There is a controversy over whether London has a pollution problem or not. According to UK government data and the Friends of the Earth (FoE), air quality deteriorated more in 1999 than in any year since 1993 when records began. The number of days on which air pollution exceeded health standards rose by 20 percent in cities and 53 percent in rural areas. The Department of Health has estimated that 24,000 people may die prematurely each year due to air pollution.

However, according to a study commissioned by the National Health Service (NHS) Executive, the level of toxic emissions is falling, especially rapidly in London, due to catalytic converters on cars, better vehicle technology, and the use of cleaner fuels. As a result, London's air is more breathable than in New York, Tokyo, and Los Angeles. The air in Cairo is three times worse. The problem that remains is argued to be due to a small number of old or badly maintained cars. Healthy people should not be at risk. The study's author believes that congestion charges, such as road tolls and workplace parking surcharges, might help reduce congestion, but that air pollution would not be significantly reduced; in general, he cautions that air pollution standards may increase economic costs more than they provide benefits.

(Updated April 1, 2000)