While everyones' arteries harden gradually with age, a team of researchers led by epidemiologist（流行病学家） Sara Adar of the University of Michigan School of Public Health discovered that higher concentrations of fine particulate air pollution were linked to a faster thickening of the inner two layers of the carotid（颈动脉的） artery³.

 

Because the carotid artery feeds blood to the neck, head, and brain, a narrowing or blockage⁴ there can trigger strokes. And general atherosclerosis, or hardening of the arteries, is a major risk factor for cardiovascular disease, heart attack, and heart failure.

 

Past research has demonstrated that the rates of stroke and heart attack are higher in polluted areas, but experts haven't been able to pinpoint⁵ just how polluted air is raising peoples' risk for heart attack or stroke. This time, Adar's team, along with Joel Kaufman, professor of environmental and occupational health sciences and medicine at the University of Washington, was able to directly measure carotid artery thickness and link it to air pollution data.

 

The study involved 5,362 people between the ages of 45 and 84 living in six different cities that are part of the MESA AIR (Multi-Ethnic Study of Atherosclerosis and Air Pollution) research project, led by Joel Kaufman. Each participant underwent two carotid artery ultrasounds three years apart. These measurements were then correlated with data on fine particulate air pollution.

 

While the artery walls of all participants increased by 14 micrometers per year, the arteries of those who were exposed to higher levels of fine particulate air pollution in their homes thickened faster than their neighbors in other parts of the city. 

 

Interestingly, the researchers also found the reverse effect to be true: reducing fine particulate air pollution levels slowed down atherosclerosis progression. Carotid artery measurements are considered by experts to be an indicator⁶ for arterial plaque⁷（血小板，斑块） and hardening throughout the body.

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