Controversies in cancer epidemiology.

The histories of three controversies are described: fluoridation of water supplies and the risk of cancer; whether oral contraceptives cause breast cancer; and the role of self-examination in the prevention of cancer. For the future, some new controversies are already predictable. As well as the scientific debate around these topics, the roles of politics, the media, and pressure groups are discussed. The epidemiologist's responsibility to ensure that the correct interpretation of data is made clear to the public is considered.