of the report
Current mercury exposures and risk evaluations for humans
Impacts of mercury on the environment
Sources and cycling of mercury to the global environment
Current production and use of mercury
Prevention and control technologies and practices
Initiatives for controlling releases and limiting use and exposure
Data and information gaps
Options for addressing any significant global adverse impacts
CHAPTER 1 -
report responds to the request of the Governing Council (GC) of the United
Nations Environment Programme (UNEP), through GC decision 21/5, that UNEP
undertake a global assessment of mercury and mercury compounds, in
cooperation with other members of the Inter-Organization Programme for the
Sound Management of Chemicals (IOMC), to be presented to the Governing
Council at its 22nd session in 2003.
The assessment would include contributions from Governments,
intergovernmental and non-governmental organizations and the private
sector, and cover a number of specific elements defined in the GC
decision. These elements are
covered as far as possible in the different chapters of the report.
As part of
the implementation of GC decision 21/5, UNEP established a Global Mercury
Assessment Working Group to assist in the drafting and finalization of
this report, first through a comment round by mail, then through a meeting
of the Working Group, which took place 9-13 September 2002 in Geneva,
Switzerland. The Working
Group was open-ended and consisted of members nominated by Governments,
intergovernmental organizations and non-governmental organizations.
report will be forwarded to the Governing Council for consideration at its
22nd session in February 2003.
By having initiated the development of this assessment report, the
Governing Council will have a better basis for considering if any
international action on mercury is called for in order to promote
environmentally sound management of mercury and its compounds. The report
will contribute to increased awareness and understanding among decision
makers of the major issues related to mercury and its compounds, thereby
facilitating the debate on the issue at the next session of the Governing
2 – Chemistry
occurs naturally in the environment and exists in a large number of forms.
Like lead or cadmium,
mercury is a constituent element of the earth, a heavy metal.
In pure form, it is known alternatively as “elemental” or
“metallic” mercury (also expressed as Hg(0) or Hg0).
Mercury is rarely found in nature as the pure, liquid metal, but
rather within compounds and inorganic salts.
mercury is a shiny, silver-white metal that is a liquid at room
temperature and is traditionally used in thermometers and some electrical
switches. If not enclosed, at room temperature some of the metallic
mercury will evaporate and form mercury vapours. Mercury vapours are
colourless and odourless. The higher the temperature, the more vapours
will be released from liquid metallic mercury. Some people who have
breathed mercury vapours report a metallic taste in their mouths.
is mined as mercuric sulphide (cinnabar ore). Through
history, deposits of cinnabar have been the source ores for commercial
mining of metallic mercury. The
metallic form is refined from mercuric sulphide ore by heating the ore to
temperatures above 540 º C. This vaporises the mercury in the ore, and
the vapours are then captured and cooled to form the liquid metal mercury.
mercuric compounds include mercuric sulphide (HgS), mercuric oxide (HgO)
and mercuric chloride (HgCl2). These mercury compounds are also
called mercury salts. Most
inorganic mercury compounds are white powders or crystals, except for
mercuric sulphide, which is red and turns black after exposure to light. Some mercury
salts (such as HgCl2) are sufficiently volatile to exist as an
atmospheric gas. However, the water solubility and chemical reactivity of
these inorganic (or divalent) mercury gases lead to much more rapid
deposition from the atmosphere than for elemental mercury. This results in
significantly shorter atmospheric lifetimes for these divalent mercury
gases than for the elemental mercury gas.
mercury combines with carbon, the compounds formed are called
"organic" mercury compounds or organomercurials. There is a
potentially large number of organic mercury compounds (such as
dimethylmercury, phenylmercury, ethylmercury and methylmercury); however,
by far the most common organic mercury compound in the environment is
methylmercury. Like the
inorganic mercury compounds, both methylmercury and phenylmercury exist as
"salts" (for example, methylmercuric chloride or phenylmercuric
acetate). When pure, most forms of methylmercury and phenylmercury are
white crystalline solids. Dimethylmercury, however, is a colourless
forms of mercury occur naturally in the environment. The most common
natural forms of mercury found in the environment are metallic mercury,
mercuric sulphide, mercuric chloride, and methylmercury. Some
micro-organisms and natural processes can change the mercury in the
environment from one form to another.
mercury in the atmosphere can undergo transformation into inorganic
mercury forms, providing a significant pathway for deposition of emitted
most common organic mercury compound that micro-organisms and natural
processes generate from other forms is methylmercury. Methylmercury is of
particular concern because it can build up (bioaccumulate and biomagnify)
in many edible freshwater and saltwater fish and marine mammals to levels
that are many thousands of times greater than levels in the surrounding
can be formed in the environment by microbial metabolism (biotic
processes), such as by certain bacteria, and by chemical processes that do
not involve living organisms (abiotic processes).
Although, it is generally believed that its formation in nature is
predominantly due to biotic processes.
Significant direct anthropogenic (or human generated) sources of
methylmercury are currently not known, although historic sources have
existed. Indirectly, however, anthropogenic releases contribute to the
methylmercury levels found in nature because of the transformation of
other forms. Examples of direct release of organic mercury compounds are
the Minamata methylmercury-poisoning event that occurred in the 1950’s
where organic mercury by-products of industrial-scale acetaldehyde
production were discharged in the local bay, and the Iraqi poisoning
events where wheat treated with a seed dressing containing organic mercury
compounds were used for bread. Also, new research has shown that
methylmercury can be released directly from municipal waste landfills
(Lindberg et al., 2001) and sewage treatment plants (Sommar et
al., 1999), but the general significance of this source is still
element, mercury cannot be broken down or degraded into harmless
substances. Mercury may change between different states and species in its
cycle, but its simplest form is elemental mercury, which itself is harmful
to humans and the environment. Once mercury has
been liberated from either ores or from fossil fuel and mineral deposits
hidden in the earth’s crust and released into the biosphere, it can be
highly mobile, cycling between the earth’s surface and the atmosphere.
The earth’s surface soils, water bodies and bottom sediments are thought
to be the primary biospheric sinks for mercury.
exists in the following main states under natural conditions
metallic vapour and liquid/elemental mercury;
in mercury containing minerals (solid);
ions in solution or bound in ionic compounds (inorganic and
soluble ion complexes;
gaseous or dissolved non-ionic organic compounds;
to inorganic or organic particles/matter by ionic, electrophilic
or lipophilic adsorption.
of mercury speciation
different forms mercury exists in (such as elemental mercury vapour,
methylmercury or mercuric chloride) are commonly designated “species”.
