The work about the elaboration of the GHS began with the premise that existing systems should be harmonized in order to develop a single, globally harmonized system to address classification of chemicals, labels, and safety data sheets. This was not a totally novel concept since harmonization of classification and labelling was already largely in place for physical hazards and acute toxicity in the transport sector, based on the work of the United Nations Economic and Social Council's Committee of Experts on the Transport of Dangerous Goods (UNCEDTG). Harmonization had not been achieved in the workplace or consumer sectors, however, and transport requirements in countries were often not harmonized with those of other sectors in that country.

Chapter 19 of Agenda 21, adopted at the United Nations Conference on Environment and Development (UNCED, 1992), provided the international mandate to complete this task. The work was coordinated and managed under the auspices of the Interorganization Programme for the Sound Management of Chemicals (IOMC) Coordinating Group for the Harmonization of Chemical Classification Systems (CG/HCCS). The technical focal points for completing the work were:

It required a long-term commitment from all of these organizations that they maintained over the years. By resolution 1999/65 of 26 October 1999 the United Nations Economic and Social Council decided to enlarge the mandate of the Committee of Experts on the Transport of Dangerous Goods by reconfiguring it into a Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals (CETDGGHS), and by creating, besides the Sub-Committee of Experts on the Transport of Dangerous Goods (TDG Sub-Committee), a new Sub-Committee of Experts on the Globally Harmonized System of Classification and Labelling of Chemicals (GHS Sub-Committee).

In its Plan of Implementation (para 22.(c)) adopted in Johannesburg on 4 September 2002, the World Summit on Sustainable Development (WSSD) encouraged countries to implement the new GHS as soon as possible with a view to having the system fully operational by 2008.

The first version of the GHS was adopted in December 2002 by the Sub-Committee on the Globally Harmonized System of Classification and Labelling of Chemicals (SCEGHS), and endorsed by the Committee on the Transport of Dangerous Goods and the Globally Harmonized System of Classification and Labelling of Chemicals.

At its second session (10 December 2004), the Committee of Experts adopted a set of amendments to the GHS which included various revised provisions concerning classification and labelling, new provisions for aspiration hazards and new guidance on the use of precautionary statements and pictograms and on the preparation of safety data sheets. The first revised edition of the GHS, published in 2005, took account of all these amendments.

At its third session (15 December 2006), the Committee of Experts adopted a set of amendments to the first revised edition of the GHS, which were consolidated in document ST/SG/AC.10/34/Add.3 and ST/SG/AC.10/34/Add.3/Corr.1. The second revised edition of the GHS takes account of all these amendments, which include new and revised provisions concerning, inter alia, the classification and labelling of explosives; respiratory and skin sensitizers; toxic by inhalation gases and gas mixtures; additional guidance on the interpretation of the building block approach and on the evaluation of the carcinogenic potential of chemicals; and the codification of hazard and precautionary statements.

The System is now ready for worldwide implementation. Information about the status of implementation of the GHS by country is available (in English only) in the page following the link "GHS implementation" on the left hand menu.