Inhaling air pollution, specifically particulate matter, causes stress hormones to spike, which could help explain why long-term exposure to pollution is associated with heart disease, stroke, diabetes, and a shorter life span.

Researchers in Shanghai, China 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.

Researchers put working or non-working air purifiers in student dorm rooms for a period of 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.

Read the study results at