According to a study in Mar. 13's Journal of the American Heart Association, researchers have shown air pollution has a negative affect on the blood vessels of healthy humans.
In the study, 25 healthy people inhaled elevated concentrations of fine particles plus ozone for two hours. After exposure, volunteers' blood vessels constricted between 2 and 4 percent on average. Their vessels did not constrict when they were exposed to ozone-free and particle-free air.
Researchers focused on ozone and fine particulate matter. Fine particles are those with a diameter of less than 2.5 micrometers. Fine particles are emitted from burning fossil fuels, mostly from car and diesel engine exhaust, power generation and manufacturing plants. Ozone and additional particulate materials are created when the sun shines on these emissions.
"In other research, exposure to fine particles has been implicated in coronary events such as heart attacks," study co-author Dr. Robert Brook explains. "In contrast to larger particles, which are trapped in the upper airways when inhaled, the fine particles travel down to the alveoli, tiny air sacs at the base of the lungs, where they can affect the rest of the cardiovascular system by adversely impacting circulating blood. It is possible that the particles may even directly enter the blood."
Brook described the exposure as similar to those found in urban areas during peak air pollution times such as rush-hour traffic.
At least two days before or after the pollutant exposure, subjects underwent the same measurements after being exposed to air that was filtered to remove the pollutants.
The volunteers' arteries showed no change in response to breathing filtered air, but constricted from 2 to 4 percent in response to the polluted air.
"Although the degree of constriction in and of itself is unlikely to produce significant problems in healthy individuals, such a constriction could conceivably trigger cardiac events in those individuals who have or are at risk for heart disease," Brook said.
These are the first findings to show such an effect in people. Because the 25 subjects in this study were all healthy and relatively young (average age 35), these results call attention to the need for further research on the air pollution problems that plague most of the world's major cities, Brook said.
"Our results are a clear demonstration that environmentally relevant concentrations of common air pollutants that can occur in urban settings adversely affect the blood vessels of healthy people," Brook explained.
Brook adds that more research is needed to fully understand why air pollution has negative effects on blood vessels and to clarify the public health implications of the findings of these initial studies.
The study was conducted at the University of Toronto and funded by the Toxic Substance Research Initiative, a joint program of the Canadian Federal Ministries of Health and Environment, known as Health Canada and Environment Canada.
In the United States, the Environmental Protection Agency estimates that air pollution contributed to 60,000 heart-related deaths in 1996, according to figures in the Federal Register.