Millions of computers and cellphones, often containing hazardous toxic material, are being shipped to massive scrap heaps in southern China, where impoverished workers are risking their health by dismantling the waste with crude hand tools in a hunt for valuable metals such as copper, gold, iron and nickel.

Thousands of Chinese workers have been dismantling electronic trash with chisels and cutting torches since the 1980s, and the presence of Canadian waste in the Chinese dump sites has been documented since 2001. But despite a Chinese prohibition, Canadian electronic garbage is still appearing in the Chinese dumping grounds.

Five years ago, China banned the importing of electronic waste. Yet the ban is openly flouted. Environmentalists have found vast scrap heaps and dismantling centres continuing to operate freely near the southern cities of Guiyu and Taizhou, where the landscape is described as "apocalyptic."

Acid baths, commonly used to separate precious metals from circuit boards, are leaching into nearby streams. Ecologists who tested the streams have found levels of acid strong enough to disintegrate a coin within a few hours.

Medical studies have reportedly found that 82 per cent of Guiyu children have unsafe levels of lead in their blood. Another study found a high rate of skin damage, headaches, nausea, ulcers and health problems among the workers who dismantle the electronic waste.

One environmental group, Greenpeace, has provided evidence of the continuing Canadian connection to the waste exports. In a photograph given to The Globe and Mail by the group, an Industry Canada label, complete with Canadian flag and serial number, is clearly visible on a piece of electronic waste in a dump at Guiyu. A Greenpeace photographer in Guiyu took the photo last year.

An investigation in 2001 by another group, Basel Action Network, found Canadian labels on some of the electronic waste in Guiyu, including labels from the Department of National Defence and the Vancouver office of Air Canada.

"The problem today is as bad as it's ever been," Gordon Perks, a spokesman for the Toronto Environmental Alliance, said in an interview. "Canada's system for tracking the waste is as much of a leaky sieve as ever. The waste can vanish off the radar screen and we don't know where it goes. There is no tracking mechanism."

The federal government has shown little interest in regulating the disposal of electronic waste, he said. "The existence of these highly toxic dumping grounds in China is proof that the federal government doesn't care and the manufacturers don't care," he said.

"It's horrible. Our comfortable lifestyle in Canada is threatening to poison the health of people in foreign countries."

Sebastien Bois, a spokesman for Environment Canada, said the federal government advised Canadian industries not to send their electronic waste to China as soon as the Chinese import ban was announced.

"Canada is concerned about the increasing volume of obsolete electronic equipment and is active in seeking national solutions to ensure environmentally sound management of electronic scrap," Mr. Bois said. Several provincial governments, including Ontario's, are in the process of drafting regulations to govern the disposal of electronic waste, he noted.

The Basel Convention, which came into force in 1992, bans the export of hazardous waste to developing countries without a written agreement. But according to Environment Canada, some forms of electronic trash are not considered hazardous, even if they can become hazardous when dismantled.

The worldwide flow of electronic waste is increasing dramatically because of the booming consumption of computers, cellphones, televisions, video and audio equipment, photocopying machines, printers and other electronic devices. The average lifespan of these devices is rapidly dropping. Many computers and cellphones are considered obsolete after two years.

Up to 50 million tonnes of electronic waste is generated worldwide every year. Canada alone is producing 160,000 tonnes of electronic waste annually.

Environmentalists say China is becoming the world's "toxic trash bin." Migrant workers earn as little as $5 (U.S.) a day for their dangerous work of dismantling the electronic waste in unregulated conditions, without any safety equipment, such as masks or goggles. Throughout the dumping grounds are open fires that burn a hazardous mix of plastic and rubber.

The dismantling process often releases toxic ingredients such as lead, cadmium and mercury.

According to Greenpeace and the Basel Action Network, the electronic waste is exported to China in container ships and scrap-metal shipments. Hundreds of trucks carry the waste from the ports to the hundreds of scrap yards in places such as Taizhou.