Used primarily in industrial applications as a heat transfer medium and dielectric fluid in electrical equipment due to its thermal stability and non-flammability. Found in older transformers and capacitors where resistance to high temperatures and chemical degradation is required. Also used as a plasticizer and additive in polymers to enhance flame resistance. Due to environmental persistence and toxicity, its use has been largely phased out in many countries under international regulations. Historically present in some pesticide formulations as a synergist to increase effectiveness of active ingredients.