Final session on international mercury convention this week expected to culminate in agreement; UNEP Global Mercury Assessment 2013 finds industrial source Hg emissions may be rising
The fifth and final session of negotiations on the establishment of an international mercury convention—International Negotiating Committee on Mercury (INC5)—is taking place this coming week in Geneva. The session is expected to culminate in the adoption of a new convention by the 147 states attending the session to reduce mercury emissions and releases to the air, water and land.
Mercury (Hg)—the only metal that is liquid at standard conditions for temperature and pressure—is very volatile and highly toxic to humans and animals when inhaled or ingested. The United Nations Environment Programme (UNEP) estimates that 1,960 tonnes of mercury arising from human activities are currently emitted annually into the atmosphere, generated mainly by artisanal and small-scale gold mining (ASGM)—the largest single anthropogenic source globally—and coal- or lignite-fired power plants. This heavy metal is persistent and is dispersed throughout the world by atmospheric transport. Apart from contaminated sites, the mercury pollution detected today is often found in locations very far away from its original source.
INC5 comes several days after UNEP released a new assessment showing that communities in developing countries are facing increasing health and environmental risks linked to exposure to mercury.
UNEP produced its first Global Mercury Assessment in 2002 and a subsequent study in 2007. The 2013 assessment is the most comprehensive to date, and includes information on the release and impacts of mercury in aquatic environments for the first time. Key findings of the report include:
Total anthropogenic emissions of mercury to the atmosphere in 2010 are estimated at 1,960 tonnes. Despite recent progress in improving the available knowledge base, the report notes, the emissions estimate still has large associated uncertainties, giving a range of 1,010-4,070 tonnes. The work also identifies potentially important sectors that are not yet quantified, including use of mercury in vinyl-chloride monomer production; secondary metals production and ferro-alloys; oil and gas extraction and transport; and industrial and some hazardous waste incineration.
Present day anthropogenic emissions contribute to both current and future emissions to the air. Current anthropogenic sources are responsible for about 30% of annual emissions of mercury to air. Another 10% comes from natural geological sources, and the rest (60%) is from ‘re-emissions’ of previously released mercury that has built up over decades and centuries in surface soils and oceans. Although the original source of this re-emitted mercury cannot be determined with certainty, the fact that anthropogenic emissions have been larger than natural emissions since the start of the industrial age about 200 years ago implies that most re-emitted mercury was originally from anthropogenic sources, the report says. Reducing current anthropogenic sources is therefore vital to reduce the amount of mercury that is cycling in the environment.
Artisanal and small-scale gold mining and coal burning are the major sources of anthropogenic mercury emissions to air. The 2013 assessment inventory confirms the role of artisanal and small-scale gold mining (ASGM) and coal burning as the largest sources of anthropogenic emissions, followed by the production of ferrous and non-ferrous metals, and cement production.
ASGM mercury emissions are estimated at 727 tonnes, making this the largest sector accounting for more than 35% of total anthropogenic emissions. This is more than twice the figure from this sector in 2005, however, most of the increase is attributed to some new and better information. For example, West Africa was thought in 2005 to have minimal ASGM activity but is now recognized as an important source region. It is thus difficult to determine whether actual emissions from this sector have changed because their estimation involves a great deal of uncertainty. Much of the activity is unregulated or even illegal, and thus reliable official data are still hard to obtain, according to the report.
Coal burning emitted some 475 tonnes of mercury in 2010, the majority of which is from power generation and industrial use. The estimate of emissions from other coal burning (including domestic and residential burning) is lower than that reported in the previous global assessment, due to differences in estimates of the amounts and mercury content of coal burned in these uses.
(These global percentages will, of course, vary on a regional basis. The US Environmental Protection Agency (EPA), for example, notes that coal-burning power plants are the largest human-caused source of mercury emissions to the air in the United States, accounting for more 50% of all US domestic human-caused mercury emissions.)
Use of coal for power generation and industry is increasing, especially in Asia. However, wider use of air pollution controls and more stringent regulations in several countries, together with improved combustion efficiency, have reduced emissions from coal-burning power plants, helping to offset most of the increase arising from higher coal consumption, the report found.
Other highlighted sources of mercury include: consumer products such as electronic devices, switches, batteries, energy-efficient light bulbs and cosmetics such as skin-lightening creams and mascara; around 340 tonnes of mercury are used annually to make fillings and other dental products, of which up to 100 tonnes are likely to enter the waste stream; plastic production, particularly the manufacture of poly vinyl chloride (PVC; chlor-alkali industry (production of chlorine and caustic soda from salt); and primary mining—although the practice is now limited to a handful of countries with only one (Kyrgyzstan) still exporting.
Global anthropogenic mercury emissions from industrial sources may be rising. Emissions to air are thought to have peaked in the 1970s, declined over the following two decades, and have been relatively stable between 1990 and 2005, despite some indications of slight increases in emissions between 2000 and 2005.
A preliminary re-calculation, using the improved methodology, of global anthropogenic emissions in 2005 indicates that emissions from fossil fuel combustion, metal and cement production increased between 2005 and 2010, but continue to decline in other sectors such as the chlor-alkali industry. Overall, indications are that emissions from industrial sectors have increased again since 2005.