As mentioned above, the main groups of mercury species are elemental
mercury, inorganic and organic mercury forms. Speciation
is the term commonly used to represent the distribution of a quantity of
mercury among various species.
plays an important part in the toxicity and exposure of mercury to living
organisms. Among other things, the species influence:
physical availability for exposure - if mercury is tightly bound to
in-absorbable material, it cannot be readily taken up (e.g. into the
blood stream of the organism);
internal transport inside the organism to the tissue on which it has
toxic effects - for example the crossing of the intestinal membrane or
the blood-brain barrier;
toxicity (partly due to the above mentioned);
accumulation, bio-modification, detoxification in – and excretion from
– the tissues;
bio-magnification on its way up the trophic levels of the food chain (an
important feature particularly for methylmercury).
also influences the transport of mercury within and between environmental
compartments including the atmosphere and oceans, among others. For example,
the speciation is a determining factor for how far from the source mercury
emitted to air is transported. Mercury adsorbed on particles and ionic (e.g.
divalent) mercury compounds will fall on land and water mainly in the
vicinity of the sources (local to regional distances), while elemental
mercury vapour is transported on a hemispherical/global scale making mercury
emissions a global concern. Another example is the so-called "polar
sunrise mercury depletion incidence", where the transformation of
elemental mercury to divalent mercury is influenced by increased solar
activity and the presence of ice crystals, resulting in a substantial
increase in mercury deposition during a three month period (approximately
March to June).
speciation is very important for the controllability of mercury emissions to
air. For example, emissions of inorganic mercuric compounds (such
as mercuric chloride) are captured reasonably well by some control devices
(such as wet-scrubbers), while capture of elemental mercury tends to be low
for most emission control devices.
3 – Toxicology
toxicity of mercury depends on its chemical form, and thus symptoms and
signs are rather different in exposure to elemental mercury, inorganic
mercury compounds, or organic mercury compounds (notably alkylmercury
compounds such as methylmercury and ethylmercury salts, and dimethylmercury).
The sources of exposure are also markedly different for the different forms
of mercury. For alkylmercury compounds, among which methylmercury is by far
the most important, the major source of exposure is diet, especially fish
and other seafood. For elemental mercury vapour, the most important source
for the general population is dental amalgam, but exposure at work may in
some situations exceed this by many times. For inorganic mercury compounds,
diet is the most important source for the majority of people.
However, for some segments of populations, use of skin-lightening
creams and soaps that contain mercury, and use of mercury for
cultural/ritualistic purposes or in traditional medicine, can also result in
substantial exposures to inorganic or elemental mercury.
it is fully recognised that mercury and its compounds are highly toxic
substances for which potential impacts should be considered carefully, there
is ongoing debate on how
toxic these substances, especially methylmercury, are. New findings during
the last decade indicate that toxic effects may be taking place at lower
concentrations than previously thought, and potentially larger parts of the
global population may be affected. As the mechanisms of subtle toxic effects
– and proving whether such effects are taking place – are extremely
complex issues, a complete understanding has so far not been reached on this
very important question.
the organic mercury compounds, methylmercury occupies a special position in
that large populations are exposed to it, and its toxicity is better
characterized than that of other organic mercury compounds. Within the group
of organic mercury compounds, alkylmercury compounds (especially
ethylmercury and methylmercury) are thought to be rather similar as to
toxicity (and also historical use as pesticides), while other organic
mercury compounds, such as phenylmercury, resemble more inorganic mercury in
is a well-documented neurotoxicant, which may in particular cause adverse
effects on the developing brain. Moreover, this compound readily passes both
the placental barrier and the blood-brain barrier, therefore, exposures
during pregnancy are of highest concern. Also, some studies suggest that
even small increases in methylmercury exposures may cause adverse effects on
the cardiovascular system, thereby leading to increased mortality. Given the
importance of cardiovascular diseases worldwide, these findings, although
yet to be confirmed, suggest that methylmercury exposures need close
attention and additional follow-up. Moreover, methylmercury compounds are
considered possibly carcinogenic to humans (group 2B) according to the
International Agency for Research on Cancer (IARC, 1993), based on their
mercury and inorganic mercury compounds
main route of exposure for elemental mercury is by inhalation of the vapours.
About 80 percent of inhaled vapours are absorbed by the lung tissues. This
vapour also easily penetrates the blood-brain barrier and is a
well-documented neurotoxicant. Intestinal absorption of elemental mercury is
mercury can be oxidized in body tissues to the
inorganic divalent form.
and behavioural disorders in humans have been observed following inhalation
of elemental mercury vapour.
Specific symptoms include tremors, emotional lability, insomnia, memory
loss, neuromuscular changes, and headaches. In addition, there are effects
on the kidney and thyroid. High exposures have also resulted in death. With
regard to carcinogenicity, the overall evaluation, according to IARC (1993),
is that metallic mercury and inorganic mercury compounds are not
classifiable as to carcinogenicity to humans (group 3). A critical effect on which risk
assessment could be based is therefore the neurotoxic effects, for example
the induction of tremor. The effects on the kidneys (the renal tubule)
should also be considered; they are the key endpoint in exposure to
inorganic mercury compounds. The effect may well be reversible, but as the
exposure to the general population tends to be continuous, the effect may
still be relevant.
of effect levels
put the level of exposures for methylmercury in perspective, for the most
widely accepted non-lethal adverse effect (neurodevelopmental effects), the
United States (US) National Research Council (NRC, 2000) has estimated the
benchmark dose (BMD) to be 58 micrograms per litre (µg/l) total mercury in
cord blood (or 10 micrograms per gram (µg/g) total mercury in maternal hair)
using data from the Faroe Islands study of human mercury exposures (Grandjean
et al., 1997). This BMD level
is the lower 95% confidence limit for the exposure level that causes a
doubling of a 5% prevalence of abnormal neurological performance
(developmental delays in attention, verbal memory and language) in children
exposed in-utero in the Faroe Islands study.
These are the tissue levels estimated to result from an average daily
intake of about 1 µg methylmercury per kg body weight per day (1
weight per day).
adverse effects have been seen in humans with less reliability or at much
higher exposures. For methylmercury, effects have been seen on the adult
nervous system, on cardiovascular disease, on cancer incidence and on
genotoxicity. Also, effects
have been reported on heart rate variability and blood pressure in 7
year-old children exposed prenatally, and on cardiovascular mortality in
adults. For elemental mercury and inorganic mercury compounds, effects have
been seen on: the excretion of low molecular weight proteins; on enzymes
associated with thyroid function; on spontaneous abortion rates;
genotoxicity; respiratory system; gastrointestinal (digestion) system;
liver; immune system; and the skin.
are an extremely important component of the human diet in many parts of the
world and provide nutrients (such as protein, omega-3 fatty acids and
others) that are not easily replaced. Mercury is a major threat to this food
supply. Certainly, fish with
low methylmercury levels are intrinsically more healthful for consumers than
fish with higher levels of methylmercury, if all other factors are equal.
is limited laboratory evidence suggesting that several dietary components
might reduce (e.g. selenium, vitamin E, omega-3 fatty acids) or enhance
(e.g. alcohol) mercury’s toxicity for some endpoints. However, conclusions
cannot be drawn from these data at this time.
4 - Current
mercury exposure and risk evaluations for human health
mentioned earlier, the general population is primarily exposed to
methylmercury through the diet (especially fish) and to elemental mercury vapours
due to dental amalgams. Depending on local mercury pollution load,
substantial additional contributions to the intake of total mercury can
occur through air and water. Also, personal use of skin-lightening creams
and soaps, mercury use for religious, cultural and ritualistic purposes, the
presence of mercury in some traditional medicines (such as certain
traditional Asian remedies) and mercury in the home or working environment
can result in substantial elevations of human mercury exposure.
