The health impact of green cars, whether electric or hybrid, may be felt most by those not driving them. Living close to a major road, a new study finds, may increase a woman’s risk of dying from sudden cardiac arrest. "On a population level, living near a major roadway was as important a risk factor as smoking, diet or obesity," said Dr. Jaime E. Hart, an instructor in medicine at Brigham and Women's Hospital and Harvard Medical School, who added that proximity to a highway may simply indicate an increased exposure to air pollution.

Death Machines?

The average passenger vehicle emits about 411 grams of carbon dioxide per mile as compared to an electric car, which produces zero grams. While green cars are far from perfect from a pollution (and a driving) standpoint, few would argue against the idea of creating a less toxic vehicle. After all, the Environmental Protection Agency estimates that more than 45 million people in the United States lived within 300 feet of a major highway (4 or more lanes), a railroad, or an airport during 2009. Meanwhile, schools and child care centers are located within a few hundred feet of highways, particularly in urban areas and population trends suggest these numbers will only increase over time. Generally, heavier traffic, higher speeds, and more congestion (with on-and-off braking) contribute to higher emissions of certain pollutants. In fact, the combination of calm winds and rush hour often leads to the highest concentrations in the morning.

To understand how traffic might affect health, a team of researchers led by Hart studied data from 107,130 women (predominately white, average age of 60) who were part of the Nurses' Health Study from 1986-2012. After adjusting for age, race, calendar time, cigarette smoking, physical activity, diet, and other factors, the researchers calculated the distance between each participant’s residence and a high-traffic roadway and arrived at some startling conclusions.

Of these participants, 523 died of sudden cardiac arrest. For anyone living within 164 feet of a major road, the risk of a sudden cardiac death increased by 38 percent when compared to those at least 0.3 miles away. Each 328 feet closer to roadways was associated with a six percent increased risk for sudden cardiac death. In the 1,159 cases of fatal coronary heart disease, risk increased 24 percent for those living within 164 feet of a major road compared to those at a distance.

"Our next step is to try to determine what specific exposures, such as air pollution, are driving the association between heart disease and major roadway proximity," said Hart, who added that "maintaining a healthy weight, being physically active, eating nutritious foods, quitting smoking, and managing stress" could help you decrease your risk of heart ailments no matter where you find yourself at home.

Source: Hart JE, Albert C, Laden F, Chiuve SE. Circulation. 2014.