Terrence Steyer, M.D.
Chair, Department of Family Medicine
What You Need to Know About Environmental Estrogens and Breast Cancer
WHAT IS AN ENVIRONMENTAL ESTROGEN?
The term "environmental estrogen" refers to those man-made chemicals, that show estrogen-like properties, which have been found in water and soil. These products are also referred to as industrial estrogens. This is in contrast to natural estrogens made by plants (phytoestrogens: e.g. bioflavonoids) and animals. In humans, females produce much more of this hormone than do males.
WHERE DO INDUSTRIAL ESTROGENS COME FROM?
Chlorinated organic compounds, which are used in some industrial solvents, lubricants, plastics, and pesticides, have been implicated as one possible source of the man-made, estrogen-like compounds which have been found in water and soil, and secondarily, in wildlife species. Pesticides are of concern to humans because of their potential residue in the diet and persistence in the food chain.
HOW DOES OUR EXPOSURE TO INDUSTRIAL ESTROGENS, ESPECIALLY THOSE FROM PESTICIDES, COMPARE WITH OUR EXPOSURE TO PHYTOESTROGENS?
Although a number of pesticides have been classified as estrogens, these compounds are only found in trace amounts in our food. In fact, the average intake (for a 16 year old male) of these industrial estrogens has been calculated at 0.0025 mg/day. In contrast, the same 16 year old male will ingest 1,000 mg/day of phytoestrogenic bioflavonoids in his "usual" diet. Thus far, high intakes of phytoestrogens have not been correlated with hormone-related cancers.
WHY ARE INDUSTRIAL ESTROGENS LINKED TO BREAST CANCER?
Early breast cancer studies (1972), which compared DDT and PCB levels in breast tissue samples, suggested that these chemicals were higher in women with breast cancer than in women without breast cancer. Later studies showed no difference between the case group (with cancer) and the control group (without cancer). Nevertheless, the theory of a linkage intrigued researchers who were looking for a possible answer for many unexplained cases of breast cancer.
Since these studies were conducted, PCBs have been found to be only weakly estrogenic and the dominant metabolite of DDT, p-p-DDE, is not an estrogen at all. In addition, the estrogenic metabolites of DDT are only found as trace environmental contaminants.
IS BREAST CANCER ON THE RISE?
No. However, breast cancers have "increased" wherever and whenever early detection services are available. The death rate from breast cancer is actually declining in most advanced countries.
WHAT ARE SOME PRACTICAL GUIDELINES FOR A WOMAN WHO IS CONCERNED ABOUT BREAST TUMORS?
Follow your physician's advice about breast self-examination, mammography, and regular check-ups (which will be based on your family history of breast cancer as well as your own past medical history).
ARE MEN AFFECTED BY THESE HORMONE-RELATED TOXICANTS?
Everything from unexplained cases of low sperm counts to slight birth defects in infants’ penises (hypospadias) are being blamed on the accumulation of, and exposure to, man-made estrogen-like chemicals in the environment.
But once again, theory is way ahead of fact. At this time, there is little evidence of a decline in human sperm counts, or an increase in penile birth defects.
WHY ARE SCIENTISTS EXCITED, YET CONCERNED, ABOUT ENVIRONMENTAL ESTROGENS?
Any new chemical theory may be used to explain unsolved, adverse biological health effects. For example, some wildlife biologists studying such divergent anomalies as deformed bird's bills and shorter alligator penises have: 1) attributed their findings to environmental estrogen exposure, 2) proposed that similar exposures will produce similar damage in humans, and 3) used their findings, and their explanation of the "cause," to campaign for increased pollution control and additional research funding. Other scientists use the theory of environmental estrogens to promote basic research in cellular growth, cellular receptors, estrogens and anti-estrogens.
WHAT IS A COMMON-SENSE APPROACH?
Don't panic over every new "threat" which appears in the media. Exercise caution and adopt a sensible, moderate approach to health. Wait for facts and evidence from reliable sources to test any theory of widespread toxicologic damage to man and a wide variety of unrelated species.
WHAT DO CANCER EXPERTS SAY?
Doctors who are committed to early detection and prevention of breast cancer are concerned that over-enthusiastic supporters of the environmental estrogen theory are confusing women with an all-embracing pollution theory. Unfortunately, false theories lead to false hopes of an environmental "cure" for what is largely a genetically predisposed and/or life-style condition.
A more realistic approach to "conquering" breast cancer is a careful review of familial cancer history, early diagnosis and treatment, the sensible avoidance of obesity, a greater daily intake of fruits and vegetables, and the adoption of a regular exercise program.
Increasingly, genetic markers are being discovered to help in early diagnosis and treatment.