Tiny air-pollution particles can trigger inflammation in the bloodstream, potentially increasing the risk of heart attacks and even strokes, a new UC Irvine study shows.

The tiny bits of traffic-related pollution, known as ultrafine particles, reduced the presence of anti-oxidant enzymes in red blood cells in elderly people who live in Los Angeles, and whose blood was sampled weekly for up to 12 weeks.

Those samples were matched with readings from air-pollution monitoring equipment set up outside the independent-living facilities that were home to the 60 people tracked in the study between 2005 and 2007. All were 72 or older.

“We studied elderly individuals with a history of coronary artery disease,” said Ralph Delfino, a researcher in UC Irvine’s Department of Epidemiology and lead author of the report. “They’re considered to be at high risk of air pollution-related morbidity and mortality.”

Anti-oxidant enzymes remove reactive chemicals that cause oxidative stress inside cells, which can lead to inflammation. While the study did not assess heart attack risk directly, a lack of such enzymes are believed to raise those risks, he said.

“If anti-oxidant enzymes go down in red blood cells, it stands to reason oxidative stress goes up, inflammation goes up,” Delfino said. “Both those factors have been related to risk of heart disease.”

Other studies have shown that that risk could be as high as the risk linked to excessive cholesterol, he said.

Air pollution also was found to activate clotting factors in the blood called platelets; blood clots can cause stroke, and so increased air pollution could drive up stroke risk, although the study did not assess stroke risk directly, Delfino said.

He also saw seasonal variation.

“The associations were stronger in winter than in summer, which suggests that during cooler periods of air stagnation, the toxicity of particulate air pollution may be greater,” he said.

The study tracked specific types of carbon associated with auto exhaust, allowing the researchers to draw a close link between traffic-related pollution and inflammation in the blood.

The study was published online in April in “Environmental Health Perspectives.”

(Photo of air pollution monitor courtesy Ralph Delfino.)

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