Heart transplant recipients who live in areas where particulate matter air pollution levels reached above national limits for clean air had a 26 percent higher risk of mortality due to infection, according to a study published Dec. 9 in the Journal of the American College of Cardiology.

Sadeer G. Al-Kindi, MD, et al., looked at data from 21,800 patients from the United Network for Organ Sharing/Organ Procurement and Transplantation Network. Researchers compared the particulate matter levels in the air (commonly produced from power plants, motor vehicles or airplanes) of each patient's ZIP code against the U.S. National Ambient Air Quality Standards applied to outdoor air throughout the country. Approximately 21.9 percent of heart transplant recipients were living in areas where particulate matter levels exceeded NAAQS limits for clean air. ZIP codes that had higher air pollution had larger populations, higher percentages of minorities, a larger number of households and higher unemployment rates.

Results showed that heart transplant recipients who had long-term exposure to air pollution over several years had a 26 percent heightened risk for mortality due to infection for every 10 µg/m3 increase in particulate matter levels. After a follow-up of 4.8 years, 23.9 percent of patients died. The association between air pollution and mortality was consistent across all examined subgroups. Researchers also found that air pollution exposure resulted in inflammatory responses and increases in blood pressure and insulin resistance, as well as a weakened immune system.

"This study makes an important contribution to our understanding of the health effects of air pollution," said C. Arden Pope III, PhD, in an accompanying editorial comment. "It used a straightforward approach to evaluate health effects of air pollution in a unique cohort of individuals in a vulnerable health state. It provides intriguing evidence that exposure to air pollution substantially contributes to mortality risk in cardiac transplant patients."

Keywords: Particulate Matter, Blood Pressure, Insulin Resistance, Air Pollution, Blood Pressure Determination, Heart Transplantation, Immune System, Tissue and Organ Procurement

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