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If you walk on busy city streets, breathing the traffic fumes may cancel out the health benefits of the exercise, a new study suggests.
The London-based study, published online Dec. 5, 2017, by The Lancet, included 119 volunteers over the age of 60 who were either healthy or had stable chronic obstructive pulmonary disease or stable heart disease. They all walked for two hours midday at two different locations. One was in a quiet section of Hyde Park, where air pollution is usually within healthy limits. The other was on a busy shopping area on Oxford Street, where levels of pollutants such as black carbon, nitrogen dioxide, and fine particulate matter regularly reach dangerous levels. The walks were separated by three to eight weeks.
All the volunteers benefited from a stroll in the park. Their lung capacity improved within an hour, an effect that lasted for 24 hours for many people. In contrast, a walk along Oxford Street barely registered any such benefit. Exercise also improves blood flow and makes arteries less stiff. But these improvements were limited among the volunteers following a walk along Oxford Street.
As the study authors advise: "Walking exercise should be enjoyed in urban green space areas away from high-density traffic."