Scientists have determined that a specific class of PCB causes significant developmental abnormalities in rat pups whose mothers were exposed to the toxicant in their food during pregnancy and during the early weeks when the pups were nursing.
This class of PCB traditionally has not been considered particularly hazardous.
The pups were estimated to have levels of the toxicant in their blood that were roughly equivalent to those found in the blood of breast fed babies of mothers exposed to extremely high levels of the toxicant from contaminated fish, soil, water and air in high-risk environments.
The study, reported in the on line, Early Edition of Proceedings of the National Academy of Sciences the week of April 23-27, showed that the toxicant altered the rat pups auditory cortex, the part of the brain that processes sound. The neural circuitry of this region was disorganized and the nerve cells had a decreased capacity to change, or "learn," in response to sound. The capacity of the brains cortex to change in response to stimuli contributes to the progressive development of cognitive function.
In children with a variety of developmental disorders, including language impairments and autism, the auditory cortex responds abnormally to sound. Some scientists believe this is the basis of the conditions.
While the scientists emphasized that their finding did not demonstrate that the toxicant causes developmental disorders, they said that, given its severe impact in the rat pups and the prevalence of this class of PCB in the environment known as non-coplanar PCBs -- and related chemicals warrant serious attention.
"The study indicates that there are chemicals out there, this being just one example, that could profoundly affect development," says Tal Kenet, PhD, who led the research while a postdoctoral fellow in the lab of senior author Michael Merzenich, PhD, UCSF Francis A. Sooy Professor of Otolaryngology
Contact: Jennifer OBrien
University of California - San Francisco