A national, GIS-based risk assessment for intersex in fish arising from steroid oestrogens – England and Wales

The occurrence of intersex fish is widespread in the rivers of England and Wales and is believed to be strongly linked to their exposure to steroid oestrogens from sewage treatment plants. A national concentration-based risk assessment has been carried out. Predictions of exposure using the LF2000-WQX model have been made for the inland waters of England and Wales. It incorporates spatial and physical data for > 2,000 STPs serving over 29 million people. The mean and 90th percentile concentrations of oestradiol (E2), oestrone and ethinyloestradiol and their associated endocrine disruption risk were predicted for 21,452 km of river. Mean concentrations of the combined steroids were compared with a risk classifications based on a review of ecotoxicology studies. 61% of the river length modelled in England and Wales was predicted to be not ‘at risk’ from endocrine disruption (< 1 ng/L E2 eqv), meaning that 39% of that modelled was ‘at risk’. Factors influencing the proportion of river reaches being at risk are the population density, their location and aggregation, and the available dilution. Around 1% of river length was predicted to be at high risk (>10 ng/L E2 eqv).