PCBs, or Polychlorinated Biphenyls, are a class of organic compounds that can appear as odorless or slightly aromatic solids or oily liquids. Historically, they were utilized in the United States for various applications, including hydraulic fluids, plasticizers, adhesives, fire retardants, wax extenders, de-dusting agents, pesticide extenders, inks, lubricants, cutting oils, heat transfer systems, and carbonless copying paper.In 1974, the Safe Drinking Water Act was enacted by Congress, mandating the Environmental Protection Agency (EPA) to identify safe chemical levels in drinking water that might pose health risks. These levels, termed Maximum Contaminant Level Goals (MCLG), are non-enforceable and based solely on potential health hazards and exposure. The MCLG for PCBs is set at zero, though this is not a practical enforceable limit. Consequently, the EPA has established an enforceable standard known as the Maximum Contaminant Level (MCL), which is 0.5 parts per billion (ppb). This standard reflects the lowest concentration current technology and resources can feasibly achieve to remove PCBs from drinking water. The FDA also regulates PCBs in food, stipulating that infant foods, dairy products, fish, shellfish, poultry, and red meat should contain no more than 0.2-3 parts per million (ppm).Although the EPA prohibited most PCB uses in 1979, contemporary levels primarily result from the environmental cycling of this persistent pollutant from soil to air and back to soil. PCBs continue to be released from sources such as landfills, the burning of municipal waste and sewage sludge, and improper or illegal disposal of PCB-containing materials like waste transformer fluid.PCBs are notably persistent in soil and water, with degradation occurring only through slow microbial processes. They tend to bind to soils or evaporate, typically preventing leaching into groundwater. In aquatic environments, contaminated sediments in lakes or rivers can gradually release PCBs into the water, where they eventually evaporate. While a fraction of PCBs may dissolve in water, the majority attach to organic particles and sediments. They enter the food chain through small aquatic organisms and fish, subsequently accumulating in higher concentrations in predators, including marine mammals and farmed salmon, the latter often exhibiting higher PCB levels due to their diet of contaminated smaller fish.Short-term exposure to PCB levels exceeding the MCL can lead to acne-like skin eruptions, hearing and vision issues, and muscle spasms. Long-term exposure may result in symptoms akin to acute poisoning, respiratory and liver function disturbances, and increased cancer risk. This summary is based on information from the Consumer Factsheet on Polychlorinated Biphenyls from the National Primary Drinking Water Regulations and FDA Guidance for Industry: Action Levels for Poisonous or Deleterious Substances in Human Food and Animal Feed.
