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# What are PCBs?

## PCBs, or polychlorinated biphenyls, are industrial products or chemicals.

PCB contamination is high in the Housatonic River and New Bedford Harbor in Massachusetts. According to the EPA, PCBs belong to a broad family of human-created organic chemicals known as chlorinated hydrocarbons. PCBs were manufactured domestically from 1929 until manufacturing was banned in 1979. They have a range of toxicity and vary in consistency from thin, light-colored liquids to yellow or black waxy solids. Image credit: U.S. Fish and Wildlife Service

PCB chemicals were banned in the U.S. in 1979 because these chemicals harm human and environmental health. From the 1920s until their ban,  an estimated 1.5 billion pounds of PCBs  were made for things such as microscope oils, electrical  insulators, capacitors, and electric appliances such as television sets or  refrigerators. PCBs were also sprayed on dirt roads to keep the dust down prior  to knowing some of the unintended consequences from widespread use. 

Prior to the ban in 1979, PCBs  entered the air, water, and soil during manufacture and use. Wastes from the  manufacturing process that contained PCBs were often placed in dump sites or  landfills. Occasionally, accidental spills and leaks from these facilities or  transformer fires could result in PCBs entering the environment.

PCBs can be found worldwide. In the  1960s, when initial research results were released, traces of PCBs could be  detected in people and animals around the world – not only in heavily populated  areas such as New York City, but also in remote areas as far as the Arctic. These findings of such widespread and persistent contamination contributed to  the banning of the chemical in 1979. 

PCBs can degrade or breakdown in the environment, but the process  greatly depends on the chemical makeup of the PCBs. The degrading process also  depends on where the PCBs are in the environment. Typically, PCBs are either  broken down in the environment by sunlight or by microorganisms. Sunlight plays  an important role in the breakdown of PCBs when they are in the air, shallow  water, or surface soils. Microorganisms, such as bacteria, algae, or fungi,  biodegrade PCBs when found in soil or sediments.

Because PCBs exist in sediments, scientists need to determine if it is better to dredge and remove contaminated sediments from waterways or if it is safer to leave the sediments in place and cover with clean sediments, allowing them to naturally biodegrade. A cap or barrier can also be placed over contaminated sediments to prevent them from entering the environment. There are environmental, human health, and financial concerns with all of these alternatives.

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          - Office of Response and Restoration
          - PCBs: Why Are Banned Chemicals Still Hurting the Environment Today?			
          - Environmental Protection Agency

**Last updated:**   01/20/23**Author:** NOAAHow to cite this article

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