” Barrett says. “He saw this as not just a health issue, but as an economic vitality issue.”

With the help of a grant from the Robert Wood Johnson Foundation, AIRLouisville garnered 1,100 patients and 12 different partners, including city agencies like sustainability, innovation, transportation and planning. In addition to providing personal data for patients and their doctors, Propeller shared information on around 250,000 emergency inhaler uses to help the city develop a way to think about air and health—and how to improve both. In the end, Barrett says, the project had wider local and national implications than even they expected.

Tracking helped patients reduce their rescue inhaler use by 82 percent, and doubled their symptom-free days. More broadly in Louisville, Propeller found a significant connection between air pollutants, urban heat and asthma flare-ups, and mapped for the city the neighborhoods most at risk for asthma based on data, not just anecdotes, down to the census tract level. (Unsurprisingly, the most at risk neighborhoods—as is the case in Philly—were poor black communities close to industry.)

The study discovered that the air safety thresholds laid out by the EPA—and that industry followed—were insufficient. In fact, patients were having asthma attacks when the amount of pollution in the air was well below what was allowed.

Propeller then helped the city develop ideas around how best to affordably reduce that risk. As a result, Louisville—which had already budgeted for more tree planting—shifted its attention to greening up those neighborhoods, which also happened to have the fewest trees, to help clean the air. And, the city’s Transportation Department has set out to create a recommended truck route that would divert diesel trucks from those neighborhoods with highest asthma rates.

The study also discovered that the air safety thresholds laid out by the EPA—and that industry followed—were insufficient. In fact, patients were having asthma attacks when the amount of pollution in the air was well below what the EPA—and therefore local government—allowed. Propeller has since launched an asthma forecast, based on data from thousands of sufferers across the country, to help people know when conditions outside might aggravate their symptoms, and is hoping to influence EPA policy to change the national air quality standards. The information is also something Louisville officials, community and environmental activists are studying.

As word got out about AIRLousiville, Barrett says she started fielding calls from cities around the country—not including Philadelphia—and the company is excited to do another study, both for the sake of research and to grow their business. To do so, it needs a local partner—the city, a health system, clinics—to provide patients and parameters for a study. They also need to secure funding, which Barrett estimates in the hundreds of dollars per patient.

Jefferson’s Kane, who envisions all sorts of policy changes that could come as a result of a similar project here, is clear on one thing: Philly needs all the tools it can get to help asthma patients breathe better, more often. In particular, the city needs better and more support for patients in the hardest-hit neighborhoods, those that are poor and underrepresented in the medical field. He considers himself a good doctor, who is attentive to his patients and asks all the right questions: Are they able to work? Sleep? Exercise?

But Kane knows he is only as good as his patients’ memories. Sure, they might say they can work and sleep and exercise now; but do they remember to tell him about what happened two months ago? The week they couldn’t get off the couch, had to use their emergency inhaler several times a day? Perhaps, but likely not.“Maybe I’m missing things I don’t realize I’m missing from five months ago,” Kane says. “If I don’t know something, I can’t treat it.”

Propeller’s sensor would provide that data, to help him better manage his patients’ heath. But more than that, he says, the data, like in Louisville, could be used to answer questions not in the survey—about what’s happening to the air the rest of us breathe—and make real policy changes in a city that needs them, from something as simple as better education to planting trees to changing clinic hours to changing the way industries and individuals take care of the air.

“Imagine,” Kane says, “running wild with what you could do with the information you know about air quality and other factors.”