Breast cancer occurs when a single cell, usually in the ducts and lobules begins to multiply out of control and forms a tumour in the tissues of the breast. Like all cells, breast cells usually grow and rest in cycles regulated by the cell nucleus (the cell control room). Sometimes however, the ability to control the cell growth and rest cycle is lost, leading to uncontrolled cell growth and the formation of a tumour.
Cancer of the breast is a major health burden worldwide. Despite the billions of dollars spent on breast cancer research, incidence rates have been climbing steadily in industrialised countries since the 1940s . Female breast cancer represents one in ten of all new cancers diagnosed and almost one in four cancers diagnosed in women worldwide. Every year, more than 1.1 million women are diagnosed with breast cancer and the numbers of women being diagnosed annually worldwide has almost doubled since 1975 .
Figure 1 The rise in the number of new breast cancer cases in several countries 
Figure 2 Breast cancer incidence trends over time in selected cancer registries in Europe, the Americas and Asia: age-standardised (world population).
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Figure 3 Breast cancer incidence worldwide: age-standardised rates (world population).
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In Europe, breast cancer is the third most common incident form of cancer (13%) after lung cancer (13.3% of all incident cases), and colorectal cancer (13.2%). In 2004 there were an estimated 2 886 800 incident cases of cancer diagnosed and 1, 711, 000 cancer deaths .
Historically, breast cancer rates have been the highest in the United States, Australia and Western Europe and the lowest in Africa and Asia. In Europe, women in the western and northern countries are almost twice as likely to develop breast cancer as those in the south, with the risk of developing breast cancer in Western Europe 60% greater than in Eastern Europe. , 
Breast cancer develops as a result of a complicated mix of multiple factors. Research indicates that less than one in ten cases occur in women with a genetic predisposition, and as many as half occur in women who have no known risk factors at all. Other factors must be at work. Geographic variations in disease incidence and research on laboratory animals and cell behaviour, all point towards environmental exposures as a possible cause.
The role of oestrogen in breast cancer development has raised the possibility that environmental contaminants that mimic oestrogen might be involved. The chemicals implicated by scientific research in the aetiology of breast cancer, include dioxins, PCBs and pesticides such as DDT and dieldrin, part of a group of chemicals called organochlorines, which possess oestrogenic activity. Bisphenol A is another xenoestrogen of concern. Furthermore, research into cohorts or community residents exposed by a 1976 industrial accident in Seveso, Italy, and contamination from a chemical plant in Chapaevsk, Russia suggest a link with dioxins.
The cost of breast cancer treatment to health care systems represents a significant economic burden. Treatment requires hospitalisation, physician services, medication, nursing, home care, home healthcare and emergency department visits. Whilst there is little EU-wide information on the economic burden that breast cancer places on health care system in the U.S. the National Institutes of Health estimate that in 2004 the overall cost for cancer was $189.8 billion. This includes $69.4 billion in direct medical costs, $16.9 billion in indirect costs, and $103.5 billion in indirect mortality costs.
Breast cancer represents a growing public health crisis. Given estimates of breast cancer health care costs and rising incidence rates, the need for primary prevention as a major public health priority, alongside screening and treatment, is evident. Like all cancers, breast cancer is a very complex disease, the causes of which have to date, been inadequately clarified. What is becoming clear however is that the rising incidence of breast cancer has been accompanied by significant changes in lifestyle and exposure to environmental toxicants, such as: changes in lifestyle and diet, increased production and use of industrial chemicals; and increased levels of pollutants in the environment.
For more information please see the Collaborative on Health and Environment Cancer Working Group
 Nancy Evans (2006) State of the Evidence, Fourth Edition, Breast Cancer Fund and Breast Cancer Action, p4
 Freddie Bray, Peter McCarron and D Maxwell Parkin (2004) The changing global patterns of female breast cancer incidence and mortality, Breast Cancer Research, Volume 6, Pages 229-239
 Dr. Andreas Kortenkamp (2006) Environmental contaminants and breast cancer: the growing concerns about endocrine disrupting chemicals, A briefing paper for WWF-UK
 Jerzy E. Tyczynski, Freddie Bray, D. Maxwell Parkin (2002) Breast Cancer in Europe, International Agency for Research on Cancer Fact Sheets, 2.
 J.L. Botha, F. Brayc, R. Sankilac, D.M. Parkin (2003) Breast cancer incidence and mortality trends in 16 European countries, European Journal of Cancer, 39:1718–1729