Exposure to Air Pollution from Vehicles in Illinois Is Inequitable — It Doesn’t Have to Be

February 19, 2020
Benjamin Cruz/Pexels
David Reichmuth
Senior Engineer, Clean Transportation Program


Cars, trucks, and buses are a significant source of air pollution in Illinois. But how much pollution is attributable to these vehicles and who is exposed to it?

To help answer these questions, I’ve used a computer model to estimate the amount of fine particulate matter air pollution (known as PM2.5) created by using on-road vehicles (cars, trucks, and buses). While air pollution from vehicles affects everyone in Illinois, the findings show that people of color on average are exposed to higher levels of harmful particulate matter air pollution. Asian Americans, African Americans, and Latinos are exposed to PM2.5 pollution 32, 21, and 19 percent higher, respectively, than the state average. At the same time, whites are on average exposed to 13 percent less PM2.5 pollution than the state average. In addition, the over 5 million people living in Cook County, including Chicago, experience air pollution from transportation that is among the worst in the nation.

What is PM2.5 and why is it important?

Exposure to PM2.5 (particulate matter smaller than 2.5 micrometers in diameter) is linked to increased illness and death, primarily from heart and lung diseases. These particles are small—20 times smaller than the diameter of fine human hair—so they can penetrate deeply into the lungs; the smallest particles can even enter into the bloodstream. While not the only air pollutant that adversely affects health, PM2.5 is estimated to be responsible for approximately 95 percent of the global public health impacts from air pollution. Long-term exposure to PM2.5 causes increased death rates attributed to cardiovascular diseases, including heart attacks, and it has been linked to lung cancer, miscarriages, mental health problems, and other adverse impacts. Chronic exposure to PM2.5 in children has also been linked to slowed lung-function growth and the development of asthma, among other negative health impacts.

On-road vehicles like cars, trucks, and buses are a significant source of harmful emissions in Illinois. Tailpipe emissions caused by burning gasoline and diesel are a source of climate-changing emissions such as carbon dioxide and also compounds that directly and indirectly lead to airborne particulate matter. In addition, vapors from gasoline refueling and vehicles’ fuel systems add compounds to the atmosphere that are transformed into further particulate matter pollution.

Greater PM2.5 pollution for African Americans, Asian Americans, and Latinos

We estimated exposure to particulate matter air pollution using a recently developed model from the University of Washington and data from the US Census Bureau. The model lets us calculate how vehicle tailpipe and refueling emissions ultimately lead to exposure to ground-level particulate matter pollution so we can understand how exposure to PM2.5 varies among racial groups and where people live.

The results are clear: the burden of PM2.5 pollution from cars, trucks, and buses is inequitable when looking at the exposure experienced by racial groups in Illinois. As noted, Latinos are, on average, exposed to 19 percent higher PM2.5 concentrations than the average Illinois resident. African Americans experience concentrations 21 percent higher than average. Those identifying as Asian Americans have the highest average exposure, over 30 percent higher. White residents in Illinois have average exposure that is 13 percent lower than the average for the state.

It’s important to note that these results pertain to exposure to PM2.5 from on-road transportation, which accounts for only a portion of exposure to air pollution. Other sources of exposure include industrial facilities, electricity generation, aviation, and rail. These, too, can have a disproportionate impact on communities of color.


Asian Americans, African American, and Latino residents of Illinois are exposed to higher than average levels of particulate matter pollution from cars, trucks, and buses. Exposure by racial group is based on US Census race and ethnicity data from the American Community Survey. Exposure for the Latino or Hispanic category reflects all respondents that chose either Latino or Hispanic Origin. Data are not shown for racial groups that are less than 5 percent of statewide population due to model and analysis limitations.


PM2.5 Exposure from Cars, Trucks, and Buses Varies Greatly Within Illinois

PM2.5 pollution from on-road transportation is highest in Chicago and surrounding Cook County. The darkest shading on the map indicates areas that are in the most-polluted 20 percent of census tracts.

Exposure to PM2.5 pollution from cars, trucks, and buses varies greatly within Illinois. Concentrations are highest in urban areas and downwind of those areas; Chicago and its immediate surroundings are affected the most.

Cook County, including Chicago, not only has the state’s highest PM2.5 pollution exposure, but it also is one of the nation’s worst affected counties. Air pollution from on-road vehicles is a problem in major cities across the US.  The average exposure for Cook County is 90 percent higher (or nearly double) the average for the continental United States (the data exclude Alaska and Hawaii). Given the health impacts of PM2.5 pollution, the 41 percent of state residents that live in Cook County shoulder a significantly larger burden from on-road vehicles than the average American.


Cook County is Among the Metropolitan Counties with the Highest Exposure to On-Road Pollution

Rank County Metro Area PM2.5 Concentration (µg/m3) Percent Higher than US Average
1  Queens County, NY New York, NY 4.09 212%
2  New York County (Manhattan), NY New York, NY 3.93 200%
3  Kings County (Brooklyn), NY New York, NY 3.54 171%
4  Bronx County, NY New York, NY 3.30 153%
5  Nassau County, NY New York, NY 2.98 128%
6  Los Angeles County, CA Los Angeles, CA 2.68 105%
7  Philadelphia County, PA Philadelphia, PA 2.57 97%
8  Cook County, IL Chicago, IL 2.48 90%
9  Harris County, TX Houston, TX 2.27 73%
10  St. Louis County, MO St. Louis, MO 2.24 71%
   US Average 1.31

Cook County has the 8th highest exposure to PM2.5 pollution from on-road sources among counties

with populations greater than 1 million people.

Opportunities to Reduce Harmful Impacts of Vehicle Use

Illinois can avoid much of the burden from particulate matter air pollution due to on-road transportation. Reducing tailpipe and refueling emissions would reduce exposure to PM2.5 pollution, and several ways to do that are available now.

Electrifying vehicles, both passenger and freight, could greatly reduce emissions. Battery-electric vehicles have no tailpipe emissions (although there are minor amounts of PM2.5 emissions from tire and brake wear). They also completely avoid the need for gasoline refueling and the emissions associated with it. Electricity generation can produce emissions, but these are falling as the state and region move to cleaner sources of electricity.

While people in Illinois can make a difference by choosing cleaner cars (including electric vehicles), much of the pollution comes from sources like heavy-duty trucks and buses. Cook County is a major national hub of freight transportation, and nearly half a billion tons of freight move on the county’s highways each year. The state needs to move forward on regulations, incentives, and other policies to reduce emissions from both passenger vehicles and larger trucks and buses.

As a first step, Illinois should pass the Clean Energy Jobs Act (CEJA). CEJA would create a beneficial electrification program to incentivize electric vehicle charging, focused on medium- and heavy-duty vehicles. Electrifying these larger vehicles can benefit all in the state, but especially those in communities currently burdened with high levels of traffic from these vehicles. CEJA would also create the EV Access for All program to ensure that all Illinois residents are able to benefit from electric vehicle ownership.

Illinois can also reduce emissions by adopting California’s tailpipe vehicle emission standards. It should also adopt California’s Zero Emission Vehicle (ZEV) program, requiring automakers to increase the percentage of ZEVs sold in Illinois.

Equity and meaningful involvement of impacted communities should be key considerations when designing or evaluating policies to reduce pollution. For example, local and state governments should work with communities to evaluate proposed industrial projects that might increase freight pollution, and therefore exposure to PM2.5 emissions, in Chicago and other densely populated areas. Illinois has the opportunity to demonstrate leadership in addressing the exposure inequities among its residents and move towards a cleaner transportation future.