Enhanced hepatotoxicity induced by repeated exposure to polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin in combination in male rats

2,3,7,8-Tetrachlorodibenzo-p-dioxin(TCDD) and polychlorinated biphenyls(PCBs) are among persistent polyhalogenated aromatic hydrocarbons that exist as complex mixtures in the environment worldwide.The present study was attempted to investigate the hepatotoxicity following repeated exposure to TCDD and PCBs in combination in male rats,and to reveal the involvement of potential mechanisms.Male Sprague-Dawley rats were exposed to TCDD(10 μg/kg) and Aroclor 1254(10 mg/kg,a representative mixture of PCBs) alone ...  

Intrinsic chemiluminescence production from the degradation of haloaromatic pollutants during environmentally-friendly advanced oxidation processes: Mechanism, structure–activity relationship and potential applications

The ubiquitous distribution of halogenated aromatic compounds (XAr) coupled with their carcinogenicity has raised public concerns on their potential risks to both human health and the ecosystem. Recently, advanced oxidation processes (AOPs) have been considered as an “environmentally-friendly” technology for the remediation and destruction of such recalcitrant and highly toxic XAr. During our study on the mechanism of metal-independent production of hydroxyl radicals (UOH) by halogenated quinones and H₂O₂, we found, unexpectedly, that an unprecedented UOH-dependent two-step intrinsic chemiluminescene (CL) can be produced by H₂O₂ and tetrachloro-p-benzoquinone, the major carcinogenic metabolite of the widely used wood preservative pentachlorophenol. Further investigations showed that, in all UOH-generating systems, CL can also be produced not only by pentachlorophenol and all other halogenated phenols, but also by all XAr tested. A systematic structure–activity relationship study for all 19 chlorophenolic congeners showed that the CL increased with an increasing number of Cl-substitution in general. More importantly, a relatively good correlation was observed between the formation of quinoid/semiquinone radical intermediates and CL generation. Based on these results, we propose that UOH-dependent formation of quinoid intermediates and electronically excited carbonyl species is responsible for this unusual CL production; and a rapid, sensitive, simple, and effective CL method was developed not only to detect and quantify trace amount of XAr, but also to provide useful information for predicting the toxicity or monitoring real-time degradation kinetics of XAr. These findings may have broad chemical, environmental and biological implications for future studies on halogenated aromatic persistent organic pollutants.