US President Barack Obama's administration supports the creation of a legally binding document to control mercury pollution, in contrast with the Bush administration, which had stubbornly refused to enter into any agreement.
Green groups, including the European Environmental Bureau (EEB) and the Zero Mercury Working Group, praised this agreement as a "breakthrough".
"The treaty will ensure that the EU and other countries of the world make a serious commitment to reduce global mercury emissions, supply and demand," claimed Elena Lymberidi, coordinator of the EEB's 'Zero Mercury' campaign.
Eurochlor, which represents EU and EFTA chlor-alkali producers, also claimed to "support efforts through the United Nations Environment Program (UNEP) to protect the environment and public health," welcoming "enhanced efforts by the global community to reduce releases of mercury".
The industry association stated that the agreement to negotiate a treaty is in line with its "long-standing commitment to share best practices globally for reducing the use and emissions of mercury from mercury-cell chlor-alkali facilities".
The chlor-alkali industry is known for using the mercury cell process, during which mercury is used to support chemical reactions that produce chlorine and caustic soda.
The treaty aims to reduce the supply of mercury, minimise its use in products and processes and lower atmospheric mercury emissions.
To achieve this, participants in the UN gathering agreed to "enhance the capacity for the environmental storage [of mercury]".
This is likely to translate into a major reduction of human exposure to mercury, as the US is responsible for 40% of mercury emissions.
A working group will be set up by the second half of 2009 to discuss the negotiating priorities and timetable of the intergovernmental negotiating committee.