For example, elevated air levels in homes have resulted from mercury
spills from some old gas meters and other types of spills. Also, elevated
mercury levels in the working environment have been reported for example in chlor-alkali plants, mercury mines, thermometer factories,
refineries and dental clinics, as well as in mining and manufacturing of
gold extracted with mercury. Additional
exposures result from the use of Thimerosal/Thiomersal (ethylmercury
thiosalicylate) as a preservative in some vaccines and other
pharmaceuticals. The relative impacts of mercury from local pollution,
occupational exposure, certain cultural and ritualistic practices and some
traditional medicines may today vary considerably between countries and
regions in the world, and are significant in some regions.
chapter gives examples of data on total mercury and methylmercury exposures
primarily from fish diets, but also other sources in different parts of the
world, including Sweden, Finland, the United States of America (USA), the
Arctic, Japan, China, Indonesia, Papua New Guinea, Thailand, Republic of
Korea, Philippines, the Amazonas and French Guyana. For example, in a study
of a representative group of about 1700 women in the USA (aged 16-49 years)
for years 1999-2000, about 8 percent of the women had mercury concentrations
in blood and hair exceeding the levels corresponding to the US EPA’s
reference dose (an estimate of a safe dose). As shown in the chapter, data
indicate exposures are generally higher in Greenland, Japan and some other
areas as compared to the USA.
some of these countries and areas, local and regional mercury depositions
have affected the mercury contamination levels over the years and
countermeasures have been taken during the last decades to reduce national
emissions. Mercury emissions are, however, distributed over long distances
in the atmosphere and oceans. This means that even countries with minimal
mercury emissions, and other areas situated remotely from dense human
activity, may be adversely affected. For example, high mercury exposures
have been observed in the Arctic far distances from any significant sources.
on mercury concentrations in fish have been submitted from a number of
nations and international organisations. Additionally, many investigations
of mercury levels in fish are reported in the literature. Submitted data,
giving examples of mercury concentrations in fish from various locations in
the world, are summarised in the chapter. The mercury concentrations in
various fish species are generally from about 0.05 to 1.4 milligrams of
mercury per kilogram of fish tissue (mg/kg) depending on factors such as pH
and redox potential of the water, and species, age and size of the fish.
Since mercury biomagnifies in the aquatic food web, fish higher on the food
chain (or of higher trophic level) tend to have higher levels of mercury.
Hence, large predatory fish, such as king mackeral, pike, shark, swordfish,
walleye, barracuda, large tuna (as opposed to the small tuna usually used
for canned tuna), scabbard and marlin, as well as seals and toothed whales,
contain the highest concentrations. The available data indicate that mercury
is present all over the globe (especially in fish) in concentrations that
adversely affect human beings and wildlife. These levels have led to
consumption advisories (for fish, and sometimes marine mammals) in a number
of countries, warning people, especially sensitive subgroups (such as
pregnant women and young children), to limit or avoid consumption of certain
types of fish from various waterbodies.
Moderate consumption of fish (with low mercury levels) is not likely
to result in exposures of concern. However,
people who consume higher amounts of contaminated fish or marine mammals may
be highly exposed to mercury and are therefore at risk.
CHAPTER 5 – Impacts of mercury on the environment
of mercury in food webs
very important factor in the impacts of mercury to the environment is its
ability to build up in organisms and up along the food chain.
Although all forms of mercury can
accumulate to some degree, methylmercury is absorbed and accumulates to a
greater extent than other forms. Inorganic mercury can also be absorbed, but
is generally taken up at a slower rate and with lower efficiency than is
methylmercury. The biomagnification of methylmercury has a most
significant influence on the impact on animals and humans. Fish appear to
bind methylmercury strongly, nearly 100 percent of mercury that
bioaccumulates in predator fish is methylmercury. Most of the methylmercury
in fish tissue is covalently bound to protein sulfhydryl groups.
This binding results in a long half-life for elimination (about two
years). As a consequence, there
is a selective enrichment of methylmercury (relative to inorganic mercury)
as one moves from one trophic level to the next higher trophic level.
term bioaccumulation refers
to the net accumulation over time of metals within an organism from
both biotic (other organisms) and abiotic (soil, air, and water)
refers to the progressive build up of some heavy metals (and some
other persistent substances) by successive trophic levels – meaning
that it relates to the concentration ratio in a tissue of a predator
organism as compared to that in its prey (AMAP, 1998).
contrast to other mercury compounds the elimination of methylmercury from
fish is very slow. Given steady environmental
concentrations, mercury concentrations in individuals of a given fish
species tend to increase with age as a result of the slow elimination of
methylmercury and increased intake due to changes in trophic position that
often occur as fish grow to larger sizes (i.e., the increased fish-eating
and the consumption of larger prey items). Therefore, older fish typically
have higher mercury concentrations in the tissues than younger fish of the
mercury concentrations are lowest in the smaller, non-predatory fish and can
increase many-fold on the way up the food chain.
Apart from the concentration in food, other factors affect the
bioaccumulation of mercury. Of most importance are the rates of
methylation and demethylation by mercury methylating bacteria (e.g.,
sulphate reducers). When all of these factors are combined, the net
methylation rate can strongly influence the amount of methylmercury that is
produced and available for accumulation and retention by aquatic organisms.
As described in chapter 2, several parameters in the aquatic environment
influence the methylation of mercury and thereby its biomagnification. While
much is generally known about mercury bioaccumulation and biomagnification,
the process is extremely complex and involves complicated biogeochemical
cycling and ecological interactions. As a result, although accumulation/magnification can be
observed, the extent of mercury biomagnification in fish is not
easily predicted across different sites.
the top levels of the aquatic food web are fish-eating species, such as
humans, seabirds, seals and otters. The larger wildlife species (such as
eagles, seals) prey on fish that are also predators, such as trout and
salmon, whereas smaller fish-eating wildlife (such as kingfishers) tend to
feed on the smaller forage fish. In
a study of fur-bearing animals in Wisconsin, the species with the highest
tissue levels of mercury were otter and mink, which are top mammalian
predators in the aquatic food chain. Top avian predators of aquatic food
chains include raptors such as the osprey and bald eagle.
