From circa 1932 until 1977, General Electric polluted the Housatonic River with PCBs discharges from the General Electric plant at Pittsfield, Massachusetts. Aroclor 1254 and Aroclor 1260, made by Monsanto was the primary contaminant of the pollution. The highest concentrations of PCBs in the Housatonic River are found in Woods Pond in Lenox, Massachusetts, just south of Pittsfield, where they have been measured up to 110 mg/kg in the sediment. About 50% of all the PCBs currently in the river are estimated to be retained in the sediment behind Woods Pond dam. This is estimated to be about 11,000 pounds of PCBs. Former filled oxbows are also polluted. Waterfowl and fish who live in and around the river contain significant levels of PCBs and can present health risks if consumed.