Coarse particulate matter in outdoor air raises bad cholesterol

May 10 2007

Breathing air containing coarse particulate matter such as road or construction dust may cause heart problems for asthma sufferers and other vulnerable populations, according to a new study led by the University of North Carolina at Chapel Hill School of Public Health.

The researchers found that in people with asthma, a small increase in coarse particulate matter in outdoor air raised bad cholesterol and increased the count of inflammation-linked white blood cells, among other changes.

"This research was all done with study participants just being outside and breathing outdoor air," said Dr. Karin Yeatts, research assistant professor of epidemiology at the UNC School of Public Health, a member of the UNC Center for Environmental Medicine, Asthma and Lung Biology, and the study's principal investigator. "Our results indicate that susceptible people really need to pay attention to air pollution warnings and stay inside when the air pollution is bad. This is particularly the case for people with asthma."

The study, published in the May 2007 issue of Environmental Health Perspectives, was a collaboration by researchers from the School of Public Health, the School of Medicine's Center for Environmental Medicine, Asthma and Lung Biology and the U.S. Environmental Protection Agency (EPA).

The team found that when adult asthma sufferers were exposed to a one microgram per cubic meter increase in coarse particulate matter in ambient air their triglyceride levels increased by nearly five percent. Elevated levels of triglycerides have been shown to increase one's risk of coronary heart disease. The amount of eosinophils in study participants, blood also increased by 0.16 percent after exposure to the higher levels of coarse particulate matter. Eosinophils are a type of white blood cell created by the human body to fight infections, allergies and diseases like asthma among other things. Finally, the same increase in coarse particulate matter resulted in a three percent decrease in a measure of heart rate variability, the variation of the beat-to-beat intervals of the heart. A healthy heart has wide heart rate variability, while decreased variability can indicate stress or cardiac disease.

Surprisingly, there was no relationship between coarse particulate matter and rescue medication use, asthma symptoms, lung function or airway inflammatory markers, Yeatts said. However, 10 of the 12 adult asthmatics in the study were taking anti-inflammatory controller medication for their disease, and nine of the 12 had mild disease. It is possible that anti-inflammatory treatment mitigated the effects in their airways, or that adults with asthma are less susceptible to the effects of coarse particulate matter.

Study participants consisted of 12 adults between the ages of 21 and 50 with persistent asthma. All lived within a 30-mile radius of the study's particulate matter monitor, located on the EPA Human Studies Facility at the Carolina campus. Each study participant took part in nine clinic visits: five the first week, and four spaced randomly over the subsequent six to 11 weeks. Data collection took place between September 2003 and July 2004. During the study, outdoor air levels of coarse particulate matter ranged between zero to 14.6 micrograms per cubic meter and did not exceed safety levels set by the EPA of 150 micrograms per cubic meter.