Millions of Americans live in areas without air quality monitoring

In June 2023, smoke from Canadian wildfires blanketed cities like New York and Washington, D.C. The air turned orange. Headlines called it the worst air quality in the world. People wore masks again, not for COVID-19, but to avoid inhaling toxic particles. But what if you lived in a place with no way to measure that danger?

A study from Penn State University reveals a chilling reality. More than 50 million people in the U.S. live in what researchers call “air quality monitoring deserts.”

These are counties with no official monitoring stations to assess air pollution. Without these stations, we don’t know what people are breathing.

Air quality monitoring deserts

Monitoring deserts are places with zero air-quality stations. That means no sensors, no alerts, and no data on the pollutants people are exposed to each day.

According to the study, 1,848 counties in the U.S. qualify as monitoring deserts. That’s nearly 59% of all counties and covers about 40% of the land area in the country.

“Exposure to air pollution has been directly and indirectly to cancers, cardiovascular disease, respiratory disease, immune disorders and more,” said Alexis Santos, co-author of the study and associate professor at Penn State.

“If we are not measuring air quality in large regions of the country, then we do not know how significant air pollution problems are.”

The danger of data gaps

Air quality data helps determine public health responses. If a wildfire breaks out and there’s no monitoring, people cannot know whether it’s safe to go outside.

There is a growing need to assess whether children should stay indoors or whether vulnerable people should wear masks. And yet, millions live in this uncertainty every day.

These gaps don’t just delay emergency responses. They affect how we understand long-term health risks.

Studies link air pollution to asthma, heart attacks, dementia, and premature death. But in unmonitored counties, those links remain invisible and unquantified.

Minority areas lack air quality monitoring

The study linked demographic and economic factors to the presence – or absence – of monitoring.

Counties with high poverty, low high school completion, or larger Black and Hispanic populations are more likely to be unmonitored. These patterns held even after accounting for population size.

“Air pollution affects everyone’s health, so it is important for everyone in the nation to have access to accurate information about the quality of the air they breathe,” said Nelson Roque, assistant professor at Penn State and the study’s lead author.

The Southern region was especially affected. In states like Mississippi, Georgia, and Arkansas, more than 75% of counties are monitoring deserts. These regions include parts of the “Southern Black Belt,” a historically marginalized area with persistent social and economic disadvantages.

Air monitoring is old and unreliable

Air monitoring in the U.S. began in 1957. Since then, more than 20,000 stations have been installed at some point. But by 2024, only 4,821 remained active. Many stations were decades old, with a median age of 26.1 years. Some stopped reporting due to technical issues or lack of funding.

“We ran this same analysis just a couple months apart, and we found that the number of air-quality monitoring sites had changed over that short period of time,” Roque said.

“These stations are in flux all the time, and data-reporting intervals also vary, which points to the need for investment in and modernization of this infrastructure.”

This lack of consistency adds uncertainty. Researchers and communities rely on these stations for accurate trends. If the equipment goes offline, so does our ability to respond in real time.

Smartphones can’t replace sensors

Apps may show air quality ratings, but they don’t gather air directly. These apps use data from nearby stations. If you live far from a monitoring site, your app could show safe air when, in fact, pollution levels are high. That’s misleading and dangerous.

Monitoring deserts, by definition, depend on estimates from surrounding regions. In rural areas, that might mean using data from stations dozens or even hundreds of miles away. Local factors – like nearby industry, agriculture, or wildfires – can vary dramatically from region to region.

This means people in these counties might make poor health decisions based on faulty information. And public health officials lack the tools to guide them differently.

Air quality monitoring gaps reflect injustice

Environmental monitoring follows patterns of social inequality. The researchers found that counties with more agricultural or mining jobs and fewer educated adults were more likely to be unmonitored. Higher poverty levels also increased the odds of being a monitoring desert.

Initially, areas with more Hispanic residents appeared less likely to be deserts. But when population size was factored in, this trend reversed. Counties with more Black residents consistently had higher odds of lacking monitoring, regardless of other factors.

These patterns are not accidental. “Generally speaking, infrastructure for health care, transportation, education and other areas are underdeveloped in rural counties,” Santos said. “This study demonstrated the pattern holds true for air-quality monitoring, as well.”

A call for broader monitoring

In 2021, Executive Order 14008 urged environmental equity. The Climate and Economic Justice Screening Tool now includes air quality as a measure of community disadvantage. Despite these efforts, monitoring deserts persist.

Monitoring infrastructure is concentrated in urban areas, where populations are dense. This makes sense for national averages, but fails millions in sparsely populated or economically struggling areas.

The EPA and local partners must rethink this model. Where there is no data, there is no protection.

Local efforts and global parallels

Some states and cities try to fill the gap. For example, the New York City Community Air Survey collects seasonal data at multiple points across the city. These local programs give better insights into neighborhood conditions, yet not all regions have the resources or expertise to launch their own systems.

Globally, many countries face similar problems. Citizen science, wearable sensors, and community-led efforts are helping close gaps. But in the U.S., a wealthier country with strong scientific institutions, the scale of unmonitored areas is concerning.

The researchers warn that areas without monitoring may actually experience worse air quality than we realize. Without data, these communities are invisible in national health research and policy.

What needs to happen next

Fixing the system requires more than adding a few monitors. The technology must be modern, reliable, and consistent. It must cover both cities and rural areas. Most importantly, it must reflect a commitment to environmental justice.

The study’s authors argue for equitable expansion of monitoring sites. Only then can we understand exposure, assess disparities, and design better public health responses. Until that happens, millions will keep breathing air they cannot see, cannot measure, and cannot trust.

Monitoring deserts expose more than air pollution. They reveal the cracks in how we protect public health. When a wildfire erupts or pollutants rise, people in these places won’t know. They’ll just keep breathing – and hoping it’s safe.

The study is published in the journal Proceedings of the National Academy of Sciences.

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