GUIYU, China - When discarded computers vanish from desktops around the world, they often end up in Guiyu, which may be the electronic-waste capital of the globe.

The city is a sprawling computer slaughterhouse. Instead of offal and blood, its runoff includes toxic metals and acids. Some 60,000 laborers toil here at primitive electronic-waste recycling - if it can be called that - even as the work imperils their health.

Computer carcasses line the streets, awaiting dismemberment. Circuit boards and hard drives lie in huge mounds. At thousands of workshops, laborers shred and grind plastic casings into particles, snip cables and pry chips from circuit boards. Workers pass the boards through red-hot kilns or acid baths to dissolve lead, silver and other metals from the digital debris. The acrid smell of burning solder and melting plastic fills the air.

''I don't think this is recycling,'' said Wu Song, an environmentalist from nearby Shantou University. ''They ignore the environment.''

What occurs is more akin to scavenging. Though China bans imports of electronic waste, its factories clamor for raw materials, even those yanked from the guts of discarded computers, and ill-informed workers seek out computer-recycling jobs. So the ban is ignored, and the waste comes in torrents. Under the guise of ''recycling,'' U.S. brokers ship discarded computers and dump an environmental problem on China.

In the United States, consumers, manufacturers and retailers are only beginning to pay attention to the cost of safely ending the lives of electronics.

By next year, obsolete computers amassed in the United States will number 500 million, according to the U.S. National Safety Council.

''People just don't know what to do with them,'' said Jim Puckett, the coordinator of the Basel Action Network, a Seattle-based group that advises consumers about sustainable methods to dispose of the waste.

Hewlett-Packard of Palo Alto, Calif., committed this year to eliminate a variety of hazardous chemicals from its products and has helped lobby for state laws requiring manufacturers to take back old equipment.

Still, a lot of electronic waste from the United States continues to seep into China and West Africa, where corruption is large and smuggling rampant.

The U.S. government does not ban or monitor such exports.

What's more, the Environmental Protection Agency has no certification process for electronic-waste recyclers. Any company can claim it recycles waste, even if all it does is export it.

Guiyu (pronounced GWAY-yoo), a few hours' drive northeast of Hong Kong, is by far China's biggest electronic scrap heap. The city comprises 21 villages with 5,500 family workshops handling the waste. According to the local government Web site, city businesses process 1.5 million tons of electronic waste a year, pulling in $75 million in revenue. As much as 80 percent of it comes from overseas.

City officials are proud of the waste industry but are sensitive about its reputation as a dirty business that feeds off smuggled waste and abuses labor rights. Journalists who probe quickly find themselves detained by local thugs or police officers, and their digital photographs or video footage erased.

One recent visitor was stopped within two hours of arriving and ordered to leave.

''They don't want the media . . . to write articles about the negative aspect of the Guiyu area,'' Wu said. ''[They think] maybe the central government will punish them.''

Local bosses pay little regard to workers' health or regulations that prohibit dumping acid baths into rivers and venting toxic fumes.

In one district of Guiyu, a migrant worker stood amid piles of capacitors and small circuit boards as fellow workers with pliers tore off soldered metal parts and burned electronic components over braziers to determine their content.

''If you burn it, you can tell what kind of plastic it is,'' said the man, who gave only his surname, Wang. ''They smell different. There are many kinds of plastic, probably 60 or 70 types.''

An average computer yields $1.50 to $2 worth of commodities such as shredded plastic, copper and aluminum, according to a report in November by the U.S. Government Accountability Office, a watchdog arm of Congress.

Electronic-waste recyclers in the United States can't cover their costs with such low yields, especially while respecting environmental regulations. So they charge an average of 50 cents a pound for taking in old computers, about $20 to $28 per unit. At that price, experts say, recycling can be done safely and profitably.

But some U.S. brokers then ship the waste abroad for greater profits.

''Up to 80 percent of all obsolete electronics that gets collected ends up getting exported,'' said Ted Smith, the founder of the Silicon Valley Toxics Coalition and a director of the national Computer Take Back Campaign, which advocates safe domestic recycling of discarded electronics and directs consumers to recyclers that pledge to use environmental best practices and not to export the waste.

The flow of U.S. waste abroad ''is not diminishing,'' he said. ''If anything, it is increasing.''