The levels of NDL PCBs in human and environmental samples are far greater than the levels of DL congeners, with NDL PCB153 and PCB138 being the most abundant. They are often subdivided into congeners that share a structural and toxicological similarity with dioxins, the dioxin-like (DL) PCBs and non-dioxin-like (NDL) PCBs. PCBs are a group of organochlorine compounds comprised of 209 structurally similar analogues, or congeners. For decades, PCBs have been used as insulators, coatings, and caulks, and have persisted to date in the environment where they have globally accumulated in wildlife tissue and human cord blood, amniotic fluid, and mother’s milk 5, 6. Among the top industrial-derived contaminants thought to be involved in developmental neurotoxicity are polychlorinated biphenyls (PCBs) 2, 3, 4. Humans and wildlife are exposed to a wide range of contaminants in the environment and the role of these chemical pollutants in developmental neurotoxicity and neurodegenerative disorders has become a global environmental health concern 1. The effects on important and broadly conserved signaling mechanisms in vertebrates suggest that NDL PCBs may contribute to neurodevelopmental abnormalities in humans and increased selection pressures in vertebrate wildlife. A similar delay was observed for other NDL congeners but not for the potent dioxin-like congener PCB126. Morphological and biochemical data demonstrate that even though PCB153-induced swelling of afferent sensory neurons, the disruption of dopaminergic and GABAergic signaling appears to contribute to PCB-induced motor deficits.

Zebrafish that were exposed during development to concentrations similar to those found in human cord blood and PCB contaminated sites showed a delay in startle response. We investigated the effects of the abundant non-dioxin-like (NDL) congener PCB153 on neuronal morphology and synaptic transmission linked to the proper execution of a sensorimotor response. In this study, we uncover currently unknown links between PCB target mechanisms and neurobehavioral deficits using zebrafish as a vertebrate model. This is of particular concern for early life stages because the exposure of the more vulnerable developing nervous system to neurotoxic chemicals can result in neurobehavioral disorders. The most abundant polychlorinated biphenyl (PCB) congeners found in the environment and in humans are neurotoxic.

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