About 20 million students in the United States ride to school each day on the familiar yellow bus. The vast majority of the nation’s roughly 490,000 school buses — which comprise the nation’s largest public-transportation fleet — are powered by diesel engines. “We’re poisoning our kids on the way to school,” said Jessica Keithan, cofounder and director of the Texas Electric School Bus Project, of the exhaust that inevitably infiltrates bus interiors and children’s lungs. But that’s slowly beginning to change. Thanks to a slate of federal and state incentive programs, school districts all over the country are starting to swap out old diesel buses for new, zero-emissions electric-powered models. This transition is reaching districts of all sizes and demographics, from Martinsville Independent School District in East Texas — which last year became the first in the country to go fully electric with four new buses — to Oakland Unified School District in California — which last month became the first large urban district to fully electrify its fleet, with 74 buses. As the Environmental Protection Agency, through its $5 billion Clean School Bus program, and state initiatives continue to fund electric bus purchases, advocates are identifying challenges to wider adoption and grappling with how to surmount them. Replacing decades-old buses may lead to benefits in educational performance and school attendance rates, said one study.
Five years ago, there were fewer than a thousand electric school buses operating nationwide, the majority of them in higher-income suburban districts. But since the EPA launched its Clean School Bus (CSB) program in 2022, authorized by the Bipartisan Infrastructure Law, the number of electric buses on the road has climbed to nearly 5,000. And more than 7,000 additional buses are under contract, awaiting delivery, or have been awarded funding and will soon be ordered.
From a health perspective, there’s urgency to replacing the nation’s diesel buses with cleaner alternatives. Health experts have long known that children are uniquely vulnerable to air pollution because their lungs, brains, and other major organs are still developing. They breathe faster and take in a higher volume of air relative to their body weight. Diesel exhaust is classified as a carcinogen by the World Health Organization and contains fine particles and nitrogen oxides, both of which are well-documented asthma triggers. Research shows that children in lower-income areas and communities of color are exposed to higher levels of outdoor air pollution — from major roadways, industries, and ports with diesel truck operations. They also suffer much higher rates of asthma and respiratory illness. And so it’s particularly important, say public health experts and school officials, to get polluting school buses off the streets.
Meredith Pedde, an environmental epidemiologist at the University of Michigan’s School of Public Health, led a study published earlier this year that found that replacing decades-old buses may lead to proportionately greater benefits in educational performance and attendance rates. She and her colleagues drew on data from an earlier EPA program that randomly allocated funding for cleaner diesel, gas, or propane school buses from 2012 through 2017. They found that districts that received funding for bus upgrades saw significant improvements in students’ attendance rates and in math and literacy test scores. “One of our hypotheses is that higher exposures could lead to missed days of school, and that’s associated with lower performance,” said Pedde. “But there’s also evidence that air pollution can directly impact the brain and impair cognitive performance.”
Pedde and her colleagues found that those educational performance gains happened only in districts that replaced pre-1990 diesel buses (there are nearly 5,000 pre-1990 buses in the U.S. fleet, her paper estimated). Those that replaced newer diesels saw test-score changes comparable to scores in districts that were not selected for funding to receive cleaner buses. Her research suggests there are greater health benefits from getting the oldest diesel buses off the road than from replacing more recent models, which must meet more stringent emissions standards. Low-income and minority communities still have the highest shares of older, polluting diesel buses. The EPA’s CSB program stipulates that electric buses must be replacing diesel buses from 2010 or earlier. Many state programs have similar requirements. “In addition to socioeconomic factors, we need to make sure that programs are also targeting the oldest buses,” Pedde said. In Texas, there are at least five school districts still running buses made in the 1970s, according to Keithan. The CSB program is designed to give preference for new bus funding to the highest-need districts. According to a recent report from the World Resources Institute’s Electric School Bus Initiative, districts with higher shares of low-income households generally have more students riding polluting buses to school than do other districts. The good news is that 74 percent of the grants or rebates awarded to date are in low-income, rural, or tribal school districts, according to the EPA.
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