Trends in urban air pollution in the United Kingdom in relation to lung cancer mortality.

The substantial reduction in air pollution, and particularly in components such as benzo[a]pyrene in urban areas of the United Kingdom during the past few decades has presented an opportunity to consider further the possible role of carcinogens in the air in relation to lung cancer. While the overall trends in lung cancer mortality have undoubtedly been dominated by changes in smoking, the marked contrasts that at one time existed between these death rates in urban and rural areas have gradually diminished. This may indicate that air pollution contributed appreciably to the urban/rural differences in lung cancer at one time, but it is still difficult to disentangle any effects it may have had from those of changing smoking habits.