Air pollution may harm your heart even below EPA safety limits

Most of us assume that air quality regulations exist to protect us. If the pollution in your city is within the legal limits set by the EPA, you’re probably fine. 

A new review says that assumption deserves a rethink, at least when it comes to your cardiovascular system.

Researchers at the University of Mississippi reviewed 95 studies from around the world to investigate how low-level exposure to fine particulate matter (PM2.5) affects the heart. 

PM2.5 includes tiny airborne particles produced by traffic, industrial activity, wildfires, and agricultural dust.

Two thirds of the studies found significant associations between PM2.5 and cardiovascular disease, even at concentrations that fall below current EPA regulatory thresholds.

Study lead author Courtney Roper is an assistant professor of environmental toxicology at the University of Mississippi.

“If we were looking to make a regulation that was just focused on human health, our reviews suggest that the regulation should be lowered because we are seeing cardiovascular impacts,” said Professor Roper.

Why PM2.5 does so much damage

PM2.5 refers to particles smaller than 2.5 microns in diameter. A human hair is between 50 and 70 microns wide. 

These particles are, in other words, extraordinarily tiny – and that’s exactly the problem.

They’re small enough to pass straight through the lungs and into the bloodstream, where they can travel to the heart, the liver, the kidneys, and anywhere else blood flows.

Once in the circulatory system, PM2.5 can contribute to plaque buildup in arterial walls, raising the risk of clots, heart attacks, and strokes. 

Cardiovascular disease is already the leading cause of death worldwide. Adding a source of risk that operates below the threshold of regulatory concern makes the picture worse.

“While this article was looking only at cardiovascular effects, it doesn’t just stop there,” said co-author James Stewart, an associate professor of pharmacology at the University of Mississippi. 

“Once it gets into the circulatory system, it can impact other organs like the liver, pancreas, kidneys or any organ that deals with blood, and blood goes everywhere.”

Pollution sources and vulnerable groups

Professor Stewart noted that the health risks are also dependent upon the source of PM2.5.

“Whether it’s traffic pollution or manufacturing industrial pollution, or even rural pollution, where you have harvesting or plowing generating dust, that can impact human health on so many levels. We, the public, don’t recognize how detrimental it can be.”

Some groups are more exposed and more vulnerable than others.

Older adults, young children, people with existing heart or lung conditions, and people in lower-income or marginalized communities face higher risk. 

In Mississippi, where the research team is based and where industrial, urban, and rural pollution sources all overlap with high rates of underlying health conditions, the combination is particularly concerning.

Professor Roper’s own earlier research found elevated soot levels – one component of PM2.5 – at multiple sites across the state, and linked that exposure to increased respiratory hospital admissions in Jackson.

Problems with the regulatory threshold

The EPA’s PM2.5 regulations exist for a reason. They provide a framework for identifying areas where pollution is clearly too high and something must be done about it. 

But the evidence here raises an uncomfortable possibility: the threshold may be calibrated to define regulatory compliance rather than actual safety. 

Areas that never trigger enforcement action may still be slowly damaging the cardiovascular health of the people who live there.

“In the United States, having regulations in place through the EPA allows us to track areas of nonattainment, or when the concentrations are above regulations,” Roper said. 

“If we can identify that an area is above regulation, then we have the power to do something about it.”

What people can actually do

For people who want to do something about their own exposure in the meantime – particularly those in vulnerable groups – the researchers have practical suggestions.

Air quality data is available daily through most smartphone weather apps. On days when it’s poor, spending less time outdoors helps. 

HEPA air filters at home can remove particles far smaller than PM2.5. N95 masks, when worn outside on bad air days, filter the relevant particle range effectively. 

None of these are perfect solutions to a systemic problem, but they’re available now.

The next step is public awareness

The deeper issue is that most people simply don’t know this is a problem. PM2.5 is invisible and odorless so you can’t tell when you’re breathing it. 

And if the numbers on the regulatory dashboard look fine, there’s no obvious signal that anything is wrong.

“Public awareness is the next step,” Stewart said. “We need to increase education and general public awareness around this problem.” 

“Health care workers should be paying attention to fluxes in pollution to better address health needs of patients.”

“The question is not just, ‘How can we treat exposure?’ but ‘How can we prevent it?’ That starts with public awareness.”

The study is published in the journal Environmental Pollution.

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