Page last updated at 23:46 GMT, Saturday, 15 May 2010 00:46 UK

Urban pollution 'raises blood pressure'

Car pollution
Pollution has been linked to poor respiratory health

City pollution, previously linked to poor respiratory health, has now been linked to raised blood pressure.

German researchers looked at 5,000 people and found long-term exposure increased blood pressure, even when other key factors were considered.

The team, which has presented its work to the American Thoracic Society, says efforts should be made to reduce exposure to pollution.

UK experts said the paper offered an "interesting theory".

High blood pressure increases the risk of atherosclerosis, a hardening of the arteries, which leads to cardiovascular diseases like heart attacks and strokes.

We know there's a link between air pollution and heart and circulatory disease
Judy O'Sullivan, British Heart Foundation

The researchers, from the University of Dusiburg-Essen, used data from an ongoing population study called the Heinz Nixdorf Recall Study, which focuses on the development of heart disease.

They looked at the effects of air pollution exposure on blood pressure between 2000 and 2003.

Past studies have shown day-to-day increases in air pollution levels can raise blood pressure, but little was known about medium and long-term exposure.

The average "background concentrations" of pollution over a year were recorded and blood pressure readings taken over the course of the study.

The average arterial blood pressure rose with exposure level 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.

'Higher risk'

Dr Barbara Hoffman, head of the Unit of Environmental and Clinical Epidemiology at the University of Duisburg-Essen who led the research, said: "Our results show that living in areas with higher levels of particle air pollution is associated with higher blood pressure."

She said the link remained even when other factors were taken into account that influence blood pressure like age, gender, smoking and weight.

Dr Hoffman added: "This finding points out that air pollution does not only trigger life-threatening events like heart attacks and strokes, but that it may also influence the underlying processes, which lead to chronic cardiovascular diseases.

"It is therefore necessary to further our attempts to prevent chronic exposure to high air pollution as much as possible."

More research

The team will now look at whether exposure to high levels of pollution leads to a faster development of atherosclerosis.

Judy O'Sullivan, a senior cardiac nurse at the British Heart Foundation, said: "We know there's a link between air pollution and heart and circulatory disease but we don't yet fully understand its exact nature.

"This paper offers an interesting theory that air pollution may cause high blood pressure, a known risk factor for heart disease.

"There is extensive ongoing research into the link between air pollution and heart disease, including work we are funding.

"This will help us understand what needs to be done to minimise harm to heart health and protect people most at risk from pollution."

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