Used primarily as an industrial insulating fluid in electrical equipment such as transformers and capacitors due to its chemical stability and non-flammability. Also found in heat transfer systems and hydraulic fluids. Its persistence in the environment led to widespread contamination, resulting in strict regulations and eventual phase-out in many countries. Historically present in commercial PCB mixtures, it contributes to the toxic and bioaccumulative effects associated with polychlorinated biphenyls.