The quality of air varies from day-to-day depending on a range of factors, including the volume of traffic and weather conditions.
In cities such as Paris, a range of emergency measures are in place when air pollution climbs above safe levels. These include making public transport free, allowing only registration numbers with odd or even number plates on particular days, and health warnings on radio and television. Not all these measures would be practical in London, and the range of factors influencing the quality and cleanliness of air on a given day can make accurate forecasting difficult.
Do you change your daily routine on high pollution days? Would knowing about the level of pollutants in the air help make decisions about how you move around London?