Thus, mercury is transferred and accumulated through several food web
levels (US EPA, 1997). Aquatic food webs tend to have more levels than
terrestrial webs, where wildlife predators rarely feed on each other, and
therefore the aquatic biomagnification typically reaches higher values.
compounds toxic to wildlife
is a central nervous system toxin, and the kidneys are the organs most
vulnerable to damage from inorganic mercury. Severe
neurological effects were already seen in animals in the notorious case from
Minamata, Japan, prior to the recognition of the human poisonings, where
birds experienced severe difficulty in flying, and exhibited other grossly
abnormal behaviour. Significant effects on reproduction are also
attributed to mercury, and methylmercury poses a particular risk to the
developing fetus since it readily crosses the placental barrier and can
damage the developing nervous system.
birds, adverse effects of mercury on reproduction can occur at egg
concentrations as low as 0.05 to 2.0 mg/kg (wet weight). Eggs of certain
Canadian species are already in this range, and concentrations in the eggs
of several other Canadian species continue to increase and are approaching
levels of mercury in Arctic ringed seals and beluga whales have increased by
2 to 4 times over the last 25 years in some areas of the Canadian Arctic and
Greenland. In warmer waters as well, predatory marine mammals may also be at
risk. In a study of Hong Kong’s population of hump-backed dolphins,
mercury was identified as a particular health hazard, more than other heavy
evidence suggests that mercury is responsible for a reduction of
micro-biological activity vital to the terrestrial food chain in soils over
large parts of Europe – and potentially in many other places in the world
with similar soil characteristics. Preliminary critical limits to prevent
ecological effects due to mercury in organic soils have been set at 0.07-0.3
mg/kg for the total mercury content in soil.
the global scale, the Arctic region has been in focus recently because of
the long-range transport of mercury. However, impacts from mercury are by no
means restricted to the Arctic region of the world. The same food web
characteristics - and a similar dependence on a mercury contaminated food
source - are found in specific ecosystems and human communities in many
countries of the world, particularly in places where a fish diet is
water levels associated with global climate change may also have
implications for the methylation of mercury and its accumulation in fish.
For example, there are indications of increased formation of methylmercury
in small, warm lakes and in many newly flooded areas.
6 – Sources
and cycling of mercury to the global environment
releases of mercury to the biosphere can be grouped in four categories:
sources - releases due to natural mobilisation of naturally occurring
mercury from the Earth's crust, such as volcanic activity and weathering
anthropogenic (associated with human activity) releases from the
mobilisation of mercury impurities in raw materials such as fossil fuels
– particularly coal, and to a lesser extent gas and oil – and other
extracted, treated and recycled minerals;
anthropogenic releases resulting from mercury used intentionally in
products and processes, due to releases during manufacturing, leaks,
disposal or incineration of spent products or other releases;
of historic anthropogenic mercury releases previously deposited in
soils, sediments, water bodies, landfills and waste/tailings piles.
figure below shows these release categories with main types of possible
recipients of mercury releases to the environment include the atmosphere,
water environments (aquatic) and soil environments (terrestrial). There are
continuing interactions – fluxes of mercury – between these
compartments. The speciation
– the chemical form – of the released mercury varies depending on the
source types and other factors. This also influences the impacts on human
health and environment as different mercury species have different toxicity.
the understanding of the global mercury cycle, current releases add to the
global pool of mercury in the biosphere – mercury that is continuously
mobilised, deposited on land and water surfaces, and re-mobilised. Being an
element, mercury is persistent – it cannot be broken down to less toxic
substances in the environment. The only long-term sinks for removal of
mercury from the biosphere are deep-sea sediments and, to a certain extent,
controlled landfills, in cases where the mercury is physio-chemically
immobilised and remains undisturbed by anthropogenic or natural activity
(climatic and geological). This also implies that even as the anthropogenic
releases of mercury are gradually eliminated, decreases in some mercury
concentrations – and related environmental improvements – will occur
only slowly, most likely over several decades or longer.
However, improvements may occur more quickly in specific locations or
regions that are largely impacted by local or regional sources.
releases – global effects
origins of atmospheric mercury deposition (flow of mercury from air to land
and oceans) are local and regional as well as hemispherical or global.
Several large studies have supported the conclusion that, in addition to
local sources (such as chlor-alkali production, coal combustion and waste
incineration facilities), the general background concentration of mercury in
the global atmosphere contributes significantly to the mercury burden at
most locations. Similarly, virtually any local source contributes to the
background concentration – the global mercury pool in the biosphere - much
of which represents anthropogenic releases accumulated over the decades.
Also, the ocean currents are media for long-range mercury transport, and the
oceans are important dynamic sinks of mercury in the global cycle.
majority of atmospheric anthropogenic emissions are released as gaseous
elemental mercury. This is capable of being transported over very long
distances with the air masses. The remaining part of air emissions are in
the form of gaseous divalent compounds (such as HgCl2) or bound
to particles present in the emission gas. These species have a shorter
atmospheric lifetime than elemental vapour and will deposit via wet or dry
processes within roughly 100 to 1000 kilometers. However, significant
conversion between mercury species may occur during atmospheric transport,
which will affect the transport distance.
atmospheric residence time of elemental mercury is in the range of months to
roughly one year. This makes transport on a hemispherical scale possible and
emissions in any continent can thus contribute to the deposition in other
continents. For example, based on modelling of the intercontinental mercury
transport performed by EMEP/MSC-E (Travnikov and Ryaboshapko, 2002), up to
50 percent of anthropogenic mercury deposited to North America is from
external sources. Similarly, contributions of external sources to
anthropogenic mercury depositions to Europe and Asia were estimated to be
about 20 percent and 15 percent, respectively.
as mentioned, mercury is also capable of re-emissions from water and soil
surfaces. This process greatly enhances the overall residence time of
mercury in the environment. Recent findings
by Lindberg et al. (2001) indicate
re-emission rates of approximately 20 percent over a two-year period, based
on stable mercury isotope measurements in north-western Ontario, Canada.
sources of mercury releases
large portion of the mercury present in the atmosphere today is the result
of many years of releases due to anthropogenic activities. The natural
component of the total atmospheric burden is difficult to estimate, although
a recent study (Munthe et al.,
2001) has suggested that anthropogenic activities have increased the overall
levels of mercury in the atmosphere by roughly a factor of 3.
there are some natural emissions of mercury from the earth’s crust,
anthropogenic sources are the major contributors to releases of mercury to
the atmosphere, water and soil.
of important sources of anthropogenic releases of mercury
mobilisation of mercury impurities:
power and heat production (largest single source to atmospheric
production from other fossil carbon fuels
production (mercury in lime)
and other metallurgic activities involving the extraction and
processing of virgin and recycled mineral materials, for example
production of :
- iron and steel
- other non-ferrous metals
intentional extraction and use of mercury:
gold and silver mining (amalgamation process)
of fluorescent lamps, various instruments and dental amalgam
of products containing mercury, for example:
- manometers and other instruments
- electrical and electronic switches
Releases from waste treatment, cremation
etc. (originating from both impurities and intentional uses of
are significant uncertainties in the available release inventories, not only
by source, but also by country. The
best available estimates of mercury emissions to air from various
significant sources are shown in the table below.
- Estimates of global atmospheric releases of mercury from a number
of major anthropogenic sources
in 1995 (metric
tons/year). Releases to other media are not accounted for here. *1.
metal production *5
iron and steel production
gold mining *4
quantified sources *3
quantified sources, 1995 *3,4
et al. (2001)
et al. (2001)
et al. (2001)
et al. (2001)
et al. (2001)
1 Note that releases to aquatic and terrestrial
environments - as well as atmospheric releases from a number of other
sources - are not included in the table, because no recent global estimates
have been made. See chapter 6 for description of this issue.
2 Considered underestimated by authors of the
inventory, see notes to table 6.10.