Comparing emissions estimates reported under different reporting systems is not straightforward. The 2010 global inventory results were generally consistent with nationally reported emissions estimates for 2010, providing a degree of confidence in the methods used. However, comparing estimates for individual countries and sectors is complicated by differences in reporting methods, in particular the specification and categorization of sectors used in different national and international reporting systems.
Asia contributes almost half of global anthropogenic mercury emissions. Increasing industrialization has made Asia the main source region of mercury emissions to air, with East and Southeast Asia accounting for about 40% of the global total, and South Asia for a further 8%.
The new data on ASGM and the related increase in emission estimates from this sector have increased South America and sub-Saharan Africa’s share of global emissions. However, modeling results continue to indicate that East Asia is the dominant source region for long-range airborne mercury transport worldwide.
Anthropogenic releases of mercury to water total 1000 tonnes at a minimum. Previous UNEP global mercury assessments considered only atmospheric emissions. Three types of sources of aquatic releases were considered. Point sources are industrial sites such as power plants or factories, and they release an estimated 185 tonnes of mercury per year. Contaminated sites, including old mines, landfills, and waste disposal locations, release 8 - 33 tonnes per year. Artisanal and small-scale gold mining was evaluated separately, with total releases to water and land totaling more than 800 tonnes per year.
Deforestation mobilizes another 260 tonnes of mercury into rivers and lakes. Other sources remain to be quantified, and so these estimates comprise only a partial total. Thus, anthropogenic releases to waters are likely to be at least 1000 tonnes per year.
Mercury concentrations in the oceans and in marine animals have risen due to anthropogenic emissions. Anthropogenic emissions and releases have doubled the amount of mercury in the top 100 meters of the world’s oceans in the last 100 years. Concentrations in deeper waters have increased by only 10-25%, because of the slow transfer of mercury from surface waters into the deep oceans.
In some species of Arctic marine animals, mercury content has increased by 12 times on average since the pre-industrial period. This increase implies that, on average, over 90% of the mercury in these marine animals today comes from anthropogenic sources.
Monitoring capability continues to improve, but whether this can be sustained is uncertain. Existing mercury monitoring networks such as the European Monitoring and Evaluation Programme (EMEP), the Arctic Monitoring and Assessment Programme (AMAP), the North American Mercury Deposition Network (NAMDN), and others in the northern hemisphere have been complemented by new monitoring sites in the southern hemisphere, in particular, some sites established under the Global Mercury Observing System (GMOS) initiative. The longer-term status of many of the newly established sites however depends on availability of sustained funding to continue operations.
Anthropogenic emissions and releases over time have increased mercury loads in the environment, so the effects of reductions in emissions will often take time to become apparent.
Large amounts of mainly inorganic mercury have accumulated in the environment, in particular in surface soils and in the oceans, as a result of past emissions and releases. Owing to their larger volumes, intermediate and deep ocean waters below 100 metres actually store much larger tonnages of anthropogenic mercury than surface waters. There are also relatively large tonnages of natural mercury circulating in the intermediate and deep waters. A significant fraction of the mercury in intermediate waters is recycled back to the surface each year by upwellings.
Today’s anthropogenic emissions continue to load the oceans, and the catchments and sediments of lakes and rivers, with inorganic mercury. This mercury, which is the “feed-stock” for toxic methylmercury production, is stored and re-cycled in the bioavailable part of the environment for decades or centuries before it eventually is removed by natural processes. One consequence is that there will likely be a time-lag of years or decades, depending on the part of the water column, before emissions reductions begin to have a demonstrable effect on mercury levels throughout the environment and in the fish and marine mammals which are part of the human food-chain.
At the same time, mercury levels in parts of the Atlantic Ocean are decreasing, likely due to reduced emissions in past decades in North America and Europe, indicating that emissions reductions can eventually lead to decreases in mercury levels in surface oceans.
Global climate change may also complicate the response of global ecosystems to mercury emission reductions, through its profound effects on many aspects of the movement and chemical transformations of mercury in the environment. For example, warmer temperatures may increase rates of organic productivity in freshwater and marine ecosystems, and rates of bacterial activity, possibly leading to faster conversion of inorganic mercury to methylmercury. Thawing of the enormous areas of northern frozen peatlands may release globally-significant amounts of long-stored mercury and organic matter into Arctic lakes, rivers and ocean.—Global Mercury Assessment 2013
Along with a parallel UNEP publication Mercury: Time to Act, the new assessment will be formally presented at INC5.
Mercury, which exists in various forms, remains a major global, regional and national challenge in terms of threats to human health and the environment. In 2009 at the UNEP Governing Council, nations agreed to launch negotiations for a legally binding treaty aimed at bringing down releases from sources such as industry and mining, address mercury-containing products, and tackle historical pollution sites-the final negotiations begin in just a few days' time.
Mercury has been known as a toxin and a hazard for centuries-but today we have many of the alternative technologies and processes needed to reduce the risks for tens of millions of people, including pregnant mothers and their babies. A good outcome can also assist in a more sustainable future for generations to come.—United Nations Under-Secretary-General and UNEP Executive Director Achim Steiner
The agreement. The draft convention regulates in particular:
the supply of and trade in mercury;
the use of mercury in products and industrial processes;
the measures to be taken to reduce emissions from artisanal and small-scale gold mining;
the measures to be taken to reduce emissions from power plants and metals production facilities;
the storage and treatment of waste containing mercury and the management of contaminated sites;
financial and technical support for the implementation of the convention; and
the resolution of disputes.