The absence of effective air-quality monitoring across the United States has serious health implications for millions, with minority and low-income communities facing the greatest impact, according to researchers in ACS’ Environmental Science & Technology Letters. Prompted by a new air pollution standard established by the U.S. Environmental Protection Agency (EPA), the team utilized a model to create detailed air pollution maps based on actual data, revealing an immediate need to fill gaps in the EPA’s monitoring framework.
“The national air pollution monitoring network is designed to protect all Americans,” states lead author Yuzhou Wang. “However, our findings indicate that countless individuals, particularly those from marginalized groups, remain inadequately protected by these monitors. As a result, they will benefit less from the stricter standards.”
The majority of the detrimental effects of outdoor air pollution in the U.S. can be attributed to fine particulate matter (PM). These tiny particles, which can be composed of substances like soot or liquid droplets, measure less than 2.5 micrometers in diameter and are referred to as PM2.5. In February 2024, the EPA implemented a more stringent standard to better shield Americans from health risks linked to inhaling these particles. To ensure compliance with air pollution rules, the EPA relies on approximately 1,000 expensive and precise monitoring stations spread across cities and towns nationwide. Previous studies indicate that marginalized populations experience greater exposure to outdoor PM2.5. However, these communities have fewer monitoring stations compared to other regions, which means they may not receive adequate protection under the new air quality standards.
Although the EPA is in the process of updating the national air pollution monitoring network to address environmental justice, the effectiveness of this network in accurately pinpointing areas that breach new air pollution regulations remains unexamined. Thus, researchers led by Joshua Apte employed a statistical model to pinpoint deficiencies in the monitoring network’s coverage throughout the continental U.S. This empirical model is based on observed data and geographic factors, helping to detect potential areas where PM2.5 levels surpass the agency’s newly established lower threshold.
To evaluate the gaps in monitoring, Apte and his colleagues compared PM2.5 levels from 2017 to 2019 at both monitored and unmonitored sites, utilizing PM2.5 predictions from the U.S. Center for Air, Climate, and Energy Solutions along with population statistics from the 2020 U.S. Census. Their analysis uncovered that the monitoring network overlooks pollution hotspots and fails to accurately account for exposure disparities, underscoring the necessity for improved monitoring in historically overlooked communities. Overall, they concluded that:
- Approximately 44% of densely populated metropolitan areas in the U.S., impacting around 20 million people, lack adequate monitoring systems to meet the new EPA air quality standards.
- PM2.5 hotspots identified through monitoring data and model predictions contain a significantly higher percentage of people of color and individuals with low socioeconomic status compared to the general population.
- Approximately 2.8 million individuals reside in PM2.5 hotspots that are not monitored by the existing network.
“Fortunately, adding even 10 monitors in strategic locations could greatly enhance our ability to identify cities with unhealthy air quality,” explains Apte. However, he points out, “the network of about 1,000 official regulatory air monitors is not generally equipped to address exposure disparities in every city across the country. There are simply not enough monitors to cover every hotspot.”
The team has identified metropolitan areas for new air pollution monitors throughout the U.S. that could aid in detecting large populations exposed to air that exceeds the EPA’s new pollution standards. These areas include locations in Texas, Ohio, California, Wisconsin, Pennsylvania, Missouri, and Idaho.
