Results from a study led by Professor Fan Chung, consultant physician at Royal Brompton & Harefield NHS Foundation Trust and professor of respiratory medicine at Imperial College London, have shown that just two hours of exposure to particles of soot or dust, found in traffic fumes on busy roads, appears to counteract the benefits of walking on the heart and lungs of older adults.
In the UK, polluted air contributes to 40,000 deaths each year, nearly a quarter of them in London. Earlier research showed that exposure to fine particulate matter found in diesel exhaust fumes increases the risk of cardiovascular disease and death, and can reduce lung function, particularly in the elderly and those with chronic obstructive pulmonary disease (COPD).
Professor Chung’s study, carried out in collaboration with the National Heart & Lung Institute at Imperial College London, compared the health effects of walking through a busy shopping street and a park.
The study included participants aged 60 and over with either COPD or ischaemic heart disease (IHD), and healthy volunteers. All were randomly assigned to spend two hours walking along London’s Oxford Street where traffic is restricted to diesel-powered vehicles, or through a traffic-free section of Hyde Park, London. Three to eight weeks later, participants swapped groups and completed the alternate walk.
Levels of traffic-related air pollutants and measures of lung and cardiovascular function were taken before and during each walk. One such measure was arterial stiffness, which indicates the ease with which blood flows through the arteries. In healthy participants, walking in Hyde Park led to an improvement in measures of lung capacity and arterial stiffness. In contrast, walking on Oxford Street led to only a small increase in lung capacity and substantial worsening of arterial stiffness.
For participants with COPD, the negative health effects of pollution were particularly marked with a narrowing (obstruction) of the small airways - with participants reporting more symptoms such as cough, shortness of breath, and wheeze - and increased arterial stiffness after walking in Oxford Street compared with Hyde Park.
For participants with IHD, the results differed between those that were taking medication for their IHD and those that weren’t. Participants not taking medication experienced worsening arterial stiffness after the Oxford Street walk compared to those taking medication, suggesting that cardiovascular drugs may have protective effects.
Despite the results, Professor Chung is keen to highlight the importance of walking as a form of exercise for older patients. “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. However, this should not be seen as a barrier to many older people for whom walking is the only exercise they do. We suggest that, where possible, older adults walk in parks or other green spaces away from busy roads.”
Professor Chung also emphasised the importance of cleaner air for London and other major cities: “Our study provides a clear message to improve the quality of the air we all share. In London, the introduction of the low emission zone has had little impact on particulate matter levels. More radical solutions, such as those recently announced to phase out diesel-powered black cabs and replace them with battery powered electric alternatives, are needed.”
If you would like to find out more about this research or any other research that we do at the Trust please email us.