Abstract-It is becoming evident that an increasing number of widely used industrial and agricultural chemicals are estrogenic. The biodegradation products of a major group of nonionic surfactants, the alkylphenol polyethoxylates, are one such group. Some of these chemicals are widespread aquatic pollutants, and bioconcentrate in aquatic biota. Exposure of male rainbow trout (Oncorhynchus mykiss) to four different alkylphenolic chemicals caused synthesis of vitellogenin, a process normally dependent on endogenous estrogens, and a concomitant inhibition of testicular growth. The magnitude of these estrogenic effects was dependent on the estrogenic potency of the chemical, the stage of reproductive development of the fish, and the concentration of the chemical in the water. These results support the contention that exposure of wildlife to environmentally persistent estrogenic chemicals can result in deleterious reproductive consequences.

The occurrence of certain natural and synthetic steroidal estrogens in the final effluent from STW has been demonstrated. 17β-Estradiol and estrone were present at concentrations in the tens of nanograms per liter range, and the synthetic estrogen 17R-ethynylestradiol was also identified, albeit in the low nanogram per liter range. The findings from subsequent in vivo tank trial experiments, in which adult male rainbow trout (Oncorhynchus mykiss) and adult roach (Rutilus rutilus) were exposed for 21 days via the water to environmentally relevant concentrations of 17β-estradiol and estrone are presented. In addition, the response of adult male and female roach following exposure to 17β-estradiol (1, 10, and 100 ng/L) was compared to the response to the alkylphenolic xenoestrogen, 4-tert-octylphenol (1, 10 and 100 µg/L). Plasma levels of vitellogenin were determined using previously validated radioimmunoassays in order to measure the estrogenic response of the fish to the varying concentrations of the compounds tested. The results indicate that environmentally relevant concentrations of natural steroidal estrogens are sufficient to account for the levels of vitellogenin synthesis observed in caged male fish placed downstream of certain STW effluent discharges in British rivers.

Abstract-It was recently demonstrated that most, if not all, effluents of sewage-treatment works (STWs) in the United Kingdom are estrogenic to fish. As many STWs discharge into rivers, it is possible that some stretches of rivers downstream of where the effluent enters might also be estrogenic. To assess this possibility, the induction of vitellogenin synthesis in caged male trout placed at various distances downstream of the effluent entry point was used as a biomarker of estrogen exposure. Individual discharges into five rivers in England were studied. In four cases, fish placed in the neat effluent, or close to where it entered a river, showed very marked and rapid increases in their plasma vitellogenin concentrations, demonstrating that the effluent was estrogenic. In two of these four cases, none of the downstream sites were estrogenic, whereas in one of the four, fish placed at a site 1.5 km downstream did respond by synthesizing appreciable amounts of vitellogenin, although sites further downstream were not estrogenic. The situation in the fourth river was quite different; not only was the effluent extremely estrogenic (a maximum vitellogenin response in the mg/ml range was attained), but so were all the other study sites on the river, the last of which was 5 km downstream of where the effluent entered. This particular river receives trade effluent from wool-scouring mills, which contains much higher concentrations of alkylphenolic chemicals than any of the other discharges studied. It is suggested that these chemicals probably account for the estrogenic activity of this river. The final (fifth) river showed no estrogenic activity, not even in the neat effluent. This discharge comes from a very small STW, which receives no trade waste, and one or both of these factors may account for why the effluent (and hence the river) was not estrogenic.

It is becoming evident that an increasing number of widely used industrial and agricultural chemicals are estrogenic. The biodegradation products of a major group of nonionic surfactants, the alkylphenol polyethoxylates, are one such group. Some of these chemicals are widespread aquatic pollutants, and bioconcentrate in aquatic biota. Exposure of male rainbow trout (Oncorhynchus mykiss) to four different alkylphenolic chemicals caused synthesis of vitellogenin, a process normally dependent on endogenous estrogens, and a concomitant inhibition of testicular growth. The magnitude of these estrogenic effects was dependent on the estrogenic potency of the chemical, the stage of reproductive development of the fish, and the concentration of the chemical in the water. These results support the contention that exposure of wildlife to environmentally persistent estrogenic chemicals can result in deleterious reproductive consequences.

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Abstract-Vitellogenin, a yolk-precursor protein normally found only in the blood plasma of sexually mature female teleosts and other egg-laying vertebrates, was used as an indicator of exposure of male rainbow trout (Oncorhynchus mykiss) to exogenous estrogens. Vitellogenin concentrations were measured using a specific radioimmunoassay for trout. Cages containing adult male trout were placed at the points of discharge and at varying distances downstream of treated sewage effluent outfalls into the 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 downstream 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 compared to the first survey is thought to be due to dilution of both the influent sewage to the treatment works and of the river water itself by increased rainfall, the overall increase in dilution being approx. 36%. Trout were also placed in 15 raw water storage reservoirs in southeast England during the summer of 1993 for an exposure period of 6 weeks. No biologically significant increases in plasma vitellogenin concentration were observed in any of the reservoirs.

No abstract

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