Study Finds That Air Pollution Increases Diastolic Blood Pressure

Researchers have found that inhaling air pollution for over just two hours caused a significant increase in diastolic blood pressure, the lower number on blood pressure readings.

Blood pressure is expressed with two numbers; the first number (systolic pressure) is the pressure when the heart beats while pumping blood and the second number (diastolic pressure) is the pressure in large arteries when the heart is at rest between beats.

High blood pressure (hypertension) is defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg.

Nearly one in three Americans suffer from high blood pressure, a significant health problem that can lead to heart attack, heart failure, stroke, and other life-threatening problems.

"Although this increase in diastolic blood pressure may pose little health risk to healthy people, in people with underlying coronary artery disease this small increase may actually be able to a trigger heart attack or stroke," says Robert D. Brook, lead author of the research.

In the study, researchers hoped to identify which air pollutants are harmful and how the pollutants work to damage the cardiovascular system.

Eighty-three people in Ann Arbor and Toronto were involved in testing and breathed air pollution, concentrated by a mobile air quality research facility, that was similar to what would be found in an urban environment near a roadway.

"We looked at their blood vessels and then their responses before and after breathing high levels of air pollution," explains Robert Bard, overall research project manager.

Ozone gases, a well-known component of air pollution, were not the biggest culprit. Rather, small microscopic particles about a 10th of the diameter of a human hair caused the rise in blood pressure and impaired blood vessel function, tests showed. The blood pressure increase was rapid and occurred within two hours, while the impairment in blood vessel function occurred later but lasted as long as 24 hours.

It's believed these fine particles deposit deep into the lungs and certain components may gain entrance to the blood stream, or cause an inflammatory response throughout the body. There is also evidence that functions in the body's nervous system are also disrupted.

The research is the latest in the relatively new field of Environmental Cardiology which looks at the association between air pollution and heart disease. Brook says that at the very least the findings support efforts to maintain current ambient air quality standards set by the Environmental Protection Agency.

"It really bolsters and strengthens the importance of maintaining air quality for human health," says Brook.

There are practical ways to avoid exposure to high levels of air pollution, such as avoiding unnecessary travel or commutes and not exercising during rush hour, or near busy roadways, Brook says. In modern society, the burning of fossil fuels is the primary source for air pollution.

"If air pollution levels are forecasted to be high, those with heart disease, diabetes or lung disease should avoid unnecessary outdoor activity," he says.

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References:
1. Robert D. Brook, et al. Insights Into the Mechanisms and Mediators of the Effects of Air Pollution Exposure on Blood Pressure and Vascular Function in Healthy Humans. Hypertension. 2009;54:659-667. doi: 10.1161/HYPERTENSIONAHA.109.130237.