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Abstract-Ralnbow trout (Oncorhynchus mykiss) were exposed to 1.5 and 15% viv secondary treated sewage etlluent for 32 wecks in ftow-through mesocosms. The exposure encompassed the full periocl of reproductive development for rainbow traut. Traut dicl not show any evidence of a dose-c1ependent change in growth. Fish exposed to 15% effluent were the only group to show morlality (5%) over the duration of the experiment. Trout at the highest effluent concentratlon had significantly higher liver size than reference water fish. Both male and femalc trom in the 15% cxposure group also exhibited significantly higher gonad wcight tban thc rcfcrcnce graul'. In female trout, this gonad size increase could be explained by higher egg numbers. Female antt male traut both displayed a significant increase in plasma 17ß-estradiollevels after exposure to 15% effluent, while neither sex had dose-dependent differences in plasma testosterone. Male trout displayed elevated vitellogenin levels and reduced plasma 11-ketotestosterone concentration after exposure to 15% eftluent. Chemical examination of steraidal compounds, including both estrogens and androgens, in the wastewater revealed that only estrane was detectable at a mean concentratioll of 4.5 ng/L. It is assumed that the effects observed in trout exposed to 15% eftluent were consistent witb stimulation 01' reproductive development due to very low levels of estrogens. Overall, long-term exposure to treated sewage eftluent containing low levels of estrogen did not have significant negative implications for reproductive development in rainbow trout.

This study examined the hypothesis that chlorine dioxide bleaching used in pulp and paper production causes the formation of reproductive-endocrine disrupting compounds from plant sterols. This was tested by conducting a laboratory simulation of the chlorine dioxide oxidation of two plant sterols, beta-sitosterol and stigmasterol. Oxidation products of the plant sterol beta-sitosterol were purified and identified and found to be cholestan-24-ethyl-3-one, 4-cholestene-24-ethyl-3-one, and 4-cholestene-24-ethyl-3,6-dione. The first two compounds were found in a number of pulp and paper effluents and biosolids. The sterols and their oxidation products were tested in vitro using bioassays for androgenicity and estrogenicity. A 28 d in vivo bioassay was employed to examine masculinization in female mosquitofish. In vitro bioassays revealed little estrogenic activity in the parent sterols or in mixtures of their oxidation products. Androgenic activity as measured by the androgen receptor binding bioassay was in the order of 19-96 microg/g testosterone equivalents but with no increase or decrease with chlorine dioxide oxidation. The mosquitofish bioassay did not show significant masculinization for any of the preparations tested. A number of androstane steroids were identified in the sterols tested, however, those compounds could only account for a small fraction of the androgenic activity in the sterols. It was clear that the parent sterols were not themselves acting as androgens in the bioassays used. This study indicated that chlorine dioxide oxidation of sterols produced predominantly oxidized sterols that were not likely to act through androgenic or estrogenic mechanisms.