Hamburg - Big-city air pollution may contribute to higher blood pressure levels being observed among city residents, as compared to people who live in less polluted areas, according to a team of German researchers.

The researchers from the University of Duisburg-Essen studied more than 4,000 people and found long-term exposure to high-particulate air pollution appeared to increase blood pressure, even when other key factors were considered.

Dr Barbara Hoffmann, head of the environmental and clinical epidemiology unit at the university, and colleagues from several other sites analyzed the effects of air pollution exposure on blood pressure using data from the Heinz Nixdorf Recall Study.

That ongoing population-based cohort study, which involves 4,352 people, focuses on the development of heart disease.

The researchers assessed yearly average fine particulate pollution and coarse particulate pollution exposure using a dispersion and chemistry transport model and measured participants' blood pressure.

The average arterial blood pressure rose with exposure levels to fine particulate matter, which tends to come from traffic, heating, industry and power plants. Increases in blood pressure were greater in women than in men.

Hoffmann presented the study findings at the American Thoracic Society's 2010 International Conference in New Orleans. The findings were also reported in the Cardiology Today magazine.

Results of previous studies have shown an association between elevated blood pressure and heart disease and chronic noise exposure resulting from living close to a major road.

However, Hoffmann emphasized that air pollution levels in this study represented average background concentration. Thus, observed blood pressure increases were not likely to be attributable to noise exposure.

"This finding points out that air pollution does not only trigger life-threatening events like heart attack and strokes, but that it may also influence the underlying processes which lead to chronic cardiovascular disease," Hoffmann said in a news release.

She suggested that efforts to prevent chronic exposure to high air pollution are necessary.