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Mass Flow Analyses of Mercury 2001

1 Introduction

1.1 Purpose and methods of the mass flow analysis
1.2 Introduction to mercury

1.1 Purpose and methods of the mass flow analysis

The overall purpose of this mass flow analysis is to update our present knowledge of the use, consumption and dispersal of mercury in Denmark.

The circulation of mercury in Denmark is relatively well-described, as mass flow analyses have been carried out for the years 1982-83 (Hansen, 1985) and 1992-93 (Maag et al., 1996). These analyses contain detailed information on all of the major areas where mercury is used. There has been a significant drop in the consumption of mercury since 1992-93. The latest statutory order on mercury prohibiting the sale of mercury with a few specific exceptions entered into force in 1998.

Methods
This mass flow analysis has been executed in conformity with the guidelines for mass flow analyses listed in the Danish EPA's revised paradigm for this type of analysis (Hansen & Lassen, 2000), as mass flow analyses are conducted at the level designated "detailed level" in the paradigm.

This mass flow analysis was implemented by combining information obtained from Statistics Denmark, trade organisations, the Danish Product Register, literature studies and by personally approaching a large number of manufacturers, importers, know-how centres and public institutions.

References to the data sources are generally given in the case of information obtained from literature studies, statistics, know-how centres, and public institutions. Information from enterprises, dealers and importers has generally been used without reference to the source thereof, as this has often been desired by the sources themselves, although Appendix 2 contains a list of the enterprises to which application was made in conjunction with this mass flow analysis.

Almost all quantitative information in this form of analysis has an inherent uncertainty, which is not susceptible to assessment with conventional statistical methods. The "confidence" intervals given should be considered to be intervals, within which the authors have subjectively assessed that there is a 90% probability of the correct value being found. This means that there is a certain probability that the correct values are outside the stated intervals and that, in the case of individual groups of goods or emission values, it is possible that the correct value is far from the interval. However, summation of the intervals means that the probability of the correct sum being found within the resulting interval increases in proportion to the number of quantities summated.

The intentional use of mercury has dropped considerably over the last decades. This means that, with the exception of a couple of major specific uses, the data on the use and consumption of mercury is very scattered. Thus, as use decreases, it becomes increasingly difficult to find quantity data, and the uncertainty of the quantity calculations used in this type of mass flow analysis increases.

1.2 Introduction to mercury

Mercury is the only pure metal that is a liquid at room temperature. It has a mirror-like surface, as can be seen, e.g., from old thermometers and barometers. Due in particular to the danger it presents to the environment, the use of mercury in Denmark has been reduced considerably over the last two decades. In fact it is now probable that many of the younger generation have not seen products that obviously contain mercury - with the possible exception of the classical U-pipe pressure gauge or in the materials collections of school physics laboratories.

The chemical symbol for mercury is Hg and its atomic weight is 200.6 u. Mercury's melting point is -39°C, which is the lowest of all pure metals. Its boiling point is also low, 357°C, which means that there is considerable evaporation from mercury at room temperature, should it be left exposed, e.g., a lost drop from a broken thermometer, concealed in a carpet. This also means that mercury vapour can be carried thousands of kilometres from the point of emission, and that a low concentration of mercury vapour is continuously present in the atmosphere. As it is the only liquid metal, and because of a number of other technically advantageous properties, man has used mercury for thousands of years, in a great variety of applications.

Mercury can be found in many minerals, although cinnabar (mercury sulphide) is in practice the only ore from which mercury is extracted as the principal product. As the use of mercury decreases, especially in the Western world, but also globally, only a few mines dedicated to the extraction of mercury are in operation. However, mercury is also widely extracted together with other metals, particularly zinc, and gold, and these sources constitute an ever greater proportion of the supply, as the dedicated mercury mines are being closed. Certain countries are considering (and perhaps already implementing to some extent) the deposition in landfills of this by-product, rather than marketing it on a rapidly declining market.

