Basel Action Network, a US-based lobby group that recently conducted an investigation in Africa's most populous country, found that around 500 giant containers, packed with old computers, televisions and mobile phones, were arriving every month at the main city and port, Lagos.

These electronics are supposed to be for repair and re-use, but BAN estimates that 75 percent of the items are neither repairable nor of any economic value.

So they often end up being dumped at official landfill sites or offloaded illegally by the side of the road or in swamps where they are either burnt or simply left.

BAN says chemicals like lead can leak into the groundwater. And materials used in circuit boards, although safe when the computer is on a desk, can produce carcinogenic particles once set alight.

"Residents breathing in the fumes from the fires or drawing water from contaminated areas are going to be taking in some seriously dangerous substances," Jim Puckett, the BAN official who led the investigation, told IRIN by phone from the group's headquarters in Seattle.

"Re-use is a good thing, bridging the digital divide is a good thing, but exporting loads of techno-trash in the name of these lofty ideals and seriously damaging the environment and health of poor communities in developing countries is criminal," he said.

The organisation traces most of the items back to the United States and Europe, and says the export of useless electronic equipment is illegal under the Basel Convention governing the international movement of toxic waste.

Washington has not ratified the treaty, and BAN says many other governments fail to enforce the laws by not certifying that electronic items are fit for re-use before they are shipped abroad.

When repairable products do arrive among the sea of junk, researchers noted that Lagos does have a legitimate and healthy market for restoring old electronic equipment.

Oludayo Dada of the pollution control unit at the Environment Ministry, says that the flow of electronic waste arriving on Nigerian shores has caught the authorities' attention.

"We are still trying to quantify the magnitude of the electronic waste we have in Nigeria and the components that are toxic," Dada told IRIN, adding that the government would need to update its laws to criminalise the import of such products.

"We have regulations covering toxic products in general, but we need to zero in on electronic waste," Dada said.

BAN says another solution is for manufacturers to stop using toxic chemicals in their products, such as brominated flame retardants, beryllium alloys, lead-based solders and mercury lamps.

"Things are completely out of control," said activist Puckett. "It's time we all get serious about what is now a tsunami of toxic techno-trash making its way from rich to poorer countries."