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Air Pollution Linked to Heart Disease
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). 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.
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 60 or older, with a 15.7 percent increase in CIMT for every 10 ug/m3 increase of PM2.5. Air pollution causes the body to produce oxidants (unstable molecules) that cause inflammatory reactions in both the respiratory tract and blood vessels, triggering artery damage.
Some air particles find their way into the blood or even the brain. Other constituents of air pollution may be neutralized locally, but secondary reaction products may still cause systemic responses. Given that cardiovascular disease is the leading cause of death, and that large populations are exposed to ambient PM2.5 at the levels observed in this study, these findings need to be corroborated by additional research.
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