Clearing the Air: The Link Between Air Pollution and Heart Disease

By Dorothy L. Tengler, via Multibriefs

Whether you live in a city where smog forecasts are routine or in a less populated place, tiny pollution particles in the air can lead to big problems for your heart. Over the last decade, a growing body of epidemiological and clinical evidence has led to a heightened concern about the potential deleterious effects of ambient air pollution on health and its relation to heart disease and stroke.

People living in areas with more outdoor pollution — even at lower levels common in the United States — accumulate deposits in the arteries that supply the heart faster than do people living in less polluted areas. Although long-term exposure to air pollution has been linked to an increased risk of heart disease, the biological process has remained unclear.

Now, direct evidence from the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air), a 10-year epidemiological study of more than 6,000 people from six U.S. states, shows that air pollution — even at levels below regulatory standards — accelerates the progression of atherosclerosis, with the danger of causing heart attacks.

Researchers repeatedly measured calcium deposits in the heart's arteries by using computed tomography (CT) scans. They also assessed each person's exposure to pollution based on home address.

According to Dr. Joel Kaufman, who directs MESA Air and is a University of Washington professor of environmental and occupational health sciences, the study provides important new information on how pollution affects the main biological process that leads to heart disease.

The research team collected thousands of air pollution measurements in the study participants' communities and at their homes, then developed and applied computational models that included local information on land use, roadway and traffic volumes, weather conditions, and local sources of air pollution. These models could generate accurate pollution concentrations at each person's home.

Meanwhile, between the years 2000 and 2012, participants visited study clinics several times to undergo CT scanning to determine the amount of calcium deposits in their heart arteries.

Results were strongest for fine particulate matter and the traffic-related pollutant gases called oxides of nitrogen. The study found that for every 5 µg/m3 higher concentration of PM2.5, or 35 parts per billion higher concentration of oxides of nitrogen — about the difference between more and less polluted areas of a U.S. metropolitan area — individuals had a 4 Agatston units/year faster rate of progression of coronary artery calcium scores, which is about a 20 percent acceleration in the rate of these calcium deposits.

The effects were seen even in the U.S. where efforts to reduce exposure have been notably successful compared with many other parts of the world. Exposures were low when compared to U.S. ambient air quality standards, which permit an annual average PM2.5 concentration of 12 µg/m3.

The participants in this MESA Air study experienced concentrations between 9.2 and 22.6 µg/m3. The evidence in the present study supports worldwide efforts to reduce exposures to ambient air pollutants and was the most in-depth study of air pollution exposures ever applied to a large study group specifically designed to examine influences on cardiovascular health.

In terms of fatal harm, the increase in disease rates related to air pollution may appear to be small when viewed in percentage terms. For example, the studies on particulate matter found hospital admissions increasing on the order of a single percent.

However, the large number of Americans who suffer from heart ailments translates the result into a large effect when measured nationally, in terms of total hospital admissions, numbers of illnesses, patient deaths and the costs to the economy of healthcare and days lost from work and school. Reducing our population's exposure to air pollutants remains an important aspect of improving cardiovascular health for the whole U.S. population.

Dorothy L. Tengler, MA, is a freelance medical writer/communication specialist with nearly 20 years of experience in the pharmaceutical and medical communication industries. She has developed educational and medical marketing materials, including monographs, slide kits, health articles, primary and review manuscripts, and pharmaceutical sales training materials.