3 Represents total of the sources mentioned in this
table, not all known sources. Sums are rounded and may therefore not sum up
4 Estimated emissions from artisanal gold mining
refer to late 1980's/early 1990's situation. A newer reference (MMSD, 2002)
indicates that mercury consumption for artisanal gold mining - and thereby
most likely also mercury releases - may be even higher than presented here.
Production of non-ferrous metals releasing mercury, including
mercury, zinc, gold, lead, copper, nickel.
emissions from stationary combustion of fossil fuels (especially coal) and
incineration of waste materials accounts for approximately 70 percent of the
total quantified atmospheric emissions from major anthropogenic sources. As
combustion of fossil fuels is increasing in order to meet the growing energy
demands of both developing and developed nations, mercury emissions can be
expected to increase accordingly in the absence of the deployment of control
technologies or the use of alternative energy sources. Control technologies
have been developed for coal combustion plants and waste incinerators with
the primary intention of addressing acidifying substances (especially SO2
and NOX), and
particulate matter (PM). Such existing technologies may provide some level
of mercury control, but when viewed at the global level, currently these
controls result in only a small reduction of mercury from these sources.
Many control technologies are significantly less effective at reducing
emissions of elemental mercury compared to other forms. Optimised
technologies for mercury control are being developed and demonstrated, but
are not yet commercially deployed.
global estimates of atmospheric emissions from waste incineration, as well
as other releases originating from intentional uses of mercury in processes
and products, are deemed underestimated, and to some degree incomplete.
However, recorded virgin mercury production has been decreasing from about
6000 to about 2000 metric tons per year during the last two decades, and
consequently, related releases from mining and usage of mercury may also be
emissions from a number of major sources have decreased during the last
decade in North America and Europe due to reduction efforts.
Also, total anthropogenic
emissions to air have been declining in some developed countries in the last
decade. For example, Canadian emissions
were reduced from about 33 metric tons to 6 metric tons between 1990 and
sources of mercury releases
sources include volcanoes, evaporation from soil and water surfaces,
degradation of minerals and forest fires.
The natural mercury emissions are beyond our control, and must be
considered part of our local and global living environment. It is necessary
to keep this source in mind, however, as it does contribute to the
environmental mercury levels. In some areas of the world, the mercury concentrations in the
Earth's crust are naturally elevated, and contribute to elevated local and
regional mercury concentrations in those areas.
emissions of mercury from soil and water surfaces are composed of both
natural sources and re-emission of previous deposition of mercury from both
anthropogenic and natural sources. This makes it very difficult to determine
the actual natural mercury emissions.
estimates of natural versus anthropogenic mercury emissions show significant
variation, although more recent efforts have emphasized the importance of
human contributions. Attempts to directly measure natural emissions are
ongoing. Nonetheless, available
information indicates that natural sources account for less than 50 percent
of the total releases.
average around the globe, there are indications that anthropogenic emissions
of mercury have resulted in deposition rates today that are 1.5 to 3 times
higher than those during pre-industrial times. In and around industrial
areas the deposition rates have increased by 2 to 10 times during the last
from intentional uses versus impurities in high volume materials
anthropogenic releases, the relative importance of intentional uses versus
mobilisation of mercury impurities varies between countries and regions,
particularly depending on:
of substitution of intentional uses (products and processes);
on fossil fuels for energy production, particularly coal, and the
presence of controls for other pollutants, which also reduce mercury
of mining and mineral extraction industry;
disposal pattern – incineration/landfilling;
of implementation of release control technologies in power production,
waste incineration and various industrial processes.
a number of countries, estimated contributions of intentional uses vary
between 10 and 80 percent of the total domestic emissions to air, depending
on the influence of the factors listed above. Rough estimates of
distribution by main anthropogenic source types in each of these countries
are shown in the chapter.
an illustration, the figure below shows the overall turnover of mercury in
the Danish society in 1992/93 in kilograms mercury/year (based on Maag et
al., 1996). (Note that inputs and outputs in the figure do not balance
because outputs reflect higher inputs from previous years. Net change in
stocks was negative.)
is a quite small country with relatively accurate monitoring of the flows of
products and waste in the economy and the environment. Therefore, it has
been possible to perform rather detailed balances, so-called substance flow
assessments for mercury, which provide useful information on the
contributions from different sectors to the total mercury burden in society
and the environment. As shown in the figure, the majority of the input –
more than two thirds – originated from intentional uses (chlor-alkali
production and products), and the contributions from intentional uses to
releases to air in 1992/93 could roughly be estimated at 50-80 percent of
the total releases to air from Denmark. It should be noted that primary
mineral extraction and processing is not as large a sector in Denmark, as in
many other countries.
of national distributions of anthropogenic mercury releases from different
individual source types are given in the chapter. In countries where mercury
mining or intentional use of mercury for small-scale gold mining is taking
place, these sources can be significant.
7 – Current
production and use of 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
of mercury to the market
mercury available on the world market is supplied from a number of different
sources, including (not listed in order of importance):
production of primary mercury (meaning extracted from ores within the
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;
primary mercury from refining of natural gas (actually a by-product,
when marketed, however, is not marketed in all countries);
or secondary mining of historic mine tailings containing mercury;
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";
from government reserve stocks, or inventories;
stocks (such as mercury in use in chlor-alkali and other industries),
some of which may later be returned to the market.
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.
mining of primary mercury
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
annual, global primary production
(in metric tons)
See section 7.2.1.
supplies of recycled mercury may be marketed
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.
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.
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 Miñas de Almadén in Spain. The
agreement provides that Miñas 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.
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).
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.
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
the metal (among others):
extraction of gold and silver (for centuries)
a catalyst for chlor-alkali production
manometers for measuring and controlling pressure
electrical and electronic switches
dental amalgam fillings
chemical compounds (among others):
batteries (as a dioxide)
in paper industry, paints and on seed grain
antiseptics in pharmaceuticals
and dyes (may be historical)
(may be historical)
(may be historical)
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.
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
8 – Prevention
and control technologies and practises
noted in chapter 6, the sources of releases of mercury to the biosphere can
be grouped in four major categories. Two of these categories (releases due
to natural mobilisation of mercury and re-mobilisation of anthropogenic
mercury previously deposited in soils, sediments and water bodies) are not
well understood and largely beyond human control.
other two are current anthropogenic mercury releases. Reducing or
eliminating these releases may require:
in controlling releases from and substituting the use of
mercury-contaminated raw materials and feedstocks, the main source of
mercury releases from “unintentional” uses; and
or eliminating the use of mercury in products and processes, the main
source of releases caused by the “intentional” use of mercury.
specific methods for controlling mercury releases from these sources vary
widely, depending upon local circumstances, but fall generally under the
following four groups:
Reducing mercury mining and consumption of raw materials and products
Substitution (or elimination) of products, processes and practices
containing or using mercury
with non-mercury alternatives;
Controlling mercury releases through end-of-pipe techniques;
Mercury waste management.
first two of these are “preventive” measures – preventing some uses or
releases of mercury from occurring at all. The latter two are “control”
measures, which reduce (or delay) some releases from reaching the
environment. Within these very general groupings are a large number of
specific techniques and strategies for reducing mercury releases and
exposures. Whether or not they
are applied in different countries depends upon government and local
priorities, information and education about possible risks, the legal
framework, enforcement, implementation costs, perceived benefits and other
Reducing consumption of raw materials and products that generate
consumption of raw materials and products that generate mercury releases is
a preventive measure that is most often targeted at mercury containing
products and processes, but may also result from improved efficiencies in
the use of raw materials or in the use of fuels for power generation.
