Switching to electric school buses could yield significant health and climate benefits, researchers suggest in a new analysis that seeks to quantify those gains in dollar terms.

Published in the journal PNAS, the study estimated the per-mile benefits of replacing diesel buses with electric ones in 3,108 U.S. counties. Researchers combined data about average diesel bus pollution with statistical estimates of the cost of maintenance and repair, the environmental impact of diesel emissions, and the dollar value of new childhood asthma cases and deaths that could be attributed to such pollution.

A substantial portion of the half-million school buses in the United States are “highly polluting old diesel vehicles,” the researchers write. Though emissions have fallen over time thanks to increased regulation, they add, older, more polluting diesel models are still common. As of June 2023, they write, just 2,277 electric school buses had been ordered or delivered, or were operating nationwide.

Replacing the average diesel bus would generate a benefit of $84,200 per bus, split nearly evenly between health and climate effects. Such a replacement would cut 181 metric tons of carbon dioxide emissions per bus and reduce childhood deaths and asthma cases from diesel emissions, the researchers conclude.

The benefits would vary depending on the location, with buses generating as much as $247,600 in benefits in dense metropolitan areas. Impacts would be smaller in rural areas because diesel emissions affect smaller populations there.

The benefits would come at a cost, the researchers acknowledge; they estimate an unsubsidized electric school bus costs an average of $156,000 more than a new diesel school bus over the vehicle’s lifetime. But in large metropolitan areas, they write, “replacing a relatively small number of miles driven by diesel buses could lead to substantial public health benefits.”

“In a dense urban setting where old diesel buses still comprise most school bus fleets, the savings incurred from electrifying these buses outweigh the costs of replacement,” Kari Nadeau, a professor of climate and population studies and environmental health at the Harvard T.H. Chan School of Public Health and the study’s senior author, said in a news release. “Not to mention how the tangible benefits of electric school buses can improve lives — especially for racial minorities and those living in low-income communities who are disproportionately impacted by the everyday health risks of air pollution.”

Black, Hispanic and low-income Americans would probably experience the greatest health benefits of large metropolitan areas electrifying their school bus fleet, the researchers write. They call for more research on the exposure of the children riding the buses to particulate pollution, because data on in-cabin pollution generated by newer buses is still unclear.