Air pollution and respiratory health in patients with COPD: should we focus on indoor or outdoor sources?

This eye-opening study continuously measured individual exposure to indoor and outdoor-generated air pollution, in 76 patients with COPD, for an average of 134 days. They compared this with information collected daily about patient's symptoms and peak flow readings. The study found that exposure to both indoor and outdoor sources was associated with increased exacerbations and respiratory symptoms. For example, an increase by the IQR in exposure to NO2 was associated with a 33% increase in the odds of an exacerbation. The association was stronger for indoor (odds ratio 1.19) compared to outdoor (odds ratio 1.12) air pollution. Higher NO2 and carbon monoxide exposure were both associated with more reported respiratory symptoms. The most common source of NO2 indoors is from gas cookers (and to a lesser extent, heating), whilst outdoors it is road transport.

The authors conclude "Regulating day-to-day exposure to both indoor and outdoor sources of gaseous pollution is important to the respiratory health of patients with COPD in London. There are actions that patients can take to reduce these exposures as well as legislative interventions. Those caring for patients with COPD should be aware of these actions and provide appropriate advice. Those with respiratory conditions should avoid the use of gas cookers where possible."