In the second week of December 1952 London experienced a period of stagnant weather when the wind speed fell to virtually zero for almost 5 days. The attendant accumulation of fog and air pollution produced a smog containing principally particles and sulfur dioxide that reached extremely high airborne concentrations – up to 4 mg/m3 of particles. This air pollution episode caused more than 4000 deaths in the following few weeks.1 Such was the severity of the pollution that cattle at an agricultural show died and there were cancellations of theater performances because the audience could not see the stage. Although it was more than 20 years until the term COPD was to be adopted, many of those who died or became ill had chronic bronchitis and no doubt were smokers with COPD. This episode caused a resurgence of public and political concern regarding the issue of air pollution, culminating in ‘the clean air acts’, legislation that limited the burning of coal in urban areas – the main factor responsible for these pollution episodes. This type of pollution, dominated by sulfur dioxide and smoke particles, was known in the UK for hundreds of years but is now largely a thing of the past.