Of estrogen mimics and breast cancer

D.E.S. and Breast Cancer

One woman in eight contracts breast cancer. Fifty years ago the figure was one in twenty. Also fifty years ago, North America embarked upon the widespread use of organochlorines, beginning with DDT and PCB’s.

Is there a connection between the soaring rates of breast cancer and organochlorines? No one has proved categorically that there is or that there is not. But there is evidence that suggests a connection.

Chlorine has been put to many uses, ranging from purifying drinking water to being a key ingredient in pesticides and a wide range of consumer products. To give an idea of its commercial importance, a spokesperson for the Chlorine Chemical Council of the U.S. Chemical Manufacturers’ Association has estimated that chlorinated synthetic chemicals, and the products made from them, account for 45 per cent of the world’s gross national product.

The problem with chlorine is that it is notoriously unstable and, given the slightest opportunity, it will combine with something else. Its favoured partner is carbon and their union results in organochlorines, many of which act as hormone disruptors.

One way disruptors operate is to mimic estrogen, the female hormone. It has been established that a woman’s total estrogen exposure is the single most important risk factor in breast cancer.

What has not been established is that estrogen-mimicking compounds, whether they are organochlorines or compounds from another family, such as the phthalates (which are widely used to add flexibility to plastic products), increase the risk.

Any number of experiments with mice and rats show that estrogen mimics substantially increase risk. But for women, this points only to probabilities, not to certainty, and so the issue becomes how far society should go in gambling the lives of women on the proposition that mimics do not increase the risk of breast cancer?

The International Joint Commission has decided that the gamble has already gone too far. It wants a ban on any release of the worst organochlorines.

Moreover, with an eye on the 1,000 new synthetic chemicals introduced worldwide every year and the 100,000 already on the market, the IJC is saying that if a chemical belongs to a problem family, manufacturers, importers, and users should have to prove it is not persistent and toxic before it can be introduced or remain on the market.

Hormone disrupters work in two ways, one by altering inheritance, the other by altering the daily workings of the human body.

During pregnancy, hormones play a key role in the development of the fetus, which means that before birth, disruptors may alter a baby girl’s physical inheritance so that, as an adult woman, she is more susceptible to breast cancer, probably because her immune system has been impaired.

In addition, her intake of hormone disruptors from day to day may increase her total exposure to what her body identifies as estrogen and thereby increase her risk of breast cancer.

Experiments with mice show that hormone disruptors operate in both ways to increase the risk. But there is no similar proof involving women.

However, in what has turned out to be the greatest human experiment of all time, inadvertent though it has been, evidence concerning inheritance will be available soon. It will involve DES babies.

Between 1947 and 1972, five million women across North America took DES (diethylstilbestrol) because it was supposed to prevent miscarriages and premature births. Instead, as an estrogen mimic, it produced a host of problems for their children.

There were about 2.6-million DES daughters, the oldest of whom are just now reaching their fifties, an age when the incidence of breast cancer rises. Pat Cody, of Oakland, California, was a DES mother and a founder of DES Action. She was one of the ones lobbying the U.S. Congress for research funds so the medical histories of DES mothers and their children could be studied. In 1992 Congress earmarked $3-million (U.S.) for what Cody describes as the biggest study ever undertaken.

Questionnaires went out in 1994. The responses are now being analyzed and by 1998 results should be available.

For Cody, the Congressional decision was a great victory. For the rest of us it will either confirm or refute some of our worst fears.

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