In a recent set of marathon talks that went down to -- and past -- the wire, delegates from more than 120 countries hashed out the first international treaty designed to eliminate some of the world's most toxic chemicals.

Although most of the substances have been banned in Japan for years, some are still in circulation, making the task of finding and destroying them tricky.

The preliminary text of a treaty to remove 12 toxic chemicals known as the "dirty dozen" -- including polychlorinated biphenyls (PCBs), dioxin and DDT -- was agreed upon Dec. 10 in Johannesburg. After its approval at a diplomatic gathering in May, and later ratification and entry into force, signatories will be obligated to eliminate these Persistent Organic Pollutants.

POPs have drawn the attention of policymakers and the public at home and abroad. Many are known or suspected carcinogens, with mounting evidence showing some of them to impair sexual, mental and other development.

Exactly how and by when Japan will tackle its new obligations is not clear, and governments' and nongovernmental organizations' divergent expectations and interpretations of the treaty could create turbulence. However, the pact has nonetheless been warmly welcomed by governments and NGOs alike.

"These are chemicals that penetrate the womb, are in breast milk and threaten the next generation. Now we have a means for tackling them in the next century," said Yuko Nakashita, of Japan POPs Elimination Network, who attended the negotiations.

"This is a very significant agreement for Japan and other countries. We hope that countries will fully implement the treaty with the aim of eliminating POPs," she said.

Nakashita, a lawyer, anticipates that after the treaty is signed in May and later takes force, Japan will be compelled to streamline its disparate web of laws on chemicals.

Rather than a law regulating pesticides, a dioxin law for dioxins and a chemical manufacturing law for industrial chemicals, a more overarching legal framework will be needed to approve, oversee, reduce and control the release of chemicals, she said.

Although the government has announced plans to pen a law to deal specifically with PCBs, it intends to tackle the elimination of the 12 chemicals using extant legislation.

"We are confident that we can meet treaty requirements under existing laws," said Keiko Terui of the International Trade and Industry Ministry's Chemical Management Policy Division.

For Japan, the most pressing issue is the collection and destruction of PCBs.

"PCBs are a tough issue and one on which there has not been much progress," Terui said.

Citizen opposition to the incineration of PCBs -- the traditional means of destroying them -- has stalled processing. But government officials hope that new technologies will help persuade citizens to move ahead with PCB elimination projects.

Under the POPs agreement, countries will have to collect all known PCBs by 2025 and destroy them by 2028. The latitude for the compliance date is largely to accommodate the special needs of countries such as Russia. Japan has said it could complete destruction of the mountains of PCBs in storage, as well as those still in use, within 15 years.

Japan has destroyed about one-tenth of its 54,000 tons of the chemical. Although production was banned in 1974, much of it sits in storage facilities gathering dust while awaiting processing, some of it is still in use in electrical equipment and some has been lost.

"The government needs to reconfirm how much (PCB) is in use, how much is in storage, and reconfirm the locations of both. Then these figures should be made public," argues Masaaki Hosomi, a professor at Tokyo University of Agriculture and Technology.

Only in this way can the government convince citizens of the need to push ahead with the destruction of the chemicals and prevent further PCB pollution, he said.