It’s a fascinating substance – a metal that’s liquid – and mercury’s effects on the human nervous system have been known for more than 100 years: hat-makers, like the Mad Hatter in Lewis Carroll’s Alice in Wonderland, were affected as they breathed in poisonous fumes from mercury used to strengthen brims. Today, mercury is commonly used in small-scale goldmining, and an estimated 10 million miners and their families – from Brazil and Venezuela to India, Indonesia, Papua New Guinea and Zimbabwe – may be suffering from related problems, including impaired thyroid and liver function, irritability, tremors, disturbances to vision, memory loss and perhaps cardiovascular problems.
Around 6,000 tonnes of mercury enter the environment each year, some 2,000 tonnes from power stations and coal fires in homes. Once in the atmosphere or absorbed in water, mercury can travel thousands of kilometres and continues to circulate in the environment for many years. In Sweden, for example, around 50,000 lakes have pike with mercury levels exceeding international health limits, while one study in the USA has found that almost 5 million women – that’s about 1 in 12 – have more mercury in their systems than is considered safe.
Governments have recognized the threats mercury poses and have taken action on a voluntary basis. Following an assessment of the concerns, it was agreed in 2009 that a global legally binding agreement was needed. Spearheaded by UNEP, the Minamata Convention on Mercury will be open for signature in October 2013.