Researchers at the University’s Cardiovascular Center recently uncovered the short-term effects of air pollutant exposure on heart health.
Led by Dr. Robert Brook, an assistant professor of internal medicine, the study documented cardiovascular responses in subjects who were exposed for two hours to environmental levels of ozone and fine particulate matter.
The results, they report, were not promising.
Brief exposure was shown to cause an increase in diastolic blood pressure — the lower number in general blood pressure readings representing the pressure between heart contractions. Brook said the increase in blood pressure was associated with vasoconstriction, a narrowing of blood vessels.
The study also concluded that, 23 hours after the initial exposure, subjects’ blood vessels did not function properly which could be attributed, in part, to inflammation throughout the body.
“The bottom line evidence was that the very rapid increase in the diastolic blood pressure that occurred within minutes of exposure and lasted for up to two hours was caused by a disruption in the body’s sympathetic nervous system,” Brook said.
Conducted in downtown Toronto and Ann Arbor, the study placed subjects in a controlled experimental chamber that drew in air from outside, maintaining environmentally relevant levels of air pollutants.
“Even though we are living in an area and time that is cleaner than ever before, the levels we have seen within Washtenaw County still pose a discernible health risk to people,” Brook said.
As it turns out, the most serious offender in pollution-linked heart disease is not ozone, as many believe, but rather fine particulate matter measuring a miniscule 2.5 micrometers in diameter or smaller.
Over time, persistent exposure to fine particulate matter could lead to premature heart disease or similar cardiac issues in people with susceptibilities such as underlying high blood pressure, heart disease and heart failure, Brook said.
Brook said the study aimed to “see how it’s possible that a tenth of what you would encounter in a smoky bar can trigger heart attacks, stroke, heart failure, arrhythmia or death in 24 hours.”
Moreover, he said the findings were intended to provide additional support and plausibility to the epidemiologic studies that have shown a correlation between air pollutants and heart disease.
Between 25,000 and 60,000 people in the United States die prematurely each year from air pollution exposure, and, worldwide, air pollution is the 13th leading cause of mortality.
“Over the last few years, there has been increasing levels of evidence that air pollutants, even if they’re at lower levels here in the United States and North America, still pose a significant health risk,” Brook said.
Brook cited epidemiologic studies showing that exposure over a five-year period to ten micrograms per cubic meter in fine particulate matter increases the risk of dying from heart disease by up to 75 percent.
He said studies have already shown that long-term effects of air pollution can lead to atherosclerosis — a condition defined by hardening of the arteries.
“Although the responses were small and didn’t cause problems in healthy people, the thought process is that this is something that could be harmful if distributed to tens of millions of people throughout the United States,” he said.
But Brook said he was confident that the healthy student population was unlikely to contract premature cardiovascular disease as a result of air pollutants, but susceptible people with underlying conditions should consider minimizing exposure whenever possible. Avoiding long commutes, second-hand smoke and major roadways when outside are among the best precautions, he said.
“I’m not asking people to wear masks, and I’m not asking them to move to completely pristine areas,” Brook said. “But there’s a lot of personal responsibility you can take for the level of pollutants that you’re exposed to.”