Some scientists argue that the cause may be an increased exposure to a number of environmental chemicals, a claim taken up by campaigners in the US and the UK who urge the government to provide better health protection. However, whereas the UK government has been keen to engage people in debate about genetics, GM crops and mobile phone masts, some say it is less enthusiastic about debate on breast cancer, where the research is officially regarded as equivocal.

A research team led by Laura Potts, Reader in Public Health and Environment, York St. John College has undertaken a project in which a number of interviews, focus groups and discussions with key people were set up. "Opinions on the cause of the rise in breast cancer were divided," Potts says. "Most participants agreed that an explanation of the increased incidence and its highly complex origins were certainly needed but even on this there was no consensus."

Theories about what might cause the disease tended to cite genetic factors, internal hormone factors such as HRT and the contraceptive pill, smoking, drinking, dairy products, plastics, pesticides and the relation between the immune system, stress and the environment. Difficulties in finding out what caused breast cancer were compounded by a lack of comparable studies and controls and differing interpretations of the same data.

The science of epidemiology, the study of the incidence and distribution of disease in populations, which would normally be looked on as a prime source of information, was regarded by some research participants as being unable to provide answers, with some epidemiologists speaking of leverage and power, and it being impossible to ask questions about suspected environmental hazards.

Even the epidemiological studies that have been done may have been misfocussed. One research scientist interviewed said, "All the big, solid epidemiology studies we've got have all been done on blood and they don't show any association. But the few that have been done using breast tissue, breast fat, do show an association."

MEDICA.de; Source: Economic and Social Research Council (ESRC)