How safe is the air? I don’t know about 50 million people in the US

In 2024, more than 50 million U.S. people lived in the county, according to a new study from researchers in Pennsylvania State University.

Rural counties, particularly the Midwest and Southern counties, are less likely to have airborne surveillance sites. Air quality measurements are used to estimate people’s exposure to air pollution, according to Nelson Roque, assistant professor of human development and family research and the study’s lead author.

In an article published today (April 21) in the minutes of the National Academy of Sciences, researchers looked into places where air quality is not monitored and which demographic and social factors are more common in unsurveillanced counties.

“Exposure to air pollution is directly and indirectly in cancer, cardiovascular disease, respiratory disease, immune disorders, and more,” said Alexis Santos, an associate professor of human development and family research and co-author of the state of Pennsylvania and the study.

“If you don’t measure air quality in a large part of the country, you don’t know how important the air pollution issue is. For example, if you have a wildfire in a county that doesn’t have air quality monitoring sites, how do you know if it’s safe to sleep at home or if you work in a business location?”

The research team analyzed data from the Environmental Protection Agency (EPA) AirData Active Sites directory. They found that 1,848 counties in the US (58% of all counties) do not have active aviation quality monitoring sites. State-by-state surveillance varies widely across the country. Pennsylvania, for example, ranks in the top 15 states, with 67% of the counties having at least one aviation quality monitoring site.

By matching data with information from the US Community Survey, created by the US Census Bureau, researchers were able to use logistic regression. This is a statistical model that uses two options to predict results using available data.

The analysis revealed that rural counties are most likely lacking monitoring sites. Furthermore, taking population size into consideration, researchers found high levels of poverty in counties without air surveillance, low levels of high school completion, high percentages of Hispanic residents, and high percentages of Black residents.

“Air pollution affects the health of everyone, so it’s important for anyone across the country to have access to accurate information about the quality of the air you breathe,” Roque said. “If we don’t collect data, we don’t see the threat and impact of pollution.”

The country had 4,821 active aviation quality monitoring stations when the analysis was conducted, but researchers said the number of sites was constantly changing. Some surveillance sites are decades old and often go offline. During 1957, when national air quality monitoring began when this study was conducted, and in September 2024, 20,815 air quality sites were active at one time.

“We did this same analysis a few months apart and found that over that short period of time the number of air quality monitoring sites changed,” Roque said. “These stations are always fluid and the time between reporting data is different, indicating the need for investment and modernization in this infrastructure.”

Air quality data is collected primarily by the region in collaboration with the EPA or EPA, the researchers said.

“Generally speaking, infrastructure for healthcare, transportation, education and other areas is underdeveloped in rural counties,” Santos said. “This study demonstrated that patterns also apply to atmospheric monitoring, making rural people vulnerable to increased exposure to air pollution from wildfires, agriculture, industrial activities and other sources.

Hailey Andrews, a human research technician at Penn State Aging Center, also contributed to the study.