On days when wildfire smoke is bad, it looks like Chicago is covered in fog. The iconic city skyline disappears in a hazy sea of grays and blues. It’s hard to even see buildings a couple of blocks away.
This smoke doesn’t just give the city a spooky atmosphere. It brings in fine particulates–microscopic pieces of soot that create a foggy effect.
Although it’s easy to see how poor the air quality is during wildfire season, it’s not the only time particulate matter pollutes Chicago’s air. The American Lung Association ranked the city 13th in the country for long-term exposure to fine particulate matter, which includes year-round industrial emissions and vehicle exhaust.
The tiny particles can have a big effect on health. A report by the Respiratory Health Association estimated diesel exhaust alone would cause over 2,500 asthma attacks and cases of upper respiratory illness in Cook County in 2023.
What is fine particulate matter?
Unlike pollutants like nitrogen dioxide, particulate matter isn’t a single chemical – it can take the form of any solid or liquid particle that’s floating in the air. Particulate matter can be natural, like pollen or bits of dirt, or man-made, like diesel exhaust or complex pollutants from power plants.
Because particulate matter can be so many different things, scientists track it by size instead of type. Fine particulates are 2.5 microns across or less, which is why they’re sometimes called PM 2.5. For comparison, that’s about 30 times smaller than the width of a human hair.
Why is fine particulate matter bad for your health?
The human body is equipped with natural defenses to block harmful substances from entering. The mucus in your nose, throat and airways captures chunky particles you inhale, like pet dander and dust. But fine particulate matter is so small it can slip through your body’s defense system.
“Fine particles that are made out of carbon kind of look like asteroids or bits of English muffin, all these nooks and crannies,” said Urbaszewski. “Metals and hydrocarbons, some of which are toxic, can hide on those particles, so they’re this magical delivery device that gets deep into the body and delivers all this other junk.”
The tiny specks that make it past can carry harmful chemicals deep into your lungs or even your bloodstream. Scientists are still working to understand the many different ways exactly how PM 2.5 affects health, but studies have found connections to heart and lung diseases, dementia and even premature birth.
Any exposure to particulate matter is harmful, but the length of time matters. Short-term exposure to PM 2.5 can cause asthma attacks and is linked to heart attacks. But according to the EPA, long-term exposure can lead to reduced lung function and premature death.
Who does particulate matter pollution in Chicago affect?
Poor air quality is bad for everybody, but it’s more dangerous for some groups than others. EPA research shows children, older adults, pregnant people and people with heart or lung conditions are especially vulnerable to the health impacts of air pollution.
Physical factors can affect how well someone’s body can fight air pollution, but socioeconomic factors can affect how likely someone is to experience air pollution. People of color are disproportionately exposed to PM 2.5 across the country, in part due to practices like historic redlining that bring polluting industries to neighborhoods of color.
This pattern is consistent in Chicago. The Metropolitan Planning Council’s Zoning and Land Use Assessment found PM 2.5 disproportionately impacts Latinx people in the city. Latinx Chicagoans are 30 percent of the city’s total population but 50 percent of residents in areas with the highest concentrations of fine particulate pollution.
How can I protect myself from fine particulate matter pollution?
The best way to protect yourself from PM 2.5 pollution is to avoid it when possible. Airnow.gov has daily air quality forecasts that can be used before Chicago’s air sensor network dashboard is available.
It’s important to stay indoors as much as possible on days when the air quality is poor. Keep doors and windows closed, and consider using an air filter to keep indoor air clean. On hot summer days with air pollution spikes, it’s important to keep out pollution without overheating or becoming dehydrated in a sweltering home. Running an air conditioner or going to a cool space like a library or community center, as well as drinking extra liquids, can help to ensure bodies are safe from pollution and heat.
Finally, avoid additional sources of fine particulate matter on bad air quality days. Burning wood or using a gasoline-powered appliance like a lawnmower could exacerbate your respiratory health when PM 2.5 levels are already higher than usual.