What is Askarel transformer oil and why is it being phased out?

Askarel transformer oil is a synthetic dielectric fluid, primarily composed of polychlorinated biphenyls (PCBs), used in electrical transformers for insulation and cooling. It is being phased out due to environmental and health concerns, as PCBs are toxic, persistent in the environment, and can accumulate in living organisms. Regulatory measures and advancements in safer alternatives have prompted the transition away from Askarel oil to minimize ecological and human health risks.