Traffic-related air pollution can worsen respiratory symptoms during daily exercise for people with chronic lung disease.
RT’s Three Key Takeaways:
- Traffic Pollution Risk: Exposure to black carbon during daily walks is linked to increased cough and sputum production for individuals with COPD.
- Route Selection: Researchers recommend that patients choose low-traffic walking routes to maintain physical activity levels while minimizing exposure to harmful pollutants.
- Airway Clearance Benefits: Despite the risks of pollution, regular walking remains essential for COPD prognosis as it helps clear airways and expel secretions.
Daily walking is associated with increased respiratory symptoms among people with COPD when exposure to traffic-related air pollution is high, according to a study published in Thorax.
The relationship between physical activity and symptom aggravation depends partly on exposure to black carbon, a pollutant strongly associated with road traffic. Researchers found that longer walking duration was associated with higher cough and sputum levels only on days when black carbon concentrations were high.
The multicenter panel study included 105 people with COPD from Catalonia, Spain, who were assessed during two separate seven-day periods. Participants had a mean age of 68 years, 20% were female, and the mean forced expiratory volume in 1 second was 53% of the predicted value.
Activity monitors measured daily walking duration and step count, while researchers used geolocation data and land-use regression models to estimate daily exposure to fine particulate matter measuring less than 2.5 µm, black carbon, and nitrogen dioxide. Participants recorded dyspnea, cough, sputum production, and wheezing each evening on a scale from 0 to 10.
All three pollutants were individually associated with greater cough, while black carbon was also linked to increased sputum, dyspnea, and wheezing. However, the interaction analysis showed that longer walking only worsened cough and sputum when black carbon levels were elevated. The interaction incidence rate ratio was 1.8 for cough and 2.0 for sputum. No significant interaction was identified between walking duration and either fine particulate matter or nitrogen dioxide.
The findings do not suggest that healthcare providers should discourage walking for people with COPD. Regular physical activity remains important for prognosis, and walking may help airway clearance by increasing ventilation and helping expel secretions, the researchers said.
Instead, the results support recommending low-traffic walking routes when possible. Black carbon particles may penetrate deeply into the lungs and contribute to oxidative stress, mucus production, epithelial injury, and airway inflammation.
The researchers noted several limitations, including a short monitoring period, a limited number of female participants, and estimated rather than directly measured outdoor pollution exposure.
Accessible, low-traffic spaces may help people with COPD gain the long-term benefits of walking while reducing exposure to traffic-related air pollution, the study authors concluded.
Reference
Josa-Culleré A et al. Effects of the interaction between walking activity and air pollution on daily respiratory symptoms in people with COPD. Thorax. 2026;doi:10.1136/thorax-2025-224411.
This article was originally published by AMJ and was made available under the terms of the Creative Commons Attribution-Non Commercial 4.0 License.
