Oxidative degradation of BPA using TiO2 in water, and transition of estrogenic activity in the degradation pathways.

The oxidative degradation behavior of bisphenol A (BPA) using titanium dioxide (TiO(2)) in water was investigated. The main purposes were to clarify the relationship with estrogenic activity from the degradation pathways demonstrated by oxidation of BPA in water. Approximately 99% of the BPA decomposed within 300 min, and gas chromatography (GC) mass spectrometry (MS) and liquid chromatography (LC) MS analysis revealed many intermediates during the degradation process. Intermediates by decomposition of BPA, such as hydroxylated-BPA (OH-BPA), carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. Estrogenic activities of the degradation pathways of the BPA in water were assessed by using a constructed yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha) and Japanese medaka fish (Oryzias latipes) estrogen receptor alpha (medERalpha). Estrogenic activity for hERalpha and medERalpha was reduced to less than 20% of the initial activity for BPA after 240 min of UV irradiation. However, estrogenic activity for medERalpha was increased by 110% from the initial activity for BPA at 60 min of UV irradiation. It was estimated that medERalpha assay was more sensitive for BPA and the intermediates than was the hERalpha assay. From these findings, we estimate that the intermediates by the oxidation of BPA have the behaviors of xenoestrogen to the aquatic wildlife in the environment.

Endocrine effects generated by photooxidation of coplanar biphenyls in water using titanium dioxide.

The oxidative photodegradation behaviors of selected three coplanar polychlorinated biphenyls (PCBs), (CB77, CB81, and CB169) using titanium dioxide (TiO(2)) in water were investigated. The main purposes were to clarify the structural relation between the original PCBs and the intermediates derived by TiO(2) oxidation and to evaluate the estrogenic and thyroid hormonal activity in the treated three coplanar PCBs during the oxidative reactions. Approximately 90% of the three coplanar PCBs decomposed within 180 min. Intermediates from the decomposition of the three coplanar PCBs, such as some hydroxylated-PCBs (OH-PCBs), carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. In the degradation pathways, the produced amounts of OH-PCBs increased within 60 min of irradiation time. The estrogenic activity and thyroid hormonal activity of the intermediates from the three coplanar PCBs in water at 0, 60, 120, 180 and 240 min of irradiation time were assessed by using a yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha) and human thyroid hormone receptor alpha (hTRalpha). The maximal estrogenic activities were induced by the solutions of decomposed PCBs with irradiation time at 60-120 min similar and slightly lower than those after the irradiation time. We found that the solutions occuring during the irradiation times of 60-120 min contained several 4-OH-PCBs substituted with OH and Cl at para- and para'-positions having estrogenic activity. The thyroid hormonal activity was not detected in the decomposed three coplanar PCBs solutions.

Production mechanism of hydroxylated PCBs by oxidative degradation of selected PCBs using TiO2 in water and estrogenic activity of their intermediates.

The oxidative photodegradation behaviors of selected polychlorinated biphenyls (PCBs) [2,3,3',4'-tetraCB (BZ number: CB56), 2,3',4',5-tetraCB (CB70), and 3,4,4',5-tetraCB (CB81: coplanar PCB)] using titanium dioxide (TiO2) in water were investigated. The main purposes were to clarify the structural relation between the original PCBs and the intermediates derived by TiO2 oxidation and to evaluate the estrogenic activity in the treated PCBs during the oxidative reactions. Approximately 90% of the three tetraCBs decomposed within 120 min. Intermediates by decomposition of three tetraCBs, such as some OH-tetraCBs and OH-triCBs, carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. In the degradation pathways, the produced amounts of OH-tetraCB and OH-triCB increased within 60 min of irradiation time. Estrogenic activities of the intermediates from the three tetraCBs in water were assessed by using a yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha). The maximal estrogenic activities were induced by the solutions of decomposed CB81 with irradiation time at 60 min. We found that the solutions at an irradiation time of 60-120 min contained several 4-OH-tetraCBs and 4-OH-triCBs substituted with OH and Cl at para- and para'-positions. It is presumed that the chemical structures of the 4-OH-PCBs are similar to that of 17beta-estradiol (beta-E2); these intermediates present strong estrogenic activities. Moreover, we learned that there is a high possibility of conversion from some low toxic PCBs congeners to strong estrogenic OH-PCBs.