Byron Keys always looks forward to the Detroit Jazz Festival on Labor Day weekend. But this year, he wasn’t sure he’d actually be able to attend until the very last minute. What was he waiting on? Air quality. 

“I checked first,” Keys said. “I don’t want to have an asthmatic episode down there.” (Editor’s note: Byron Keys is a member of our Detroit Documenters network.)

A close-up of a smiling man with a beard and a black hat with a yellow logo.
Byron Keys regularly checks the air quality in Detroit using his phone since being diagnosed with asthma three years ago. Photo credit: Photo courtesy of Byron Keys

Keys has learned to look at air quality data on his phone before leaving the house like some people check the weather. Asthma can make breathing a struggle for him even on a clear day, but he’s especially careful when the air is heavily polluted. If it’s smoggy, he tends to stay home.

About 1 in 6 Detroiters have asthma and already understand the power of knowing what we’re breathing in. This summer, when smoke from Canadian wildfires caused some of the worst air quality ever recorded in the city, the rest of the city learned, too.

But the topic is still hazy for many folks. How do we know what’s in the air? How reliable is the data? 

There’s a lot we know — and much we don’t — about the air Detroiters breathe. Here’s a guide to the basics.

So how’s the air, anyway?

Poor air quality in Detroit is still a problem, but in the last two decades air quality has gotten a lot better.

Wayne County received an F for air quality on this year’s State of the Air report from the American Lung Association.

Detroit still ranks as the fifth-worst city in the country for people with asthma in a report released this month by the Asthma and Allergy Foundation of America. The report also pegged Detroit as having the second-highest rate of asthma in the country.

Air quality often plays a central role in battles against asthma and environmental racism in Detroit. Plenty of industrial facilities in the city are just feet away from people’s homes. Advocates in these places draw a direct line from air pollution to poor health.

Air pollution was linked to an estimated 2,200 deaths in Michigan in 2019, largely through cancer, heart disease and respiratory illnesses. The state’s roughly 23 deaths per 100,000 people that year were more than the national rate of 18.

Still, the air in Detroit used to be much worse.

“There have been remarkable changes,” Stuart Batterman, a professor of environmental sciences at the University of Michigan who studies air quality, said. The air quality has “gotten a lot better” compared to 20 years ago, though some pollutants are still at problematic levels.

Between 2000 and 2017, the level of fine particulate matter, or PM2.5, detected in Wayne County fell by 50%, according to a study co-authored by Batterman and published this year. The declines for some other kinds of pollutants were even larger. Deaths in Michigan linked to air pollution fell by nearly 50%, during the same period.

The improvements are likely tied to stricter emissions standards for cars and trucks, the closure of coal plants and increased industry regulation, Batterman said.

The gains, though, are being eroded by wildfire smoke that is becoming more common as the global climate warms. A study published this month in Nature, a weekly science journal,  estimated that wildfire smoke eliminated 25% of all U.S. air quality improvements from 2000-16.

What do we mean by ‘air quality?’

Broadly, high-quality air is healthy air. Does breathing the air outside right now increase your chances of an asthma episode or heart attack? If you breathe the air for decades, does it increase your chance of getting cancer or a respiratory disease? If so, the air quality is poor.

Federal law puts limits on airborne quantities of six pollutants: particulate matter (including smoke and dust), ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide and lead.

Detroit is under the limit for all those pollutants except sulfur dioxide, which remains above legal levels in an industrial zone of southwest Detroit.

Air quality reports generally use a measurement known as the Air Quality Index (AQI), which is formulated to communicate the health implications of current amounts of air pollution. For instance, an AQI of 125 for particulate matter means that, according to the Environmental Protection Agency (EPA), “members of sensitive groups may experience health effects. The general public is less likely to be affected.”

Air quality is a very local phenomenon. There are legitimate concerns about the average air quality in Detroit, but don’t sleep on the ways the air varies between neighborhoods and even between streets in the same area. Industrial facilities, major roads, truck traffic and tree cover all have an especially large impact on the air in their immediate areas.

Where is air pollution coming from?

