California, USA – The United States reversed its policy on mandatory mercury emissions reductions last week and joined roughly 140 countries in agreeing to treaty negotiations.

The reversal in U.S. policy prompted other countries, including China and India, to consent to talks that will begin later this year and conclude by 2013. The Bush administration, critical of the negotiation process, reportedly opposed mandatory emissions cuts in favor of voluntary reductions.

According to the U.S. Environmental Protection Agency, the largest source of human-caused mercury emissions in the U.S. is coal-fired power plants, but less than half of all mercury deposits in the U.S. originate in the country. Crude oil refining is also a significant but less publicized source of mercury emissions, said Greg Karras, senior scientist for Communities for a Better Environment. “There’s sort of a history of cover-ups on the sources, and therefore, the solutions to the problem,” Karras said.

Once it hits bodies of water, mercury is transformed into methylmercury, which accumulates in seafood, the main source of exposure for humans.

An interim Global Mercury Partnership will be put in place until the treaty is finalized. The voluntary commitment will include provisions aimed at reducing mercury in products and processes, such as thermometers and papermaking, as well as help countries safely stockpile mercury and raise awareness of the risks for miners and their families.

The agreement marks a swift about-face on an issue that, until just a few weeks ago, divided countries, Achim Steiner, UN undersecretary general and UNEP executive director, said in a statement last week, adding that the the agreement sent a clear signal to the world that the environment has moved back to the top of the global agenda.

“I believe this will be a major confidence-building boost for not only the chemicals and health agenda but right across the environmental challenges of our time from biodiversity loss to climate change,” he said.

On Monday the Supreme Court opted not to hear a case brought by electric utilities over mercury emissions regulations for power plants. The Bush administration sought to remove mercury from a list of controlled power plant pollutants and create a mercury cap-and-trade program that would have allowed facilities to buy mercury emissions offsets rather than make the reductions directly.