Global study warns of mercury threat to humans and wildlife

Posted: 7 February 2003

Mercury poisoning of the planet could be significantly reduced by curbing pollution from power stations, says a new report released by the United Nations Environment Programme (UNEP).

The report, compiled by an international team of experts, says that coal-fired power stations and waste incinerators now account for around 1,500 tons or 70 per cent of new, quantified man-made mercury emissions to the atmosphere. The lion's share is now coming from developing countries with the highest emissions from Asia, at 860 tons, followed by Africa, 197 tons; Europe, 186 tons; North America, 105 tons; Australia and Oceania, 100 tons and South America, 27 tons. "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," says the report.

"There are many compelling scientific, environmental and health arguments for curbing pollution linked with energy production. The mercury report gives us another compelling reason to reduce society's dependence on carbon intensive energy supplies," said, Klaus Toepfer, Executive Director of UNEP.

Mercury is a naturally occurring metal released into the environment from rocks, soil and volcanoes. However, human activities, from gold mining to burning coal in power stations, have boosted atmospheric levels threefold since pre-industrial times, says the report.

Hot spots

Artisinal mining of gold and silver, which is happening in an increasing number of less developed nations, is another significant source of mercury pollution, releasing an estimated 400-500 tons of mercury annually to the air, soils, and waterways.

Mercury is used to extract these precious metals from ores, resulting in elevated exposures and risks for the miners and their families, as well as contamination of the local and regional environment.

The report cites studies in a gold-mining area near Mount Diwata on the island of Mindanao in the Philippines where 70 per cent of workers were found to be suffering chronic mercury intoxication. For those workers involved directly in smelting using mercury, the percentage was even higher at 85 per cent. Around one third of people not directly employed in the industry, but living in the area, also showed signs of chronic mercury intoxication including, tremors, fatigue, sensory disturbances and bluish discolouration of the gums.

Other countries where there may be hot spots as a result of an upsurge in gold mining since the 1970s include Brazil, Venezuela, Bolivia, Indonesia, Vietnam, Papua New Guinea, Ghana, Zimbabwe, Burundi, India, Mongolia and Suriname. In total some 10 million people involved in the industry could be at risk of mercury poisoning.

Once in the atmosphere, this hazardous heavy metal can travel hundreds and thousands of miles, contaminating places far away from the world's sites where the pollution was originally discharged.

Contaminated fish

Temperature can also influence releases of mercury from contaminated sediments and soils into rivers, lakes and other freshwaters, converting mercury to methylmercury, one of it's most poisonous and hazardous forms, which can build up in fish and other aquatic life forms with potentially harmful impacts on adults and infants. Numerous studies have linked brain damage in babies to mercury poisoning of their mothers as a result of eating contaminated fish.

The biggest source of human exposure is from eating fish. Low to moderate consumption is considered safe and a healthy dietary practice, but those eating higher amounts may be at risk of mercury poisoning.

Predatory fish, towards the top of the food chain, are generally more contaminated and include species such as king mackerel, pike, shark, swordfish, walleye, barracuda, large tuna, scabbard and marlin.

In some parts of the world like the Arctic, where marine mammals such as seals are a major part of the diet along with fish, the risks of mercury poisoning are even higher. The report cites studies from North Greenland, where 16 per cent of the population have blood levels exceeding a level that can be toxic to non-pregnant adults. These levels are much higher than the levels considered safe for pregnant women.

Canadian experts, contributing to the report, say that flooded lands can become an important source of mercury contamination in fish because more mercury is released and converted to the more toxic form, methylmercury. One study found that flooded land increases rates of conversion of mercury to the more toxic form 30 fold.

"The available data indicate that mercury is present all over the globe, especially in fish, in concentrations that adversely effect human beings," says the report.

Human exposure

Most people are primarily exposed to methylmercury through eating contaminated fish. However, additional mercury exposures can occur through dental amalgams and certain occupational activities. Also, personal use of skin lightening creams and soaps, mercury use for religious, cultural and ritualistic purposes, use in some traditional medicines, use of vaccines and some other pharmaceuticals containing mercury preservatives (such as Thimerosal/Thiomersal) and mercury in the home and working environment can contribute to elevated exposures.

A study of women in the United States has found that about 1 in 12, or just under five million have mercury levels in their bodies above the level considered safe by the United States Environmental Protection Agency.

Just three years ago, the United States Research Council estimated that about 60,000 babies born each year in the US could be at risk of brain damage with possible impacts ranging from learning difficulties to impaired nervous systems. However, based on more recent exposure data published by the US Centers for Disease Control and Prevention, some scientists think the number of at risk babies could be as high as 300,000. Globally the number could run into the millions.

Side effects

Effects on the brain from the build up of mercury in humans can include irritability, tremors, disturbances to vision, memory loss, impaired co-ordination and other adverse effects. Fetuses, the newborn and young children are particularly vulnerable because of the sensitivity of the developing nervous system.

The report also cites some recent scientific evidence linking mercury exposure to cardiovascular problems including raised blood pressure, palpitations and heart disease. Other effects have been found on the thyroid gland, which regulates growth, the digestive system, the liver and the skin including peeling on hands and feet, itching and rashes.

Animals such as otter, mink, osprey, eagles, seals and some whales that rely on fish as a large part of their diet, have the highest mercury levels and may also be at risk. The eggs of certain Canadian birds, such as Leach's Storm Petrel, Atlantic Puffin and Northern Fulmars, have mercury levels that threaten reproduction, the report says.

Environmental factors

Acid rain, again often the result of power station pollution, may be aggravating the problem. High levels of acidity in rivers, lakes and streams, also appears to trigger releases of mercury from soils and sediments and its conversion into methylmercury.

The findings may explain why so many fish in parts of the world where acid rain has been an issue are contaminated. For example in southern and central Finland, an estimated 85 per cent of pike weighing a kilo or more, have methylmercury concentrations that exceed international health limits.

Other important sources of mercury releases include cement production, chlor-alkali production, crematories, manufacture of electrical switches, thermometers, fluorescent lamps, dental amalgams and rubbish tips containing wastes such as old batteries and other mercury-containing products.

Slash and burn agriculture and the clearing of forests may be increasing releases of mercury to rivers. Meanwhile, mercury contamination in parts of Europe may be affecting the tiny organisms that regulate the fertility of soils, says the study.

This may also be having an indirect effect on climate change as soil micro-organisms play a key role in the storage of carbon from the atmosphere.

Reducing risks

The report offers goverments a list of options for addressing the dangers of mercury. These include reducing risks by reducing or eliminating the production, use and release of mercury; substituting other non-mercury based products and processes; launching talks for a legally-binding treaty; establishing a non-binding global programme of action; and strengthening co-operation amongst governments on information-sharing, risk communication, assessment and related activities.

They also recommend around a dozen "immediate actions" including public awareness programmes targeted at sensitive populations such as pregnant women; waste disposal facilities for the safe destruction of obsolete, mercury-containing pesticides and pollution control technologies for power stations.

Source: UNEP

Related links:

UNEP Global Mercury Assessment Report

UNEP Global Mercury Assessment Programme

Mercury danger in fish, warns study