One of the most persistent and insidious pollution problems visited by the West on the developing world has taken a huge step towards a permanent solution this weekend.

A UN environmental conference in Cartagena, Colombia, attended by more than 170 countries, has agreed to accelerate a global ban on the export of hazardous waste, including old electronics and discarded computers and mobile phones, from developed to developing countries.

Environmental campaigners, who have been battling to broker a deal on the dumping of toxic waste for more than 20 years, said they were "ecstatic" about this "major breakthrough".

Kevin Stairs, Greenpeace's EU chemicals policy director, told The Independent on Sunday: "This is a great breakthrough for the environment and human health. Finally, the way forward into forcing developed countries to assume responsibility for their own hazardous waste and stop shipping it to developing countries has been agreed.

"All forms of hazardous waste including that sent for recycling, to obsolete electronic waste, will be banned from leaving wealthy countries destined for developing countries."

The ban will be introduced when 17 more countries ratify an amendment to the 1989 Basel Convention, a treaty aimed at making nations manage their waste at home. It is expected that this could be achieved in two to five years. More than 50 countries have already ratified it.

The ban was adopted as an amendment to the Convention in 1995, but a disagreement, about how it would be translated in law, left it inactive for years.

Now, after a deal was brokered by Indonesia and Switzerland at the conference, a legal obstacle has been lifted by the 178 parties in attendance.

Jim Puckett, the executive director of the Basel Action Network (BAN), said he was "ecstatic" with the decision: "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."

Mr Puckett added that there are no reliable estimates on how many tons of toxic waste are exported as nations do not accurately record or report what they ship abroad.

He said a private US company will, for example, list waste as "exports" when sending them to a developing nation so they can avoid paying taxes and other fees. The UN has estimated that, worldwide, up to 50 million tons of electrical and electronic goods which had come to the end of their lives were being thrown away every year – of which only 10 per cent is recycled – and often end up in landfills in developing countries.

Up to 1.2 million second-hand televisions, refrigerators, washing machines and air conditioners were estimated to have entered the Philippines between 2001 and 2005, and, according to a study by the Japan International Cooperation Agency and the Philippine Board of Investment, 60-70 per cent of it came from Japan.

An investigation by CBS News at a landfill in Manila found an increasing prevalence of tuberculosis among workers and their children, which a doctor treating them attributed to chronic exposure to burning copper from the electrical goods. One community youth leader had brought more than 200 people suffering from TB to a health centre.

The chemical, which coats much of the e-waste burned by the women and children at the dump, polyvinyl chloride plastic, is even more dangerous due to its emission of carcinogenic gases, according to scientists.

A 2008 Greenpeace report found containers of e-waste from Germany, Korea, Switzerland and the Netherlands being opened at Tema harbour, the biggest port in Ghana. The team documented children, most between the age of 11 and 18, but some as young as five, taking the electronic scraps apart with their bare hands, releasing toxic fumes.

The Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal allows members to ban imports and requires exporters to gain consent before sending toxic materials abroad. But critics say insufficient funds, widespread corruption and the absence of the US as a participant have undermined the convention, leaving millions of poor people exposed to heavy metals, PCBs and other toxins.

The issue took centre stage in 2006 when hundreds of tons of waste were dumped around the Ivory Coast's main city of Abidjan, reportedly killing at least 10 people and making tens of thousands ill. The waste came from a tanker chartered by the Dutch commodities trading company Trafigura Beheer BV, which had contracted a local company to dispose of it.

China has received global attention over electronic waste export issues since 2002, when environmental groups exposed "egregious" electronics recycling and disposal practices in the city of Guiyu, a place reported by scientists to have the highest levels of cancer-causing dioxins in the world. Scientists found pregnancies in the city to be six times more likely to end in miscarriage, with seven out of 10 children reported to have too much lead in their blood – a metal which can have irreversible effects on a child's nervous system.

The US, the world's top exporter of electronic waste, is among nations that have yet to ratify the original convention. "Unless the US joins the treaty they are just going to be a renegade," Mr Puckett said, adding that the US has no rules for exporting electronic waste, which it sends mostly to China but also to Africa and Latin America.

Mr Puckett said shipping companies had opposed their inclusion in the ban, wanting to keep sending old ships to India, Pakistan and Bangladesh to scrap them. "Earlier this week another six people died on the beaches of Bangladesh," he said.

The global ban has been strongly backed by African countries, China, Colombia and the EU, which already prohibits toxic exports. Opponents have been led by Canada, Australia, New Zealand and Japan, and recently joined by India, said Mr Puckett.