Mercury

5. Where do the world's supplies of mercury come from?

• 5.1 How does mercury reach the world market?
• 5.2 How important is mercury recycling?
• 5.3 What is mercury used for?

5.1 How does mercury reach the world market?

The source document for this Digest states:

Mercury is a natural component of the earth, with an average abundance of approximately 0.05 mg/kg in the earth’s crust, with significant local variations. Mercury ores that are mined generally contain about one percent mercury, although the strata mined in Spain typically contain up to 12-14 percent mercury. While about 25 principal mercury minerals are known, virtually the only deposits that have been harvested for the extraction of mercury are cinnabar. Mercury is also present at very low levels throughout the biosphere. Its absorption by plants may account for the presence of mercury within fossil fuels like coal, oil, and gas, since these fuels are conventionally thought to be formed from geologic transformation of organic residues.

The mercury available on the world market is supplied from a number of different sources, including (not listed in order of importance):

• Mine production of primary mercury (meaning extracted from ores within the earth’s crust):
  • either as the main product of the mining activity,
  • or as by-product of mining or refining of other metals (such as zinc, gold, silver) or minerals;
• Recovered primary mercury from refining of natural gas (actually a by-product, when marketed, however, is not marketed in all countries);
• Reprocessing or secondary mining of historic mine tailings containing mercury;
• Recycled mercury recovered from spent products and waste from industrial production processes. Large amounts ("reservoirs") of mercury are "stored" in society within products still in use and "on the users’ shelves";
• Mercury from government reserve stocks, or inventories;
• Private stocks (such as mercury in use in chlor-alkali and other industries), some of which may later be returned to the market.

The mining and other mineral extraction of primary mercury constitute the human mobilisation of mercury for intentional use in products and processes. Recycled mercury and mercury from stocks can be regarded as an anthropogenic re-mobilisation of mercury previously extracted from the Earth.

Despite a decline in global mercury consumption (global demand is less than half of 1980 levels), supply from competing sources and low prices, production of mercury from mining is still occurring in a number of countries. Spain, China, Kyrgyzstan and Algeria have dominated this activity in recent years, and several of the mines are state-owned. The table below gives information on recorded global primary production of mercury since 1981. There are also reports of small-scale, artisanal mining of mercury in China, Russia (Siberia), Outer Mongolia, Peru, and Mexico. It is likely that this production serves robust local demand for mercury, often for artisanal mining of gold – whether legal or illegal. Such mercury production would require both accessible mercury ores and low-cost labor in order for it to occur despite low-priced mercury available in the global commodity market.

Source & ©: UNEP Global Mercury Assessment report, Summary of the Report, 
Chapter 7, paragraphs 100 to 103

For more information, see Chapter 7: Current production and use of mercury 

5.2 How important is mercury recycling?

The source document for this Digest states:

Large quantities of mercury have come onto the market as a result of ongoing substitution and closing of mercury-based chlor-alkali production in Europe and other regions. Market analysis indicates that 700 - 900 metric tons per year of recycled mercury (corresponding to about 30 percent of the recorded primary production) has been marketed globally since the mid-1990’s, of which the majority originated from chlor-alkali production facilities. However, to the extent there remains a legitimate demand for mercury, the re-use and recycling of mercury replaces the mining and smelting of virgin mercury, which would involve additional releases and would result in mobilising new mercury into the market and the environment.

The preference for reuse and recycling of mercury over mining - especially in the context of large mercury inventories coming onto the market? is complicated by the generally accepted economic rule that an excess supply of mercury drives the market price lower, which in turn encourages additional use or waste of mercury. For this reason, certain precautions are being taken, as described below.

Within the current decade and beyond, vast supplies of mercury will become available from conversion or shutdown of chlor-alkali facilities using the mercury process, as many European countries press for a phase-out of this process before 2010. From the European Union alone, this may introduce up to 13,000 metric tons of additional mercury to the market (equal to some 6-12 years of primary mercury production). In response to this potential glut of mercury, Euro Chlor, which represents the European chlor-alkali industry, has signed a contractual agreement with Minas de Almadén in Spain. The agreement provides that Minas de Almadén will buy the surplus mercury from the West-European chlor-alkali plants and put it on the market in place of mercury Almadén would otherwise have mined. All EU members of Euro Chlor have agreed to sell their surplus mercury to Almadén according to this agreement, and Euro Chlor believes most of the central and eastern European chlorine producers will also commit to this agreement. While this agreement clearly represents an effort by all parties to responsibly address the problem of surplus mercury, some people have the view that there are not yet adequate controls on where this mercury would be sold or how it would be used.

Similarly, large reserve stocks of mercury held by various governments have become superfluous, and are subject to future sales on the world market if approved by the relevant national authorities. This is the case in the USA, for example, which holds a 4,435 metric ton inventory of mercury. The sale of this mercury has been suspended since 1994, awaiting a determination of its potential environmental and market impacts. Prior to that, however, the sale of some of these stocks contributed significantly to the supply of mercury on the domestic US-market, and to exports as well. US government sales were equivalent to 18 to 97 percent of the domestic US demand for mercury in the years 1990-94 (US EPA, 1997; Maxson and Vonkeman, 1996).

Source & ©: UNEP Global Mercury Assessment report, Summary of the Report, 
Chapter 7, paragraphs 104 to 107

For more information, see Chapter 7: Current production and use of mercury 

5.3 What is mercury used for?

The source document for this Digest states:

The element mercury has been known for thousands of years, fascinating as the only liquid metal, and applied in a large number of products and processes utilising its unique characteristics. Being liquid at room temperature, being a good electrical conductor, having very high density and high surface tension, expanding/contracting uniformly over its entire liquid range in response to changes in pressure and temperature, and being toxic to micro-organisms (including pathogenic organisms) and other pests, mercury is an excellent material for many purposes.

In the past, a number of organic mercury compounds were used quite broadly, for example in pesticides (extensive use in seed dressing among others) and biocides in some paints, pharmaceuticals and cosmetics. While many of these uses have diminished in some parts of the world, organic mercury compounds are still used for several purposes. Some examples are the use of seed dressing with mercury compounds in some countries, use of dimethylmercury in small amounts as a reference standard for some chemical tests, and thimerosal (which contains ethylmercury) used as a preservative in some vaccines and other medical and cosmetic products since the 1930’s. As the awareness of mercury's potential adverse impacts on health and the environment has been rising, the number of applications (for inorganic and organic mercury) as well as the volume of mercury used have been reduced significantly in many of the industrialised countries, particularly during the last two decades.

Examples of uses of mercury As the metal (among others): for extraction of gold and silver (for centuries) as a catalyst for chlor-alkali production in manometers for measuring and controlling pressure in thermometers in electrical and electronic switches in fluorescent lamps in dental amalgam fillings As chemical compounds (among others): in batteries (as a dioxide) biocides in paper industry, paints and on seed grain as antiseptics in pharmaceuticals aboratory analyses reactants catalysts pigments and dyes (may be historical) detergents (may be historical) explosives (may be historical)

However, many of the uses discontinued in the OECD countries are still alive in other parts of the world. Several of these uses have been prohibited or severely restricted in a number of countries because of their adverse impacts on humans and the environment.

Furthermore, while there is a general understanding of mercury production and use around the world, it is crucial to gain an even better understanding of global mercury markets and flows in order to assess demand, to design appropriate pollution prevention and reduction measures, and to monitor progress towards specific objectives.

Source & ©: UNEP Global Mercury Assessment report, Summary of the Report, 
Chapter 7, paragraphs 108 to 111

For more information, see Chapter 7: Current production and use of mercury