April 12, 2004 -- Spending a lot of time in your car may put your heart's health at risk. A new study shows that prolonged exposure to dirty air inside vehicles could trigger potentially dangerous changes in heart function.
Prior studies have shown that exposure to fine airborne particulate matter is associated with cardiovascular events and mortality in older and cardiac patients. But now researchers say air pollution levels inside cars which are generally lower than outside, may also increase the risk of heart attack or stroke in people with existing health problems by changing the way the heart functions.
The study showed that exposure to in-car air pollution caused changes, such as increased markers of inflammation and increased blood clotting proteins, variations in heart rate, and other changes in the functioning of the cardiovascular system, in nine healthy state highway patrol troopers who worked in their cars.
In-Car Air Pollution Hazards
In the study, which appears in the April issue of the American Journal of Respiratory and Critical Care Medicine, researchers equipped each of the North Carolina State Highway Patrol cars with air quality monitors. Each of the troopers also wore a monitor that measured heart rates during four consecutive 3 p.m. to midnight shifts and until the next morning, and had their blood drawn 14 hours after each shift.
"Pollutant levels in the patrol cars of the analyzed troopers were highly variable but were always well below occupational threshold values," says researcher Michael Riediker, in a news release. "In-vehicle [particulate matter] was 24% lower than ambient and roadside concentrations, whereas in-vehicle carbon monoxide, nitrogen dioxide, aldehydes, hydrocarbons, and some metals were elevated."
Researchers say that, on average, troopers spent 35% of their shift away from their cars, mostly inside buildings, such as offices, jail, hospitals, or at dinner.
Overall, researchers say that the troopers were in excellent health and appeared to be at low risk for heart or other health problems. But they found prolonged exposure to air pollution inside the troopers' vehicles prompted changes in the heart rate that could be hazardous in less healthy individuals.
Heart rate variability measures the nervous system function of the heart, which controls blood vessel widening or stiffening, blood pressure, the heart's electrical activity and its ability to contract and pump blood. Previous studies have shown that heart rate variability is decreased in heart conditions such as coronary heart disease and heart rhythm abnormalities like arrythymias.
"This study shows a strong and consistent increase of heart rate variability in association with [particulate matter]," says Riediker. He says that the pattern of change seen in the officers suggested changes in the cardiovascular system.
Researchers say those changes do not seem desirable and show that exposure to in-car air pollutants "should be minimized."