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Xenoestrogens

There are a series of about four main natural compounds found in humans and other animals which are the estrogens. These are female sex hormones which are steroids. These are E1 (Estrone), E2 (Estradiol), E3 (Estriol) and E4 (Estetrol).

Xenoestrogen means an artificial estrogen, some artificial estrogens such as EE2 which is commonly used in oral contraceptives is not particularly bad. The xenoestrogens all are molecules which can fit the estrogen receptor, some are steroidal like the natural estrogens while others are not steroids. Here is a picture of EE2. The reason why EE2 is used instead of estrogen in oral contraceptives is that many of the natural sex hormones are not very active when swallowed. They tend to be converted into other things by the body before they can get into the main part of the blood system. Here is a picture of EE2.

I have seen many people making the argument that urine from women who are taking “the pill” will turn male fish into female fish. But when I look at the evidence it is interesting that the pregnant woman releases estrogens which have a far higher estrogenic effect on the environment than a woman who is “on the pill”. Here is a bar chart showing the amount of the three most important estrogens released per person per day.

You can see here now a woman who is menstruating does emit more estrogens in their urine than a man. A woman who has gone through the menopause emits less estrogen than before she stopped, but a little more than a man. When pregnant women emit a lot of estrogens in their urine. The three compounds I have data for are not equal in strength as estrogens. The relative strength of the estrogens will depend on the receptor which they are binding to. But in the paper I was reading you can give a score of 2.8 micrograms worth of E2 to a man, the menopausal woman has a score of 3.5 micrograms worth of E2, the menstruating woman has a score of 6.0 micrograms of E2 and the pregnant woman 589 micrograms worth of E2 per day.

The typical dose in the oral contraceptive is about 30 to 35 micrograms per day, as women will fully metabolize between 20 and 50 % of the EE2 which they swallow. Then the dose to the environment of EE2 from a woman on the pill is between 15 and 28 micrograms for the days that they are taking it. As EE2 is twice as potent an estrogen as E2 (the standard one), I can reason that the woman on oral contraceptives is somewhere in the range of 20 to 40 micrograms worth of E2 per day.

I have seen data that in 2001 that indicated that 43 % of Dutch women of reproductive age took oral contraceptives while in the USA it was 28 % of women of reproductive age. So if we use these values it can be estimated that on average women of reproductive age are releasing between 12 and 24 microgram worth of E2 per day.

Compared with the 6 micrograms worth of E2 per day this is not a vast increase. What is interesting is the question of how stable is EE2 compared with the other estrogens in a sewage plant. The paper I was reading indicates that many sewage plants are able to remove more than 80 % of both E2 and EE2. Thus the sewage plant will mitigate any effect of EE2 use on the fish in the river.

The truly scary worst of the worst xenoestrogen is DES, the jury is out regarding the question of “does it cause breast cancer when an adult woman is exposed to it ?”.

DES

But it is very clear that in utereo exposure to DES does increase a woman’s chance of getting an unusual gynological cancer at a young age (teens or 20s). The cancer is such that DES is close to a perfect storm, the cancer is one which is not normally seen in women before the menopause. Also a normal gynological examination is likely to fail to spot signs of this cancer. A word of warning if you are easily shocked or horrified then do not go googling “DES daughter cancer”, the topic is a nasty horror show.

Other xenoestrogens include bisphenol A, in rats this is a very weak estrogen. But there are some related compounds which are much stronger as estrogens in rats.

Another one which is interesting is DDE which is a breakdown product of DDT. This is an interesting xenoestrogen as it does not have a hydroxyl group. Here is a picture of DDE.

Thankfully in Sweden the birds of prey whose numbers declined due to the use of some chlorine containing pesticides have started to increase again.

Another xenoestrogen of note relates to the surfactant triton X-100, this surfactant is not an estrogen but it breaks down in nature into a surfactant. The reason it is a problem is that the branched alkyl chain is only very slowly digested by bacteria. But when the corresponding compound with a C9 linear chain (Nonoxynol9) is released into rivers it is degraded much faster.

I have drawn all the xenoestrogens to try to suggest a similar structure to estrogens like E1. I may come back and write some more later on this topic.

By Mark Foreman

I am a Swedish / British chemist who works in Sweden at Chalmers University of Technology as an Associate Professor. I am based in the Chemistry and Chemical Engineering Department and I work in the Nuclear Chemistry / Industrial Materials Recycling units. My academic interests include things from both nuclear chemistry, recycling and some other unrelated things.

I originally come from the UK (England). I have degrees from Imperial College (BSc + ARCS) and the University of Loughborough (PhD).

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