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

Abstract

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 α (hERα) and human thyroid hormone receptor α (hTRα). 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.