Old transformers (pre 1980) had PCBs in the cooling oil. Most have been changed out over the years and now a mineral oil or, as I have seen, a soybean oil coolant is used. In some places they have "no PCBs" stickers on the transformers. Here in CA, the idiots at Pacific Gas & Electric (PG&E) put them on the inside of the case. They probably had to spend a few minutes determining if it contained PCBs before replacing it. The balloons shorted out the wires to the transformer, which then caused the transformer to blow. In CA, the wires and sometimes the transformers are underground, which isn't as feasible in Buffalo, because of the frost.