Polychlorinated Biphenyls (PCBs) are a group of 209 closely related chemicals. PCBs do not occur naturally in the environment and are challenging to manufacture as individual chemicals. Instead, most PCBs were manufactured and sold in mixtures that contained many different PCBs. For example, several different mixtures of PCBs were manufactured and sold in the United States under the trade name Aroclor. PCB mixtures were commonly used in products like electrical transformers and capacitors, some caulks, and hydraulic oils. PCB manufacture in the United States stopped in 1977.
Environmental Fate and Transport
PCBs are highly persistent in the environment. Though PCBs tend to bind to soil, most can slowly evaporate and if the soil is moved the PCBs will go with it. PCBs can be carried in flowing water and attach to sediments. PCBs also tend to bioaccumulate in some plants and animals, especially aquatic animals. For these reasons, PCBs have been found throughout the world in soil, air, water, sediments, and in the tissues of plants and animals, especially higher-level predators and bottom-feeding fish.
Because PCBs are so ubiquitous, exposure is difficult to avoid. However, levels of PCBs in the environment are falling over time. Important potential exposure sources include consumption of game fish and animals, meat and dairy products, spills from older electrical devices that contain PCBs, waste disposal sites that contain PCBs, municipal and industrial incinerators, some older caulks, and older elastic sealants.
Our bodies transform some of the PCBs that enter our bodies into related chemicals called metabolites, some of which may also be hazardous. PCBs and PCB metabolites are principally excreted in feces but can also be stored in our bodies, mostly in body fat and the liver, where they may remain for years. Infants may be exposed to PCBs through breast feeding.
Reported effects from workplace PCB exposure include acne and rashes, and there is evidence that workplace exposure is associated with certain types of cancer, especially liver cancer. Animal studies have shown anemia, skin problems, damage to the liver, stomach, and thyroid gland, as well as immune system and reproductive problems.
The preceding paragraphs are summarized from the Public Health Statement for Polychlorinated Biphenyls (PCBs) published by the Agency for Toxic Substances and Disease Registry.
Additional Cancer Assessments
U.S. EPA's Integrated Risk Information System states that PCBs are probable human carcinogens based on sufficient evidence of carcinogenicity in animals.
The National Institutes of Health Report on Carcinogens (15th Edition) states that PCBs are reasonably anticipated to be carcinogens.
The International Agency for Research on Cancer has determined that "PCBs are carcinogenic to humans" (IARC, page 439).