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Traffic pollution cancels out CV walking benefits
Short-term exposure to traffic pollution may prevent the beneficial cardiopulmonary effects of walking in people with chronic obstructive pulmonary disease, ischemic heart disease and those free from chronic cardiopulmonary diseases, according to new data published in The Lancet.
The study by Rudy Sinharay, MBBS, from the National Heart and Lung institute and MRC-PHE Center for Environment and Health Imperial College in London, and colleagues, also suggests that medication use may reduce the adverse effects of pollution in those with ischemic heart disease.
“Air pollution currently represents one of the world’s most important environmental health risks and has been associated with increase in premature deaths, mostly caused by ischemic heart disease and chronic obstructive pulmonary disease,” the researchers wrote. “Short-term exposure over days to higher pollution levels has been associated with increased exacerbations and hospital admissions with a reduction in lung function in patients with chronic obstructive pulmonary disease and has also been implicated in triggering acute episodes of cardiac ischemia and in causing excess deaths from ischemic heart disease.”
The researchers conducted a randomized, crossover study to assess the effects on respiratory and CV responses of 135 participants walking down a busy street with high pollution levels compared to walking down a traffic-free street with lower levels of pollution.
The researchers enrolled men and women aged 60 years and older with angiographically proven stable ischemic heart disease (n = 39) or stage 2 Global Initiative for Obstructive Lung Disease chronic obstructive pulmonary disease who were deemed clinically stable for 6 months (n = 40), as well as age-matched healthy volunteers (n = 40).
All participants refrained from smoking for a minimum of 12 months and medications were taken as recommended by their physicians during the study.
Participants were randomly assigned to a 2-hour walk either along Oxford Street, a commercial street in London, or Hyde Park, an urban park.
The researchers took baseline measurements of participants before the walk in the hospital laboratory and measured black carbon, particulate matter (PM) concentrations, ultrafine particles, and nitrogen dioxide (NO2) concentrations during each walk session.
According to the results, concentrations of black carbon, NO2, PM10, PM2.5, and ultrafine particles were higher on Oxford Street than in Hyde Park.
Adverse effects
Participants with COPD reported more coughing (OR = 1.95; 95% CI, 0.96-3.95), sputum (OR = 3.15; 95% CI, 1.9–7.13), shortness of breath (OR = 1.86; 95% CI, 0.97-3.57), and wheezing (OR = 4; 95% CI, 1.52–10.5) after walking down Oxford Street compared with Hyde Park.
All participants who walked in Hyde Park showed an increase in forced expiratory volume in the first second and forced vital capacity and a decrease in pulse wave velocity and augmentation index up to 26 hours after the walk.
There was a reduction in forced expiratory volume in the first second and forced vital capacity, as well as an increase in during-walk exposure to NO2, ultrafine particles and PM2.5, and an increase in pulse wave velocity and augmentation index with NO2 and ultrafine particles among participants with COPD.
The researchers also found a link between black carbon and ultrafine particles in pulse wave velocity and augmentation index among healthy volunteers.
“Our findings suggest that healthy people, as well as those with chronic cardiorespiratory disorders, should minimize walking on streets with high levels of pollution because this curtails or even reverses the cardiorespiratory benefits of exercise,” the researchers wrote.
Pollution control vital
In a related editorial, Gregg D. Thurston, ScD, from the department of environmental medicine from the New York University School of Medicine and Jonathan D. Newman, MD, from the department of medicine and division of cardiology at NYU, wrote that the study by Sinharay and colleagues is important in providing patient-level data for both parameters of air pollution exposure and measures of vascular function during a controlled period of physical activity.
“The changes in arterial stiffness reported in the study by Sinharay and colleagues are biologically consistent with the air pollution and CVD health associations found in the population-based studies of hospital admissions and mortality, further strengthening the consensus that the association between particulate matter and CVD is causal,” they wrote. “Although more studies are needed on the respective health effects of all the individual constituents and sources of PM, the results of this and other recent urban studies already indicate that policy makers and health professionals should make the reduction in public exposures to diesel particulate matter a high priority in PM air pollution control and patient avoidance strategies.”– by Dave Quaile
Disclosure: Sinharay, Newman and Thurston report no relevant financial disclosures. One author reports he receives honoraria and speaker fees from various pharmaceutical companies.