Fish emasculated by chemical cocktail

A new study suggests that testosterone-blocking chemicals in the UK's rivers that reduce fish fertility are more widespread than previously thought.

In a paper published in the journal Environmental Health Perspectives, researchers from Brunel University, the Universities of Exeter and Reading and the Centre for Ecology and Hydrology report that they have detected anti-androgens chemicals that inhibit the function of the male hormone testosterone – in river water.

Anti-androgens are found in certain medicines, and in some pesticides and plasticisers.

The researchers sampled over 1,000 fish from thirty English rivers, and examined possible links between exposure to pollutants and effects using statistical hierarchical modelling.

Lead author Dr Susan Jobling at Brunel University’s Institute for the Environment said: “We have identified a new group of chemicals in our study on fish, but do not know where they are coming from.”

The researchers are now trying to identify the source of these anti-androgens.

Earlier research by Brunel and the University of Exeter suggested that female sex hormones (oestrogens) found in the contraceptive pill and industrial chemicals that mimic oestrogens were entering rivers through sewage-treatment works, leading to the ‘feminisation’ of male fish.

This latest research, however, suggests that a wider range of chemicals, from a wider variety of sources, is to blame.

The researchers are now considering the possibility of a link between hormone disruption in fish and the increase in human male fertility problems associated with testicular dysgenesis syndrome, a spectrum of disorders originating in early foetal life.

Testicular dysgenesis may be caused by environmental factors, including maternal smoking during pregnancy, and by genetic abnormalities. It has not been linked to exposure to oestrogens, but experiments on rats suggest that the syndrome may be triggered by exposure to anti-androgens.

The new research findings therefore open up the possibility that fertility problems in fish and humans are caused by similar combinations of chemicals.

The paper’s senior author, Professor Charles Tyler of the University of Exeter, said: “There are likely to be many reasons behind the rise in male fertility problems in humans, but these findings could reveal one, previously unknown, factor.”

Emma Waghorn

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