Breathing particulate-laden air causes stress hormones to spike, according to new research. This could help explain why long-term exposure to pollution is associated with heart disease, stroke, diabetes, and a shorter life span.

Dr. Haidong Kan of Fudan University in Shanghai, China, and colleagues looked specifically at the health effects of particulate matter (PM), small particles less than 2.5 millimeters in diameter, from industrial sources, that can be inhaled and become lodged in the lungs. While PM levels have gone down in North America in recent years, they are on the rise worldwide.

The study, published in Circulation, included 55 healthy college students in Shanghai, a city with pollution levels in the middle range compared to other Chinese cities, according to Dr. Kan.  He and his colleagues put working or non-working air purifiers in each student’s dorm and left them in place for nine days. After a 12-day period during which the filters were removed, the researchers did another nine-day test: the students in the original functioning-filter group got non-working filters, and those in the original nonfunctioning-filter group got filters that worked. At the end of each nine-day period, the researchers tested levels of a wide range of small molecules in students’ blood and urine as indication of their exposure to PM.

Students’ levels of the stress hormones cortisol, cortisone, epinephrine and norepinephrine rose with dirtier air, as did their levels of blood sugar, amino acids, fatty acids and lipids. Higher exposure to PM was also associated with higher blood pressure, a worse response to insulin, and markers of molecular stress on body tissues - all of which can, over time, increase the risk for heart disease, diabetes and other problems.

Air purification cut the amount of PM students were exposed to in half, from 53 micrograms per cubic meter of air to 24.3 micrograms per cubic meter – but that was still well above the World Health Organization’s Air Quality Guideline of 10 micrograms per cubic meter.

Source: Reuters Health