PCBs Adversely Affect Brain Development

Concern has arisen over the possibility that chemical substances that have been released into the environment are responsible for developmental disabilities among children such as behavioral disorders, learning disability (LD), attention deficit hyperactivity disorder (ADHD) and autism.

Various hormones are associated with brain development, with the most important role being played by hormones secreted by the thyroid gland (thyroxine and triidotrysine). A research group associated with the national government's Science and Technology Agency and headed by Dr. Yoichiro Kuroda, director of the Tokyo Metropolitan Institute for Neuroscience, found that polychlorinated biphenyls (PCBs), especially hydroxide PCBs, which have similar chemical structure to thyroid hormone disrupted the hormone system and inhibited the mechanisms of brain development. The group published their findings in the November 2003 issue Kagaku ("Science") published by Iwanami Shoten, Publishers.

In an experiment using cultured cells, the research group found that PCBs and hydroxide PCBs inhibited the expression of thyroxine-dependent genes and suppressed the development of nerve cells essential for neural circuit formation. The minimum inhibitory concentrations of both the gene expression and the development were on the order of dozens of pMs (pM: picomol; one trillionth of a mole).

Contamination caused by PCBs, which are stable and persistent in the environment, has reached as far as the Arctic Zone, and extraordinarily highly levels of PCBs concentrated through the food chain are found even in the bodies of Inuits who eat marine products such as seals. Although more than 30 years have passed since the use of PCBs in open systems was banned in Japan, concern about PCB contamination is still spreading due to the massive amounts that were disposed when the ban came into effect.

Dr. Kuroda points out that various other persistent organic pollutants may have accumulated and spread out inside the human body, and that these chemicals may adversely affect human health even after laying dormant over several decades. He has also expressed concern regarding the current situation in which some of these chemicals are simply left unattended. He emphasizes the necessity to urgently clarify what chemical substances are toxic and what adverse effects they have, and to assess the risks to human health.

http://www.jst.go.jp/EN/

Posted: 2004/08/06 10:18:17 AM
Japanese version