Guided by the lived experiences of community partners, Northwestern University scientists have simulated the effects of zero-emission vehicle (ZEV) adoption on future air quality for the greater Chicago area.
The results were published today (March 18) in the journal Frontiers of Earth Science.
Motivated by California's Advanced Clean Trucks (ACT) policy, Neighbors for an Equitable Transition to Zero-Emissions (NET-Z) Illinois members partnered with Northwestern researchers to explore how a similar strategy might play out in Cook County and the surrounding areas.
To develop a model that more realistically simulates the greater Chicago area's current pollution levels, the researchers augmented an Environmental Protection Act (EPA) air-quality model to better reflect satellite observations and the lived experience of local community groups. Then, the researchers compared the model of current air quality to simulated future conditions under the ACT policy.
By implementing an ACT policy in Illinois, researchers found the Chicago region would reduce enough nitrogen dioxide (NO2) pollution to avoid 500 premature deaths and 600 new cases of childhood asthma per year. The largest health improvements from this policy would occur in neighborhoods currently experiencing the highest pollution levels, which are areas with more residents of color. So, not only would reducing air pollution reduce health problems, it also would help address existing racial disparities in pollution exposure.
"As a mom who personally has asthma, I was struck by these results," said Northwestern's Victoria Lang, who led the study. "Avoiding 600 new pediatric cases of asthma per year is sparing 25 classrooms of students from a chronic lung disease. Kids should not have to suffer from a life-long illness just because of where they live or the location of their school."
Lang is a Ph.D. candidate in Northwestern's Department of Earth, Environmental and Planetary Sciences at the Weinberg College of Arts and Sciences. She is advised by the study's senior author Daniel Horton, an associate professor of Earth, environmental and planetary sciences. Insights from members of the Respiratory Health Association, Warehouse Workers for Justice, Little Village Environmental Justice Organization and other NET-Z coalition members helped inform the study.
ACTing on air pollution
Exposure to traffic-related pollutants is associated with a myriad of substantial negative health outcomes, including asthma, emphysema, chronic bronchitis and ultimately premature death. To combat these issues, California adopted the ACT policy in June 2020. Several other states have since followed suit. The intervention policy aims to gradually replace approximately 50% of on-road medium- and heavy-duty vehicles, like trucks and buses, with ZEVs by the year 2050.
"ACT aims to reach an approximately 50% ZEV fleet by 2050 because trucking companies have economics to consider," Horton said. "They can't cost effectively replace their diesel fleets overnight. But, as the vehicles age and companies need to renew their fleets, ACT incentivizes gradual adoption of zero-emission vehicles."
Wondering if a similar policy might help curb pollution-related health risks in the Chicago area, members of NET-Z Illinois approached Horton's laboratory at Northwestern. Horton's group previously modeled air-quality scenarios in which 30% of current on-road heavy-duty vehicles in the Chicago region shifted to electric versions. His lab also previously examined how pollution varies from neighborhood to neighborhood. After reviewing these studies, members of the community noticed some critical gaps in the data.
"The community asked us if we could simulate the effects of the ACT policy, so they could advocate for it in Illinois," said Horton, who leads Northwestern's Climate Change Research Group. "But they also suspected we were getting the emissions data wrong in certain areas of the city. So, first, we had to figure that out."
Community groups fill in the blanks
In Horton's air-quality models, his team pulls data from the EPA, which provides essential national-scale emission estimates. Because these estimates are designed for broad applicability, however, they may not capture localized variations in emission patterns.
"To determine emissions on a national scale, the EPA selects representative counties that may or may not include Chicago," Horton explained. "They assign typical emission levels based on factors like traffic volume, road type and population density. It's useful but not custom-designed for Chicago."
"The default EPA model also uses a coarser resolution," Lang added. "We run our model at one-kilometer resolution, allowing us to capture local impacts at the neighborhood scale. However, some assumptions used at coarser resolutions may not translate as well to higher-resolution applications."
Community partners living in Chicago's West Side noticed the emissions included in earlier models seemed low. To explore this intuition, citizen scientists deployed 35 truck-counting cameras at intersections along the I-55 corridor. The cameras revealed that communities along I-55, southwest of downtown Chicago, frequently experience thousands of truck passages per day. Beyond roadways, heavy-duty trucks also often idle - in driveways, pick-up lines and while loading and unloading freight - for extended periods of time. These idling episodes were underrepresented in the data.
"We tried to align our model with those lived experiences," Lang said. "We found the EPA simulates short-duration idling from heavy-duty vehicles by distributing them across the entire city. We knew that wasn't representative of where these vehicles operate, which is predominantly near warehouses and distribution centers, such as those on the west side of Chicago. We modified the spatial distribution of that short-duration idling to better represent real-life operations."
Health and economic benefits of ZEV adoption
After augmenting their model with this new information, the researchers ran a baseline simulation to create a full high-resolution snapshot of current air pollution in Cook County and its surrounding collar counties - DuPage, Kane, Kendall, Lake, McHenry and Will. According to this baseline simulation, tailpipe exhaust from medium- and heavy-duty vehicles contributes to about 22% of NO2 pollution, which is linked to 1,330 premature deaths and 1,580 new cases of childhood asthma per year.
To simulate pollution after adopting ACT regulations, the team removed tailpipe emissions from nearly 50% of medium- and heavy-duty vehicles. Then, the researchers compared current pollution to 2050's projected pollution levels under the ACT policy. If Illinois adopted the policy, then by 2050, NO2 levels would decrease by 8.4% across the whole region, they found. This reduction would result in roughly 500 fewer premature deaths per year and about 600 fewer new cases of childhood asthma annually.
Beyond health benefits, adopting ACT regulations in Illinois would have significant benefits for the economy and for addressing longstanding systemic pollution exposure disparities. The study authors estimate Illinois could save $731 million annually in avoided health costs and climate damages. Communities of color - who often live closer to major roadways and warehouses where truck traffic is heaviest - are disproportionately affected by current pollution levels. So, these communities would experience the greatest improvements.
As the Illinois Pollution Control Board considers a proposal to adopt the ACT policy, this new research underscores the tangible importance of adopting ZEVs to improve public health for Illinois residents. Northwestern Pritzker School of Law Professor Robert Weinstock serves as lead counsel for the community groups urging the Board to adopt the measure, and Horton provided expert testimony on the projected public health benefits from vehicle electrification in Illinois. This work demonstrates the uniquely powerful real-world impact of community-academic collaborative research.
"Ultimately, it's up to individual states to adopt the ACT standard," Horton said. "This is an opportunity for Illinois to lead - by adopting a policy that is good for both Illinois residents' health and for global climate."
The study, "Assessing air quality, public health, and equity implications of an Advanced Clean Trucks policy for Illinois," was supported by the National Science Foundation and Environmental Defense Fund.
