Feature

Breast cancer on the map

While screeening for and treating breast cancer attract plenty of media coverage, little attention is paid to the environmental causes of the disease. Laura Potts says it’s time to redress the balance

The Women’s Environmental Network is running an innovative project to map the incidence of breast cancer in the UK, and to look at the relationship between breast cancer and environmental pollution.

Financially supported by the National Lottery Charities Board, the project has issued hundreds of comprehensive information packs, encouraging women to respond to a detailed questionnaire, and to join with other individuals and groups in their locality to produce maps of where they live. There is no prescribed format for the maps, the intention rather being that they visually represent, in whatever form seems appropriate to those compiling them, a picture of their local environment, including sources of local environmental pollution, breast cancer risk factors, or any outside influence that is thought to be having an adverse effect on health.

The pack suggests how people might go about collecting information to put into their map, and lists useful resources. All the responses will be computer processed to create a map of the UK which includes all the local maps, and links them to information derived from the questionnaires.

The project grew out of work WEN had previously done on polluting chemicals, and from a petition submitted to the Department of Health in 1995 as a National Action Plan for Breast Cancer, calling for more emphasis on prevention, alongside better treatment, support and care. But the emphasis has still not shifted: most media coverage of Breast Cancer Awareness Month last October neglected any mention of primary prevention. ‘One may speculate about why so little attention has been paid to efforts to prevent a disease that afflicts so many women, but the fact of this deficit remains glaringly clear. Prevention is less glamorous than treatment, and fewer profit financially if it succeeds,’ says Devra Davis, a US researcher and campaigner.

It has been known for some time that the majority of human cancers are caused by external factors, and the impact on human and animal health of industrial, pharmaceutical and agricultural chemicals has recently become clearer. The link was clearly articulated at the First World-wide Conference on Breast Cancer in Canada last summer. There are over 70,000 chemicals in commercial use today and another 1,000 are added each year; while a chemical may not of itself cause cancer it may work, in combination with many other substances both natural and synthetic, to add to the risk of developing disease, including breast cancer.

Current, though controversial, indicators for increased breast cancer risk include high socio-economic status, older first-time mothers, poor diet, lack of exercise, obesity, alcohol consumption and cigarette smoking; and risk factors over which we have no control such as family history of breast cancer, age at onset of menarche and menopause, and also our lifelong environment. But all these factors fail to explain the high incidence of breast cancer and the existence of breast cancer clusters in certain geographic areas. Some researchers are now investigating chemicals and pesticides that mimic the action of the hormone oestrogen.

The three main types of oestrogen present in the human body — oestradiol, oestriol and oestrone — are produced mainly in the ovaries, with smaller quantities produced by the adrenal glands, the placenta during pregnancy and from fat cells. Both oestradiol and oestriol are known to cause breast cancer, while oestrone, a much weaker oestrogen, appears to inhibit it.

The fact that larger quantities of oestrone are produced during pregnancy seems to support the observation that the more children women have, the greater their protection against breast cancer. As oestradiol breaks down in the body it divides into two pathways: 16a-hydroxyestrone (16a-OHE), associated with a higher breast cancer risk and 2-hydroxyestrone (2-OHE), associated with a lower breast cancer risk.

There is evidence that toxic chemicals exist in the environment which can mimic oestrogen and interfere with human hormone production, transport or action through a range of well-understood mechanisms. They may also make the body produce too much 16a-OHE which is undesirable in terms of breast cancer, whereas a higher ratio of 2-OHE is likely to be beneficial and possibly protective.

With their capacity to increase our hormonal load as they accumulate in body fat over time, many of these compounds, generally referred to as endocrine disrupting chemicals, hormone disrupting chemicals, xenoestrogens or gender-benders can influence the way in which hormones work in our bodies.

We know little about the effects any one of these substances may have on human health but we know nothing about their combined effects. The US Environmental Protection Agency is proposing to screen 15,000 industrial chemicals for hormone-disrupting effects but current testing does not cover endocrine disrupting effects. In the UK, the responsibility for monitoring and reporting pesticide residues in food lies with Ministry of Agriculture, Fisheries and Food and its Working Party on Pesticide Residues. It was MAFF that ‘Free radicals’, a group of women campaigning on breast cancer and the environment, chose to target with their protest last October.

One chemical in particular, Lindane, which is widely used in UK agriculture, has been shown to interfere with oestrogens in the body. Included in the government ‘Red List’ of dangerous substances, Lindane is an organochlorine pesticide which is classified as a ‘possible human carcinogen’ by the International Agency for Research on Cancer and listed as one of the world’s most dangerous substances by the Pesticide Action Network.

Lindane is used widely on arable crops, particularly sugar beet, to kill the leather jacket beetle. Some 70 per cent of the UK sugar beet crop is grown in Lincolnshire, the county with the highest rate of breast cancer in the country. It has been banned, withdrawn or severely restricted in 28 countries because of its ability to build up in the environment. Unison is campaigning to have it banned in the UK. The government signed a treaty at the International Conference on the Protection of the North Sea agreeing to reduce the levels of chemicals, including Lindane, by 50 per cent between 1985 and 1995. This is implemented by substances listed under the ‘Red List’ but the UK has failed to meet its target and figures from the National Rivers Authority indicate emissions of Lindane have increased by up to 50 per cent during this time.

In the last 10 years, breast cancer has increased world-wide by 33 per cent; the UK has the highest mortality rate in the world, and the incidence in Lincolnshire is 40 per cent higher than the national rate. While the exact reasons for these dramatic figures are still to be uncovered, many studies implicate our environment and the substances we are exposed to as prime suspects. Putting Breast Cancer on the Map will contribute to research being conducted all over the world, by helping to reveal the contribution that environmental contaminants may be making to the UK pattern of breast cancer incidence. The maps and questionnaires will identify exactly what women are, and have been, exposed to by the way of chemicals in their local communities, at home and at work, and what effect those may have had on breast cancer.

If you would like to get involved in Putting Breast Cancer on the Map, contact the Women’s Environmental Network, 87 Worship Street, London EC2A 2BE; tel. 0171 247 3327; fax 0171 247 4740; email artemis@gn.apc.org. Enclose an sae for 50p if you would like to be sent the information pack.