"To agree on global targets is not easy to do," Achim Steiner, the executive director of the U.N. Environment Program, told reporters. "There was no delegation here that wished to leave Geneva without drafting a treaty."
Over the past 100 years, mercury found in the top 100 meters (yards) of the world's oceans has doubled, and concentrations in waters deeper than that have gone up by 25 percent, the U.N. environment agency says, while rivers and lakes contain an estimated 260 metric tons of mercury that was previously held in soils.
The treaty was originally blocked by powers such as the United States, but President Barack Obama's reversal of the U.S. position in early 2009 helped propel momentum for its adoption. China and India also played key roles in ensuring its passage; Asia accounts for just under half of all global releases of mercury.
"We have closed a chapter on a journey that has taken four years of often intense, but ultimately successful, negotiations and opened a new chapter toward a sustainable future," said Fernando Lugris, the Uruguayan diplomat who chaired the negotiations.
Some supporters of a new mercury treaty said they were not satisfied with the agreement.
Joe DiGangi, a science adviser with advocacy group IPEN, said that while the treaty is "a first step," it is not tough enough to achieve its aim of reducing overall emissions. For example, he said, there is no requirement that each country create a national plan for how it will reduce mercury emissions.
His group and some of the residents of Minamata have opposed naming the treaty for their city because they feel it does not do enough to fix the problem.
"This treaty should be called the 'Mercury Convention,' not the 'Minamata Convention," said Takeshi Yasuma, a Japanese activist. "Water pollution resulting in contaminated sediment and fish caused the Minamata tragedy, but the treaty contains no obligations to reduce mercury releases to water and no obligations to clean up contaminated sites."
Treaty proponents called it a good first step, however, and Steiner said the document would evolve over time and hopefully become a stronger instrument.