Some of them were donated by people who thought they were helping satisfy the rapidly growing appetite for modern technology in a developing country where few can afford it. And some of them came from individuals or organizations that simply wanted to get rid of their obsolete equipment at the lowest cost.

Only a portion of the used electronic equipment that Nigeria imports can be repaired and resold. The rest is dumped and often burned.

Either way, at least half of the used equipment that arrives in Lagos by the ton is unusable and ends up in landfills, a Seattle-based nonprofit discovered recently after sending a team to survey the situation. The Basel Action Network (BAN) found that much of the junked equipment is adding to the considerable hazardous waste problems of a country that lacks facilities to properly handle it.

"There's an amazing expertise in repair, but so much of what's coming in is worthless that it is just dumped," said BAN's executive director, Jim Puckett. Photos taken by the group show enormous piles of junked electronics in wetlands, along roadsides, and burning in uncontained landfills that are routinely set ablaze to reduce bulk. These open dumps are often in cities and in residential neighborhoods. The pictures show children wandering near smoldering piles of computer and television parts.

The United Nations Environment Program estimates that 20 million to 50 million tons of electronics are discarded each year. Less than 10 percent of the discards get recycled, and half or more end up overseas, much exported for inexpensive, often unsafe and environmentally unsound recycling, primarily in China and India.

What is different about the exports to Africa, said Puckett, is that unusable equipment sent under the guise of recycling is also being trashed.

"We saw some kids taking copper off equipment in the dumps, and we were told some people were collecting circuit boards, but we saw no organized materials recovery at all," he said. Most major electronics manufacturers have take-back and recycling programs, but those efforts have yet to extend in a meaningful way to developing markets such as Nigeria, which has no electronics-recycling facilities.

Intact computer equipment is not hazardous, but when computer and television screens, circuit boards, batteries, and other high-tech electronics are broken up or burned or degrade, they release toxic materials that include lead, cadmium, barium, mercury and chromium. Plastic components contain brominated flame retardants that accumulate in human blood and fat tissue and can disrupt the body's hormonal balance. When burned, some of these plastics release dioxins and furans, persistent pollutants linked to a host of health problems, including cancer.

Reuse advocates such as Jim Lynch of San Francisco-based CompuMentor, which provides technology assistance to nonprofits, believe that extending the life of a computer by putting it into the reuse market is an environmentally sound solution. But many of the electronics that BAN members saw in and around the Ikeja "Computer Village" in Lagos were shipped by what Puckett called "waste cowboys acting as e-scrap brokers." Both said there are legitimate nonprofits that arrange donations of tested, working equipment to qualifying recipients, but much of the unusable equipment dumped in Lagos comes in with the large lots of used electronics imported as commercial resale.

"I call it environmental doom for the developing country and economic boom for the unscrupulous traders," said Oladele Osibanjo of the University of Ibadan, who was interviewed for BAN's recently released report, "The Digital Dump."

Most of the equipment sold for reuse by the thousands of electronics dealers in the Ikeja Computer Village, which has been dubbed the Silicon Valley of Lagos, comes from abroad, from the United States, Europe, Asia and the Middle East.

Among the computers BAN saw for sale and stockpiled were many that originally belonged to government agencies, businesses, schools and hospitals in the United States, Europe, Japan and Israel, all bearing original identification tags.

The United States, unlike the European Union and Japan, has no government-mandated system for recycling used electronics -- and no regulations to prevent the export of high-tech equipment for environmentally unsound recycling.

The United States also remains the only developed country that has not ratified the Basel Convention, a treaty designed to control international trade in hazardous waste. "This makes the U.S. a haven for a renegade scrap trade," Lynch said.

"It's a shadowy industry, and there's a lot more scrap than working computers," said Robert Houghton, president of Redemtech Inc. in Columbus, Ohio, which handles electronics recycling for Fortune 500 companies.

U.S. regulations allow export of used electronics and parts destined for reuse or recycling, but "unfortunately our government does nothing to distinguish between true reuse and the abuse of dumping on our global neighbors," Puckett said.

"It's extremely difficult to peel back the onion far enough to find out where the equipment goes. It may change hands two, three or four times before it leaves the country," Houghton said.

The lack of tracking of disposed material also raises data security issues. The Basel group purchased disk drives in Ikeja's Computer Village and had them analyzed by the Swiss firm NetMon. Among those that were readable were hard drives that belonged to the Wisconsin Department of Health and Family Services and the World Bank.

Typically, U.S. government agencies dispose of used electronics through surplus property offices. Equipment that cannot be used by other agencies and is not part of a donation program is sold at public auctions, most now conducted online.

Some buyers want the equipment for personal or small-business use, but much is bought by brokers or auctioneers who resell for reuse, parts or scrap value.

The General Services Administration, which handles these sales for the federal government, has a record of its buyers but does not follow up.

Many local governments and private businesses use private electronics recyclers, numbering in the hundreds. Numerous surplus property managers interviewed said they did not know what the recyclers did with the equipment; a number of recyclers declined to say or were vague about where they send the electronics they collect for processing or resale.

"Africa needs its own local industry, to be able to evolve its own local computers, to meet its own local need," Shina Badaru, editor of Nigeria's Technology Times, told BAN. "Africa does not need the used equipment coming in from the north to pose long-term threats to our environment."

But until substantial changes are made in materials used in electronics and how used equipment is handled, the bridge across the digital divide will ultimately lead, Puckett said, "to a digital dump."