Pollution in the city cancels out benefit of a walk

POLLUTION wipes out the benefits of walking, a study suggests. Researchers from Imperial College London found that the toxic air in built-up city centres prevents the positive effects on the lungs and heart that are usually gained from exercise.

The experiment was carried out in the over-60s, but scientists say the effects could apply to other groups.

To determine the impact of pollution on exercise, researchers asked 119 people to take a two-hour stroll through London’s Hyde Park and also Oxford Street, a busy shopping area.

Levels of black carbon, nitrogen dioxide and fine particulate matter in Hyde Park are typically well within healthy boundaries, but air in Oxford Street regularly breaches dangerous pollution levels.

The researchers found that everyone in the study benefited from a stroll in the park, with their lung capacity improving within just one hour, an effect that lasted for 24 hours for many people.

By comparison, a walk along Oxford Street barely registered any improvement at all. Likewise the increase in blood flow usually associated with exercise was virtually absent in those walking along the busy shopping street. And while the arteries of those walking in the park became 24 per cent less stiff, they improved by just 4.6 per cent for people on Oxford Street.

“These findings are important as for many people, such as the elderly or those with chronic disease, very often the only exercise they can do is to walk,” said Fan Chung, senior author and professor of respiratory medicine and head of experimental studies medicine at the National Heart & Lung Institute at Imperial College.

“Our research suggests that we might advise older adults to walk in green spaces, away from built-up areas and pollution from traffic. For people living in the inner city it may be difficult to find areas where they can go and walk, away from pollution.” Previous research has found that diesel exhaust fumes have been associated with an increased risk of cardiovascular disease and death, and can cause a worsening of diseases of the airways, such as asthma. It is estimated that pollution is linked to 40,000 early deaths in Britain each year.

Prof Kevin Mcconway, emeritus professor of applied statistics at The Open University, said: “The research does convince me that poor air quality does play an important role in the short-term benefit one can get from taking a walk.”

But Prof Ian Colbeck, professor of environmental science at the University of Essex, said: “It’s important that people continue to exercise. The findings were published in The Lancet.