Air pollution may trigger and accelerate narrowing of carotid arteries, according to a study presented at the American Heart Association's Scientific Sessions 2004.
Researchers found an association between long-term air pollution exposure and the early stages of atherosclerosis (hardening of the arteries).
"We knew that people in more polluted areas die earlier from cardiovascular disease, but it was not clear how early in the disease process air pollution contributes. Our study found that air pollution may contribute to cardiovascular problems at a very early stage of the disease, similar to smoking, and enhances atherosclerosis, which is the underlying disease process of cardiovascular diseases," said study author Nino Kuenzli, M.D., Ph.D., associate professor, division of environmental health, Keck School of Medicine at the University of Southern California in Los Angeles.
Researchers reviewed data from two clinical trials on 798 people age 40 and older who lived in the Los Angeles area. The data included baseline measurements of the thickness of the inner lining of participants' neck arteries (carotid artery intima-media thickness or CIMT). CIMT is measured by ultrasound and used to determine the level of subclinical atherosclerosis.
Researchers then assigned a PM2.5 particle level to the study subjects' home ZIP codes. PM2.5 particles are pollutants with a diameter of 2.5 micrometers or less. They are commonly produced by burning fossil fuels such as driving cars, and smelting and processing metals. They are tiny enough to be inhaled into the smallest airways.
PM2.5 levels are measured in micrograms per meter cubed (ug/m3). In this study, readings ranged from 5.2 to 26.9 ug/m3.
For every 10 ug/m3 increase of PM2.5, CIMT increased by 5.9 percent. After adjusting for age, socio-demographic, lifestyle (including active and passive smoking) and physiological factors, researchers determined that CIMT rose by 3.9 percent to 4.3 percent for every 10 ug/m3 increase in PM2.5. The association between air pollution and CIMT was even greater among people over age 60, women and people taking cholesterol-lowering medication.
Overall, the strongest association was seen in women age 60 or older, with a 15.7 percent increase in CIMT for every 10 ug/m3 increase of PM2.5.