The researchers, led by Patricia Coogan at Boston University, found that black women living in neighborhoods with high levels of nitrogen oxides, pollutants found in traffic exhaust, were 25 percent more likely to develop diabetes and 14 percent more likely to develop hypertension than those living in sections with cleaner air.

Previous research has linked air pollution to health problems such as diabetes, stroke, heart disease and even higher rates of death.

"The public health implications are huge," said Dr. Jiu-Chiuan Chen, who studies the effects of air pollution at the University of Southern California Keck School of Medicine in Los Angeles, especially for black women, who have higher rates of diabetes and high blood pressure than white women. He was not involved in the current work.

Forty-four percent of all black women in the U.S. have high blood pressure and about 11 percent have diabetes compared with 28 percent and roughly seven percent, respectively, of white women, according to the Centers for Disease Control and Prevention.

Black Americans also experience higher levels of air pollution than white Americans, according to the study authors.

For their investigation, published in Circulation, the researchers followed participants in the ongoing Black Women's Health Study for 10 years. The women were mainly recruited from subscribers to Essence magazine, and none had diabetes or high blood pressure when the study began in 1995.

Over the course of a decade, 531 women developed high blood pressure and 183 women were diagnosed with diabetes.

The findings on their relative risks for those conditions take into account several other potential influences, including how heavy the women were, whether they smoked and other stressors, including noise levels at participants' homes.

Although researchers measured average pollution levels near participants' homes for only one year of the ten-year study, Coogan told Reuters Health that air pollution patterns remained relatively constant over the entire study period.

While Coogan and her colleagues estimated nitrogen oxide concentrations near participants' homes, they did not account for commuting habits or exposure to air pollution at work. According to the researchers, Americans, on average, spend about 70 percent of their time at home.

In addition to measuring nitrogen oxides, a proxy for traffic pollution, the researchers evaluated levels of fine particulate matter. Many sources contribute to this type of air pollution, including traffic, power plants and industrial processes.

Women who lived in areas with higher fine particulate exposures also faced an increased risk of diabetes and high blood pressure, although statistically the link was weak and could have been due to chance.

Previous reports have suggested that air pollution particles small enough to make their way into the blood stream may contribute to a narrowing of blood vessels, which can lead to high blood pressure and reduce sensitivity to insulin.

More research needs to be done before these results can be generalized to all women or even all black women living in the U.S., Coogan cautions. Earlier studies did not find a link between air pollution and increased incidence of diabetes or high blood pressure in men, she said.

Because people don't always have control over where they live, policy makers must recognize the dangers of living and working in areas with high air pollution, Chen said.

To reduce the risk of high blood pressure and diabetes, he added, individuals can take steps, such as exercising, losing excess weight, quitting smoking and limiting salt intake.

SOURCE: bit.ly/w70IyH Circulation, online January 4, 2012.

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