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Fine Particle Pollution: Unevenly Distributed, Driven by Heavy Traffic, and Supercharged by E-commerce

Public Protections Air Environmental Justice

On February 7, the U.S. Environmental Protection Agency (EPA) finalized new and stronger air quality standards for fine particle pollution (commonly known as soot), a harmful pollutant and byproduct of burning coal, manufacturing, oil refining, and motor vehicles. Soot is one of the nation’s most dangerous air pollutants, and one of the most widespread, though it disproportionately impacts the health of structurally marginalized communities.

Multiple reports have found that people living within half a mile of warehouses have higher rates of asthma and heart attacks than residents in the area overall, increased risk of cancer, and nervous system effects. The new standard would reduce the annual health limit from 12 micrograms per cubic meter (ug/m3) to 9.

This change is long overdue, as it represents the first update of soot limits in 12 years. It’s also extremely consequential: the EPA projects that the new limit will prevent “up to 4,500 premature deaths and 290,000 lost workdays, yielding up to $46 billion in net health benefits in 2032. For every $1 spent from this action, there could be as much as $77 in human health benefits in 2032”, according to a recent press release from the agency. For those who like to tally the “costs and benefits,” according to agency officials, “every $1 spent from this action, there could be as much as $77 in human health benefits in 2032.”

Several jurisdictions that were compliant under the current limit will have to adjust to the new standard. Illustrative air quality data collected by the EPA between 2020 and 2022 shows the potential impact of the rule: Although final nonattainment determinations will be made using new measurements taken between 2022–2024, 118 counties in the United States currently fall outside the new 9 ug/m3 limit. In the following map, these counties are shown in blue (Figure 1). These potentially noncompliant counties cluster around large urban and metro areas, which are some of the most diverse and unequal areas in the country, both racially and economically.

Figure 1

Fine particle pollution stems from natural and human-made sources, including vehicles, industrial processes, and wildfires. Heavy-duty trucks and other diesel-burning vehicles represent a considerable portion of vehicle pollution in the United States and are a major source of soot. This markedly increases around areas that act as nodes in the distribution chains, such as storage facilities and warehouses (like those used by Amazon, Walmart, and other industries). The exponential growth of “e-commerce” in the past decade, combined with profound changes in shopping habits driven by the COVID-19 pandemic, has driven a massive proliferation of warehouses across the landscape.

To understand the scale of the problem, we retrieved information from the Bureau of Labor Statistics about the distribution of warehouses by county and singled out “General warehousing and storage,” the category that includes storage and distribution facilities used by Amazon and Walmart. The data shows that the 118 counties that would not meet the new standard are home to a total of 5,587 warehouses, with nearly half — 2,700 — in just 10 counties (Table 1). To be clear, warehouse-related traffic is not the only driver of soot pollution in these counties, but it is certainly an important one, especially given the growing trend in e-commerce.

Table 1: Top 10 counties, by number of warehouses, that would not meet the new soot limit

How does this connect to environmental justice? The location of warehouses is not random, nor are the locations of where people live and work. Corporations factor road and highway access, local zoning laws, and proximity to major regional markets into their considerations. These warehouses tend to be closer to low-wealth and nonwhite neighborhoods, subjecting them to increased exposure to soot and other harmful contaminants.

Extensive research has documented the spatial distribution of warehouses alongside the demographic and income makeup of communities nearby. In an authoritative white paper from April 2023, Environmental Defense Fund found that 15 million people live within a half mile of warehouses in 10 states, and “Black, Latino, Asian and American Indian people bear the brunt of risk from living in proximity to warehouses. In some states like Illinois, Massachusetts and Colorado, the concentration of Black and Latino residents around warehouses is double what would be expected, given the state population.” Similarly, based on multiple studies of large metropolitan areas in California, researchers Quan Yuan and Genevieve Giuliano found that the majority of warehouses in their study are located in non-white neighborhoods, especially medium-income neighborhoods.

Future steps and policy developments

Despite the new limit being an important change, air quality remains a challenging policy area in which further improvements must be made. These include boosting monitoring near major polluting infrastructure — like mega-warehouses and distribution centers — and increasing the number and functioning of monitoring stations. Currently, EPA only monitors pollution in approximately 1,000 out of the roughly 3,000 U.S. counties. To put it another way: About 120 million Americans live in counties that have no EPA pollution monitors at all for small particle pollution, according to agency data.

But county-level data can only get us so far, concealing much-needed nuance at the smaller scale. Another important area for improvement is the ability to measure block-to-block variability in air quality. Fortunately, along with strengthening the primary annual soot standard, EPA is modifying the air quality monitoring network design criteria to include considerations of proximity of populations at increased risk of soot-related health effects to sources of air pollution. These important steps will advance environmental justice by ensuring that contextualized and granular data collection in overburdened areas will inform future policy decisions.

Public Protections Air Environmental Justice

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