That stability became a threat when it was discovered that PCBs caused cancer in lab animals. PCBs in humans Starting in the early 1970s, PCBs were found in fish, wildlife and in human organs, blood, fatty tissue and milk. Worse, PCBs tend to become more concentrated as they move up the food chain toward humans, where they can cause skin lesions, liver disease and may cause birth defects or cancer. More than half the people in the United States have some PCBs in their bodies, researchers say. Despite the ban on PCB production, Smith says, there are probably many PCB-insulated transformers still on utility poles.
Pathologists now use a different set of criteria to call a cell a cancerous cell.
Because of the new standards, a group of pathologists brought together in 1990 by the Food and Drug Administration, the Environmental Protection Agency and business re-evaluated the original slides of tissues from laboratory rats. The study results showed that all PCBs are not equally potent in causing cancer, according to Smith. This means that most environmental PCBs are probably less carcinogenic than we thought. And we are starting to see a change in focus regarding PCBs. At one time, we focused all our regulations on how carcinogenic PCBs are, but maybe some other things need to be driving the regulations now.