Revisiting oestrogenic effects in wild fish: assessing and comparing contemporary and historical impacts
Endocrine disruption, most notably the feminisation of males, has been reported in fish populations globally. Much of this work stemmed from the original studies based in the UK, where it was identified that male fish exposed to effluents from sewage treatment works produced a female protein vitellogenin, a precursor of egg yolk normally only produced in female fish. In addition, male fish living downstream of sewage treatment works more frequently exhibit an “intersex” condition whereby both male (sperm) and female (eggs) cells are found in the gonad.
In 1996, the Environment Agency (EA) commissioned a series of studies to investigate the feminisation (including levels of intersex) in wild fish populations. These studies (conducted at Brunel) demonstrated that intersex was largely attributed to discharges from sewage treatments works and further work identified that steroid oestrogens contained in these effluents were major contributors to these effects. Additional larger surveys in the early 2000’s replicated these findings.
The study of fish intersex remains of interest to researchers, policy makers and the general public. Since the initial surveys some oestrogenic pollutants have been banned, and some sewage works may have improved their treatment processes (possibly removing oestrogenic chemicals more effectively). Although human population densities in some areas may have also increased, putting more chemicals into the sewage system. Therefore, it is unknown if fish intersex levels in England have improved, got worse or are much the same as they were in the 1990s/early 2000s.
This specifically designed study will revisit sites previously known to have high, medium and low levels of intersex (effluent exposure) to provide robust data on the current situation in the field for comparison to the historic data. This type of information will be extremely valuable to UK and international regulators, to understand if more stringent environmental quality controls are required to protect aquatic wildlife from these types of pollution, or if measures already in place are sufficient.