Used primarily as a heat transfer agent and dielectric fluid in electrical equipment such as transformers and capacitors due to its thermal stability and non-flammability. Also found in hydraulic fluids and lubricants where high chemical resistance is required. Its persistence and toxicity have led to discontinued use, but it may still be present in older industrial systems. Was occasionally used in pesticide formulations as a synergist to enhance efficacy of active ingredients. Environmental monitoring focuses on its presence as a persistent organic pollutant due to bioaccumulation in the food chain.