Mercury (Hg) is of world-wide concern because of its toxicity not only to humans but also to other higher forms of life as well as microorganisms in natural environments. Methyl-Hg is the species of particular concern for birds, fish and mammals, where biomagnification in long food chains results in hazardous exposure of top predators including humans. Elemental Hg is transformed to methyl-Hg in nature by processes difficult to control, and any emission of inorganic Hg will ultimately result in increased levels of methyl-Hg in our environment. Restricting anthropogenic emissions of Hg is thus a priority for counteracting an increase of methyl-Hg levels in biota. To eliminate the sources is a cost-effective way of eliminating related emissions.
There are three primary sources of anthropogenic Hg emissions: 1.) combustion of fossil fuels; 2.) dedicated mining of Hg; and 3.) refining processes and mining of minerals for recovering of other elements than Hg. Mercury produced by mining and refining is used in a wide variety of products such as thermometers, dental amalgam, lamps, and batteries, resulting in Hg emissions at production, usage, and disposal. Swedish authorities were first to act by enforcing nationwide legislation against the use of Hg, to avoid tragedies such as those in Minamata, Japan. Consequently, seed dressing with methyl-Hg was prohibited in 1966, and fenyl-Hg in slimicides was prohibited in 1967. Total emissions of Hg from Swedish chlor-alkali plants to air and waters were reduced from more than 30 t per year in the 1950’s and 1960’s to less than 0.1 t nowadays. Sale of clinical thermometers containing Hg is prohibited since 1992, and Hg exports are banned since 1997. A general ban on the use of Hg in processes and products is presently considered by the government. From the ban there will be exceptions only where Hg free alternatives still have a limited market share, such as energyefficient lamps.
Recycling of Hg is discouraged in Sweden, since continued use of Hg-containing products inevitably results in losses of Hg to air, soil and water, thus adding to the risks of human exposure. Mercury-containing equipments, products, and waste are instead collected for permanent disposal in a safe deep-bedrock repository with minimal losses. This has by Swedish authorities been considered as the only feasible solution to obtain zero Hg emissions from the Swedish technosphere. Further information may be obtained from the Swedish Chemicals Agency (www.kemi.se) and the Swedish Environmental Protection Agency (www.naturvardsverket.se).
Minamata City, Kumamoto, Japan.: Ministry of the Environment, Japan, National Institute for Minamata Disease , 2008. 16-27 p.