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 natural levels of mercury in the Earth’s crust vary from place to place, but average about 50 mg per tonne of rock. Mercury is mined when present in cinnabar ores, which generally contain about 10 kg per tonne of rock.

Mercury is also present at very low levels throughout the biosphere. Thus, mercury absorbed by ancient plants may account for its presence in fossil fuels like coal, oil and gas.

Today, the world market is supplied by mercury that is:

• newly extracted from mines;
• recovered as a by-product of the mining or refining of other metals, minerals, natural gas and old mining waste;
• recycled from spent products and waste from industrial processes;
• held in government reserve stocks; and
• held in private stocks, such as in chlor-alkali and other industries.

By the year 2000, the production of mined mercury had fallen to a third of its level in the early 1980s. Despite low demand, low prices and the alternative sources available, mercury is still mined in a number of countries such as Spain, China, Kyrgyzstan and Algeria. Moreover, unrecorded small-scale mercury mines have been reported in Asia and Latin America. More...

5.2 How important is mercury recycling?

Since the 1990s, about 700 to 900 tonnes of recycled mercury have been put on the world market every year. Most of this has come from recently closed mercury-based chlor-alkali factories. Their equipment employs a lot of mercury, though it is not consumed in the chemical process.

Over the next decade and beyond, up to 13 000 tonnes of mercury will become available from the European Union alone. Similarly, large stocks of mercury held by various governments have become surplus and could be put on the market. For instance, the US government has a large mercury stock of 4 435 tonnes and has suspended sales since 1994 pending an evaluation of the potential environmental and market impacts.

The reuse and recycling of mercury replaces the mining processes, and prevents new mercury entering the market and the environment. However, giving preference to recycled mercury creates complications, because an excess supply may drive the market price down. This would encourage increased use, and thus disposal of mercury. For this reason, certain steps are being taken to manage supply, for example in Europe. More...

5.3 What is mercury used for?

Mercury is a versatile material known for thousands of years. It is the only metal that is liquid at room temperature. It is a good electrical conductor, has a very high density and high surface tension, expands and contracts uniformly when pressure and temperature change, and it can kill micro-organisms, including pathogenic organisms and other pests.

Elemental mercury has been used:

• to extract gold and silver from ore (for centuries);
• to assist the manufacture of chlor-alkali chemicals;
• in manometers, which measure and control pressure;
• in thermometers;
• in electrical and electronic switches;
• in fluorescent lamps; and
• in dental amalgam fillings

Mercury compounds have been used:

• in batteries;
• as biocides, to control or destroy micro-organisms, e.g. in the paper industry, in paints and on seed grain;
• as antiseptics in pharmaceuticals;
• for chemical analysis;
• as catalysts, to make the manufacture of other chemicals more efficient; and
• in pigments and dyes, detergents, and explosives (mainly in the past).

In industrialised countries, awareness of the potential adverse impacts of mercury on health and the environment has led to a reduction of both the volume and the range of uses of mercury and its compounds, particularly during the 1980s and 1990s. Nonetheless, mercury is still used in many ways in some other parts of the world. More...