A recent American study published in the Journal of Circulation Research has suggested that very fine particles emitted from vehicles triggers an inflammatory response in the arteries which in turn leads to atherosclerosis and an increased risk of heart attacks and strokes.
The five week study involved exposing mice to ultra-fine particles sourced from a Los Angeles freeway. These mice experienced a 55% increase in the formation of atherosclerotic lesions when compared to mice breathing filtered air free of the particles.
“Ultrafine particles may deliver a much higher effective dose of injurious components, compared with larger pollutant particles,” said research leader Dr. Andre Nel who is chief of nano-medicine at UCLA.
These small particles, measuring less than 0.18µm, are too small to be regulated by the Environmental Protection Agency (EPA) under current legislation.
The study adds to a growing body of evidence suggesting that the dramatic increases in heart disease over the past century can be attributed, at least in part to the increasing number of people living in heavily polluted areas. A 2006 study, published in The Journal of the American Medical Association, found that a 10 µg per cubic meter increase in particulate matter in the atmosphere corresponded to a 28% increase in hospital admissions for heart failure in that area.
The most polluted cities in the United States, as measured by PM10 levels (particulate matter less than 10 µm), are Cleveland, Detroit, and Los Angeles, while the least polluted cities are San Diego, San Antonio, and Dallas. Not unsurprisingly, heart disease rates tend to be lower in less polluted cities. In San Diego county for example, the age adjusted coronary heart disease rate for 2006 was 118.5 per 100,000 which is 20% lower than the national average.
A report, published in the Journal of Toxicology and Environmental Health in 2005 estimated that 3% of cardiopulmonary deaths, and 1% of cancer deaths globally can be attributed to outdoor air pollution.
Researchers believe that the particles use arteries to harden by inactivating the protective properties of HDL cholesterol. HDL or high density lipoprotein cholesterol is known as the “good cholesterol” as it helps reduce arterial inflammation which is the precursor to atherosclerosis.
Atherosclerosis leads to both the hardening of the arteries and the restriction of blood flow through the artery due to the formation of plaques. This in turn can lead to potentially fatal events such as myocardial infarction (a heart attack), and the formation of an aneurysm (a blood filled bulge in the arterial wall). The rupture of an aneurysm is a catastrophic event that frequently leads to death.
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