Hydroxylated polychlorinated biphenyls in the environment: sources, fate, and toxicities

Abstract

Hydroxylated polychlorinated biphenyls (OH-PCBs) are produced in the environment by the oxidation of PCBs through a variety of mechanisms, including metabolic transformation in living organisms and abiotic reactions with hydroxyl radicals. As a consequence, OH-PCBs have been detected in a wide range of environmental samples, including animal tissues, water, and sediments. OH-PCBs have recently raised serious environmental concerns because they exert a variety of toxic effects at lower doses than the parent PCBs and they are disruptors of the endocrine system. Although evidence about the widespread dispersion of OH-PCBs in various compartments of the ecosystem has accumulated, little is currently known about their biodegradation and behavior in the environment. OH-PCBs are, today, increasingly considered as a new class of environmental contaminants that possess specific chemical, physical, and biological properties not shared with the parent PCBs. This article reviews recent findings regarding the sources, fate, and toxicities of OH-PCBs in the environment.

Fig 1

Potential mechanisms of formation of hydroxylated polychlorinated biphenyls (OH-PCBs). Pathway a: aerobic bacterial transformation of 4-chlorobiphenyl (CB) through the upper biphenyl pathway (adapted from Furukawa and Fujihara 2008), pathway b: oxidation of 2,2′,4,5,5′-pentachlorobiphenyl (PeCB) by reaction with hydroxyl radicals (adapted from Letcher et al. 2000), pathway c: cytochrome P-450-mediated oxidation of 2,2′,4,5,5′-PeCB through the formation of an arene oxide (adapted from Letcher et al. 2000). The structure under brackets shown in pathway b represents the resonance forms of a hypothetical radical intermediate.