Air pollution tied to 60% higher COVID-19 risk in pregnant low-income New Yorkers

In the early months of the pandemic, when New York City was still learning how to test and count cases, researchers at Columbia University began noticing something in their data: pregnant women on Medicaid who lived in neighborhoods with dirtier air were getting COVID-19 at markedly higher rates than their counterparts in cleaner areas. The finding, published in the American Journal of Epidemiology, quantified a disparity that had been invisible until someone looked for it—a 60 percent increase in infection risk for every microgram per cubic meter of fine particulate matter in the air around their homes.

The study examined 3,318 pregnant individuals who delivered at Columbia University Irving Medical Center between March and December 2020. All were tested for COVID-19 at the time of delivery. Researchers cross-referenced their test results against air quality measurements from 2018 and 2019 at their residential addresses, creating a picture of long-term exposure to PM2.5—the microscopic particles that lodge deepest in the lungs and bloodstream. They adjusted their analysis to account for both individual and neighborhood-level economic factors, trying to isolate the effect of pollution itself.

What emerged was a stark pattern. When they looked at the entire cohort, air pollution showed no clear connection to COVID-19 infection. But when they separated out the pregnant people covered by Medicaid—the federal insurance program for low-income Americans—the association became unmistakable. For every unit increase in particulate matter exposure, the odds of testing positive climbed by 60 percent. Among those who tested positive, 69 percent were Medicaid recipients, even though they represented a smaller share of the overall study population. Only 22 percent of positive cases reported any symptoms at all, yet the symptomatic ones were overwhelmingly low-income.

The stakes of this finding extend beyond infection itself. Pregnant people with COVID-19 face substantially higher risks of severe respiratory illness and death compared to non-pregnant people with the virus. They are more likely to deliver prematurely, to develop preeclampsia—a dangerous spike in blood pressure—and possibly to experience stillbirth. Meanwhile, exposure to PM2.5 during pregnancy independently increases the risk of preterm birth and low birth weight, compounding the hazards. A pregnant person breathing polluted air faces two separate pathways to harm, and if she contracts COVID-19, those risks converge.

Joan Casey, the study's lead author and an assistant professor of environmental health sciences at Columbia's Mailman School of Public Health, offered a straightforward explanation for why low-income pregnant people showed such heightened vulnerability. Many could not afford to stay home during the pandemic. They worked jobs that required them to be in public, to use transit, to be around others. They lived in neighborhoods where industrial facilities, highways, and other pollution sources clustered—the geography of inequality that has long shaped American cities. They had less ability to isolate, less access to clean air, and less margin for error when illness struck.

The research team included epidemiologists from Johns Hopkins University, Colorado State University, and the University of California San Diego. Their work is part of a broader reckoning with how COVID-19 did not strike evenly across the population but instead followed the contours of existing disadvantage. The pandemic exposed health disparities that were already there, baked into neighborhoods and economic systems. This study shows that one of those disparities—the unequal distribution of air pollution—made a measurable difference in who got sick and how vulnerable they were when they did.