After decades of work showing that people die from heart attacks on days when pollution is stifling, researchers have finally garnered the first proof of a possible explanation for the link: Breathing ozone and fine particles of pollutants constricts arteries. The work points to a mechanism that puts people with chronic heart disease at greater risk of attacks on smoggy days.
A number of epidemiological studies have found that deaths from heart and lung disease spike on pollution-heavy days. And recent research has demonstrated that chronic exposure to air pollution, particularly tiny particles called fine particulate matter that are released when fossil fuels are burned, increases the risk of dying from heart and lung diseases. Still, how pollution upped that risk has remained murky, and consequently, industry representatives and scientists continue to debate the link between pollution and disease.
To determine whether air pollution impacts blood vessels, which are commonly overburdened in heart and lung disorders, vascular biologist Robert Brook of the University of Michigan, Ann Arbor, and his brother, atmospheric scientist Jeffrey Brook of the University of Toronto, in Canada, exposed 25 healthy men and women with no known risk of heart disease to levels of ozone and fine particles comparable to peak amounts in some smoggy cities. For 2 hours, the participants breathed laboratory-altered air that contained approximately 150 micrograms of fine particles per cubic meter and 120 parts per billion of ozone. Using an ultrasound machine, the scientists measured changes in the diameter of arteries in the upper arm after exposure ended. Each participant's arteries constricted by approximately 2% to 4%, a change that would do little damage to a healthy individual but could trigger heart trouble in someone with cardiovascular disease. When the same group breathed filtered air for 2 hours, the researchers observed no changes in the arteries, they report in the 12 March issue of Circulation.
The work is the first to show that air pollution constricts blood vessels, said chemical toxicologist John Froines of the University of California, Los Angeles. "It's an important preliminary study," said Froines, who also directs the Southern California Particle Center and Supersite, one of five centers established by the Environmental Protection Agency (EPA) to study the health effects of particulate matter. Ongoing studies at many of the U.S. centers are taking the next step, he said, examining the health effects of individual pollutants and particles of varying sizes, including their impact on blood vessels.