Negotiations should start later this year and conclude by 2013. In the meantime, countries will encourage voluntary efforts to reduce exposure to mercury, for example, by lowering the amounts in thermometers and in mining.
According to NRDC:
The treaty will include actions to reduce global mercury pollution and human exposure to the chemical, by reducing intentional use of mercury in industrial processes and products and reducing emissions from coal plants and smelters. It will also address the problems posed by mercury waste sites.
And the Guardian saw inklings of Copenhagen in the development:
The new-found consensus in Nairobi, which saw the US, India and China lifting their resistance to a binding global mercury treaty, raised hopes for progress later this year at the crucial UN meeting in Copenhagen on an international climate change deal.
"There was a seismic shift from the American government from its previous position," said Nick Nuttall, the spokesman for the UN environment programme. "It was clear from the beginning of this week that the US negotiators had been given a clear line from Washington, and indeed the White House, to come together with the rest of the world and do something."