At the same time, recycled mercury constitutes an increasing share of the market. In particular, used mercury from disused or converted chloro-alkali manufacturing plants is a primary contributor, although there are also smaller contributions from used and collected products. Because of plans to phase out the use of mercury in chloro-alkali manufacturing in many European countries (parties to the OSPAR and HELCOM Conventions), there is international concern that the market will become swamped with mercury, with the concomitant risk of increasing use in countries where less strict regulations apply to the use of mercury. Because of the hemispheric and global atmospheric transportation of mercury, such use in other countries would locally and globally contribute to the environmental impact caused by mercury - also in such countries as Denmark, where a great effort has been made to reduce such impacts.

Mercury can cause various types of serious harm to human health and the environment. Perhaps most serious is harm to the human nervous system in the embryo phase which, even under quite ordinary conditions, is considered to cause retarded learning and development in children. Studies in the Faeroe Islands have shown that such damage probably occurs at even very low concentrations of mercury. Recent studies in the USA have shown that as many as 8% of a representative group of women had concentrations of mercury in their blood, at levels that cannot be precluded from causing such injuries in the children they bear. There is no immediate basis for believing the situation to be significantly different in Denmark. As far as can be ascertained, however, there are no up-to-date studies of this in Denmark (UNEP, 2002).

Table 1.1 below reviews the development of the known global production of newly extracted mercury. In addition there is, as mentioned above, the sale of recycled mercury, probably together with a certain amount of unrecorded, newly extracted mercury.

Table 1.1 Recorded annual global production of newly extracted mercury (tonnes; source: Jasinski, 1994); Reese, (1997; 1999); and Hylander & Meili (2002), all as quoted by UNEP (2002).

There are no satisfactory estimates of the distribution by use of global mercury consumption. At the global level, chloro-alkali manufacturing, gold extraction on a smaller scale, test and monitoring equipment and dental fillings are included among the major single applications. For the sake of comparison to the Danish figures presented in this mass flow analysis, Table 1.2 shows the estimated distribution of mercury use in the USA for 1990 and 1996.

Table 1.2 Recorded consumption of mercury in the USA in 1990 and 1996 (tonnes/year; source: Jasinski (1994) and Sznopek & Goonan (2000); both as reviewed in UNEP, 2002).

People ingest mercury from a number of different sources. The greatest quantity is normally ingested from the mercury-silver amalgam used in dental fillings, but the present body of knowledge indicates that the most disturbing source is fish and other food products associated with the aquatic environment. This is because the mercury here occurs mainly in the form of methyl mercury, which due to its ease of absorption, and accumulation in the body has an actual toxicity greater than (elementary) metallic mercury.

Metallic mercury is converted naturally by micro-organisms in the environment to methyl mercury, which bioaccumulates rapidly in the food chain. Thus, the greatest concentrations are to be found in large, old, predatory fish, animals, and birds high in the food chain. The presence of fish with a mercury content that can be harmful through high ingestion has been demonstrated in most places in the world. Mercury also occurs naturally in the environment. It is extremely difficult to assess precisely the relationship between man-made and natural sources, but the body of knowledge indicates that man-made sources have the greatest impact. Over the past several years, man-made sources seem to have diminished globally, however this is presumably mainly the case in the Western world.

For the above reasons these years (2001, 2002 and 2003) have therefore witnessed renewed deliberations on the need for expanded international collaboration on reducing the release of mercury (see the discussion of this process on the mercury pages of the UNEP Chemicals web site, www.chem.unep.ch/mercury).

The sale and purchase of toxic substances, such as mercury and its compounds, requires a special licence, which is administered by the National Working Environment Authority (purchase for own commercial use), the Danish EPA's Chemical Inspection Service (sale/purchase for reselling) and the police (purchases for own use e.g., by private purchasers and schools).

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Version 1.0 June 2004, © Danish Environmental Protection Agency