This group of measures could potentially include the choice of an
alternative raw material such as using natural gas for power generation
instead of coal, or possibly by using a coal type with special constituents
(such as more chlorine), because the mercury emissions from burning this
type of coal might be easier to control than other coal types.
possible approach in some regions might be the use of coal with a lower
trace mercury content (mercury concentrations appear to vary considerably in
some regions depending on the origin of the raw materials).
However, there are some limitations and potential problems with this
approach. For example, as in
the case of the utility preference for low-sulfur crude oil, it is likely
that some utilities might be willing to pay more for low-mercury coal, which
effectively lowers the market value of all high-mercury coal, which in turn
might lead to higher consumption of high-mercury coal in regions where
utilities have less rigorous emission controls.
Moreover, data collected recently in the US indicate that coal
supplies in the US do not vary significantly in mercury content.
such preventive measures aimed at reducing mercury emissions are generally
cost-effective, except in cases where an alternative raw material is
significantly more expensive or where other problems limit this approach.
Substitution of products and processes containing or using mercury
of products and processes containing or using mercury with products and
processes without mercury may be one of the most powerful preventive
measures for influencing the entire flow of mercury through the economy and
environment. It may
substantially reduce mercury in households (and reduce accidental releases,
as from a broken thermometer), the environment, the waste stream,
incinerator emissions and landfills. Substitutions
are mostly cost-effective, especially as they are demanded by a larger and
larger market. This group of
measures would also include the conversion of a fossil-fueled generating
plant to a non-fossil technology.
the same time, it would be a mistake to assume that substitution is always a
clear winner. For example, in the case of energy-efficient fluorescent
lamps, as long as there are no competitive substitutes that do not contain
mercury, it is generally preferable from a product-life-cycle perspective to
use a mercury-containing energy-efficient lamp rather than to use a less
efficient standard incandescent lamp containing no mercury, as a result of
current electricity production practises.
Controlling mercury emissions through end-of-pipe techniques
mercury emissions through end-of-pipe techniques, such as exhaust gas
filtering, may be especially appropriate to raw materials with trace mercury
contamination, including fossil-fueled power plants, cement production (in
which the lime raw material often contains trace mercury), the extraction
and processing of primary raw materials such as iron and steel,
ferromanganese, zinc, gold and other non-ferrous metals and the processing
of secondary raw materials such as iron and steel scrap.
Existing control technologies that reduce SO2, NOx
and PM for coal-fired boilers and incinerators, while not yet widely used in
many countries, also yield some level of mercury control. For coal-fired
boilers, reductions range from 0 to 96 percent, depending on coal type,
boiler design, and emission control equipment. On average, the lower the
coal rank, the lower the mercury reductions; however, reductions may also
vary within a given coal rank. Technology for additional mercury control is
under development and demonstration, but is not yet commercially deployed.
In the long run, control strategies that target multiple pollutants,
including SO2, NOx, PM and mercury, may be a
cost-effective approach. However,
end-of-pipe control technologies, while mitigating the problem of
atmospheric mercury pollution, still result in mercury wastes that are
potential sources of future emissions and must be disposed of or reused in
an environmentally acceptable manner.
Mercury waste management
wastes, including those residues recovered by end-of-pipe technologies,
constitute a special category of mercury releases, with the potential to
affect populations far from the initial source of the mercury.
Mercury waste management, the fourth “control” measure mentioned
above, may consist of rendering inert the mercury content of waste, followed
by controlled landfill, or it may not treat the waste prior to landfill. In Sweden, the only acceptable disposal of mercury waste now
consists of “final storage” of the treated waste deep underground, although
some technical aspects of this method are yet to be finalised.
waste management has become more complex as more mercury is collected from a
greater variety of sources, including gas filtering products, sludges from
the chlor-alkali industry, ashes, slags, and inert mineral residues, as well
as used fluorescent tubes, batteries and other products that are often not
recycled. Low concentrations of mercury in waste are generally
permitted in normal landfills, while some nations only allow waste with
higher mercury concentrations to be deposited in landfills that are designed
with enhanced release control technologies to limit mercury leaching and
evaporation. The cost of
acceptable disposal of mercury waste in some countries is such that many
producers now investigate whether alternatives exist in which they would not
have to produce and deal with mercury waste.
Mercury waste management, as it is most commonly done today, in
accordance with national and local regulations, increasingly requires
long-term oversight and investment. Proper
management of mercury wastes is important to reduce releases to the
environment, such as those that occur due to spills (i.e. from broken
thermometers and manometers) or releases that occur over time due to leakage
from certain uses (e.g., auto switches, dental amalgams).
In addition, given that there is a market demand for mercury,
collection of mercury-containing products for recycling limits the need for
new mercury mining.
prevention and control measures
well thought-out combination of emission prevention and control measures is
an effective way to achieve optimal reduction of mercury releases.
If one considers some of the more important sources of anthropogenic
mercury releases, one may see how prevention and control measures might be
combined and applied to these sources:
emissions from municipal and medical waste incinerators may be
reduced by separating the small fraction of mercury containing waste
before it is combusted. For example, in the USA,
free household mercury waste collections have been very successful in
turning up significant quantities of mercury-containing products and
even jars of elemental mercury. Also,
separation programmes have proved successful in the hospital sector and
a number of hospitals have pledged to avoid purchasing
mercury-containing products through joint industry-NGO-Government
separation programmes are sometimes difficult or costly to implement
widely, especially when dealing with the general public.
In such cases a better long-term solution may be to strongly
encourage the substitution of non-mercury products for those containing
mercury. As a medium term
solution, separation programmes may be pursued, and mercury removed from
the combustion stack gases. Mercury emissions from medical and municipal
waste incineration can be controlled relatively well by addition of a
carbon sorbent to existing PM and SO2 control equipment,
however, control is not 100% effective and mercury-containing wastes are
generated from the process;
emissions from utility and non-utility boilers, especially those
burning coal, may be effectively addressed through pre-combustion coal
cleaning, reducing the quantities of coal consumed through increased
energy efficiency, end-of-pipe measures such as stack gas cleaning
and/or switching to non-coal fuel sources, if possible. Another
potential approach might be the use of coal with a lower mercury
content. Coal cleaning and
other pre-treatment options can certainly be used for reducing mercury
emissions when they are viable and cost-effective. Also, additional
mercury capture may be achieved by the introduction of a sorbent prior
to existing SO2 and PM control technologies. These
technologies are under development and demonstration, but are not yet
commercially deployed. Also, by-products of these processes are
potential sources of future emissions and must be disposed of or reused
in an environmentally acceptable manner;
emissions due to trace contamination of raw materials or feedstocks such
as in the cement, mining and metallurgical industries may be reduced by
end-of-pipe controls, and sometimes by selecting a raw material or
feedstock with lower trace contamination, if possible.
emissions during scrap steel production,
scrap yards, shredders and secondary steel production, result primarily from convenience light and anti-lock brake system (ABS)
switches in motor vehicles; therefore a solution may include effective
switch removal/collection programmes;
releases and health hazards from artisanal gold mining activities
may be reduced by educating the miners and their families about hazards,
by promoting certain techniques that are safer and that use less or no
mercury and, where feasible, by putting in place facilities where the
miners can take concentrated ores for the final refining process. Some
countries have tried banning the use of mercury by artisanal miners,
which may serve to encourage their use of central processing facilities,
for example, but enforcement of such a ban can be difficult;
releases and occupational exposures during chlor-alkali production
may be substantially reduced through strict mercury accounting
procedures, “good housekeeping” measures to keep mercury from being
dispersed, properly filtering exhaust air from the facility and careful
handling and proper disposal of mercury wastes.
