What are PCBs in transformer oil and why are they hazardous?

PCBs, or polychlorinated biphenyls, are synthetic organic chemicals previously used in transformer oil for their insulating and cooling properties. They are hazardous due to their toxicity, persistence in the environment, and potential to bioaccumulate in living organisms. Exposure to PCBs can lead to serious health issues, including cancer and immune system damage. Consequently, regulations have restricted their use, and proper disposal of PCB-contaminated transformer oil is critical for environmental safety.