A 10-year study involving more than 6,000 people in six U.S. cities provides information on the health impacts of particulates, nitrogen oxides and black carbon.

During the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) study, pollutants were monitored near participants’ homes and communities. Computational models that accounted for weather influences, traffic volumes, and other factors were applied to yield accurate pollutant levels at each subject’s home. Calcium deposits in participants’ heart arteries were tracked by routine CT scans.

An air pollution monitor used during the research. Image source: MESA Air.The MESA Air study was funded in 2004 by the U.S. Environmental Protection Agency. Other funding came from the National Heart, Lung, and Blood Institute and the National Institute of Environmental Health Sciences. The project involved researchers at a number of institutions, and characterized air pollutant exposures experienced by people in the National Heart, Lung, and Blood Institute’s Multi-Ethnic Study of Atherosclerosis.

The study finds that even at levels below regulatory limits, air pollution was shown to accelerate the progression of atherosclerosis – hardening of the arteries which can lead to heart attacks. For every 5 µg/m³ higher concentration fine particulate matter that is less than 2.5 microns in diameter, 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 — study subjects had a 4 Agatston units/year faster rate of progression of coronary artery calcium scores. This is about a 20% acceleration in the rate of these calcium deposits.

While U.S. ambient air quality standards which permit an annual average particulate concentration of 12 µg/m³, study participants were exposed to fine particulate concentrations in 9.2 - 22.6 µg/m³ range.

Researchers from University of Washington, Columbia University, University of California (Los Angeles), Wake Forest University, and other institutions were involved in the MESA Air project. The clinics were in Baltimore, Chicago, Los Angeles, New York City, St. Paul and Winston-Salem. Of the people in the study, 39% were white, 27% black, 22% Hispanic, and 12% Chinese.