Long-term effects of polychlorinated biphenyls: Neuropsychological outcomes of a longitudinal cohort study

Polychlorinated Biphenyls (PCBs) are known for several adverse health consequences and their neurotoxicity. As part of the HELPcB cohort, in this study neuropsychological outcomes of five consecutive measurements in occupationally exposed individuals were examined. The longitudinal effects of plasma PCB levels on neuropsychological functions were investigated, specifically differentiating chronic from acute effects. Neuropsychological outcomes included performance in verbal fluency, sensorimotor processing and alertness. PCB levels of low-chlorinated, high-chlorinated and dioxin-like congeners were analysed. Linear Mixed Models were applied, differentiating between accumulated PCB body burden and short-term fluctuations. Results suggest negative effects of plasma PCB levels on all three cognitive domains when examining chronic effects, whereas acute fluctuations of PCB values did not affect performance in neuropsychological tests. This finding points towards the effects of PCBs to be driven by a persistent neurobiological damage that affects cognitive functioning even years after cessation of occupational exposure, while short-term fluctuations in PCB levels are considered to be of lesser importance. An alteration of fronto-striatal dopamine circuits is discussed as a possible mechanism underlying the neurotoxic properties of PCBs.