People exposed to high levels of traffic-related air pollution may have an increased risk of stroke, Danish researchers have found.
The study, published in the November issue of the medical journal Stroke, suggests that residents living urban areas with high concentrations of nitrogen dioxide from car exhausts were 22 percent more likely to have a fatal stroke than in areas with less traffic.
But the researchers could not say for certain that other factors, such as obesity, heart problems, high blood pressure, smoking, and other health problems and environmental factors, did not play a role in the number of strokes that occurred over the 10-year period of the study.
They also could not state for sure that nitrogen dioxide was a direct cause of strokes.
The study, which focused on two major cities in Denmark, is believed to be one of the largest ever undertaken to examine whether strokes can be linked to long-term exposure to air pollution. The researchers collected data and information from more 52,215 people over a decade. During that time, some 1,984 people experienced a stroke that put them in the hospital and 142 died with 30 days. Researchers noted that participants ranged in age from 50 to 65 at the start of the study.
Overall, the researchers found residents living in high traffic areas with greater concentrations of nitrogen dioxide were five percent more likely to have a stroke than people breathing clean air. They were 22 percent more likely to die.
Other studies have found that air pollution particles can be small enough to get into the blood stream, increasing the risk of heart attack, stroke. High concentrations of nitrogen dioxide have been linked to asthma and other respiratory illnesses, and even premature births. The Environmental Protection Agency moved last year to strengthen its standard for exposure to the pollutant, limiting it to 1 hour per day at 100 parts per billion. The annual exposure standard, however, has been the same since 1971 – an average of 53 parts per billion, which many health experts believe is still too high.