Caught between breath and movement: should we recommend outdoor activity for patients with COPD in polluted environments?

Public health campaigns promoting physical activity, through exercise and active transport such as walking and cycling, have become central strategies to combat the global pandemic of physical inactivity.1 Promotion of active transport options instead of car usage in the cities is also increasingly relevant as a solution for air pollution, traffic noise and traffic congestion problems as well as climate adaptation strategies.2 These recommendations are also embedded in the clinical management of chronic respiratory diseases, including chronic obstructive pulmonary disease (COPD), where regular physical activity is associated with improved symptoms, functional capacity and prognosis.3 However, in urban environments, these benefits are increasingly entangled with a competing risk: exposure to air pollution. Physical activity increases ventilation, thereby enhancing the inhalation and deposition of airborne pollutants, particularly fine particulate matter.4 For individuals with COPD, who have already experienced impaired airway defence and heightened susceptibility to environmental insults,5 this creates a fundamental tension. The very behaviour promoted to improve respiratory health may simultaneously amplify exposure to harmful pollutants.