They could not immediately identify the source, but research determined that the toxins came from sources such as the Hudson River. After evaporating, Hudson River PCBs are carried to the far north on prevailing winds. The chemical falls as precipitation and enters the food chain, ending up in fish and seals that the Inuit eat. Although PCBs are listed as hazardous at 50 ppm, that status is based on the effects of the chemical on a healthy adult male. In some cases, harm occurs at concentrations of parts per billion.
Carpenter heads an interdisciplinary research team studying PCBs.
PCBs are a class of manufactured chemicals, with 209 theoretical variations, of which about 140 were actually produced. The different sorts of PCBs have different properties that variously affect health and the environment. They also have various mechanisms whereby they affect the brain. It used to be concern about cancer. But lately we are concerned about the immune system, the endocrine system and the nervous system.