The UK’s pollution problems of the last week remind us that when winds stop, air pollution builds up; especially when fog shields the ground from the sun. These conditions caused the now infamous 1952 London smog, when about 12,000 people died. Less attention has been paid to smogs in other cities. In November 1953 still air settled over New York, causing the city’s first documented smog. For the first time, air pollution was tracked by a municipal laboratory. News of between 170 and 200 extra deaths attracted little media attention but when the city was again enveloped in smog in 1966, authorities knew that they had to take emergency action. Conrad Simon, one of New York’s air pollution scientists, said: “We came close to closing the city down.” Power stations were temporarily switched from coal to oil, building owners were asked to turn down thermostats to 15C (59F) and the city’s waste incinerators were switched off, but again about 200 people died. Today, emergency plans are used in European cities, including Paris, Madrid and Oslo to reduce impacts of smogs. These include restrictions on industry, reduced speed limits and partial traffic bans.