Note: This is the second in a pair of columns about mercury in the environment.
Consider the cycle of mercury pollution.
Clif CleavelandMercury released into the atmosphere from natural sources and the burning of coal eventually ends up in fresh or saltwater. Mercury released into water as a pollutant from mining or manufacturing may travel with currents or become a component of localized sediment. Once in water or sediment, elemental mercury is slowly converted by micro-organisms into highly toxic methyl-mercury (MM), which is rapidly absorbed by all organisms. MM is chemically unstable and may be converted back to mercury, which may evaporate to circulate in the atmosphere. In fish and shellfish, MM may concentrate to levels millions of times higher than in surrounding water.
In other words, once released into air or water, mercury and its compounds never disappear.
A multi-year, environmental disaster in the coastal waters of Japan in the 1950s and 1960s highlighted the danger inherent in MM. The calamity was centered in Minamata, a fishing village on the west coast of Japan’s southernmost island. Initially, pet cats were afflicted with bizarre movements that preceded death. Infants and young children soon manifested muscle spasms, seizures and progressive intellectual impairment. Initial studies identified high levels of MM in the seafood which provided most of the community’s nutrition.