Xeno-oestrogens & Fertility

This article is about the disruption that environmental chemicals are causing our hormones and includes references. Published in IVF Friends Newsletter in April 2003.

Synthetic chemicals are ubiquitous in our environment and many are capable of behaving like hormones in humans. Chemical hazards to women with infertility cannot be underestimated. In the past 50 years, not only has there been a dramatic increase in oestrogen dependent diseases such as endometriosis and breast, endometrial and prostate cancers, but there has also been a 50 per cent decline in male fertility. This time frame strongly correlates with the large scale production and release into our environment of synthetic chemicals.

Whilst it can be difficult to eliminate all hormone disrupting chemicals from your immediate environment, when you are aware of the major areas of concern, it is possible to significantly reduce your exposure and increase the elimination of these chemicals from the body. Last month I discussed the detoxification of the liver and digestive systems. Between these two systems, they break down and eliminate the poisons that may contaminate us and assist our body to resist storing these chemicals.

Chemicals that behave like oestrogen in the body are called xeno-oestrogens (which means “foreign”) and are also known as hormone (or endocrine) distruptors or mimics, and have several effects on the body. Natural hormones are chemical messengers that work by binding with receptors on specific cells in the body. Normally receptors are highly discriminatory about what chemicals they will bind with, but oestrogen receptors have a reputation for being “promiscuous” and can bind with hormone mimics which have an entirely different structure to that of natural oestrogen. Hormone mimics bind with the receptor and behave in the same way as the natural hormone, while hormone blockers bind with the receptor and have no effect except to prevent the natural hormone from binding, thus disrupting the activity of the cell. A pesticide derivative of DDT, called DDE, is known to disrupt cell activity by accelerating the breakdown and elimination of hormones like oestrogen and testosterone, leaving the body depleted of the natural hormone.

The most disturbing quality of these chemicals is that many of them accumulate in body fat and resist breaking down, in some cases, for centuries. As a consequence, animals that are high on the food chain (such as humans) accumulate a significant amount of hormone disrupting chemicals and are therefore the most affected. Hormone disruptors not only affect male and female fertility but also deplete the immune system.

Since the synthetic chemical industry began last century there has been an explosion in the number and type of synthetic chemicals being produced and released into the environment. For example, worldwide there are about 100,000 synthetic chemicals on the market and another one thousand new ones are introduced every year, mostly without adequate testing. All the testing facilities in the world can only test 500 substances a year, but in reality only a small number are actually tested.

The types of chemicals known for their hormone disrupting abilities, mainly because they are the most researched chemicals, include pesticides, dioxin, some plastics, PCBs and some drugs. There are many thousands of other chemicals that have never been researched.


“Pesticides are a special class of chemicals as they are biologically active by design and intentionally dispersed into the environment” (Colburn et al, 1996). In 1989, the world market of pesticides amounted to 2.5 billion kilograms and included sixteen hundred chemicals.

DDT, discovered in 1938, is a well known and well documented endocrine disruptor that was initially hailed a “miraculous pesticide”. It’s discoverer was awarded a Nobel Prize in 1948 as a result. DDT was used in huge quantities throughout the world and was subsequently implicated as the cause of cancer in humans and several catastrophic events involving animal populations. It was banned in America in 1972, but the US is still manufacturing DDT, even today for export to other nations.


Dioxin is the most toxic chemical on earth. It is an inadvertent by-product of the manufacture of chlorine based chemicals and of chlorine bleaching.

Some very interesting studies have shown a strong correlation between exposure to dioxin and endometriosis. American scientists researching the effect of dioxin on monkeys, found that 79 per cent of the animals exposed to dioxin had developed endometriosis and that the severity of the disease was directly related to the dose of dioxin. (Martin et al, 1993) The monkeys were given either 25 parts per billion or 5 parts per billion, with controls given no dioxin. The United States Food and Drug Administration defines allowable levels of dioxin in fish for human consumption as 50 parts per billion, twice the level that caused severe endometriosis in the monkeys.

