Environmental Estrogens

Queensland opposition leader, Lawrence Springborg, raised the issue of ‘environmental estrogens’ this week. Predictably, various newspapers and blogs were jammed with arguments about whether chemicals in sewage can change the sex of fish and whether they could turn a male human into a female. Seriously, they were. So let’s get a few facts straight.

A one-paragraph biology lesson: Human sexuality is determined by DNA chromosomes. Most of us have two chromosomes, either XX or XY (yes, I know there are other possibilities, but lets keep this simple). You got one of these from your father (an X or a Y) and one from your mother (an X). If you scored XX, you are genetically female. If you scored XY, you are genetically male. No amount of exposure to chemicals (such as hormones) in the environment can change this. You can not change a man to a woman or a woman to a man. Yes, I accept that people may identify as “male” or “female” regardless of chromosomes...I don’t mean to offend anyone...I simply want to deal with this complex topic in a single paragraph…woah…a can of worms that I really didn’t mean to open...Move on!

But fish and reptiles are different to mammals. Changing sex is natural for many species and it is common to do this in response to chemical signals.

Researchers have found that if they paint a turtle's egg with estrogen, the turtle inside can change from male to female. Strangely enough, the same thing can be achieved using industrial chemicals called polychlorinated biphenyls (PCBs). These (artificial) PCBs have some chemical similarities to (natural) estrogen, which causes them to interact with the estrogen-receptors. In other words, the PCBs ‘mimic’ the action of estrogen.

Male frogs’ eggs or embryos exposed in the lab to the widely used pesticide, atrazine, develop ovaries and are infertile. In fact, not only do the males (which normally only have testes) develop ovaries, they develop multiple ovaries, sometimes six or seven. Unlike the PCBs, atrazine does not mimic estrogen. Instead, it enhances the conversion of testosterone to estrogen.

Even mammals can be affected by these chemical ‘endocrine disruptions’ (although they don’t change sex). For example, sheep that graze on clover ingest natural plant estrogens (phytoestrogens) which can make them infertile.

Recently, researchers at the Cincinnati Zoo were trying to work out why some cheetahs were not breeding. It turned out that phytoestrogens in soy-based materials included in their diet was acting as a contraceptive. When the cheetahs were given a diet without soy several quickly gave birth to kittens.

There are lots of compounds that can act like estrogen. From the above examples, we know that they include natural estrogens, industrial compounds, pesticides and natural phytoestrogens (plant estrogens). Many of these compounds can wind up in sewage, so it is no surprise that poorly treated sewage can also have these sorts of effects.

For example, there are reports of fish in the Potomac River (USA) being “feminised” by water-borne pollutants. This was identified by an increase in the production of the protein that is involved in egg-production, by male fish. This protein, called ‘vitellogenin’ is not usually made by male fish unless they are treated with estrogen. It turns out that some detergents in the water are likely to be responsible for tricking male fish into producing vitellogenin. These detergents can be major constituents of municipal sewage. Human estrogens (excreted in urine) and synthetic steroids such as the contraceptive pill can have the same effect.

So what does all of this have to do with recycled water? Well that depends on how we define ‘recycled water’. If we are talking about advanced water treatment (processes such as reverse osmosis, granular activated carbon, advanced oxidation), then the answer is 'absolutely nothing'.

The concentrations of estrogenic substances in advanced treated recycled water are miniscule (or unmeasurable). We know this both by chemical analysis (measuring the concentrations of chemicals) and by estrogenic activity (running assays to measure the effect of any estrogens or estrogen mimics that may be present).

However, if we are talking about conventionally-treated (or poorly-treated) sewage, then yes, discharging poorly-treated sewage into creeks and rivers can be expected to disrupt the sexuality of some species including fish. All the more reason why we should pay better attention to treating water to a higher level than what we generally get away with today.

If you've come this far, leave a comment...tell me what you reckon.