Salmon and Trout Association: Endocrine Disrupting Chemicals

Endocrine Disrupting Chemicals (EDCs) are silent killers, threatening biodiversity on a huge scale. An EDC is a substance which interferes with the bodies’ endocrine system and hormonal activities.

Aquatic organisms are at enormous risk from EDCs, which enter watercourses through both diffuse and point source pollution. There are a wide range of known EDCs, including natural and synthetic hormones (such as compounds found in contraceptive pills), industrial chemicals, pesticides, fungicides and herbicides.

Impacts

EDCs have been shown to cause the most damage to fish at larval or development stages, by causing abnormalities in sexual development, behaviour and fertility. The adverse alternations reported in the sexual development of exposed fish include:

• Gonadal intersex (gonads contain eggs and sperm developing simultaneously)
• Feminisation of reproductive ducts
• Reduced gonad (testis and ovary), growth rate and size
• Reduced gamete quality
• Increased levels of egg-yolk protein, indicative of exposure to feminizing chemicals.

The molecular pathways causing these effects are poorly understood, and the wide range of effects caused by EDC exposure makes them difficult to assess and monitor. As well as causing intersex and feminisation, EDCs have been shown to affect fish courtship and territorial behaviour. Research on Atlantic salmon (Salmo salar) has also shown EDCs can significantly inhibit the development of smolt physiology.

Research from the U.K clearly shows an association between the occurrence of fish feminisation and their exposure to effluent discharges. Research on wild roach (Rutilus rutilus) in the UK indicates more severely feminized fish are found in the older year classes, suggesting the condition is progressive. Other studies indicate some EDCs have the ability to bioaccumulate and can be passed on to offspring.

The occurrence of intersex individuals in fish populations can severely affect reproductive success.

EDCs are a widespread problem, now known to affect freshwater, estuarine and even marine fish.

Actions being taken

In 2004 the Environment Agency concluded that the effects of endocrine disruption on fish were sufficient to develop a risk management strategy for biologically active effluents that discharge into the aquatic environment. The Endocrine Disruption Demonstration Programme was established to assess the effectiveness and costs associated with removing steroid hormones at sewage treatment works (STW). This programme is running from 2005-2010.

The well-documented endocrine disruptor TBT, which leaches into aquatic systems from boat anti-fouling paint, was shown to cause imposex in dog whelks, oysters and mussels. It is now totally banned in Europe, having come into force on the 1st January 2008.

The Salmon and Trout Association led the NGO lobby for a ban on cypermethrin, a pyrethroid insecticide used in sheep dipping, which was shown to cause endocrine disruption in fish and fatal impacts on aquatic invertebrates. The lobbying resulted in a temporary suspension on the sale of cypermethrin sheep dips in February 2006. Further action is still awaited from the Government, as to whether the ban will become permanent or if this destructive chemical will be reintroduced (see: Sheep Dip).

The EA has funded the development of a model which predicts the concentrations of three steroid oestrogens, and their associated risk of causing endocrine disruption in fish in 10,313 UK river reaches. The model predicted the regions with rivers at greatest risk of causing endocrine disruption to fish were Thames, Midlands and Anglian regions (for further details see briefing paper)

Call for Further Action

The S&TA feels the severity of this problem requires urgent attention. We feel precautionary action should be implemented now to reduce the exposure to EDCs in the aquatic environment before it is too late. We feel sufficient evidence exists to demand;

• By 2012, universal threshold levels for total endocrine loads and specific oestrogen threshold standards, in STW discharges.
• Immediate action to reduce natural and synthetic steroid estrogens in priority STW discharges in ‘at risk’ areas.
• Reduction and phasing out of other manufactured chemicals with endocrine activity and replacement with safer alternatives. Priority should be given to the prevention of the release, rather than end of pipe solutions.
• Reassessment of current toxicity tests and chemical standards, as current assessments are dominated by single-chemical exposure studies; however these chemicals are mixed in effluents, which are likely to result in additive effects. Precautionary limits/standards should therefore be set to take this into account.
• Investigations into population level impacts caused by EDC exposure, including population declines and loss of genetic diversity.

Conclusion

The full extent of endocrine disruption and its effects on the environment is not fully understood. However, many experts believe that one thing is certain; that they are far more widespread than currently confirmed.

The future of commercial and recreational, marine and freshwater fish populations could be threatened by the effects of EDC exposure. The S&TA strongly believe this issue needs addressing now to help safeguard our native fish populations, and enable us to obtain the Water Framework Directive (WFD) requirement of ‘good ecological status’ in all of our waterbodies by 2015.

For further information see;

S&TA Scientific Briefing Paper: The Effect of Endocrine Disruptors on Fish
EA. (2008). Catchment risk assessment of steroid oestrogens from sewage treatment works.
EA. (2004). Proposed predicted no-effect-concentrations (PNECs) for natural and synthetic steroid oestrogens in surface waters
EA. (2001). The endocrine modulating effects of wastework treatment works effluents.
EA. (2002). The identification of oestrogenic substances in sewage treatment work effluents.
Cefas. (2002). Endocrine disruption in the marine environment (EDMAR)