A four year study from the UK has shown that the effects of hormone-like pollutants are very damaging to fish populations, reducing their reproductive performance by up to 76 percent. Led by the universities of Exeter and Brunel, the new study has important implications for understanding the impacts of these chemicals on ecosystem health and humans.
The pollutants in question, known as endocrine disrupting chemicals (EDCs), disrupt how hormones work in animals, including humans. EDCs can be found in everything from female contraceptive drugs and hormone replacement therapy pills, to washing up liquid. Most EDCs mimic the female hormone estrogen.
EDCs do not break down easily and they have been observed seeping into rivers through the sewage system for several decades. It was believed that they could alter the male biology of fish to make them more female – hence the ‘gender bending’ reputation. Until now, there had been no solid evidence to show the long-term impact of this effect on fish in the wild, but the new research focusing on wild roach in two UK rivers (the Bourne and Arun) has provided the confirming evidence.
The study found that intersex fish – those that had their sexuality compromised by EDCs and which contain both male (sperm) and female (eggs) sex cells – had their reproductive performance reduced by up to 76 percent.
“This is the first time we’ve seen firm evidence that the intersex fish, males that have been feminized by EDCs, have a reduced ability to breed,” noted study leader Charles Tyler, from the University of Exeter. “Clearly this raises concerns about the implications on the future for wild fish populations living in UK rivers, but there’s also much wider issues raised by these findings. Some of the effects seen in fish could occur in other animals too as hormone systems are quite similar across all vertebrates.”
EDCs have been tentatively linked with a number of human health impacts, including falling sperm counts and cardio-vascular disease, but Tyler is reticent to extrapolate the findings to humans. “They soak them [EDCs] up in far larger quantities than humans ever would, concentrating any potential side-effects.”
He does, however, think the findings should sound a cautionary note. “Fish still share many biological links with humans and the fact that their reproduction has the potential to be affected by EDCs is certainly a cause for concern. From a risk assessment point of view, these results are very significant.”
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