English river fish exposure to sex-altering pollutants continues

Fish in English rivers are exposed to lower levels of hormone-altering chemicals than 20 years ago, yet current amounts are concerning, according to findings from a study funded by the Environment Agency.

Researchers at Brunel University, London and the University of Exeter found that treated sewage released into rivers carries the female sex hormone, oestrogen and other related chemicals arising from plastics, shampoos and sunscreens. When wild fish absorb these through their gills, some develop a mix of male and female sex characteristics.

Endocrine (hormone) disruption can cause male fish to produce female proteins and develop eggs in their testes and has been known about since the 1980s.

Despite sewage treatment works upgrades and tighter restrictions, the study findings, published in academic journal, Environmental Science and Technology, how fish hormone disruption is “still a worry.”

Lead author on the publication, Brunel University London’s Dr Alice Baynes, said: “Although the severity of male fish showing female characteristics is now reduced at many of the re-visited sites, endocrine-disrupting chemicals are still impacting wild fish living downstream of waste water treatment works in England.”

Roach, a small, hardy fish found in the UK and much of Europe in rivers near where people live, has been studied in the UK for the past 40 years. In the 90s and early 2000s, ecotoxicologists measured endocrine disruption in fish at more than 50 UK sites up and downstream of waste water treatment works.

The Brunel team also analysed endocrine disruption drivers such as oestrogens. Men as well as women excrete naturally and pharmaceutical oestrogens used in contraceptives and HRT.

While not forced to do so by regulation, water companies have upgraded sewage treatment works to reduce hormone-changing chemicals in treated water.

The Environment Agency commissioned the latest research to find out if endocrine disruption was still an issue. The study teams revisited ten of the original river sites.

Overall, wastewater treatment works discharge less oestrogen into rivers. But at 60% of the re-visited sites they found male roaches carried egg cells in their testes. This is a permanent change that worsens with constant exposure and affects breeding. And at 90% of sites, males had concentrations of female egg proteins, a sensitive biomarker for estrogen exposure, above natural levels.

Examples provided by the researchers included the Great Billing works on the River Nene which upgraded it treatment processes in 2001. In the latest study there were fewer sex-reversed roach in the river and lower levels of female egg proteins in the male fish compared to pre-2001 readings.

The river Arun had the most sex-reversed fish at 10.7%. While the River Nene showed none. The River Arun upstream had the highest count, 40%, of sex-reversed male fish.

According to Baynes: “In the past, if it was a normal, large sewage works, you’d expect lots of endocrine disruption downstream. Now it seems that those bigger sewage works that have had more investment are now actually cleaner than some of the works in smaller towns and villages. So some of these smaller sewage works still need a lot of improvement to provide healthy rivers.”