Used primarily in electrical equipment as a dielectric fluid in transformers and capacitors due to its chemical stability and insulating properties. Also found in industrial hydraulic systems and as a heat transfer fluid in high-temperature applications. Its persistence and toxicity led to widespread environmental contamination, resulting in strict regulations and eventual phase-out in most countries. Historically used as a plasticizer in paints, coatings, and sealants to improve durability and resistance to moisture.