Vulnerable Populations Shoulder Larger Number and Higher Intensity of Environmental Burdens, New Study Finds
Communities that are already socially and economically vulnerable in the United States are not just exposed to environmental pollution more often—they are exposed to more types of pollution at the same time, and often at higher intensity levels. That is the central finding of a new nationwide study that takes a much broader look at environmental inequality than most previous research.
For years, environmental justice studies have shown that certain groups are more likely to live near highways, industrial plants, hazardous waste sites, or polluted waterways. What this new research adds is a clearer picture of how multiple environmental burdens stack on top of each other in the same places—and who is most affected when that happens.
The study was led by Paul Mohai, a professor at the University of Michigan’s School for Environment and Sustainability, and co-authored by Charles Lee, a visiting scholar at Howard University School of Law and a former director of the Office of Environmental Justice at the U.S. Environmental Protection Agency. Both researchers have spent decades studying environmental justice and advising on policy efforts aimed at reducing inequality.
Looking Beyond One Pollution Source at a Time
Most environmental research has traditionally focused on one burden at a time, such as air pollution, lead exposure, or proximity to hazardous waste. This approach was largely driven by data limitations. Researchers simply did not have access to nationwide datasets that could support large-scale, multi-factor analysis.
That situation has changed over the past decade. With the development of the EPA’s EJScreen tool, it became possible to analyze multiple environmental indicators alongside detailed demographic data at the census tract level. Using this resource, Mohai and Lee examined data from more than 84,000 census tracts across all 50 U.S. states and Puerto Rico.
Instead of asking whether one pollutant affects one group, the researchers asked a broader question: where do many environmental burdens occur together, how intense are those burdens, and who lives in those places?
Thirteen Environmental Burdens, Analyzed Together
The study examined up to 13 different environmental burdens at once. These included factors such as exposure to toxic air pollutants, wastewater discharges, proximity to Superfund sites contaminated with hazardous waste, and other pollution-related risks.
Importantly, the researchers did not just count whether a burden was present. They also measured the intensity or magnitude of each burden. This distinction matters because two communities might both face air pollution, but one might experience much higher concentrations than the other.
By combining both the number of burdens and their severity, the researchers were able to create a more realistic picture of what people actually experience in their daily lives.
Strong Links to Race, Ethnicity, and Language
One of the most striking findings of the study is how closely cumulative environmental burdens align with certain demographic groups. Census tracts with the highest number and intensity of burdens were far more likely to be home to communities of color and people with limited English proficiency.
In fact, the presence of these two groups was a stronger predictor of cumulative environmental burdens than other commonly studied socioeconomic factors such as income or education level. In simple terms, if multiple high-intensity environmental burdens are concentrated in one place, there is a very strong chance that the area is also home to a racially or ethnically marginalized community or residents who face language barriers.
The study suggests that these patterns are not accidental. They reflect long-standing public policies and planning decisions that have historically segregated communities and placed industrial and polluting activities near populations with less political power.
A History That Still Shapes the Present
The findings align with decades of research showing how practices such as redlining, discriminatory zoning, and unequal infrastructure investment shaped American neighborhoods. Communities that were once denied access to loans, clean infrastructure, or political representation often became the default locations for highways, factories, landfills, and power plants.
Even as explicit discrimination has been outlawed, the legacy of these decisions continues to influence where environmental hazards are located today. The study reinforces the idea that environmental inequality is not just about current choices, but about historical systems that still shape exposure patterns.
Why Cumulative Impacts Matter
One key takeaway from the research is that people do not experience pollution in isolation. A community might simultaneously face poor air quality, contaminated water, noise pollution, and social stressors such as poverty or overcrowded housing.
These overlapping exposures can interact in ways that increase health risks, even if the exact impact of each burden is not fully documented. While the study does not measure health outcomes directly, it makes a strong case that higher numbers and intensities of environmental burdens likely translate into greater harm.
The authors note that comprehensive health and economic impact data do not yet exist for every environmental burden included in the analysis. However, they argue that it is reasonable to assume that more intense and more numerous exposures increase overall risk.
Policy Implications and Real-World Use
The study arrives at a time when policymakers are increasingly interested in cumulative impact assessments. One notable example is New Jersey, which has become the first state to require the denial of certain environmental permits in areas already considered overburdened.
New Jersey uses an environmental justice mapping and assessment tool to evaluate cumulative impacts before allowing new polluting facilities. According to the researchers, findings like these help validate and strengthen such tools, making them more defensible and effective.
Experts who reviewed the paper during the peer-review process described it as highly influential and likely to shape future environmental justice analysis across the country.
The Role and Uncertain Future of EJScreen
Much of this research was made possible by EJScreen, the EPA’s national environmental justice screening tool. EJScreen brought together environmental data and demographic indicators in a way that allowed researchers to see nationwide patterns for the first time.
However, federal support for EJScreen has recently been reduced, limiting its availability at the national level. Despite this, Mohai and Lee emphasize that state and local governments, researchers, and community organizations are continuing the work using available data and locally developed tools.
They argue that research like this will continue as long as environmental disparities persist.
Why This Study Matters Beyond Academia
This research is not just an academic exercise. It provides evidence that can be used by communities advocating for cleaner environments, by regulators deciding where to focus enforcement, and by policymakers designing fairer environmental laws.
By showing that vulnerable populations face both more environmental burdens and more intense ones, the study strengthens the case for policies that consider cumulative impacts rather than treating pollution sources in isolation.
It also serves as a reminder that environmental justice is deeply connected to social justice. Where people live, the air they breathe, and the water they drink are all shaped by decisions made over decades—and those decisions still matter today.
Research Reference
Mohai, P., Lee, C., et al. (2026). Cumulative environmental burdens and vulnerable populations: taking into account the intensity and count of burdens in environmental justice analyses. Environmental Research Letters. https://doi.org/10.1088/1748-9326/ae2c0d
