A study published in the European Heart Journal has found that exposure to traffic-related pollution may cause an increase in stroke risk.

According to Reuters, researchers used a background air pollution monitor to measure the amount of small polluting particles produced by cars over four years. Then they compared the levels of these particles on certain days with the number of hospital admissions for different kinds of strokes at hospitals close to the monitor.

They found a 21 percent increase in hospital admissions for mild, ischemic following the days when air pollution was highest.

Stroke is a disease that affects the arteries leading to and within the brain. It is the number three cause of death in the United States, behind diseases of the heart and cancer. About 795,000 Americans each year suffer a new or recurrent stroke. That means, on average, a stroke occurs every 40 seconds, according to the American Stroke Association.

Common risk factors include high blood pressure, smoking, diabetes, heart disease, high cholesterol, poor diet, physical inactivity and obesity.

Individuals can reduce exposure to air pollution by avoiding living in high-traffic areas and taking less congested roadways, when possible.