Studies Reveal How PCB Exposure Damages a Developing BrainApr 14, 2009 | Parker Waichman LLP
Although it has long been known that PCBs—polychlorinated biphenyls—cause harm to the brain, it was never really understood how the environmental toxins actually wreaked damage, often causing behavioral and developmental problems in children, reported WebMD. Now, more clues as to how PCBs cause injury have been revealed in three recent studies.
PCBs negatively affect brain cell development and also, said WebMD, “make brain circuits ‘overexcited,’” which has been associated with developmental issues, according to Isaac N. Pessah, PhD, a researcher, professor of molecular biosciences, and director of the University of California Davis Center for Children's Environmental Health. "We think we have identified the way in which a broad class of environmental contaminants influences the developing nervous system and may contribute to neuro-developmental impairments such as hyperactivity, seizure disorders, and autism," said Pessah, quoted Web MD. Pessah is a co-author on the new studies.
The studies revealed that, in some cases, low PCB levels can be more dangerous than high levels, said WebMD, which noted that PCBs were “used in electronic components, pesticides, caulking, and flame retardants,” but have been banned in the United States since 1979. PCBs were banned because they are highly toxic and do not easily break down, said Science Daily. PCB toxins can be found in the “air, water, soil, and contaminated foods such as fish,” said WebMD, and accumulate in the bodies of animals said Science Daily.
WebMD cited one study in which it was found that low PCB levels in animals adversely affected their ability to learn to swim in a maze, which is a traditional animal training test, and also negatively impacted the animals’ dendrite plasticity. Dendrites, which are critical to learning, are the tiny projections that split off from the neurons that receive signals from the body. "This plasticity is very important for learning and memory," Pamela Lein, PhD, a study researcher and associate professor of neurotoxicology at the UC Davis School of Veterinary Medicine, said, quoted WebMD. Lein pointed out that this sort of a problem has been linked to “disorders such as autism, schizophrenia, and mental retardation,” reported WebMD.
WebMD said the findings might enable scientists to look at the safety of chemicals that replaced PCBs. Science Daily explained that the studies could explain the links between PCB exposure to the developing nervous system and behavioral issues in children. "We've never really understood the mechanism by which PCBs produce neurobehavioral problems in children," said Pessah, reported Science Daily.
The studies were published within a month of each other and strengthen conclusions regarding how PCBs adversely affect neurological development, said Science Daily. One study revealed that, at low levels, PCBs in utero and neonatally affect brain cell development; another revealed how PCBs affected “brain cell circuits in the hippocampus—the brain area known to be damaged in a number of “complex neurodevelopmental disorders, including autism, ADHD, learning disabilities, sensory deficits, developmental delays, and mental retardation; and how PCBs affect ryanodine receptors, which “contributes to the over-excitations on neural circuits,” said Science Daily.