Human exposure occurs primarily through eating contaminated fish and shellfish...
The increasingly global nature of the problem is rendering local solutions inadequate…
- fish and shellfish are an important part of a healthy diet. Fish and shellfish contain high-quality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids. A well-balanced diet that includes a variety of fish and shellfish can contribute to heart health and children's proper growth and development;
- however, nearly all fish and shellfish contain traces of mercury. For most people, the risk from mercury by eating fish and shellfish is not a health concern. Yet, some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child's developing nervous system;
- elemental mercury and mercury salts, although fairly inert when deposited on the bottom of waterways, are converted into organic mercury, typically methyl-mercury, by micro-organisms. This compound then enters the food chain where it is biomagnified up to 100,000 times in predacious fish. Consumption of toxic fish and of game birds and mammals that feed on fish is the main risk to humans;
- the dangers of mercury toxicity, as with other heavy metals, has been known for some time, but it is only in recent years that the extent of the problem, and the sources of the health risk associated with these toxicities, especially mercury toxicity have become apparent. It has become so prevalent that it could be seen as a major public health concern;
- Minamata disease was named after the occurrence, in the 1950s and 1960s in Minamata, Japan, of many cases of severe mercury poisoning. It was found that a chemicals factory was discharging mercury-containing wastes into the local waters, contaminating fish that residents caught for food. More than 3,000 victims have been recognized as having ‘Minimata Disease’, meaning their life has been damaged beyond recovery by mercury poisoning;
- in the United States, EPA estimates that 8% of women of childbearing age have high mercury blood levels. A National Academy of Sciences study in 2000 estimated that 60,000 US infants a year face increased risk of brain damage because their pregnant mothers had elevated mercury levels. The number of US states that have issued mercury advisories has risen steadily from 27 in 1993 to 44 in 2002; (1)
- 17 states have issued mercury advisories for fish in every inland water body. Across the US, mercury pollution has contaminated 10.2 million acres of lakes, estuaries and wetlands (25% of the national total) and 415,000 miles of streams, rivers and coasts (12% of the national total); (1)
- an increasing amount of mercury is brought to the Arctic through pollution from all over the world. Health tests among the indigenous peoples of the northern areas (such as Greenland and Canada) already show damage caused by mercury. Children in groups, which consume large amounts of seal and whale have high blood pressure and difficulty achieving motor skills. According to the Norwegian Institute for Air Research (NILU), the mercury follows the air currents towards the north from practically all over the world, among other places from Asia, where this heavy metal comes from coal fired power stations.
- UNEP’s “Global Mercury Assessment” states that mercury is now found all over the world at levels that adversely affect humans and wildlife. UNEP estimates that anthropogenic uses account for 70% of the 5,500 tons of mercury released into the earth’s atmosphere worldwide, mainly from coal-fired power stations, waste incinerators, and as a result of artisanal mining of gold and silver; (2)
- China is already believed to be the world's largest source of non-natural emissions of mercury. Largely because of its coal-fired power plants (more than 2,000). China spews 600 tons of mercury into the air each year, accounting for nearly 1/4 of the world's non-natural emissions. And it is going to get worse. By 2020, China will have nearly 1,000 gigawatts of total electricity-generating capacity, more than twice the current amount, according to the State Power Economic Research Center. The majority of new plants will burn coal;
- in the US and Europe, releases from chlorine plants may even approach those from power plants, the presumed greatest source of mercury releases to air. The chlorine industry's reported figures for mercury releases to air are based in part on monitored stack emissions, but they also include the industry's estimates of the amount of mercury that evaporates during routine operations and escapes through unmonitored ventilation systems and other leaks - so-called ‘fugitive emissions’;
- the United States emit annually about 150 tons of mercury into the air in from manmade sources. Some scientists now say 30% or more of the mercury settling into US ground soil and waterways comes from other countries – in particular, China;
- polluted air means also more polluted water: the depth-averaged environmental concentration of mercury in the entire global ocean increased by approximately 9% between pre-industrial periods and the modern, industrial era, whereas concentrations in near-surface waters are thought to have increased 2 to 3-fold (dangerously affecting - as mentioned above - the food chain);
- the UNEP report also shows mercury levels in fish exceeding a risk-based threshold (based upon Japan's and US recommendations) in quite a few developing countries, including Cote d'Ivoire, Ghana, India, Mauritius, Philippines, Slovak Republic, and Thailand as well as Japan, Korea, Sweden.
(1) US EPA, 2002. Update: National Listing of Fish and Wildlife Advisories. EPA-823-F-02-007, May.
(2) UNEP Chemicals, “Global Mercury Assessment”, Geneva, Switzerland, December 2002 [ www.unep.org/GC/GC22/Document/UNEP-GC22-INF3.pdf]