People can come into contact with dioxin when they use bleached paper products, including milk cartons, tissues, toilet paper, disposable nappies, tampons and sanitary pads. Sanitary napkins and tampons are bleached to give women the impression that they are sterile, which they are not. Incidentally, many of these products contain cotton, which is one of the heaviest users of pesticides of any crop and may contain residual pesticides.

Some of the alternatives that are available include organically grown, chlorine free, disposable tampons and pads and reusable pads.


Several years before the dioxin study, scientists were surprised to find that a different colony of monkeys had spontaneously developed endometriosis after being given PCBs (Ballweg, 1995). Their fertility was severely compromised and of the sixty monkeys, only 26 pregnancies were achieved with 3 miscarriages, 9 stillbirths and 4 infant deaths between 1 and 11 days!

A study in Germany found that women with endometriosis have higher levels of PCBs in their body than women without endometriosis (Gerhard and Runnebaum, 1992).

PCBs are a family of chemicals that are especially resistant to breaking down and therefore persist and accumulate in the environment. They are found in every corner of the earth and in the body fat of every living creature - including every human.

The manufacture of PCBs was banned in the US in 1976 but not before 1.5 billion kilograms had been produced and most of it was already loose in the environment. Extraordinarily, the ban did not address PCBs already being used and some are still in use today.


Most plastics, including PVC and polystyrene, are known to leach hormone disrupting chemicals. Food and water stored in plastic containers can be affected, including tin cans that sometimes have a plastic lining. Food should not be heated or microwaved in plastic containers or covered with plastic wrap (use glass or “pyrex” instead).


Food and water are the most obvious sources of human exposure to hormone disrupting chemicals, but there are several other areas of concern that also should be considered.


Organic food is much less likely to be contaminated with pesticides or other chemicals, than food grown by standard farming methods. Non-organic fruits and vegetables should, at the very least, be thoroughly washed before they are consumed.

Animals that feed on plants are at the lower end of the food chain and are least likely to accumulate contaminants. This includes humans that are vegan (consume no animal products at all). It is extremely important that no animal fat is consumed and that all skin and fat is removed from meat before it is cooked, as the most dangerous chemicals are stored in fat. Cows’ milk and other dairy products can be contaminated as a result of chemical usage on pasture and on milking equipment and subsequently shed by the cow in her milk.

Fish is an extremely important food source, but large fish are usually high on the food chain because they eat smaller fish. The ocean is the least contaminated aquatic environment, so only deep sea fish, such as salmon, cod, herring, perch, tuna and mackerel should be eaten, and lake or river fish, which can be high in pollutants, should be avoided.

Another positive consequence of an increased demand for organic food is that as more farms switch to organic methods less chemical run off will enter the water supply.


Whilst the quality of our water is unsurpassed, we cannot be positive that it does not contain any of the problematic chemicals mentioned above.

Water supplied in plastic containers cannot be relied upon. Perhaps the best option, for those who are concerned, would be water filtered in your own home. Then you can be certain of what you are drinking.


Oestrogen mimicking chemicals are of particular concern to women with endometriosis or reproductive problems. These chemicals threaten not only individuals, but the survival of humans as a species. It is important that these women take steps, however difficult, to reduce exposure to these particular chemicals.


Ballweg, M.L. (1995). The Endometriosis Sourcebook. Contemporary Books, Chicago.

Colburn, T., Peterson Myers, J. and Dumanoski, D. (1996). Our Stolen Future. Little, Brown and Company, London and NY

Gerhard, I. and Runnebaum, B. (1992). “Grenzen der Hormonsubstitution bei Schadstoffbelastung und Fertilitatsstrorungen”. Zentralblatt fur Gynakologie, 114, pp. 593-602.

Martin, D.C., Rier, S.E., Bowman, R.E., Dmowski, W.P. and Becker J.L. (1993). “Dioxin-Induced Endometriosis in Rhesus Monkeys (Macaca mulatta)”. Abstracts, Annual Meeting of the Society for Gynecologic Investigation: 330 (Toronto)

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