Estrogenicity of municipal effluents assessed in vivo and in vitro.

The estrogenic potency of municipal sewage treatment plant effluents was studied by comparing in vitro and in vivo test methods. The egg yolk protein precursor vitellogenin was used as a biological indicator of estrogenicity. The in vitro screening technique, based on the synthesis and secretion of vitellogenin from isolated rainbow trout liver cells and performed in the presence of estrogenic effluents, produced a dose-response curve. Three weeks' exposure of juvenile rainbow trout to undiluted estrogenic effluents caused a very pronounced increase in their plasma vitellogenin concentration. The response was very specific, because no effect was observed in the control fish. Moreover, the multigeneration test of zebrafish provided clear evidence of the estrogenicity of one of the effluents. The sex ratio of the offspring generations was changed to favor females. Also, the diluted effluent was sufficient to induce vitellogenin production in the exposed zebrafish males. The effective concentrations of the effluents that were tested were lower in the in vitro screening test than in the zebrafish multigeneration test. Based on the results of this study, the in vitro screening approach seems to be as least as sensitive as the in vivo approach to mixed effluents. Thus, using the in vitro approach affords advantages of both practicality and sensitivity for an initial screening of effluents for estrogenicity, but to ascertain significant effects, using the multigeneration in vivo test is recommended.