Mercury has been used by man for thousands of years, especially as a red pigment in the form of sulphite or in drawings, e.g. in Ancient Egypt and Pakistan. The Romans used mercury compounds in medicines and amalgams, and during the past centuries it was not only used in alchemy in gold production but also, above all, it found both internal and external application in the medical world. Its toxic effects were recognised very early. It was regarded as a dangerous substance, even at the time when it was most widely used in the medical world for the treatment of syphilis. The symptoms of acute and chronic poisoning due to occupational exposure have been known since as early as the Middle Ages. The poisonings which occur today are basically either the result of inhaling metallic mercury, or from food contamination, mostly with methyl mercury, as for example in the Minimata Bay in Japan between 1953 and 1960 (Tsubaki and Irukayama, 1977; Harada 1978). In Niigata in Japan, and in the mass poisonings in Iraq between 1971 and 1972 which have been the result of contaminated food there were more than 6000 known cases, and 500 deaths (Bakir et al., 1973).