Sources of mercury contamination
A distinction is drawn between the intentional and unintentional consumption of mercury. The unintentional "consumption" of mercury consists of mercury as an associated substance in coal and metal production, whilst intentional consumption comprises products or processes where mercury is actively added.
At a global level, the most important sources are the combustion of fossil fuels (almost 50%), gold extraction (20%), metal production (10%), cement production (10%) and waste treatment (5%). These figures were taken from a UN report entitled "Global Atmospheric Mercury Assessment: Sources, Emissions and Transport".
The report is available here at the United Nations Environment Programme.(Link no linger active)
There are also contributions from dental amalgam and other products where mercury is used, for example energy-saving light bulbs.
The sources have changed in recent years. Previously, chlorine-alkali plants were also an important source, but this source has been reduced considerably over the past 10 years as the plants have closed or switched to using mercury-free technology. On the other hand, the combustion of coal has increased considerably at a global level, and the contribution from Asia (and particularly China and India) has increased substantially, while the contribution of coal combustion in the rest of the world has fallen. This trend is set to become even more pronounced unless global control is introduced.
Mercury sources have also changed in Denmark. Danish consumption of mercury has fallen considerably in recent decades and is now extremely modest. As regards intentional uses, consumption had in 2001 fallen to 10% of consumption levels in 1982/83 ( Environmental Project No. 808: Mass flow analysis for mercury 2001, 2003 (in Danish)). No more recent data is available, but the use of dental amalgam since this review has also fallen considerably, and this usage accounted for 70-80% of intentional use in 2001.
On the other hand, the use of energy-saving light bulbs has risen during this period, particularly during the past couple of years. Mercury is essential in ordinary energy-saving light bulbs and such bulbs must therefore be returned to e.g. a recycling centre after use. Other good advice is also available on what to do if the bulbs fail ( Kampagne: Når sparepæren går i stykker ) (in Dansih).