Official websites use. Share sensitive information only on official, secure websites. JavaScript appears to be disabled on this computer. Please click here to see any active alerts. PCBs are a group of man-made organic chemicals consisting of carbon, hydrogen and chlorine atoms. The number of chlorine atoms and their location in a PCB molecule determine many of its physical and chemical properties. PCBs have no known taste or smell, and range in consistency from an oil to a waxy solid.
PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were domestically manufactured from until manufacturing was banned in They have a range of toxicity and vary in consistency from thin, light-colored liquids to yellow or black waxy solids. Due to their non-flammability, chemical stability, high boiling point and electrical insulating properties, PCBs were used in hundreds of industrial and commercial applications including:.
Products that may contain PCBs include:. The PCBs used in these products were chemical mixtures made up of a variety of individual chlorinated biphenyl components known as congeners.
Most commercial PCB mixtures are known in the United States by their industrial trade names , the most common being Arochlor. PCBs do not readily break down once in the environment. They can remain for long periods cycling between air, water and soil. PCBs can be carried long distances and have been found in snow and sea water in areas far from where they were released into the environment.
As a consequence, they are found all over the world. In general, the lighter the form of PCB, the further it can be transported from the source of contamination. PCBs can accumulate in the leaves and above-ground parts of plants and food crops.
They are also taken up into the bodies of small organisms and fish. As a result, people who ingest fish may be exposed to PCBs that have bioaccumulated in the fish they are ingesting. Interviews and physical examinations are conducted with approximately 10, people in each two-year survey cycle. The name of a congener specifies the total number of chlorine substituents , and the position of each chlorine.
For example: 4,4'-Dichlorobiphenyl is a congener comprising the biphenyl structure with two chlorine substituents - one on each of the 4 carbons of the two rings. In , a numbering system was developed which assigned a sequential number to each of the PCB congeners. Homologs are subcategories of PCB congeners that have equal numbers of chlorine substituents. For example, the tetrachlorobiphenyls are all PCB congeners with exactly 4 chlorine substituents that can be in any arrangement.
These mixtures were created by adding progressively more chlorine to batches of biphenyl until a certain target percentage of chlorine by weight was achieved.
Commercial mixtures with higher percentages of chlorine contained higher proportions of the more heavily chlorinated congeners, but all congeners could be expected to be present at some level in all mixtures. While PCBs were manufactured and sold under many names, the most common was the Aroclor series. Aroclor is a PCB mixture produced from approximately to It is one of the most commonly known trade names for PCB mixtures.
There are many types of Aroclors and each has a distinguishing suffix number that indicates the degree of chlorination. The numbering standard for the different Aroclors is as follows:.
PCBs were manufactured and sold under many different names. Please note:. PCBs have been demonstrated to cause a variety of adverse health effects. They have been shown to cause cancer in animals as well as a number of serious non-cancer health effects in animals, including: effects on the immune system, reproductive system, nervous system, endocrine system and other health effects.
Studies in humans support evidence for potential carcinogenic and non-carcinogenic effects of PCBs. The different health effects of PCBs may be interrelated. Alterations in one system may have significant implications for the other systems of the body. The potential health effects of PCB exposure are discussed in greater detail below. EPA uses an approach that permits evaluation of the complete carcinogenicity database and allows the results of individual studies to be viewed in the context of all of the other available studies.
Studies in animals provide conclusive evidence that PCBs cause cancer. Studies in humans raise further concerns regarding the potential carcinogenicity of PCBs. Taken together, the data strongly suggest that PCBs are probable human carcinogens. PCBs are one of the most widely studied environmental contaminants. Many studies in animals and human populations have been performed to assess the potential carcinogenicity of PCBs.
At that time, data was limited to Aroclor EPA's cancer reassessment reflected the Agency's commitment to the use of the best science in evaluating health effects of PCBs.
The reassessment was peer reviewed by 15 experts on PCBs, including scientists from government, academia and industry. One case resulted in the convictions of three persons for illegally dumping PCBs along miles of roadway in North Carolina.
A fourth action is pending against another company for improper PCB storage. Today's action will prohibit the manufacture, processing, distribution in commerce, and "non-enclosed" open to the environment uses of PCBs unless specifically authorized or exempted by EPA. EPA will allow use and servicing of most existing large electrical equipment containing PCBs representing nearly million pounds of the million pounds of PCBs now in use under controlled conditions for the life of the equipment.
A requirement to immediately replace all of this equipment would be prohibitively expensive. The manufacture of new PCB electrical equipment transformers and capacitors is entirely prohibited. PCB-contaminated waste oil is now used extensively throughout the country to control dust on roadways, providing a direct source of environmental contamination.
Unlike the exposed nipples of humans and our closer kin, the mammary glands of dolphins and porpoises are concealed inside of abdominal slits. Porpoise cheese must be a decadent experience. You might want to stick with the cow stuff, though, because PCBs are pretty nasty. They are probable carcinogens and likely depress the immune, reproductive, neurological, and endocrine systems.
This new study found that porpoises living in areas most polluted with the chemicals had extremely high rates of reproductive problems. Almost 20 percent of the females had delivered stillborn babies or experienced miscarriages. One in six had tumors or infections in its reproductive organs. When porpoises will be free from the malign effects of the pollutant is not clear. When we dump toxic chemicals into our water, they can harm ecosystems for generations into the future.
Sorry, porpoises.
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