Air pollution below EPA thresholds still poses heart health risks

Air pollution does not have to exceed federal limits to potentially harm human health, according to a new review published in Environmental Pollution.

In a review of decades of air pollution studies, University of Mississippi researchers found evidence that exposure to PM2.5 – microscopic particles produced by traffic, industry and smoke – may harm heart health even at concentrations below the Environmental Protection Agency's regulatory guidelines. The review was published in Environmental Pollution.

In the United States, having regulations in place through the EPA allows us to track areas of nonattainment, or when the (air pollution) concentrations are above regulations. If we can identify that (an area) is above regulation, then we have the power to do something about it.

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."

Courtney Roper, assistant professor of environmental toxicology, University of Mississippi

PM2.5 is a size category of air pollution where particles are less than 2.5 microns across. In comparison, a human hair is about 50 to 70 microns. When inhaled, PM2.5 particles are small enough to pass through the lungs and into the bloodstream, where they can affect many areas of the body.

The researchers reviewed 95 studies from around the world on the impact of low-level PM2.5 exposure on cardiovascular health. Some 67% of the studies showed significant associations with heart disease.

Certain populations – such as older adults, very young children, people with preexisting heart conditions, impoverished individuals and marginalized populations – were particularly vulnerable to low-level exposure.

"The risk is also dependent upon the source of PM2.5," said James Stewart, associate professor of pharmacology. "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."

Exposure to PM2.5 can affect the buildup of plaque in the walls of the arteries, possibly leading to blood clots, heart attacks, strokes or other forms of heart disease. Cardiovascular disease is the leading cause of death worldwide and the No. 1 cause of death in Mississippi.

"While this article was looking only at cardiovascular effects, it doesn't just stop there," Stewart said. "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.

"In Mississippi it's very relevant because we have rural and industrial and urban pollutants. If individuals have an underlying condition, then it can make that condition worse."

Roper's previous research has found elevated levels of one PM2.5 component, soot, across multiple locations in Mississippi and linked exposure to an increase in respiratory-related hospital admissions in Jackson.

For people in vulnerable populations, Roper and Stewart advise considering certain precautions.

"What I would suggest to someone who is concerned is to look at some of the existing resources for air quality and be mindful of how that changes in your area," Roper said. "On days that the air quality is poor, limit your time outdoors or take precautions like home air filtration or wearing a mask on particularly bad days."

High-efficiency particulate air filters can remove particles as small as 0.03 microns, and N95 masks can filter PM2.5 pollution. Air quality reports are available daily on most weather applications, including those on Apple and Android smartphones.

"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."