Metal used in alloy, or in coating. Its salts are also found in accumulators, or as a catalyst.
These tars are particularly found on the sites of the old gas plants, but also in wood preservation (creosote).
PCBs are the compounds that made the oil of transformers non-flammable (under the name of Pyralene in France), they are also found in varnishes, paints...
Protective metal of very common steel, zinc, although essential for life, is toxic in high doses, in all its saline forms.
