Mercury

Pigment and Organic Fungicide Production

Cinnabar (HgS) has been used in its natural state as a pigment and also as a drug and preservative for several thousand years. The use of the bright red/orange pigment ranged from temples and the emperor's palaces to seals stamped on paper money already more than 1000 years ago in China. Quantities of cinnabar mined for these purposes in China are not recorded. In Idrija, the pigment production corresponded to 7 628 t of metallic Hg during a 500-year period. Most of this production was vermilion (cinnabar produced from elemental Hg). This was important also in the US, where 195 t Hg were sent to New York in 1882 for production of vermilion, nearly as much as used in gold and silver mining (205 t) in the USA during the same year. Another indication of the importance of vermilion at that time is that similar amounts of Hg (239 t in 1882) were exported from USA to China for production of vermilion. The American vermilion industry continued to be a large consumer of Hg for the rest of the 19th century, but was later reduced and in the 1940's entirely replaced by less expensive compounds such as antimony sulphuret, red lead, and hematite. (reference)

Organic Hg compounds are efficient biocides, which were added as an antifouling agent to paints, as a slimicide to paper pulp and as a fungicide to protect seeds and plants from fungal diseases. In Sweden, these applications started in the 1940's and the production grew rapidly, so that half of the 140 t Hg annually imported in the end of the 1950's were used to produce biocides, mainly for the pulp and paper industry (42% of the annual Hg imports), while antifouling paint used 2% of imported Hg, and agricultural chemicals used 6%. Two thirds of the agricultural chemicals produced in Sweden were exported, among others to Denmark, which contributed to the low industrial Hg consumption in Denmark. This minor use of Hg in agriculture caught the public attention by killing birds and terrestrial animals as already described. As a result, Hg was excluded from all slimicides from the end of 1967, from all antifouling paints for boats sold after 1973, and from all fungicides used in agriculture after 1988, when the National Chemicals Inspectorate did not prolong the registration of a Hg-containing fungicide, occasionally used as an exception from the ban of Hg fungicides from the 1970's.

The trend was similar but with a smaller amplitude in the USA, where 17% of totally 1830 t Hg consumed per year was used for organic Hg com¬pounds in the end of the 1950's, divided between slimicides using 3%, an¬tifouling paint using 4%, and agricultural chemicals, including insecticides, using 11%. The figures reflect the smaller relative importance of forestry and larger relative importance of agriculture in the economy of the USA. While the use of Hg-free slimicides and agricultural biocides was introduced at about the same time in the USA as in Sweden, the production of antifouling paint in the USA shows a diverging development by more than tripling until the 1980's, after which also this use of Hg decreased. In 1993, EPA canceled registrations of the last two Hg-containing fungicides at manufacturer's request.