Screening of agonistic activities against four nuclear receptors in wastewatertreatment plants in Japan using a yeast two-hybrid assay

To assess the potential endocrine disruptive e ects through multiple nuclear receptors (NRs), especially non-steroidal NRs, inmunicipal wastewater, we examined the agonistic activities on four NRs (estrogen receptor , thyroid hormone receptor , retinoic acidreceptor and retinoid X receptor ) of untreated and treated wastewater from municipal wastewater treatment plants (WWTPs) inJapan using a yeast two-hybrid assay. Investigation of the influent and e uent of seven WWTPs revealed that agonistic activities againststeroidal and non-steroidal NRs were always detected in the influents and partially remained in the e uents. Further investigation offour WWTPs employing conventional activated sludge, pseudo-anoxic-oxic, anoxic-oxic and anaerobic-anoxic-oxic processes revealedthat the ability to reduce the agonistic activity against each of the four NRs varies depending on the treatment process. These resultsindicated that municipal wastewater in Japan commonly contains endocrine disrupting chemicals that exert agonistic activities onsteroidal and non-steroidal NRs, and that some of these chemicals are released into the natural aquatic environment. Although theresults obtained in yeast assays suggested that measured levels of non-steroidal NR agonists in the e uent of WWTPs were not likelyto cause any biological e ect, further study is required to assess their possible risks in detail.