Joint PCB-Methylmercury Exposures and Neurobehavioral Outcomes

The level of intake at which methylmercury might result in neurobehavioral or neuro psychological deficits in children has been extensively debated in recent years. The human data base for methylmercury toxicity is very robust, particularly when compared with other environmental substances for which health guidance values have been developed by Federal organizations. However, despite the depth of the data base for methylmercury, some of the key studies have been clouded by the concurrent exposure of the study population to polychlorinated biphenys (PCBs) and other persistent organic pollutants (POPs). In this paper, the authors examine the key points comprising the methylmercury-PCB issue and contrast these with recent reports of concurrent methylmercury/PCB human exposures and laboratory studies. The authors conclude that research published to date concerning the Seychelles and Faroes Island populations suggests that both methylmercury and PCBs are jointly responsible for the effects reported in the Faroes. Further neurobehavioral testing in populations exposed to PCBs alone, as well as with methylmercury alone, is necessary to fully resolve the ongoing debate.