Large airborne particles may trigger heart attacks

Small particles not the only danger to people with preexisting heart conditions
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This story was originally published by Environmental Health News

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Inhaling large dust particles from farms, roads, and construction sites may have some of the same effects on people’s hearts as small particulates, according to a new study.

The study, led by the University of Michigan, is the first to link coarse particulates to increased blood pressure, adding to previous evidence that they may increase risks of heart attacks.

Many studies already have linked fine particulate matter—which comes largely from vehicles and industries that burn fossil fuels—to heart risks. Less is known about the impacts of coarse particulates, which often come from stirred-up dust or soil.

Volunteers' blood pressure, heart rates rose

The experiments were conducted in airtight chambers, where 32 adults from Dexter, Michigan (a rural town about 60 miles west of Detroit), breathed in local air containing coarse particulates.

On another day two weeks later, they breathed local air that had been filtered. The unfiltered air had levels of coarse particles that were seven times higher than the levels in the filtered air.

When the volunteers inhaled the unfiltered air, their average blood pressure (both systolic and diastolic) linearly increased every 10 minutes, and their heart rates were elevated compared with the times they inhaled the filtered air.

Danger to those with existing conditions

The changes were “small in magnitude and thus unlikely to pose direct risks to healthy people”, the researchers wrote in the study published online in the journal Environmental Health Perspectives.

However, they could trigger heart attacks or other cardiovascular events in people with preexisting heart conditions, they wrote.

“Since millions of susceptible people are likely impacted by coarse PM [particulate matter], even a very small absolute increase in [cardiovascular] risk can translate into substantial global public health concerns,” the authors wrote.

The researchers didn’t evaluate long-term heart function.

Some previous studies had mixed findings

Some previous studies have linked coarse particulates to elevated heart rates and increased heart-rate variability. However, other health studies have had mixed findings.

The study was limited in its rural setting, which means the pollutants were largely from farming, so coarse particles in cities may have different impacts.

The United States has two health standards for particulates: those that are 10 micrometres in diameter or smaller (PM10) and those that are 2.5 micrometres or smaller (PM2.5). For PM10, cities and counties are not supposed to exceed an annual mean of 50 micrograms per cubic metre of air or a daily limit of 150.

[Canadian air-quality standards are more stringent than those in the U.S. but are voluntary.—GS]

Coarse-particle levels have declined 27 percent nationwide since 2002, according to the Environmental Protection Agency.

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