Measures to reduce the millions of tons of electronic waste generated each year by manufactures of computers, mobile phones and other consumer electronic products will be the focus of a United Nations-sponsored conference in the capital of Kenya.

Delegates from about 120 governments gathered in Nairobi on Monday to begin week-long talks on how to reduce the use of toxic substances, such as lead, cadmium and mercury, found in PCs and cell phones, and to promote programs for recycling and re-using as many components as possible.

The U.N. estimates that up to 50 million metric tons of "e-waste" are generated worldwide every year, representing more than 5 percent of all municipal solid waste. In the U.S. alone, as many as 20 million PCs are thrown out every year.

A good chunk of that waste ends up in Africa and other developing countries, according to the U.N.

Every month, more than 100,000 disregarded computers are entering the Nigerian port of Lagos alone, said U.N. Under-Secretary General Achim Steiner in a speech.

Local experts estimate that up to 75 percent of the used PCs, TVs and phones sent from developed countries are unusable and end up in the landfills of developing countries, where the items are often burned, releasing toxic fumes and leaching chemicals.

On the table at this week's meeting are proposals to encourage manufacturers to take more responsibility for their products, from the design stage through the supply chain to final disposal.

In a speech, Sachiko Kuwabara-Yamamoto, executive secretary of the Basel Convention, which monitors hazardous waste, pointed to a partnership with several mobile phone manufacturers and operators, including Nokia, Sony Ericsson Mobile Communications and Vodafone Group to develop programs for recycling and re-using the millions of mobile phones now sold worldwide every year.