Boys will be girls: “zombie” chemicals are pervasive

Published Oct. 14, 2013

In Alberta rivers downstream from certain Intensive Livestock Operations – better-known as feedlots, where hundreds and even thousands of cattle are crowded together in foetid paddocks of manure and urine the more economically to supply North America’s steak and burger-loving consumers – almost all the males have disappeared from key minnow populations.

The suspected cause: the buildup in the water of chemicals that mimic hormones, the molecules that signal most life forms how to develop and function. The water-borne mimics originate in steroids and other drugs that agribusinesses pump into feedlot cattle to speed weight gain, and counter the spread of disease among animals close-packed in compounds paved with excrement.

As I’ll explain in a moment, this is a problem not limited to Alberta or to minnows living downriver from cattle feedlots. But first the latest disturbing news from the field (and streams) of ‘EDC’ – or Endrocine Disrupting Chemical – research.

It had been thought that many of the hyper-potent synthetic hormones suspected of disrupting minnow gender balances decayed fairly quickly in the wild, their molecular bonds broken apart by exposure to ultraviolet sunlight.

So much is true. But now it appears that, as surely as night follows day, those same compounds regroup after dark.

A study published in the journal Science1 late last month, titled Zombie Endocrine Disruptors, reports that trenbolone acetate, an anabolic steroid (the same type of synthetic hormone sometimes abused by body-builders and strength athletes), as well as two other chemicals similarly used to speed weight gain in cattle, do not completely decay under daylight when released to water bodies. Moreover, come the dark of night, as much as 70 percent of the original mass of the steroid pulls itself back together and is effectively regenerated.

“In daylight, it essentially hides in another form, to evade analysis and detection, and then at nighttime it readily transforms back to a state that we can detect,” study co-author David Cwiertny, of the University of Iowa, explained in a news release.2

The discovery accentuates a rising concern about exotic chemicals in the water supply of industrial nations. Some 80,000 to 100,000 such compounds are believed to be in use in North America, appearing in everything from industrial processes to personal care products. Every year, some 12 billion metric tonnes of them are manufactured or imported into the United States alone. Many are designed to be biologically or chemically reactive in amounts of milligrams or less.

Surely, I hear you say, our governments are making certain that these are safe to use, or at least used safely under appropriate precautions, and prevented from entering the environment if they pose any risk.

If only it were so. But as the case of the missing male minnows in Alberta’s Oldman and Bow Rivers illustrates, the reality is otherwise.

It is true that, in North America at least, the use of grossly toxic compounds – stuff that will kill or injure you on contact – is tightly controlled, often with specific guidelines for worker protection and limiting their release into the environment.

But the threat posed by EDCs is of a different order. Often, exposures that are a tiny fraction3 of the observed ‘lethal’ dose of such compounds, especially if the exposure occurs at a particularly sensitive moment – conception or puberty, for example – are sufficient to disrupt an organism’s development. Yet nowhere yet are such risks weighed in the regulation and control of these chemicals.

Europe, the world’s leader in toxic chemical control policies, is expected to announce a decision by the end of this year on EDC regulation – but even there, a leaked proposal has prompted a furious push-back4 from more traditional toxicologists.

Morever, even the most modern municipal water treatment systems, capable as they are of filtering out old-fashioned pathogens like those which cause typhoid or cholera, are ineffective at removing exotic EDCs. This is true at both ends of the water-management cycle: when fresh water is treated before being distributed to homes and business, and when waste water is treated again before being released back to nature.

The reasons for this failure are two-fold. The first is, quite simply, that we don’t know how to do it on the scale required at costs considered acceptable. The second has been the assumption, until now, that nature would take care of the problem, neutralizing the compounds in the wild.

That this turns out not to be so goes some way to explaining why a veritable pharmacopeia of such compounds is turning up in tap and river water wherever scientists look for them. In the United States, researchers detected drugs ranging from mood-stabilizers to anticonvulsants in the ‘treated’ tap water of 25 out of 28 municipal supplies tested (Philadelphia set the record, with no fewer than 56 detectable compounds). The St. Lawrence River has tested positive for more than a dozen drugs, including both antibiotics and, again, anticonvulsants.

Many of these compunds are capable of penetrating both male and female reproductive systems: direct pathways to offspring developing in utero and, later in mammals, nursing. They have been found in human amniotic fluid, placenta, ovarian fluid and semen.

And it’s not just minnows that are being affected. The endocrine signalling system works much the same way in all vertebrates, in any animal, that is to say, with a backbone. Chemicals that separate the boys from the girls in minnows (and does away with the former), have similar effects on other species, including ours.

Wildlife biologists have observed an epidemic of gender disruptions worldwide, from hermaphroditic polar bears to alligators with testicular abnormalities. The incidence of genital deformities has soared among human males while sperm counts have plummeted, according to studies in Britain, the United States and Scandinavia.

As one British researcher put it: “The basic male tool-kit is under threat.”

Men, in fact, may be going the way of the minnow. In Canada and many other countries, the historic balance of human births – which used to very slightly favour males, presumably to account for males’ slightly higher juvenile death rates – has reversed. By one estimate, as many as a quarter of a million boys went statistically ‘missing’ worldwide in 2007.

And now we have another clue as to why.

Copyright © 2013 Chris Wood


References and further reading:
1. Science journal: Zombie Endocrine Disruptors May Threaten Aquatic Life
2. University of Iowa news release: Study Finds Steroids May Persist Longer in the Environment Than Expected
3. Nature journal: Toxicology, the learning curve
4. Nature journal: editors trade blows over toxicology