Sewage anti-androgens feminise fish, study finds

A mix of oestrogens and anti-androgens in sewage is feminising fish in rivers, according to a study led by researchers from Brunel University. About two thirds of sewage effluents studied contained anti-androgens, but the compounds responsible are as yet unknown.

Chemicals in sewage that prevent androgens - male hormones - working properly are contributing to the feminisation of male fish in the UK.1 These anti-androgenic substances were widespread in a study of 30 effluents from sewage works in England.

Feminisation of fish has generally been attributed to oestrogenic chemicals in effluents. Mixtures of natural steroid oestrogens, synthetic oestrogens from the birth control pill and oestrogenic chemicals such as nonyl phenol can act together to feminise male fish and disrupt reproduction (ENDS Report 386, p 29 ).

Now researchers have shown that anti-androgens in sewage can also contribute to feminisation. Susan Jobling at Brunel University and colleagues at the Centre for Ecology and Hydrology and the Universities of Reading and Exeter collected samples of effluent and wild roach from 30 waters receiving sewage. Between 12 and 71 roach were caught at each site, making a total of 1,083 fish.

The researchers measured total oestrogenic activity and total anti-androgenic activity in the effluent, along with the individual levels of common oestrogens: natural oestrogens oestradiol and oestrone, the synthetic oestrogen ethinyl oestradiol from the birth control pill, and the industrial chemical nonyl phenol.

The male fish were examined for signs of sexual disruption including eggs in their testes, the egg-yolk protein vitellogenin in their blood and feminised reproductive tracts.

Using statistical methods, they looked for correlations between levels of the oestrogenic activity, individual oestrogens, anti-androgenic activity and the extent of fish feminisation.

Their analysis showed that the various effects on the fish were best explained by a combination of oestrogenic and anti-androgenic activity in the effluent.

The results are in line with earlier findings that show oestrogens have feminising effects in fish. "The data on that is unequivocal," says Professor Charles Tyler, one of the study authors. "But our paper highlights the fact that oestrogens are not the only players. It’s very likely that when you stick together anti-androgens and oestrogens they will have additive effects."

"What was key in the study overall was that at a number of sites the anti-androgenic activity was very high. Anti-androgens had a significant contribution to feminisation," Professor Tyler adds. Overall, about two thirds of effluents examined showed some anti-androgenic activity.

The researchers are now trying to identify the chemicals responsible for anti-androgenic activity in effluents, and which ones are absorbed and found in fish. Professor Tyler explains that as with oestrogens, there are probably a few potent chemicals and then a series of more minor players.

The efficiency with which a sewage works removes endocrine disruptors depends on the treatment process used at each plant. "It’s quite likely that processes in place that are effective for removing oestrogens would also be effective for stripping out anti-androgens," says Professor Tyler. "Those sites that have got activated charcoal - and not many do - are the cleanest. Sand filters are pretty effective too."

A national monitoring programme looking at the oestrogen-removal efficiency of 14 waste water treatment plants was completed late last year and a report is due for publication soon (ENDS Report 378, p 26 ).

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