Most Americans think they’re helping the earth when they recycle their old computers, televisions and cell phones. But chances are they’re contributing to a global trade in electronic trash that endangers workers and pollutes the environment overseas.

While there are no precise figures, activists estimate that 50 percent to 80 percent of the 300,000 to 400,000 tons of electronics collected for recycling in the U.S. each year ends up overseas. Workers in countries such as China, India and Nigeria then use hammers, gas burners and their bare hands to extract metals, glass and other recyclables, exposing themselves and the environment to a cocktail of toxic chemicals.

“It is being recycled, but it’s being recycled in the most horrific way you can imagine,” said Jim Puckett of the Basel Action Network, a Seattle-based environmental group. “We’re preserving our own environment, but contaminating the rest of the world.”

The gear most likely to be shipped abroad is collected at free recycling drives, often held each April around Earth Day, recycling industry officials say. The sponsors – chiefly companies, schools, cities and counties – often hire the cheapest firms and do not ask enough questions about what becomes of the discarded equipment, experts say.

Many so-called recyclers simply sell the working units and components, then give or sell the remaining scrap to export brokers.

The problem could get worse. Most of the 2 million tons of old electronics discarded annually by Americans goes to U.S. landfills, according to U.S. Environmental Protection Agency data. But a growing number of states are banning such waste from landfills, which could drive more waste into the recycling stream and fuel exports, activists say.

Safety rules drive up the cost of disposal, and it’s as much as 10 times cheaper to export the waste to developing countries.

Experts estimate that about 70 percent of the 20 million to 50 million tons of electronic waste produced globally each year is dumped in China, with most of the rest going to India and poor African nations. Upward of 90 percent of electronic waste ends up in dumps that observe no environmental standards.