EVANSTON, III.—It was a murder mystery playing out in major cities across the country and perplexing scientists. Thousands of people were dying from strokes and heart attacks within 24 hours of a spike in microscopic pollution. But scientists didn't have a smoking gun. They couldn't figure out why the pollution was triggering the deaths.

New research at Northwestern University's Feinberg School of Medicine has solved a key piece of the mystery. Northwestern researchers have discovered that microscopic air pollution, smaller than 10 microns or less than one-tenth of the diameter of a human hair, spurs hyperclotting of the blood. Gokhan Mutlu, M.D., lead author of the study and assistant professor of pulmonary and critical care medicine at the Feinberg School, and a physician at Northwestern Memorial Hospital, collaborated on the study with co-authors Scott Budinger, M.D., associate professor of pulmonary and critical care medicine, and David Green, M.D., professor of hematology and oncology, both at the Feinberg School and physicians at Northwestern Memorial Hospital.

People with previous blockages in the coronary or carotid arteries are at the highest risk. "It's important to get screened to see if you have one of these conditions. If so, when there are high levels of particulate matter, you should try to stay indoors and limit your exposure to the outside air," Budinger said.

The National Institute of Environmental Health Sciences supported the study.

ABERDEEN, Scotland—Poor indoor air quality can significantly worsen health problems in people with chronic obstructive pulmonary disorder (COPD), according to researchers in Scotland. High concentrations of fine particulate pollution were strongly linked to poorer health status. Dr. Osman and a team of researchers in Aberdeen, Scotland, measured concentrations of indoor air pollutants in the homes of 148 Scottish patients who had mild to severe COPD.

The researchers found that indoor concentrations of particulate pollution in the subjects' homes frequently exceeded standards for outdoor air. In at least one instance, the highest concentration of a home was more than 40 times that of the recommended maximum. "High levels of PM2.5 were recorded in the homes of patients with COPD," they wrote. "The highest levels of PM2.5 (particulate matter up to 2.5 g) were, on average, four times the maximum recommended by the U.S. Environmental Protection Agency for 24 hour periods," they continued, noting that a significant source of PM2.5 was environmental tobacco smoke. Nearly 40% of the subjects were current smokers, and 17 percent of non-smokers lived in "smoking environments" where others smoked in their homes. Both smokers and non-smokers were negatively affected by in­creased PM2.5, as measured by clinically significant differences in their SGRQ symptom scores. An analysis of the effect of IAQ on smokers versus non-smokers revealed that smokers suffered greater adverse effects that nonsmokers. No significant effects of NO2 or endotoxin levels were found.

Previous studies of indoor air quality tend to exclude smok­ers, which may have resulted in an overall underestimate of the impact of indoor air quality on health status, as well as painted an unrealistic picture of the COPD patient population. "The finding that indoor PM2.5 concentrations had negative respiratory health effects among both smokers and nonsmokers has important implications for future research," wrote Mark D. Eisner, M.D., M.P.H., of the University of California, San Fran­cisco, in an editorial in the same issue of the journal. "Further research is needed to elucidate the prospective effects of indoor air pollutants on adults with COPD." 

Dr. Osman in the article that appears in the first issue for Sep­tember ‘07 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.