Read further at the Wiki link if interested in the toxic affects on humans and animals:
Polychlorinated biphenyls (PCBs; CAS number 1336-36-3 ) are a class of organic compounds with 1 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx, where x = 1-10. PCBs were widely used for many applications, especially as dielectric fluids in transformers, capacitors, and coolants. Due to PCB's 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.
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New York State
Between approximately 1947 and 1977 General Electric Company (GE) released up to 1,300,000 pounds (590,000 kg) of PCBs into the Hudson River. The PCBs came from the company's two capacitor manufacturing plants at Hudson Falls and Fort Edward in New York State.
In 1976, because of concern over continuing high levels of PCBs in local fish and other aquatic organisms, and the unacceptable risk to the health of consumers of such fish, the NYSDEC banned all fishing in the Upper Hudson River, as well as commercial fishing of striped bass and several other species in the Lower Hudson River, and also issued advisories restricting the consumption of fish caught within a 20-mile (30 km) long segment of the Hudson River from Hudson Falls to Troy.
There have been many programs of remediation work to reduce the PCB pollution. In 1984, approximately 200 miles (320 km) of the Hudson River was designated a Superfund site, and attempts to cleanup the Upper Hudson River began, including the removal in 1977-8 of 180,000 cubic yards (140,000 m3) of contaminated river sediments near Fort Edward In 1991, further PCB pollution was found at Bakers Falls near the former GE Hudson Falls factory, and a program of remediation was started. In August 1995, a 40-mile (64 km) reach of the Upper Hudson was re-opened to fishing but only on a catch-and-release basis. Removal of contaminated soil from Rogers Island was completed in December 1999. In 2002, the EPA announced a further 2,650,000 cubic yards (2,030,000 m3) of contaminated sediments in the Upper Hudson River would be removed.
Indiana
From the late 1950s through 1977, Westinghouse Electric used PCBs in the manufacture of capacitors in its Bloomington, Indiana plant. Reject capacitors were hauled and dumped in area salvage yards and landfills, including Bennett's Dump, Neal's Landfill and Lemon Lane Landfill. Workers also dumped PCB oil down factory drains which contaminated the city sewage treatment plant. The City of Bloomington gave away the sludge to area farmers and gardeners, creating anywhere from 200 to 2000 sites which remain unaddressed. Over 2 million pounds of PCBs were estimated to have been dumped in Monroe and Owen Counties. Although federal and state authorities have been working on the sites' environmental remediation, many areas remain contaminated. Concerns have been raised regarding the removal of PCBs from the karst limestone topography, and regarding the possible disposal options. To date, the Westinghouse Bloomington PCB Superfund site case does not have a RI/FS (Remedial Investigation/Feasibility Study) and ROD (Record of Decision), although Westinghouse signed a US Department of Justice Consent Decree in 1985. The 1985 Consent Decree required Westinghouse to construct an incinerator that would incinerate PCB-contaminated materials. However, due to public opposition to the incinerator, the State of Indiana passed a number of laws that delayed and blocked the construction of the incinerator. Consent Decree parties began to explore alternative remedies in 1994 for six of the main PCB contaminated sites.
On February 15, 2008, Monroe County approved a plan to clean up the 3 remaining contaminated sites in the City of Bloomington, at a cost of $9.6m to CBS Corp., the successor of Westinghouse.
The Great Lakes
Much of the Great Lakes area is still heavily polluted with PCBs, despite extensive remediation work. Locally caught fresh water fish and shellfish are contaminated with PCBs and their consumption is restricted.
From 1959 to 1971, Waukegan Harbor in Illinois on Lake Michigan was contaminated with PCBs discharged by the Outboard Marine Corp.
Alabama
PCBs (manufactured through most of the 20th century) originating from Monsanto Chemical Company in Anniston, Alabama leaked into Snow creek, then Choccolocco Creek, then Logan Martin Lake. In the early 2000s, class action lawsuits (led, in at least one case, by the late Johnnie Cochran) were settled by local land owners, including those on Logan Martin Lake, and Lay Reservoir (downstream on the Coosa River), for the PCB pollution.
Today, the highest pollution levels remain concentrated in Snow and Choccolocco Creeks. Concentrations in fish have and continue to decline over time, however, sediment disturbance can resuspend the PCBs from the sediment back into the water column and food web.
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http://en.wikipedia.org/wiki/Polychlorinated_biphenyl_______________________
PCB Contamination of the Hudson River: A Chronology
1929 Monsanto co. begins manufacturing PCBs.
1968 PCB poisoning event in Yusho, Japan leads to awareness of toxic effects of PCBs.
1973 U.S. Food and Drug Administration establishes a tolerance level of 5.0 parts per million (ppm) in fish. Ft. Edward Dam removed from upper Hudson River, causing large migration of PCBs into the lower Hudson and exposing river bank "remnant deposits".
1974 An EPA survey shows high PCB levels in Hudson River fish.
1975 Administrative Hearings begin between G.E. and DEC, regarding PCB discharges.
Fall 1975 NYS DEC survey confirms findings of high PCB levels in Hudson River fish.
1976 Congress passes the Toxic substances Control Act banning the manufacture of PCBs and prohibiting all uses except in totally enclosed systems.
2/25/76 DEC bans all fishing in the upper Hudson from the Ft. Edward Dam to the federal dam at Albany, closes Hudson River commercial fisheries (including american eel and striped bass), and issues health advisories on fish consumption.
2/76 Administrative Hearing finds PCB contamination due to corporate abuse and regulatory failure.
4/76 "100 year flood" causes large movement of contaminated sediments from the upper Hudson into the lower river.
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http://www.rpi.edu/dept/environ/orgs/Clearwater/chronology.html