Traffic pollution attenuates cardiorespiratory benefits of walking
Short-term exposure to traffic pollution attenuates, even reverses, the beneficial cardiopulmonary effects of walking in patients with chronic obstructive pulmonary disorder (COPD), in those with ischaemic heart disease and in individuals free from chronic cardiopulmonary diseases, according to a study.
The study included 40 healthy volunteers, 40 stable COPD patients and 39 stable ischaemic heart disease patients who were randomly assigned to do a 2-hour walk either along a commercial street in London (Oxford Street) or in an urban park (Hyde Park). All participants had abstained from smoking for at least 12 months and were taking medications as recommended by their physicians.
Black carbon, particulate matter (PM), ultrafine particles and nitrogen dioxide (NO2) concentrations were measured during each walk session, and it was found that all measures of exposure were higher on Oxford Street than in Hyde Park.
In COPD patients specifically, the frequency of cough (odds ratio [OR], 1.95; 95 percent CI, 0.96–3.95; p<0.1), sputum production (OR, 3.15; 1.39–7.13; p<0.05), shortness of breath (OR, 1.86; 0.97–3.57; p<0.1) and wheeze (OR, 4.00; 1.52–10.50; p<0.05) increased after walking down Oxford Street than after walking in Hyde Park.
In the entire cohort, irrespective of their disease status, walking in Hyde Park resulted in an increase in lung function (forced expiratory volume in the first second [FEV1] and forced vital capacity [FVC]) and a decrease in pulse wave velocity (PWV) and augmentation index up to 26 hours after the walk.
However, the observed beneficial responses were attenuated after walking along Oxford Street.
In COPD patients, a reduction in FEV1 and FVC and an increase in R5–20 showed an association with an increase in during-walk exposure to NO2, ultrafine particles and PM2.5. Meanwhile, an increase in PWV and augmentation index correlated with increased exposure to NO2 and ultrafine particles.
In healthy volunteers, PWV and augmentation index were associated with exposure to both black carbon and ultrafine particles.
The present data suggest that healthy people, as well as those with chronic cardiorespiratory disorders, should avoid or minimize walking on streets with high levels of pollution because this curtails or even reverses the cardiorespiratory benefits of exercise, researchers said. “Instead, walking exercise should be enjoyed in urban green space areas away from high density traffic.”
“Patients with chronic cardiorespiratory disorders should be encouraged to use appropriate medication to mitigate the adverse effects of air pollution,” they added. “Policies should aim to control ambient levels of air pollution along busy streets in view of these negative health effects.”