Copper plumbing, just like lead plumbing in ancient Rome, can be a major problem in new houses and in old houses that have soft water pumped into the lines, that tends ot loosen the mineral deposits that would otherwise trap the metal toxins and keep them out of our water. Lead is also a problem in older pipes and can be liberated from years of deposits by soft water. Mercury and cadmium are among the most toxic substances, but are routinely placed in peoples' mouths as dental amalgams. Cobalt is a nutrient needed in trace quantities as vitamin B12, used by the body as methylcobalamin to transfer methyl groups to toxic homocysteine, thereby helping to eliminate it by converting to methionine. Microwaves may release carcinogenic Co from B12.