NAIROBI: Communities in developing countries are facing increased health and environmental risks linked to mercury exposure, the United Nations Environment Programme said Thursday.

"Mercury ... remains a major global, regional and national challenge in terms of threats to human health and the environment," said UNEP head Achim Steiner.

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

Such exposure "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," UNEP said.

The announcement comes ahead of a major conference on mercury to be held in Geneva next week and that aims to conclude discussions on a global treaty to minimise risks from mercury exposure.

New reports by UNEP, which will be made public at the Geneva conference, say emissions of mercury from artisanal mining alone have doubled since 2005, due in part to better reporting and rising gold prices.

Steiner said Thursday that a study by the Blacksmith Institute, a New York-based group that cleans up polluted sites, shows that a device costing less than $10 can be used to trap 90% or more of the mercury used in gold mining.

The main barriers to the use of such safer methods are socio-economic conditions and low awareness of the risks attached to mercury, a UNEP statement said.

UNEP's new studies provide the first global assessment of releases of mercury into rivers and lakes.

"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%," the agency said, adding that much human exposure to mercury is through the consumption of contaminated fish.

Serious mercury poisoning affects the body's immune system and can lead to problems including psychological disorders, loss of teeth and problems with the digestive, cardiovascular and respiratory tracts.

The reports also highlight rising levels of mercury in the Arctic, where 200 tonnes of the substance are deposited every year.

"Due to rapid industrialisation Asia is the largest regional emitter of mercury, and accounts for just under half of all global releases," the UNEP statement said.

The studies also highlight significant releases into the environment linked to contaminated sites and deforestation. The findings show that an estimated 260 tonnes of mercury -- previously held in soils -- are being released into rivers and lakes.

The International Negotiating Committee on Mercury will be held from January 13-18 in Geneva.