Used primarily in industrial applications as a dielectric fluid in transformers and capacitors due to its chemical stability and insulating properties. Also found in heat transfer systems and as a plasticizer in polymers to improve flexibility and durability. Its persistence and resistance to degradation made it useful in closed systems, though environmental and toxicity concerns have led to restricted use. Historically present in some pesticide formulations as a synergist to enhance efficacy. Limited use today due to regulatory controls on persistent organic pollutants.