Exposure to nitrogen oxides in air causes increased risk of type 2 diabetes and hypertension in African-American women, a new study has revealed.

Researchers from the Slone Epidemiology Centre (SEC) at Boston University assessed the risks of incident hypertension and diabetes associated with exposure to nitrogen oxides (NOx) and particulate matter (PM2.5) in a cohort of approximately 4,000 African American women living in Los Angeles.

NOx are indicators of traffic-related air pollution. From 1995-2005, 531 incident cases of hypertension and 183 incident cases of diabetes occurred among the participants in the Los Angeles area. The risk of diabetes increased by a significant 24 percent, and the risk of hypertension by 11 percent, for each 12 ppb increase in exposure to NOx. There also were suggestive increases in risks of both diseases associated with exposure to (PM2.5), but the evidence for this was weaker than for NOx.

"A link between air pollution and the risks of diabetes and hypertension is of particular importance to African American women, because the incidence of both conditions is almost twice as high in African American women as in white women and African Americans live in more highly polluted areas than white Americans,” said Patricia Coogan, D.Sc., the study’s lead author,” Coogan said.

"In addition, even a modest effect of air pollutants on the risks of hypertension and diabetes will have significant public health impact due to the high incidence of these conditions and the ubiquity of exposure to air pollution,” she added.

The study has been published online in the journal Circulation.

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