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.
Polychlorinated biphenyls (PCBs), used mostly as coolants and lubricants beginning in the 1930s, were banned in 1977. Early toxicology studies focused mostly on a subset of PCBs known as coplanar PCBs, which were shown in cell culture and animal models to pose a serious health risk. Recent studies, however, have shown that non-coplanar PCBs are particularly stable, are less susceptible to degradation by organisms in the environment, and predominate in environmental and human tissue samples over their counterparts.