Chemicals playing havoc with fish hormones

 

Boys will be girls - if they are trout in some of our rivers, where hormone-disrupting substances have been feminising fish, writes Dr Claire O'Connell

There's something fishy going on in Ireland's waterways. Researchers in Athlone Institute of Technology (AIT) are discovering "gender bender" trout in midland rivers.

The male fish are producing a hallmark female protein in response to hormone-disrupting compounds from treated sewage effluent being released into the water, and the study's findings could be indicative of a more widespread problem.

The waste chemicals mimic the female hormone oestrogen and are classified as endocrine-disrupting compounds because they interfere with hormones produced by the body's endocrine system. This class of chemical pollutants has long been thought to affect wildlife, particularly fish and birds, says Dr Cepta Brougham, lead researcher with AIT's endocrine disruption group.

One of the most infamous endocrine disruptors is the pesticide DDT, which causes a range of fertility problems in many animal species. But a host of other, less well-known endocrine-disrupting chemicals also lurk in everyday items. "They are also used in paints, detergents, cosmetics, shampoos and sunscreens," says Brougham.

Endocrine-disrupting chemicals feminise males and they lend male characteristics to females in many animal species, she adds. "They act by seriously reducing their fertility, they damage their development, they undermine the immune system and they make them prone to tumours."

The chemicals can enter the body through the skin, intestinal tract or airways. But it is currently difficult to measure their impact on human health, because trends such as lower sperm count and increases in hormone-dependent cancers are multi-factorial, explains Brougham.

In general, monitoring of these compounds is hampered by a lack of technology. So the interdisciplinary AIT group is now developing a range of tests to detect endocrine disruptors both in the lab and in indicator species such as fish.

They are also studying the effects of these problematic chemicals on wildlife in midland rivers. One project has discovered that brown trout are becoming feminised by endocrine disruptors in waste sewage effluent. "Downstream of the sewage treatment plants we have found high levels of oestrogen-mimicking chemicals," says Miriam Kelly, a PhD student at AIT.

The study took 10 male fish upstream and 10 downstream of sewage effluent entry points in several rivers. They then tested blood samples from the fish for a protein called vitellogenin, which is involved in egg production and is normally found only in female fish. If vitellogenin is being induced in male fish, it's an accepted marker of endocrine disruption in the form of oestrogen-mimicking chemicals, explains Kelly.

"So far in quite a few locations we have found the induction of vitellogenin in the male fish downstream, and the closer you catch the fish to the sewage discharge pipe you would see an increased level of vitellogenin," says Kelly. Her findings tie in with other results from the AIT group that indicate the brown trout males have delayed sperm production and reduced testicular size - further signs of endocrine disruption.

Dr Brougham believes we should take heed of what is happening to animals as a result of hormone-disrupting chemicals in the environment. "We call our work here a global warning," she says. The AIT group looks at issues relating to their chemistry, pharmacology and possible links with cancer and has now developed around a dozen tests for the presence and effects of endocrine-disrupting chemicals.

They hope their studies will help detect and ultimately reduce the amount of endocrine disruptors ending up in waterways. In the meantime, Brougham recommends that consumers read labels and become familiar with compounds that are causing problems, like oestrogens.

She also suggests that we reduce our exposure by, for example, keeping plastics out of children's mouths, using little shampoo and conditioner and cutting down on cosmetic use. "Everything in moderation," she says.