This article is a commentary on the following study: Hajat S, Anderson HR, Atkinson RW, Haines A. Effects of air pollution on general practitioner consultations for upper respiratory diseases in London. Occup Environ Med. 2002 May;59(5):294-9. The objective of this epidemiological study is to analyze the relationship between a new health indicator—reports of certain respiratory conditions in general practitioners’ records—and air pollution in London. Positive associations were observed between increases in atmospheric concentrations and the number of consultations for the conditions studied, recorded the following day and between 1 and 3 days later. These results were obtained for all groups of individuals and for all pollutants, with the exception of ozone, whether in summer or winter. The positive associations remain weaker among children than among the elderly, with these associations being stronger in winter for both groups. These trends remain the same when exposure to two pollutants is considered simultaneously. The authors conclude that there are significant positive relationships between low concentrations of pollutants in urban ambient air and an increase in consultations for upper respiratory tract conditions (such as pharyngitis and sinusitis), particularly for sulfur dioxide in children, and for PM10 and nitrogen dioxide in older adults. The observed effects are small in magnitude; nevertheless, given the very high number of visits to primary care physicians, the impact on service capacity can be significant. (Excerpt from the article)