There are a number of specific prevention methods to reduce
mercury emissions to the atmosphere.
The US chlor-alkali industry invented the use of ultraviolet
lights to reveal mercury vapour leaks from production equipment, so that
they could be plugged. Equipment is allowed to cool before it is opened,
reducing mercury emissions to the atmosphere. A continuous mercury
vapour analyser can be employed to detect mercury vapour leaks and to
alert workers so that they can take remedial measures. The generally
accepted long-term solution is to encourage the orderly phase-out of
chlor-alkali production processes that require mercury, and their
substitution with technologies that are mercury free;
releases and exposures related to mercury-containing paints, soaps, various
switch applications, thermostats, thermometers, manometers, and
barometers, as well as contact
lens solutions, pharmaceuticals and cosmetics may be reduced by
substituting these products with non-mercury products;
releases from dental practices may be reduced by preparing
mercury amalgams more efficiently, by substituting other materials for
mercury amalgams, and by installing appropriate traps in the wastewater
emissions from dental amalgams during cremation may only be
reduced by removing the amalgams before cremation, which is not a common
practice, or by filtering the gaseous emissions when the practice takes
place in a crematorium. Since
a flue gas cleaner is an expensive control technique for a crematorium,
prevention by substituting other materials for mercury amalgams during
normal dental care might be a preferred approach;
cases of uncontrolled disposal of mercury-containing products or
wastes, possible reductions in releases from such practises might be
obtained by making these practices illegal and adequately enforcing the
law, by enhancing access to hazardous waste facilities, and, over the
longer term, by reducing the quantities of mercury involved through a
range of measures encouraging the substitution of non-mercury products
9 - Initiatives
for controlling releases and limiting use and exposures
environmental authorities in a number of countries consider mercury to be a
high-priority substance with recognised adverse effects.
They are aware of the potential problems caused by use and release of
mercury and mercury compounds, and therefore have implemented measures to
limit or prevent certain uses and releases.
Types of measures that have been implemented by various countries
quality standards, specifying a maximum acceptable mercury concentration
for different media such as drinking water, surface waters, air and soil
and for foodstuffs such as fish;
source actions and regulations that control mercury releases into the
environment, including emission limits on air and water point sources
and promoting use of best available technologies and waste treatment and
control actions and regulations for mercury-containing products, such as
batteries, cosmetics, dental amalgams, electrical switches, laboratory
chemicals, lighting, paints/pigments, pesticides, pharmaceuticals,
thermometers and measuring equipment;
standards, actions and programmes, such as regulations on exposures to
mercury in the workplace, requirements for information and reporting on
use and releases of mercury in industry, fish consumption advisories and
consumer safety measures.
legislation is the key components of most national initiatives, safe
management of mercury also includes efforts to reduce the volume of mercury
in use by developing and introducing safer alternatives and cleaner
technology, the use of subsidies to support substitution efforts and
voluntary agreements with industry or users of mercury.
A number of countries have through implementation of this range of
measures obtained significant reductions in mercury consumption, and
corresponding reductions of uses and releases.
table below gives a general overview of some of the types of implemented
measures of importance to management and control of mercury, as related to
its production and use life-cycle and an indication of their status of
implementation, based on information submitted for this report. More
detailed descriptions of most of these measures are provided in chapter 9
and the separate Appendix to this report.
AND AIM OF MEASURE
and use phases of life cycle
or limit the intentional use of mercury in processes
bans implemented in very few countries
or limit mercury from industrial processes (such as chlor-alkali and
metallurgic industry) from being released directly to the
in many countries, especially OECD countries
emission control technologies to limit emissions of mercury from
combustion of fossil fuels and processing of mineral materials
in some OECD countries
or limit the release of mercury from processes to the wastewater
in some OECD countries
or limit use of obsolete technology and/or require use of best
available technology to reduce or prevent mercury releases
in some countries, especially OECD countries
or limit products containing mercury from being marketed nationally
bans implemented in a few countries only.
Bans or limits on specific products are more widespread, such
as batteries, lighting, clinical thermometers
products containing mercury from being exported
implemented in a few countries
or limit the use of already purchased mercury and mercury-containing
implemented in a few countries
the allowable content of mercury present as impurities in
implemented in a few countries
the allowed contents of mercury in commercial foodstuffs,
particularly fish, and provide guidance (based on same or other
limits values) regarding consumption of contaminated fish
in some countries, especially OECD countries.
WHO guidelines used by some countries.
phase of life cycle
mercury in products and process waste from being released directly
to the environment, by efficient waste collection
in many countries, especially OECD countries
mercury in products and process waste from being mixed with less
hazardous waste in the general waste stream, by separate collection
in many countries, especially OECD countries
or limit mercury releases to the environment from incineration and
other treatment of household waste, hazardous waste and medical
waste by emission control technologies
or implementation ongoing in some countries, especially OECD
limit values for allowable mercury contents in sewage sludge spread
on agricultural land
in a number of countries
the use of solid incineration residues in road building,
construction and other applications
in some OECD countries
the re-marketing of used, recycled mercury
implemented in a few countries
and international initiatives
is also apparent that because of mercury’s persistence in the environment
and the fact that it is transported over long distances by air and water,
crossing borders and often accumulating in the food chain far from it’s
original point of release, a number of countries have concluded that
national measures are not sufficient. There
are a number of examples where countries have initiated measures at
regional, sub-regional and international levels to identify common reduction
goals and ensure coordinated implementation among countries in the target
regional, legally binding instruments exist that contain binding commitments
for parties with regards to reductions on use and releases of mercury and
Convention on Long-Range Transboundary Air Pollution and its 1998 Aarhus
Protocol on Heavy Metals (for Central and Eastern Europe and
Canada and the USA);
Convention for Protection of the Marine Environment of the North-East
Convention on the Protection of the Marine Environment of the Baltic
these three instruments have successfully contributed to substantial
reductions in use and releases of mercury within their target regions.
