Endocrine disrupting chemicals also affect fish genes

It has been known for a number of years that a wide variety of chemicals disrupt reproduction by mimicking natural oestrogen, causing effects such as the development of female sexual organs in male fish.

However, researchers at the University of Maryland Biotechnology Institute’s Center of Marine Biotechnology (COMB) have been investigating the effects on genes in zebra fish of pollutants such as surfactants in detergents and pharmaceuticals, arylhydrocarbons, plasticisers, and the herbicide, atrazine. They found that EDCs influence a gene responsible for brain oestrogen production – in turn responsible for sexual differentiation, and also sexual behaviour.

“You might get males who do not display the correct behaviour,” said John Trant, COMB Associate Professor. “In order to mate with a female, he may have to court her, build a nest, chase, or show some form of dominance. So, even if the concentration of these disrupting compounds in the water are not sufficient to completely reverse their sexual physiology, small adjustments in their behaviours would be equally fruitless.”

The researchers are particularly concerned about the effects of the chemicals in their local Chesapeake Bay, which has been found to contain a variety of EDCs and has long been considered by ecologists as a very favourable habitat for fish spawning, hatching and nurseries.

“I would not say that it is severe enough that any population is becoming completely monosexed,” said Trant. “However, because the Bay is so important as a nursery, chemical-induced perturbations of the reproductive and developmental processes could lead to severe consequences.”

It is not only Chesapeake Bay that could be facing problems. A recent survey of rivers and streams across the US carried out by the US Geological Survey, revealed that they contain a plethora of chemicals, including human and veterinary drugs – such as antibiotics, natural and synthetic hormones, detergents, plasticisers, insecticides and fire retardants (see related story).

Recently, the UK Environment Agency called for changes to sewage treatment technologies due to the effects on fish of artificial female human hormones from contraceptive pills emitted from treatment works. Research had revealed that the fertility of male fish in areas in the UK is declining, with some males developing female reproductive organs (see related story).