"PCBs" redirects here. For printed circuit boards, see printed circuit board.
PCB warning label on a power transformer known to contain PCBs. Chemical structure of PCBs. The possible positions of chlorine atoms on the benzene rings are denoted by numbers assigned to the carbon atoms. Polychlorinated biphenyls (PCBs) were widely used as dielectric and coolant fluids, for example in transformers, capacitors, and electric motors. Due to PCBs' environmental toxicity and classification as a persistent organic pollutant, PCB production was banned by the United States Congress in 1979 and by the Stockholm Convention on Persistent Organic Pollutants in 2001. According to the U.S. Environmental Protection Agency (EPA), PCBs have been shown to cause cancer in animals, and there is also evidence that they can cause cancer in humans. A number of peer-reviewed health studies have shown an association between exposure to PCBs and non-Hodgkin Lymphoma, a frequently fatal form of cancer. However, other similar studies have found no such link. Studies of PCB workers have uniformally shown no statistically significant increased rates of deaths from non-Hodgkin Lymphoma. In 2013, The International Association for Research on Cancer (IARC) determined that the evidence that PCBs cause non-Hodgkin Lymphoma is limited and not consistent. Institutions devoted to cancer research and treatment such as the American Cancer Society and the Mayo Clinic do not list PCB exposure as a risk factor for non-Hodgkin Lymphoma.
Concerns about the toxicity of PCBs are largely based on compounds within this group that share a structural similarity and toxic mode of action with dioxin. Toxic effects such as endocrine disruption and neurotoxicity are also associated with other compounds within the group. The maximum allowable contaminant level in drinking water in the
