Air Quality Monitoring Gaps Threaten Millions
A recent study published in ACS Environmental Science & Technology Letters highlights the significant deficiencies in air-quality monitoring throughout the United States, which jeopardizes the health of millions, particularly among minority and low-income communities. Triggered by a new air pollution standard set by the U.S. Environmental Protection Agency (EPA), the research team utilized a detailed air pollution mapping model based on real-world data, underscoring an urgent need to fill the gaps in the EPA’s monitoring framework.
"The national air pollution monitoring network aims to act as an umbrella to protect all Americans," states lead author Yuzhou Wang. "But we saw that unfortunately, millions of people, especially underrecognized populations, will not receive adequate protection from the monitors. Thus, they will receive fewer benefits from the more stringent standard." This lack of coverage reveals a critical flaw in the monitoring network, particularly for those most vulnerable to air quality issues.
Outdoor air pollution in the U.S. predominantly affects health through fine particulate matter (PM), which consists of tiny suspended particles such as soot and aerosol droplets measuring less than 2.5 micrometers in diameter—referred to as PM2.5. In February 2024, the EPA implemented a stricter standard for PM2.5 to enhance protection against the health risks associated with inhaling these particles. The agency oversees compliance through approximately 1,000 expensive and precise monitoring stations scattered across cities and towns nationwide. However, previous research has shown that communities of color and those with lower socioeconomic status suffer disproportionately from PM2.5 exposure while lacking adequate monitoring resources.
Despite the EPA's efforts to revise the national air pollution monitoring framework to incorporate considerations of environmental justice, the effectiveness of this network in accurately identifying areas failing to meet the new standards remains largely unexplored. In response, researchers led by Joshua Apte applied a statistical model to pinpoint deficiencies in the monitoring coverage across the continental U.S. This empirical model, based on observed data and geographic variables, successfully identifies regions likely experiencing PM2.5 levels surpassing the EPA's new, stricter guidelines.
To examine these monitoring gaps, Apte and colleagues analyzed PM2.5 concentrations from 2017 to 2019 at both monitored and unmonitored sites, utilizing predictions from the U.S. Center for Air, Climate, and Energy Solutions along with population data from the 2020 U.S. Census. Their research revealed that the existing network fails to capture pollution hotspots, resulting in a significant underestimation of exposure disparities, particularly in historically marginalized communities. Key findings from the study include:
Approximately 44% of densely populated metropolitan areas, affecting around 20 million individuals, lack sufficient monitoring networks to meet the new EPA air quality standards.
PM2.5 hotspots identified via monitoring data and the predictive model have a notably higher concentration of people of color and low-income individuals compared to the general population.
About 2.8 million people reside in PM2.5 hotspots overlooked by the current air monitoring network.
"Fortunately, even adding 10 monitors in the right places could make a big difference in correctly identifying which cities are breathing unhealthy air," Apte asserts. However, he cautions that "our network of about 1,000 official regulatory air monitors is generally not well-suited for capturing exposure disparities in every city in the country. There are just too few monitors to capture every hotspot."
The researchers have identified specific metropolitan areas in Texas, Ohio, California, Wisconsin, Pennsylvania, Missouri, and Idaho that could benefit from additional air pollution monitors. These additions would help better track air quality and protect the health of large populations currently exposed to air that exceeds the EPA's newly established standards.
