Air pollution map reveals health threats from tiny particles

Air pollution causes around 50,000 deaths each year in the U.S. Yet, not all pollutants are equally harmful. Among the most dangerous are fine airborne particles.

Historically, research has focused on PM 2.5, particles smaller than 2.5 microns. Now, scientists have turned to an even finer pollutant: PM 1. These particles, less than one micron wide, are small enough to infiltrate deep into human lungs.

A recent study by a team at Washington University in St. Louis offers the first high-resolution, 25-year dataset of PM 1 levels across the contiguous United States.

Particle pollution needs to be mapped

“This measurement serves as a starting point to understand which pollutants regulators could target to make the most effective health impact,” said study co-author Dr. Randall Martin.

Unlike PM 2.5, which includes larger particles like dust, PM 1 is mostly made up of combustion products: black carbon, sulphates, and organic matter.

These smaller particles reach the alveolar regions of the lungs and cause more damage per unit mass. PM 1 can come from diesel exhaust, wildfires, and also industrial emissions.

Because the pollutant bypasses the body’s defenses more easily, its impact may be more severe. These particles are about six times smaller than red blood cells. Their size allows them to travel deep into lung tissues and even the bloodstream.

Wildfires are a setback

Thanks to environmental regulations, average PM 1 levels have dropped. From 1998 to 2022, the U.S. saw a significant decline in PM 1 levels at about 0.23 µg/m³ per year. This accounted for 86 percent of the total PM 2.5 reduction.

But since 2010, this progress has slowed due to wildfires, especially in the western states. Areas like Los Angeles and Phoenix now show higher uncertainties in PM 1 estimates because wildfires boost organic matter concentrations.

According the study, some western regions see annual PM 1 uncertainty levels exceeding 30 percent, mainly due to wildfire smoke.

Uneven distribution of particle pollution

The study shows that PM 1 levels remain highest in the eastern U.S. and in major cities. PM 1 sources are mostly human-made, making it easier to manage compared to natural dust.

Urban populations, especially Black and Asian communities, have seen the greatest improvements due to reduced combustion emissions.

But not all communities benefit equally. Native American communities, often living in the arid west, saw smaller reductions. Wildfires and natural dust contribute more heavily to their exposure, and these are harder to control.

Long-term monitoring of PM 1

This study used satellite data, chemical models, and ground stations to estimate particle levels across over eight million land pixels. The data aligns well with physical ground measurements from devices like MOUDI and TEOM.

According to the analysis, 83 percent of the U.S. population lived in areas with PM 1 uncertainty under 10 percent. “Putting the seven species together, we can calculate the total PM 1 concentration over the country,” said Dr. Chi Li, lead author of the study.

In 2022, the major components of PM 1 included organic matter, which made up 47 percent of the total, followed by sulphate at 22 percent, nitrate at 12 percent, black carbon at eight percent, and ammonium at seven percent.

In contrast, dust and sea salt, which are more prominent in PM 2.5, contributed less than five percent to PM 1.

What this means for future policy

“When EPA first promulgated a fine PM air quality standard in 1997, there was considerable discussion about regulating PM 1 or PM 2.5,” said study co-author Professor Jay Turner.

“For numerous reasons, including but not limited to the lack of health impacts studies for PM 1 compared to studies for PM 2.5, the latter was chosen.”

That may change. PM 1 is more closely tied to urban combustion, which makes it easier to regulate. Unlike mineral dust, these emissions can be managed through policy. The study strongly recommends integrating PM 1 into monitoring systems and health impact studies.

“This dataset offers unprecedented information for the United States about an important pollutant for which few other measurements exist,” said Dr. Martin.

Targeting tiny particles to save lives

As air pollution continues to change due to shifting environmental conditions and human activities, it becomes increasingly important to pay closer attention to these specific particles.

Although they are extremely small, they pose serious risks to human health and can penetrate deep into the body. For a long time, these harmful particles have not received enough attention in air quality regulations, making them a hidden danger in many communities.

However, researchers now have access to better tools, advanced monitoring technologies, and long-term data that make it possible to track and understand their impact more clearly.

With this new information, there is a real opportunity to create stronger protections and shape policies that respond more accurately to the health risks posed by particle pollution.

With continued efforts, PM 1 could become the next target for environmental health policy in the U.S. – a shift that might save thousands of lives each year.

The study is published in the journal The Lancet Planetary Health.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–