What is the meaning of PCB in transformer oil regulations?

PCB stands for polychlorinated biphenyls, a class of toxic, persistent organic chemicals historically used in transformer oils for fire resistance. Regulations strictly control PCB presence due to carcinogenicity and environmental persistence. Modern standards require non PCB oils, typically below regulatory thresholds or completely PCB free. PCB content determines handling, labeling, disposal, and decommissioning procedures for transformers.