regional and sub-regional cooperation is, however, not limited to legally
binding agreements. Six
initiatives exist at regional or sub-regional levels that inspire and
promote cooperative efforts to reduce uses and releases of mercury within
the target area without setting legally binding obligations on the
countries/regions participating. The initiatives are: the Arctic Council Action Plan, the
Canada-US Great Lakes Binational Toxics Strategy, the New England
Governors/Eastern Canada Premiers Mercury Action Plan, the North American
Regional Action Plan, the Nordic Environmental Action Programme and the
North Sea Conferences. Important
aspects of these initiatives are the discussion and agreement on concrete
goals to be obtained through the cooperation, the development of strategies
and work plans to obtain the set goals and the establishment of a forum to
monitor and discuss progress. Although
these initiatives are not binding on their participants, there is often a
strong political commitment to ensure that the agreements reached within the
initiative are implemented at national/regional level.
are also a number of examples of national/regional
initiatives being taken by the private sector in the form of voluntary
commitments that can be seen as an adjunct to public sector initiatives and
as having a good chance of success as they have, by definition, the support
of the primary stakeholders. All
these voluntary initiatives are valuable supplements to national
regulatory measures and facilitate awareness raising, information exchange
and the setting of reduction goals that benefit the target region.
the international level, two multilateral environmental agreements (MEAs)
exist that are of relevance to mercury and mercury compounds:
the Basel Convention on Control of Transboundary Movements of
Hazardous Wastes and their Disposal and the Rotterdam Convention on the
Prior Informed Consent Procedure for Certain Chemicals and Pesticides in
International Trade. These
instruments regulate trade in unwanted chemicals/pesticides or hazardous
wastes. However, they do not
contain specific commitments to reduce uses and releases of mercury
directly. The most recently
negotiated agreement relevant to chemicals, the Stockholm Convention on POPs,
does not cover mercury. In
addition, a number of international organizations have ongoing activities
addressing the adverse impacts of mercury on humans and the environment.
more detailed compilation of national initiatives, including legislation, in
each individual country is contained in an appendix to this report, entitled
“Overview of existing and future national actions, including legislation,
relevant to mercury”. The
Appendix is published in a separate document.
The information compiled therein has been extracted from the national
submissions received from countries under this project.
10 – Data gaps
research and information needs
number of countries have in their submissions to UNEP expressed a need for
establishing or improving their national “database” (i.e. knowledge of
and information on uses and emissions, sources of releases, levels in the
environment and prevention and control options) on mercury and mercury
compounds. Although the situation varies from country to country, there
seems to be a general need for information relevant to the various elements
of an environmental management strategy for mercury.
Also, countries with a longer tradition of environmental management
of mercury have expressed the need to continue to expand their knowledge
base on mercury to improve risk assessment and ensure effective risk
management. Some of the needs
include, among others:
of national use, consumption and environmental releases of mercury;
of current levels of mercury in various media (such as air, air
deposition, surface water) and biota (such as fish, wildlife and humans)
and assessment of the impacts of mercury on humans and ecosystems,
including impacts from cumulative exposures to different mercury forms;
on transport, transformation, cycling, and fate of mercury in various
and evaluation tools for human and ecological risk assessments;
and information on possible prevention and reduction measures relevant
to the national situation;
awareness-raising on the potential adverse impacts of mercury and proper
handling and waste management practises;
tools and facilities for accessing existing information relevant to
mercury and mercury compounds at national, regional and international
building and physical infrastructure for safe management of hazardous
substances, including mercury and mercury compounds, as well as training
of personnel handling such hazardous substances.
on the commerce and trade of mercury and mercury-containing
principle, some parts of this information might be exchanged nationally,
regionally or internationally, as its relevance is often universal, however,
it might need to be “translated” into the context of the individual
country’s framework of traditions, economic and industrial activities and
political reality. This, in itself, demands a substantial degree of
priority, knowledge and funding. Other
parts of the information are country specific and would require national
efforts to research, collect and process the information.
gaps of a general, global character
mercury is probably among the best-studied environmental toxicants, there
are data gaps in the basic understanding of a number of general, global
issues relevant to mercury. Based
on submitted information and the compilation and evaluation hereof, a
possible division of current data gaps of global relevance on mercury could
be as follows (not in order of priority):
and quantification of the natural
mechanisms affecting the fate of mercury in the environment, such as
mobilisation, transformation, transports and intake. In other words, the
pathways of mercury in the environment, and from the environment to
and quantification – in a global perspective – of the human
conduct in relation to mercury releases, and the resulting human
contributions to the local, regional and global mercury burden. In other
words, the pathways of mercury from humans to the environment.
of how and to what degree humans, ecosystems and wildlife are adversely
affected by the current mercury levels found in the local, regional
and global environment. In other words, the possible effects, number
affected, and the magnitude and severeness in those affected.
basic understanding has been established for all three categories mentioned
above, based on about half a century's extensive research on the impacts and
pathways of mercury. However, in a number of areas, further research is
needed to provide new information to improve environmental modelling
assessments and modern decision-making tools.
Despite these gaps in information, a sufficient understanding has
been developed of mercury (including knowledge of its fate and transport,
health and environmental impacts, and the role of human activity) that
international action to address the global adverse impacts of mercury should
not be delayed.
11 – Options for addressing any
significant global adverse impacts of mercury
UNEP Governing Council requested, as part of the global assessment on
mercury, an outline of options for consideration by the Governing Council,
addressing any significant global adverse impacts of mercury, inter alia,
by reducing and or eliminating the use, emissions, discharges and losses of
mercury and its compounds; improving international cooperation; and ways to
enhance risk communication.
part of the implementation of Governing Council decision 21/5, UNEP
established a Working Group to assist it in preparing for the Governing
Council’s discussions on the issue at its session in February 2003.
The Global Mercury Assessment Working Group, at its first meeting
held from 9 to 13 September 2002, finalized this assessment report for
presentation to the Governing Council at its 22nd session.
At this meeting, the Working Group arrived at a number of
conclusions of relevance to the Governing Council’s considerations:
on the key finding of this report, the Working Group concluded that, in
its view, there was sufficient evidence of significant global adverse
impacts to warrant international action to reduce the risks to human
health and/or the environment arising from the release of mercury into
the environment. While it
was important to have a better understanding of the issue, the Working
Group emphasized that it was not necessary to have full consensus or
complete evidence in order to take action and therefore potentially
significant global adverse impacts should also be addressed.
Working Group also agreed on an outline of options for recommendation on
measures to address global adverse impacts of mercury at the global,
regional, national and local levels.
The options include measures such as reducing
or eliminating the production, consumption and releases of mercury,
substituting other products and processes, launching negotiations for a
legally-binding treaty, establishing a non-binding global programme of
action, and strengthening cooperation amongst governments on
information-sharing, risk communication, assessment and related
the Working Group agreed to the need to submit to the Governing Council
a range of possible immediate actions in light of their findings on the
impacts of mercury, such as increasing protection of sensitive
populations (through enhanced outreach to pregnant women and women
planning to become pregnant),
providing technical and financial support to developing countries and to
countries with economies in transition, and supporting increased
research, monitoring and data-collection on the health and environmental
aspects of mercury and on environmentally friendly alternatives to