Estrogenic effects of leachates from industrial waste landfills measured by a recombinant yeast assay and transcriptional analysis in Japanese medaka

In Japan, the leachates from 'stable type' landfills for industrial wastes are not controlled, and this has given rise to concerns about the possible pollution of surrounding environmental waters, especially by endocrine disrupting chemicals leaching from plastic and rubber wastes. To accurately assess the estrogenic potential of the landfill leachates by both in vitro and in vivo approaches, we confirmed gene-transcriptional responses in recombinant yeast cells and in Japanese medaka fish to estrogenic compounds, and applied these transcription assays to leachate samples. The yeast carrying the estrogen receptor (ER) of medaka and an ER-mediated response pathway responded to both the natural estrogen, 17β-estradiol (E2), and an industrial compound, bisphenol A (BPA), and the effective concentration of BPA was about 2.0×10(3) times that of E2. Transcripts of all genes coding for precursors of yolk protein, vitellogenin (vtg1 and vtg2), and precursors of egg envelope subunit proteins, choriogenins (chgh and chgl), increased in a concentration dependent manner in the livers of male medaka exposed to BPA or E2, and, except for chgh, reached peaks at exposure times of 48h. Although many fish in control groups did not have vtg transcripts, the incidence of vtg transcriptions also increased in a concentration dependent manner with exposure. The minimum effective concentrations of BPA at 48h were 0.5mg/L for chgh and vtg2, 2mg/L for vtg1 and 4mg/L for chgl, while those of E2 were 10ng/L for chgh and chgl and 30ng/L for vtg1 and vtg2. All leachates sampled at 3 landfill sites exerted in vitro estrogenic action. The E2 equivalent of the most potent leachate was 375ng/L for the yeast ER assay. This leachate sample significantly increased the transcripts of chgh, vtg1 and vtg2, but not chgl, in the medaka. In addition, chemical analysis showed that bisphenol A, 4-tert-octylphenol and 4-nonylphenol were the main contributors to the estrogenicity of the leachates. This study indicated that this type of landfill may adversely affect the reproductive functions of fish living in the surrounding area by leakage of industrial estrogenic compounds.