The Cardiovascular Sub-study of the Detroit Exposure and Aerosol Research Study (DEARS) is the first study to show that two different aspects of exposure — community wide and personal — have differing adverse health outcomes on the heart and blood vessels.
On the other hand, community exposure, which measures pollution in a broader area from fixed monitoring stations, but cannot determine as precisely a specific individual's exposure, was associated with impaired blood vessel functioning alone.
Sixty-five men and women from diverse ethnic backgrounds participated in the study. They ranged in age from 19 to 80 years, and 80 percent were women. All were nonsmokers living in nonsmoking households, in three different areas of Detroit.
Globally, air pollution is the 13th leading cause of death, according to Brook. Air pollution blankets cities throughout the world, the cumulative yearly exposure contibutes to tens of thousands of deaths in the United States and an estimated 800,000 deaths throughout the world, he said.
For three years, researchers examined the personal and community exposure to air pollutants for five consecutive days in the summer and five consecutive days in the winter. At the end of each research day, field investigators came to each participant's home to measure the effects of pollutants on blood pressure and blood vessel function.
Researchers found that a 10 microgram per cubic meter increase in personal exposure to pollution (as measured by the level of small particulate matter):
- narrowed brachial (arm) blood vessel diameter (a potential immediate condition that could lead to heart and vascular events) by 18 percent two days after exposure; and
- led to a 1.6 millimeter of mercury (mm Hg) jump in systolic blood pressure on the day following exposure.
Furthermore, researchers found that although the participants were nonsmokers living in nonsmoking homes and told to avoid tobacco smoke during the study, approximately 30 percent were still exposed to secondhand smoke.
"At the community level, a 10 microgram per cubic meter increase in pollution leads to a 1 percent increased chance of dying the next day," Brook said. "Within a city of 1 to 5 million, that increase would lead to about one death per day."
Researchers conclude that the sources and characteristics of air pollution may be important determinants of the health responses.