Polychlorinated biphenyls (PCBs) are a group of organic compounds composed of chlorine atoms substituted at various positions on the biphenyl molecule. These substances were widely used in industry due to their thermal stability, dielectric properties, and low flammability. Historically, PCBs found applications in electrical equipment such as transformers, capacitors, and circuit breakers, as well as in heat transfer fluids, carbonless copy paper, and paint additives. PCBs are known for their persistence in the environment and bioaccumulation potential, leading to significant ecological and health concerns. Due to these hazards, production of PCBs was banned in many countries by the 1970s through regulations such as the U.S. Clean Air Act Amendments of 1976 and the Stockholm Convention on Persistent Organic Pollutants. Despite their harmful effects, residual PCBs remain a significant environmental issue requiring ongoing remediation efforts to protect ecosystems and public health. Modern alternatives are now widely used in various industrial applications to mitigate these risks.