A decade-long study of thousands of Americans has found direct evidence of how air pollution causes heart disease. The link between the two has been established a long time ago, but it’s only now that the biological mechanisms have been explained thoroughly.

air pollution

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The Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) followed 6,000 Americans living in six states over ten years. For each participant, researchers calculated the exposure to particle matter that is less than 2.5 microns (PM 2.5), as well as nitrogen oxide, nitrogen dioxide and soot. The calculations were based on air pollution measurements taken in the participants’ communities, as well as directly at their homes.

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Then, each participant underwent regular CT scans between 200 and 2012 to determine the amount of calcium deposits in their arteries.

PM 2.5 is small that you can’t see it with the naked eye, but when bulked these create haze — the main cause of reduced visibility in the United States. Being so small, the particles also easily enter the body, ending up in the lungs and even the bloodstream. Nitrogen dioxide inflames the lining of the lungs, and it can reduce immunity to lung infections.

The study found that for every 5 µg/m3 higher concentration of PM2.5 or 35 parts per billion higher concentration of oxides of nitrogen, participants had a 4 Agatston units/year faster rate of progression of coronary artery calcium scores. An Agatston score of 0 is normal (little risk of heart disease in the next 3 to 5 years), but “in this population, coronary calcium increased on average by 24 Agatston units per year (SD 58), and intima-media thickness by 12 μm per year (10), before adjusting for risk factors or air pollutant exposures,” the researchers noted. Eventually, this leads to hardened arteries causing atherosclerosis, which in turn causes heart attacks.

“The study provides important new information on how pollution affects the main biological process that leads to heart disease,” said Dr. Joel Kaufman, the lead author of the paper published in The Lancet.

“The evidence supports worldwide efforts to reduce exposures to ambient air pollutants,” Kaufman said.

“This was the most in-depth study of air pollution exposures ever applied to a large study group specifically designed to examine influences on cardiovascular health,” he added.

Previously, ZME Science reported air pollution is responsible 3.3 million premature deaths worldwide.

  • About 6 percent of all global deaths each year occur prematurely due to exposure to ambient air pollution. That’s higher than previously estimated not 10 years ago.
  • In 2050, 6.6 million people are projected to die prematurely from air pollution.
  • Air pollution kills more than HIV and malaria combined.
  • China has the most air pollution fatalities numbering 1.4 million, followed by India with 645,000 and Pakistan with 110,000.
  • In the US (2010), 54,905 fatalities were accounted to smog and soot. This ranks the country 7th on the air pollution fatality list.
  • For industrial nations, farming takes a surprisingly large share of the soot and smog pollution. For instance, in the US, agriculture caused 16,221 of those deaths, second only to 16,929 deaths blamed on power plants. But in  Europe, Russia, Japan and South Korea, agriculture was found to be the prime cause of the soot and smog deaths.