Communities in developing countries are facing increasing health and environmental risks linked to exposure to mercury, according to new studies by the United Nations Environment Programme (UNEP). 

Parts of Africa, Asia and South America could see increasing emissions of mercury into the environment, due mainly to the use of the toxic element in small-scale gold mining, and through the burning of coal for electricity generation.

The Global Mercury Assessment 2013 states that emissions of the toxic metal from artisanal gold mining are significantly greater than were reported in 2008. Rising gold prices are driving greater small-mining activity, but new and improved reporting has also provided

more accurate estimates of emissions from the sector.

Due to rapid industrialization, Asia is the largest regional emitter of mercury, and accounts for just under half of all global releases.

The UNEP study assesses for the first time at a global level releases of mercury into rivers and lakes. The report says an estimated 260 tonnes of mercury - previously held in soils - are being released into rivers and lakes.

Much human exposure to mercury is through the consumption of contaminated fish, making aquatic environments the critical link to human health.

In the past 100 years, man-made emissions have caused the amount of mercury in the top 100 metres of the world's oceans to double. Concentrations in deeper waters have increased by up to 25 per cent.

The study, which provides a comprehensive breakdown of mercury emissions by region and economic sector, also highlights significant releases into the environment linked to contaminated sites and deforestation.

The report says an estimated 260 tonnes of mercury - previously held in soils - are being released into rivers and lakes through deforestation and subsequent soil erosion.

Mercury released from industry and other man-made sources can circulate in the environment for up to centuries at a time. This means that it is likely to be several years or decades before reductions in mercury emissions have a demonstrable effect on mercury levels in
nature and the food chain.

The UNEP studies say this reinforces the need for swift action by governments, industry and civil society to strengthen efforts to reduce mercury emissions and releases. Delays in action, say the reports, will lead to slower recovery of ecosystems and a greater
legacy of pollution. Rising levels of mercury present in the Arctic are also highlighted.

An estimated 200 tonnes of mercury are deposited in the Arctic each year, generally far from where it originated. Studies have shown a ten-fold increase in levels of mercury in certain Arctic wildlife species in the past 150 years, due mainly, it is thought, to human
activity. Global Trends in Mercury Emissions and their Impacts

The UNEP reports state that global emissions of mercury have remained relatively stable in the last twenty years, with 2010 emissions from human activities thought to be just under 2,000 tonnes.

Despite improved availability of data on mercury, the emissions estimate is still subject to uncertainty, and covers a range of 1010 to 4070 tonnes.

Along with coal burning, the use of mercury to separate metal from ore in small-scale gold mining remains the chief source of emissions worldwide.

Annual emissions from small-scale gold mining are estimated at 727 tonnes, or 35 per cent of the global total.

Greater exposure to mercury poses a direct threat to the health of some 10-15 million people who are directly involved in small-scale gold mining, mainly in Africa, Asia and South America. An estimated 3 million women and children work in the industry.

Mercury-free methods and other low-cost solutions for reducing emissions during gold extraction are available, but socio-economic conditions, and low awareness of the risks of mercury, are barriers to adopting safer techniques.

"Artisanal and small-scale gold mining is recognized as a major challenge in efforts to reduce emissions from mercury," said Fernando Lugris (Uruguay), Chair of the Intergovernmental Negotiating Committee.

"While taking into account the impacts on national development, we must move to set national goals and reduction targets. Other efforts should work towards the formalization of the sector, which is largely unregulated. As well as reducing health risks from mercury, this could give workers greater rights under labour laws," added Mr. Lugris.

Coal burning is responsible for some 475 tonnes of mercury emissions annually, or around 24 per cent of the global total.

Despite increased coal combustion in certain regions, more stringent regulations on pollution in several countries have contributed to reducing overall mercury emissions from coal burning and off-setting part of the emissions arising from increased industrial

Other sources of mercury highlighted in the UNEP publications include:

Metal and cement production, through fuel extraction and combustion of fossil fuels

Consumer products such as electronic devices, switches, batteries, energy-efficient light bulbs and cosmetics such as skin-lightening creams and mascara. Mercury contained in such goods can also enter the waste stream.

Dentistry: 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). PVC is in high demand in many countries where there are extensive building projects

Chlor-alkali industry (production of chlorine and caustic soda from salt)

Primary mining - although the practice is now limited to a handful of countries with only one (Kyrgyzstan) still exporting

Action on Mercury

Efforts to tackle the environmental and health threat posed by mercury have grown over recent decades, according to the reports.

Notable actions include:

The UNEP Mercury Products Partnership has set the goal of reducing demand for mercury-containing thermometers and blood pressure devices by 70 per cent by 2017

USA has finalized the Mercury and Air Toxics Standard which predicts to reduce mercury emissions by 20 tonnes by 2016

European Union banned mercury exports in 2011 and the USA has just started an export ban from 1 January 2013

UNEP has supported National Action Plans by Argentina, Uruguay and other countries to find environmentally-sound solutions for the storage and disposal of excess mercury and waste products

Yet despite such steps, coordinated action on a global level to reduce environmental and health risks posed by exposure to mercury has been comparatively slow.

The UNEP studies state that accelerated action, such as finalizing a global, legally binding treaty, promoting the availability of low-mercury technologies, and other  measures, can support a sharp decline in demand for mercury.

To achieve this, primary mining of mercury should be ceased as soon as possible, and demand met by investing in improved recycling measures.

Governments should ensure regulatory frameworks and incentives to promote the transition to viable, safe and commercial alternatives, resulting in reduced releases of mercury and other pollutants.