Fear sparked by global recession, strains on banks and volatile paper currencies have brought the glitter back to gold. Its value has been rising rapidly in recent months, as investors seek a safe haven from the economic and financial storm. But gold's resurgence has strengthened demand for its long-time associate, mercury, a toxic heavy metal widely used in Asia, Africa and Latin America by millions of small-scale gold miners.
The United Nations Environment Programme (UNEP) estimates that about 6,000 tonnes of mercury are released each year into the air, land, rivers, lakes and seas, creating a global pollution danger. The liquid metal damages the human nervous system, and impairs the functioning of the liver and thyroid glands. It also causes memory loss and disturbed vision.
Of the 6,000 tonnes, about one-third comes from burning coal to generate electricity, power industries and heat homes. Increased coal use in Asia, especially in China, India and Indonesia, means that mercury emissions are rising in the region. Gold mining is the second-biggest source of mercury releases.
When mercury is belched into the air from power plants, smelters and incinerators, it returns to earth via rain, with bacteria and other natural processes converting it to organic methylmercury in lakes, rivers and oceans. Released into river systems that flow into the sea, the poison is widely dispersed through the world's oceans.
Scientists say that, as global warming melts the Arctic, mercury trapped in ice and sediments is being released back into the oceans. It builds up through the food chain as bigger creatures consume smaller ones, with the flesh of the biggest fish - among them tuna, swordfish, king mackerel and sharks - containing the highest mercury concentrations.
In the US, just under 5 million women, or one in 12 of the female population, have mercury in their bodies above the level considered safe by the US Environmental Protection Agency. The US and other governments have advised pregnant women, children and other groups considered vulnerable to mercury poisoning to limit fish consumption.
To tackle the mercury scourge, more than 140 nations meeting at the UNEP headquarters in Nairobi agreed last month to negotiate a binding global treaty to tighten controls on its use. The accord, backed by China, India and many Asian countries, came after the Obama administration announced it had reversed the US stance on the issue and was now in favour of a ban on mercury. The European Union has called for the ban to start by 2011. However, reaching agreement on the details of the treaty and then implementing it effectively will be difficult and might take years. It will involve finding cost-effective substitutes for mercury in products like thermometers, high-intensity lamps and liquid crystal displays, and in processes such as paper making and plastics production.