The oxidative photodegradation behaviors of selectedpolychlorinated biphenyls (PCBs) [2,3,3',4'-tetraCB (BZnumber: CB56), 2,3',4',5-tetraCB (CB70), and 3,4,4',5-tetraCB(CB81: coplanar PCB)] using titanium dioxide (TiO
2) inwater were investigated. The main purposes were to clarifythe structural relation between the original PCBs andthe intermediates derived by TiO
2 oxidation and to evaluatethe estrogenic activity in the treated PCBs during theoxidative reactions. Approximately 90% of the three tetraCBsdecomposed within 120 min. Intermediates by decompositionof three tetraCBs, such as some OH-tetraCBs and OH-triCBs, carboxylic intermediates, phenolic intermediates,and other intermediates produced by the cleavage ofa benzene ring were identified and quantified. In thedegradation pathways, the produced amounts of OH-tetraCB and OH-triCB increased within 60 min of irradiationtime. Estrogenic activities of the intermediates from thethree tetraCBs in water were assessed by using a yeast two-hybrid assay system for human estrogen receptor
![](/images/gifchars/alpha.gif)
(hER
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). The maximal estrogenic activities were inducedby the solutions of decomposed CB81 with irradiation timeat 60 min. We found that the solutions at an irradiationtime of 60-120 min contained several 4-OH-tetraCBs and4-OH-triCBs substituted with OH and Cl at
para- and
para'-positions. It is presumed that the chemical structures of the4-OH-PCBs are similar to that of 17
![](/images/gifchars/beta2.gif)
-estradiol (
![](/images/gifchars/beta2.gif)
-E2);these intermediates present strong estrogenic activities.Moreover, we learned that there is a high possibilityof conversion from some low toxic PCBs congeners tostrong estrogenic OH-PCBs.