The sex hormone oestrogen helps stimulate the development of male and female sexual organs in the foetus and later orchestrates the reproductive cycle in women. Certain drugs, industrial compounds, pesticides and plastics, which can mimic oestrogen's effect in the body, are appearing in food and water supplies and some of which are bioaccumulated. Sometimes the active principle is the breakdown product of otherwise unnoteworthy chemicals that have been metabolized by the body. Evidence is accumulating that these are disrupting human and animal reproductive and immune systems. This is affecting the biological development in many species, notably through transgenerational effects or consequences. A notable effect is the de-masculinizing of male animals which in its mildest form simply results in reduced fertility, but in more extreme forms can disrupt puberty in humans or lead to hermaphrodization in lower vertebrates such as fishes or frogs. A known source of generalized environmental pollution by oestrogenic compounds is via sewage effluent discharge into water bodies. Current water purification techniques tend not to remove these compounds from drinking water supplies. Ironically, hormones do more damage at low levels of exposure, than at high levels.
Oestrogen-like compounds can find their way into the reproductive tracts of foetuses and adults. They attach themselves to molecular receptors that are normally reserved for oestrogen. The chemical family of oestrogens is very diverse. Some variants are much more potent than others. They may also have different effects on foetuses than on adults, or on humans than animals. In addition, there are also "good" oestrogens in the environment which protect against cancer.
In 2001, the US Geological Survey reported that pharmaceuticals, hormones, and other organic wastewater-related chemicals have been detected at very low concentrations in streams across the nation. Many of the chemicals examined (81 of 95) do not have drinking-water standards or health advisories.
The classic example is diethylstilbestrol, or DES. The oestrogen-like drug was administered to millions of pregnant women between 1948 and 1971 to prevent spontaneous abortions. But it upset the delicate hormonal balance in the womb and ended up causing genital defects in many of the women's children, including vaginal deformities in girls and undescended testicles and abnormally small penises in boys. In the past decade, scientists have found that the number of environmental contaminants with oestrogen-like properties is much greater than they had imagined. The list includes: (a) DDE, a contaminant in dicolfol, an insecticide sprayed on food crops in the USA. (DDE is also the major breakdown product of DDT, an insecticide that is banned in some countries but still in wide use around the world); (b) Nonylphenols and related compounds found in spermaticides, hair colouring products and other toiletries plastic wrappings, furniture polish, herbicides and pesticides; (c) Polychlorinated biphenyls, a family of chlorine-containing industrial compounds, not longer made in certain countries but still in use. They have become widespread contaminants in food and water and are commonly found in human fat tissue and breast milk; (d) Endosulfan, a pesticide used on vegetables; (e) Bis-phenol-A, a breakdown product of polycarbonate plastics from which many plastic water jugs and baby bottles are made.
The most staggering feature of the problem is its scale. The accused chemicals are found in pesticides, refrigerators, medicines and cans of beans. They have been found in Antarctic snow and in the air almost 7,000 metres above India. Recent findings and circumstantial evidence that points to pollution by hormonally active chemicals are that sperm counts in men have fallen drastically worldwide during the past five decades, while the number of testicular cancers has tripled. There is an epidemic of endometriosis among women. Alligator eggs are failing to hatch at a biological research institute in Florida, and many male alligators have abnormally small phalluses. Cancer researchers are finding that routine cell culture experiments have suddenly stopped working because oestrogenic chemicals were leaching out of laboratory plastic tubing.