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Studies Uncover PCB Toxins Dangers

Studies Uncover PCB Toxins Dangers


Studies Uncover PCB Toxins Dangers

by Kirsten Whittaker

Exposure to PCBs (technically called polychlorinated biphenyls), may effect the development of brain cells according to three separate studies.

These toxic substances in our world have long been associated with problems in children, but science could never explain precisely how PCB toxins affected the brain.

Once PCBs were used in a large amount of goods, and the U.S. banned their use in the 1970s. And although this seems like a long ago, these chemicals hang around in the environment because they aren't easily degraded.

They're still found in the air, are found seeping into our water supply, into the ground and often contaminating foods like fish that we eat. This is why PCBs are detectable in every one of us, even today.

One study has found that these environmental toxins adversely affect the development of brain cells and overexcite brain circuits. This has been linked to developmental problems.

"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," stated researcher Isaac N. Pessah, PhD. The last of the studies appears in the April 2009 online issue of PLoS-Biology.

One surprising finding from the study was that lower levels of PCB exposures sometimes were more harmful than higher exposures.

One of the studies uncovered that exposure to low doses of PCBs detrimentally effected animal subjects' ability to learn to navigate a maze, a common way to check learning ability in the lab.

It looks like even low doses of PCBs affected the plasticity of the dendrites adversely, which are critical to learning and memory. Issues in this area have been linked to conditions like autism, schizophrenia and even mental retardation.

The initial study was published in the March 2009 issue of Environmental and Health Perspectives.

For the second of the studies, tissue from an animal's hippocampus (part of the brain that manages memory and emotion) was researched in order to analyze the excitability of neurons prior to and during exposures to two different PCBs.

The normal brain should have a balance between excitation and inhibition of the neurons, as too much excitability isn't useful. Conditions like autism and attention deficit hyperactivity disorder (ADHD) may involve an imbalance between the two states.

The report on the second study appears in the March 2009 issue of Toxicology and Applied Pharmacology.

The third study took things to the cellular level, looking at specifically how PCBs might change the cell development (as they saw from the first study) and the level of excitement (what they found from that second study).

This time, the team exposed receptors in the brain cells that regulate the release of calcium (key to keeping signalling normal from cell to cell) to PCBs. Looking with electron microscopes, they found that PCBs bind to the receptors and hinders the release of calcium.

It's actually this that might account for the results in the other two studies.

"I think that these studies represent a kind of a turning point for our recognition of how these chemicals, PCBs, can interfere with brain development," says R. Thomas Zoeller, PhD, professor of biology at the University of Massachusetts, Amherst.

With this research-backed explanation of how PCBs can potentially cause developmental problems it may open a new line of research to find better treatments.

It may also help to come up with a way to evaluate the safety of other chemicals that have taken the place of PCBs, perhaps weed out the dangerous ones before they become widely used.

What's more, the research also shows us that even low doses of PCB toxins aren't always better and may not be safe at all.

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