A SURVEY OF ESTROGENIC ACTIVITY IN UNITED-KINGDOM INLAND WATERS

Vitellogenin, a yolk-precursor protein normally found only in the bloo d plasma of sexually mature female teleosts and Other egg-laying verte brates was used as an indicator of exposure of male rainbow trout (Onc orhynchus mykiss) to exogenous estrogens. Vitellogenin concentrations were measured using a specific radioimmunoassay for trout. Cages conta ining adult male trout were placed at the points of discharge and at v arying distances downstream of treated sewage effluent outfalls into t he River Lea (UK) during the summer and winter months of 1992. After 3 weeks exposure at the majority of sites, fish held up to 15 km downst ream of inputs showed an increase in plasma vitellogenin concentration , with statistically significant elevations up to 4.5 km downstream. A repeat survey in November 1992 below Harpenden sewage treatment works showed that the only two stations to give a significant response were 3 m and 1.6 km downstream of the outfall. This reduced effect compare d to the first survey is thought to be due to dilution of both the inf luent sewage to the treatment works and of the river water itself by i ncreased rainfall, the overall increase in dilution being approx. 36%. Trout were also placed in 15 raw water storage reservoirs in southeas t England during the summer of 1993 for an exposure period of 6 weeks. No biologically significant increases in plasma vitellogenin concentr ation were observed in any of the reservoirs.