"Our findings indicate that in traffic congested streets, like London's Oxford Street, the health benefits of walking do not always outweigh the risk from traffic pollution", said senior author Professor Fan Chung, from the National Heart & Lung Institute at Imperial College London.
The researchers recruited 120 volunteers, 60 years and older, 80 of whom who had mild heart or lung disease.
Previous BHF research has shown that long-term exposure to air pollution leads to inflammation in the blood vessels, including those supplying the heart, and promotes the buildup of fatty plaques in the linings of blood vessels, which can eventually lead to a heart attack or stroke.
Chung said that majority of elderly people who have persistent illness the only exercise they can do is to walk.
Simon Gillespie, chief executive at the British Heart Foundation, said: "Air pollution contributes to around 40,000 premature deaths in the United Kingdom every year, and the extent of its damage to our cardiovascular health is becoming clearer all of the time".
For the test, 119 healthy volunteers walked for two hours in Hyde Park and a busy part of Oxford Street.
Noise and air pollution in both of the settings were also measured at the times of the walks. Data analysis was carried out at the MRC-PHE Centre for Environment and Health at Imperial College London and Kings College London, and the Rutgers School of Public Health in New Jersey. "Our study suggests that we might advise these people to walk in green spaces, away from built-up areas and pollution from traffic". A key miscreant is a auto as emanation from gasoline- and diesel-powered vehicles are the primary factors of pollution such as nitrogen dioxide and particulates. When middle-aged Londoners were forced to walk in either green and lovely Hyde Park, or along traffic-clogged Oxford Street nearby, their hearts and lungs spoke the truth. By comparison, a walk up and down Oxford Street led to only a small increase in lung capacity in participants - far lower than recorded in the park.
Blood flow also increased after exercise, with decreases in blood pressure and an increase in heart rate.
The health impact of pollution was particularly marked in participants with COPD, who experienced a narrowing of the small airways-reporting more respiratory symptoms including cough, sputum production, shortness of breath, and wheeze-and increased arterial stiffness after walking in Oxford Street compared with Hyde Park.
This effect was reduced when walking along Oxford Street, the researchers added, with a maximum change in arterial stiffness of 4.6% for healthy volunteers, 16% for those with COPD and 8.6% for heart disease patients.
"The exercise is good for you but the higher the pollution levels, the less helpful it is". They also emphasize that while the study only involved two relatively short walks, the findings suggest that repeated exposures to air pollution would not be beneficial to our respiratory and cardiovascular systems.
United Kingdom researchers explored the benefits of walking in people over the age of 60 and compared the impact on their health when they walked along polluted urban streets versus in the open spaces of a park. New research shows pollution in some parts of the capital is so bad it cancels out the benefits of doing exercise. "But for those living in inner cities, this may be hard to do, and there may be a cost associated with it as they have to travel further away from where they live or work".
"These are issues that mean we really need to reduce pollution by controlling traffic. Any policies aimed at reducing road traffic pollution in urban environments could therefore help to reduce the health impact on unborn babies and their life-long disease risk".