While walking is generally considered good exercise, especially for patients with COPD, doing so in polluted areas may increase exposure to airborne contaminants and lead to worsening respiratory symptoms.
That’s according to the paper, “Effects of the Interaction Between Walking Activity and Air Pollution on Daily Respiratory Symptoms in People With COPD,” published in Thorax.
The study, conducted by the Barcelona Institute for Global Health (ISGlobal), linked black carbon to an increase in certain respiratory symptoms in patients with COPD. First author Alicia Josa Culleré, MD, ISGlobal researcher, said in a press release that while physical activity may outweigh the effects of air pollution in the general population, not as much is known about the interaction in patients with COPD.
“Our aim was to assess how walking and exposure to air pollutants affect daily respiratory symptoms in people with COPD,” she said.
The research team tracked 105 people with COPD in Catalonia, Spain, over two seven-day periods. They recorded daily walking activity, exposure to three air pollutants (fine particulate matter, nitrogen dioxide and black carbon) and symptom intensity — including cough, sputum production, breathlessness and wheezing.
Black carbon, also known as soot, consists of microscopic particles produced by the incomplete combustion of fossil fuels, wood and biomass. The study found that when black carbon concentrations were high, longer walking duration was associated with increased cough and sputum production. The same could not be said for levels of fine particulate matter (PM2.5) and nitrogen oxide (NO2). When those levels were high, patients did not experience worsening respiratory symptoms, suggesting that it’s okay for patients with COPD to continue walking under those conditions.
“These findings may be explained by the fact that black carbon particles tend to be smaller and can penetrate more deeply into the lungs,” said Judith Garcia Aymerich, MD, PhD, deputy director and research professor with ISGlobal. “In addition, they often carry compounds that increase their toxicity and their impact on respiratory health.”
The researchers said the lack of an association between worsening symptoms and levels of PM2.5 and NO2 may be due to several factors. These include:
- Low concentrations of both elements recorded during the study (both were below limits recommended by the World Health Organization)
- Behavioral changes among participants on more polluted days, such as increased inhaler use or walking at lower intensity
- The possibility that the benefits of walking offset the negative effects of PM2.5 and NO2
The researchers cautioned that, while the study examined the short-term effects of walking on respiratory symptoms (i.e., within the same day), it did not assess the benefits of maintaining regular physical activity. Therefore, the findings do not call into question the benefits of ongoing physical activity for patients with COPD.
“Our findings support the recommendation to walk for people with COPD, provided that busy roads are avoided where black carbon concentrations are high,” said Dr. Garcia Aymerich. “It is important to provide accessible spaces for safe walking as well as to reduce black carbon emissions — a super pollutant that is harmful both to respiratory health and the climate.”
