The air pollution problems facing Los Angeles, London, Athens and Mexico City all differ in some ways, as do the topographical location and the meteorological conditions to which they are subjected. However, the similarities are greater than the differences. This arises because their pollution problems are the consequence of a rapid growth in numbers of motor vehicles and, to a varying degree, growth in the manufacturing, utility and service industries attempting to provide the needs and desires of their large urban populations. Los Angeles is attempting to improve air quality using a wide range of measures. London is where the term smog was first coined, being used to describe the polluted smoky fogs it had been experiencing for centuries. Athens is not a megacity but it highlights how even a medium-sized city generating sizeable pollutant emissions in an unfavourable topographical setting and climate can suffer pollution problems as severe as any megacity.