Mac students, professor publish research on redlining and air pollution

Mac students Elizabeth Hrycyna ‘21, Jennings Mergenthal ‘21, and Saiido Noor ‘23, along with Biology Professor Mary Heskel, published the results of their research in an academic journal over the summer. Their article, “Satellite observations of NO2 indicate legacy impacts of redlining in U.S. Midwestern cities,” appeared in Elementa: Science of the Anthropocene. The project is just the latest in a long line of examples of Macalester students and faculty collaborating to produce original research worthy of publication. It’s likely the first time, however, that the participants never met in-person while working together. 

“This project was undertaken entirely during the pandemic, with nearly all aspects occurring remotely and via Zoom, and the students were very flexible and game for taking on the additional challenges,” said Dr. Heskel.

The study originated as Hrycyna’s senior honors thesis for biology with Dr. Heskel, and she collaborated with  the other Mac students to help her examine how the legacy of redlining and other forms of housing discrimination affect modern-day air quality in 11 Midwestern cities.

How they did it

The project was a true inter-disciplinary collaboration, as the student-researchers employed their skills in biology, history, and data science to complete the project. 

By using Home Owners’ Loan Corporation (HOLC) maps that delineate redlined neighborhoods, which were digitized and made publicly available by the University of Richmond’s Mapping Inequality project, they quantified nitrogen dioxide (NO2) levels across neighborhoods and cities using satellite data of air quality on Earth, compiled by Google Earth Engine.

As the lead author, Hrycyna worked with Dr. Heskel to design the study, and led the efforts of  analyzing and visualizing the data. 

“There was a lot of learning on the go,” said Hrycyna, who was new to both satellite data and geospatial analysis. 

Mergenthal, a history and biology double major, focused their work on the front end of operations, focusing on datasets collected in the Twin Cities. “I made a bunch of maps, looked at tree cover and the redlining tracks, contextualizing what redlining is and how it integrates into things that still exist today,” Mergenthal said.

Noor, also a biology major and data science minor, worked on the back end of the project with data to assess urban areas’ proximity to major roads and highways, using statistics “to understand what biological question we’re going after.” 

What they found

Redlining refers to the systemic denial of financial services, including mortgages, to individuals living in certain geographic areas based on race and ethnicity – a discriminatory practice that traces its roots to federal home ownership programs in the early 20th century. The researchers found significantly higher NO2  levels in many Midwestern cities’ redlined neighborhoods compared to “greenlined” neighborhoods which were, and are, whiter and wealthier.

For Professor Heskel, the main takeaway was that “historic urban housing policies grounded in racism, and the associated continued government disinvestment, impact the air quality of neighborhoods – and this impact is large enough it can be detected from space.” 

Mergenthal, who now works at the Science Museum of Minnesota, echoed their mentor. 

“As much as some people would like to say, ‘Oh, redlining is a thing of the past, it doesn’t have bearing on the present,’ it’s not true,” they said 

For Hrycyna, who is now a research technician for a state natural history survey in Illinois, the collaboration and problem-solving prepared her for life after graduation. Next summer, she plans to lead a key research project for the survey.

“Thanks to this experience, I feel prepared for that now,” she said.