PCBs: PolyChlorinated Biphenyls, are a group of organic chemicals which can be odorless or mildly aromatic solids or oily liquids. They were formerly used in the USA as hydraulic fluids, plasticizers, adhesives, fire retardants, way extenders, de-dusting agents, pesticide extenders, inks, lubricants, cutting oils, in heat transfer systems, carbonless reproducing paper.
In 1974, Congress passed the Safe Drinking Water Act. This law requires the Environmental Protection Act (EPA) to determine safe levels of chemicals in drinking water which do or may cause health problems. These non-enforceable levels, based solely on possible health risks and exposure, are called Maximum Contaminant Level Goals (MCLG).
The MCLG for PCBs has been set at zero. Zero is not a realistically enforceable limit, therefore, the EPA has set an enforceable standard called a Maximum Contaminant Level (MCL). The MCL is 0.5 parts per billion (ppb) because EPA believes, given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water. The FDA requires that infant foods, eggs, milk and other dairy products, fish and shellfish, poultry and red meat contain no more than 0.2-3 parts of PCBs per million parts (0.2-3 ppm) of food.
Since EPA banned most uses of PCBs in 1979, current levels are due mainly to the cycling of this persistent contaminant from soil to air to soil again. PCBs continue to be released from landfills, incineration of municipal refuse and sewage sludge, and improper (or illegal) disposal of PCB materials, such as waste transformer fluid, to open areas.
PCBs are very persistent in soil and water, with no known break down processes other than slow degradation by microbes. They adhere to soils or evaporate, and so will not usually leach to ground water. PCB-contaminated sediments in lakes or rivers can slowly release PCB back into water, from which it eventually evaporates.
In water, a small amount of PCBs may remain dissolved, but most stick to organic particles and bottom sediments. PCBs are taken up by small organisms and fish in water. They are also taken up by other animals that eat these aquatic animals as food. PCBs accumulate in fish and marine mammals, reaching levels that may be many thousands of times higher than in water. Farmed salmon contain higher levels of PCBs than wild ones. This reflects the fact that farmed salmon may be fed ground-up smaller fish that have themselves been contaminated in polluted ocean waters.
Short-term health effects of relatively short term exposure at levels above MCL are acne-like eruptions and pigmentation of the skin; hearing and vision problems; spasms. Long-term health effects from a lifetime of exposure at levels above MCL include effects similar to acute poisonings, irritation of nose, throat and gastrointestinal tracts, changes in liver function, and cancer when people are exposed
This information is from the Consumer Factsheet on: POLYCHLORINATED BIPHENYLS from the National Primary Drinking Water Regulations and Food and Drug Administration Guidance for Industry: Action Levels for Poisonous or Deleterious Substances in Human Food and Animal Feed.