(iVillage Total Health) - Breathing in air polluted with construction or road dust may raise blood lipid levels and increase the risk of heart problems for people with asthma, a new study says.
Researchers from the University of North Carolina at Chapel Hill led a team that included the U.S. Environmental Protection Agency (EPA). They studied 12 patients between the ages of 21 and 50 who had persistent asthma. The participants lived within a 30-mile radius of the EPA's particulate matter monitor in Chapel Hill, a device that keeps track of levels of dust, soot and other small pieces of solid materials released into the air.
The study was conducted between September 2003 and July 2004. Participants were followed, had their hearts monitored and given a series of blood tests during nine clinic visits. Researchers found that increases in particulate matter levels—as monitored by the EPA—were associated with an increase risk for coronary artery disease (CAD).
CAD is a chronic disease in which blood flow is obstructed through the coronary arteries that supply the heart with oxygen-rich blood. The obstruction is caused by atherosclerosis, commonly known as "hardening of the arteries." An estimated 13.2 million Americans have CAD, which is also referred to as coronary heart disease.
Researchers measured levels of cholesterol, a waxy fat that lines blood vessels and contributes to CAD, triglycerides, another type of fat linked to increased heart disease risk, and eosinophils, types of white blood cells that are elevated in the blood of people with allergic reactions.
Five percent increases in participants' triglyceride levels were associated with a one microgram per cubic meter increase in coarse particulate matter content of the air they breathed. The same increase in pollution also raised the very low density lipoprotein (VLDL) cholesterol by more than 1 percent. After participants were exposed to higher levels of coarse particulate matter, they experienced a 0.16 percent increase in their levels of eosinophils, a type of white blood cell that increases in response to allergens.
The researchers noted that heartbeat variability was also affected by the air pollution. Decreased variability in heartbeats can be an indication of stress or cardiac disease. Participants experienced 3 percent decreases in their heart rate variability when coarse particulate matter levels increased.
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"This research was all done with study participants just being outside and breathing outdoor air," Dr. Karin Yeatts, the study's principal investigator, said in a press release. "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 found no relationship between coarse particulate matter levels and asthma symptoms, lung function, rescue medication use or airway inflammation markers, but researchers said this may have been attributed to the fact that 10 of the 12 participants took anti-inflammation medication and nine of the 12 had only mild asthma.
The study was published in the May issue of Environmental Health Perspectives.
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