More than 170 countries have agreed to accelerate adoption of a global ban on the export of hazardous wastes, including old electronics, to developing countries.
The environmental group Basel Action Network called Friday's deal, which was brokered by Switzerland and Indonesia, a major breakthrough.
"I'm ecstatic," said its executive director, Jim Puckett. "I've been working on this since 1989 and it really does look like the shackles are lifted and we'll see this thing happen in my lifetime."
The deal seeks to ensure that developing countries no longer become dumping groups for toxic waste including industrial chemicals, discarded computers and mobile phones and obsolete ships laden with asbestos, he said.
Delegates at the UN environmental conference in Cartagena agreed the ban should take effect as soon as 17 more countries ratify an amendment to the so-called 1989 Basel Convention.
"This agreement was stalled for the past 15 years," Colombia's environment minister, Frank Pearl, said in praising the vote.
Katharina Kummer, the convention's executive secretary, estimated it would take five years to reach the required 68 ratifying nations. Puckett said he thought it would be closer to two years.
Fifty-one nations have already ratified the 1995 amendment, which effectively enforces the Basel Convention, a treaty aimed at making nations manage their waste at home rather than send it overseas.
The United States, the world's top exporter of electronic waste, is among nations that have not ratified the original convention.
"Unless the US joins the treaty they are just going to be a renegade," Puckett said, adding that the US had no rules for exporting electronic waste, which it sends mostly to China but also to Africa and Latin America.
The global ban has been strongly backed by African countries, China and the European Union, which already prohibits toxic exports and Puckett said Colombia played a strong role in Friday's breakthrough.
Opponents have been led by Canada, Australia, New Zealand and Japan, and recently joined by India, said Puckett.
But in Cartagena, he said, Japan's position softened from 2008, when parties to the convention held their last meeting in Bali. It ended in a stalemate.
The issue took centre stage in 2006 when hundreds of tonnes of waste were dumped around the Ivory Coast's main city of Abidjan, killing at least 10 people and sickening tens of thousands.
The waste came from a tanker chartered by the Dutch commodities trading company Trafigura Beheer BV, which had contracted with a local company to dispose of the waste.
Puckett said shipping companies had opposed inclusion in the ban, wanting to keep sending old ships to India, Pakistan and Bangladesh to scrap them.
"Just about four days ago another six people died on the beaches of Bangladesh," he said.
He told AP there were no reliable estimates on how many tonnes of toxic waste were exported annually because developed nations did not accurately report them.