Heavy metals and humans

Heavy metal accumulation can also impact human health. Perhaps the best known case was in Minamata Bay, Japan. Between 1932 and 1968 the Chisso Corporation dumped an estimated 27 tonnes of mercury related compounds directly into this Bay, which was widely used by local fishermen. The symptoms of methymercury poisoning, which became known as Minamata Disease include neurological effects such as spasms and blurred vision, but also physical deformities in newborn babies. Over 2200 victims have been officially recognised, but some 10,000 received some level of compensation, and it has been suggested that a much larger figure may have been exposed to unsafe levels of mercury.

Heavy metals can reach dangerous concentrations in tuna

More recently, high levels of mercury have been recorded in a number of seafood products, notably large predatory fish such as shark, swordfish marlin and even tuna. A number of countries, including Canada, New Zealand, Australia and the UK have now warned pregnant mothers to avoid all consumption, and recommended only limited consumption by others.

It would appear that bioaccumulation in whales is a particular problem. Studies in the Faroe Islands showed a clear correlation between whale-meat consumption and neurological problems in children. In Japan, studies of whale and dolphin meat have shown very high levels of contamination, with over one third of whale meat products being found to contain unsafe levels of methylmercury. Many of these have also been found to contain other pollutants including PCBs, DDT and Dieldrin.