Mountains of discarded computers and mobile phones could soon pose serious threats to public health and the environment in developing countries without swift action, the UN said Monday.

"Sales of electronic products in countries like China and India and across continents such as Africa and Latin America are set to rise sharply in the next 10 years," the UN Environment Programme (UNEP) said in a report.

"And unless action is stepped up to properly collect and recycle materials, many developing countries face the spectre of hazardous e-waste mountains with serious consequences for the environment and public health."

The report entitled "Recycling -- from E-Waste to Resources" was released at a meeting of Basel Convention and other world chemical authorities prior to UNEP's Governing Council meeting in Bali, Indonesia.

It used data from 11 developing countries to estimate current and future e-waste generation such as desk and laptop computers, printers, mobile phones, pagers, digital photo and music devices, refrigerators, toys and televisions.

By 2020 e-waste from old computers in South Africa and China will have jumped by 200 to 400 percent from 2007 levels, and by 500 percent in India, it said.

Waste from discarded mobile phones would be seven times higher in China and 18 times higher in India by the same year.

"This report gives new urgency to establishing ambitious, formal and regulated processes for collecting and managing e-waste via the setting up of large, efficient facilities in China," UNEP executive director Achim Steiner said in a statement.

"China is not alone in facing a serious challenge. India, Brazil, Mexico and others may also face rising environmental damage and health problems if e-waste recycling is left to the vagaries of the informal sector."

He said raising e-waste recycling rates in developing countries could also "generate decent employment, cut greenhouse gas emissions and recover a wide range of valuable metals including silver, gold, palladium, copper and indium".

"By acting now and planning forward many countries can turn an e-challenge into an e-opportunity," he added.

China already produces an estimated 2.3 million tonnes of e-waste, second only to the United States with about three million tonnes, the report said.

It is also a major e-waste dumping ground for developed countries despite having banned such imports.

Much of this rubbish is incinerated by backyard recyclers to recover tiny quantities of metals such as gold, releasing toxic fumes.

The report also found:

-- global e-waste generation is growing by about 40 million tonnes a year

-- manufacturing mobile phones and personal computers consumes three percent of the gold and silver mined worldwide each year; 13 percent of the palladium and 15 percent of cobalt

-- more than a billion mobile phones were sold around the world in 2007, up from 896 million in 2006

The report, written jointly with the United Nations University, recommended various ways to transform e-waste into assets.

"One person's waste can be another's raw material," university rector Konrad Osterwalder said.

"The challenge of dealing with e-waste represents an important step in the transition to a green economy."

The report was issued at the Simultaneous Extraordinary Meetings of the Conferences of the Parties to the Basel, Rotterdam and Stockholm Conventions.