Unless you live right next to a factory, the main source of pollution you’re likely to experience is from cars, trucks and construction equipment. Those sources accounted for about one-third of all PM2.5 pollution in the city between 2016 and 2021.

“In most cities, the major sources are transportation,” said Batterman.

Chemicals released by coal-fired power plants, trains, and ships were also a major source of air pollution in Detroit between 2016 and 2021, though this kind of pollution has declined sharply in recent decades. Dust and road salt kicked up from roads also contribute to poor air quality in the city.

Regulatory air quality monitors: Meet the gold standard 

There are seven stations in Detroit and many more sensors that measure air quality. 

Regulatory air monitors are high-end machines that meet EPA requirements and are used by regulators to determine compliance with the Clean Air Act. A station capable of measuring three pollutants can cost $200,000, said Susan Kilmer, an air monitoring manager at the Michigan Department of Environment, Great Lakes and Energy. Trained technicians have to maintain and calibrate the monitors to make sure they work and comply with federal rules.

Data from an air monitoring station is the only data that can be used to enforce federal air quality laws. If regulators are going to fine a company for pollution or declare excessively high air pollution, they start with official air monitoring data.

Community air sensors: More accessible, less reliable

Air sensors are much cheaper than state-operated monitors and often measure the same pollutants. A sensor that detects dust goes for as little as $300.

Some sensors work better than others; even the most effective ones have their issues. They stop working after a while without maintenance — think six months at best — and maintaining cheaper models may not be feasible. 

Because air sensors are relatively cheap, they’re popular among advocates and citizen scientists who want to know more about air quality in a particular neighborhood. A plan to bring more air quality data to Wayne County relies on putting many more sensors in the community on the theory that more information about neighborhood conditions will spur action by residents and local government officials.

Where are the air monitors?

Many air quality websites allow users to view the air quality in a zip code or address, but these figures are usually just estimates. That’s because most people in the city don’t live very close to an air monitoring station.

Most air quality monitors are concentrated at the southwestern tip of the city in a heavy industrial zone that includes Marathon’s Detroit Refinery.

One is on East 7 Mile Road, a couple of miles north of the city airport. Two more are located on the city’s west side — one at the center of Rouge Park and another in Eliza Howell Park just feet away from I-96.

How does my phone calculate the air quality near me?

Byron Keys lives on the east side, close to the river and about five miles from the nearest state-run regulatory air quality monitoring station. Yet he can check his phone and get an update on the air quality at his address.

Keys uses, a website the EPA runs that relies exclusively on information from official air monitoring stations. Type your zip code into the site’s search bar, and it will give you the air quality reading at the nearest site. Pull up a map, and it will show you the estimated air quality for your exact location based on average readings around you.

Keys doesn’t live very close to major polluters or freeways, and he says the EPA data typically matches his experience of the air. But the numbers can be less helpful if you live near a major source of pollution, such as a manufacturing plant, oil refinery or busy road.

In that case, you’re better off looking up “fenceline” data for the neighborhood polluter — data from a monitor placed right next to the factory or smokestack as a condition of the facility’s permit, though the information isn’t always available or easy to access. You can get it for the Marathon refinery, for example, but not the controversial hazardous waste facility US Ecology.

Other sites, such as BreezoMeter, a subsidiary of Google, say they give more accurate local air quality readings using additional data sources such as air sensors, traffic (which produces pollution), road proximity and wind forecasts.

Keys said he hopes the city’s air quality improves, but he’s making do and wouldn’t want to live anywhere else.

“I grew up here, he said. “I don’t want to leave.”

He keeps air filters running at home and keeps an eye on his air quality app. After a tough summer, he lucked into fairly clear air the weekend of the Jazz Festival and headed downtown to hear South African pianist Nduduzo Makhathini.

“His set was fierce,” Keys said.

This piece is part of a series on Detroit’s air pollution and the role of air quality monitoring in community advocacy, in partnership with Planet Detroit and the Ecology Center.

Koby (he/him) believes that love drives people to fight for their communities, and that curiosity is food for love. He enjoys the many moods of the Detroit River.