Globally Harmonized System of Classification and Labelling of Chemicals

The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is an internationally agreed-upon standard managed by the United Nations that was set up to replace the assortment of hazardous material classification and labelling schemes previously used around the world. Core elements of the GHS include standardized hazard testing criteria, universal warning pictograms, and harmonized safety data sheets which provide users of dangerous goods with a host of information. The system acts as a complement to the UN Numbered system of regulated hazardous material transport. Implementation is managed through the UN Secretariat. Although adoption has taken time, as of 2017, the system has been enacted to significant extents in most major countries of the world. This includes the European Union, which has implemented the United Nations' GHS into EU law as the CLP Regulation, and United States Occupational Safety and Health Administration standards.
History.
Before the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) was created and implemented, there were many different regulations on hazard classification in use in different countries, resulting in multiple standards, classifications and labels for the same hazard. Given the $1.7 trillion per year international trade in chemicals requiring hazard classification, the cost of compliance with multiple systems of classification and labeling is significant. Developing a worldwide standard accepted as an alternative to local and regional systems presented an opportunity to reduce cost and improve compliance.
The GHS development began at the 1992 Rio Conference on Environment and Development by the United Nations also called Earth Summit (1992) when the International Labour Organization (ILO), the Organisation for Economic Co-operation and Development (OECD), various governments and other stakeholders agreed that "A globally harmonized hazard classification and compatible labelling system, including material safety data sheets and easily understandable symbols, should be available if feasible, by the year 2000".
The universal standard for all countries was to replace all the diverse classification systems; however, it is not a compulsory provision of any treaty. The GHS provides a common infrastructure for participating countries to use when implementing a hazard classification and Hazard Communication Standard.
Hazard classification.
The GHS classification system is a complex system with data obtained from tests, literature, and practical experience.
The main elements of the hazard classification criteria are summarized below:
Physical hazards.
Substances or articles are assigned to 8 different hazard classes largely based on the United Nations Dangerous Goods System. Additions and changes have been necessary since the scope of the GHS includes all target audiences.
Substitute substances.
Sometimes companies are able to replace hazardous substances with substances featuring a reduced health risk. As an assistance to assess possible substitute substances, the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) has developed the Column Model. On the basis of just a small amount of information on a product, substitute substances can be evaluated with the support of this table. The current version from 2020 already includes the amendments of the 12th CLP Adaptation Regulation 2019/521.
Classification of mixtures.
The GHS approach to the classification of mixtures for health and environmental hazards is also complex. It uses a tiered approach and is dependent upon the amount of information available for the mixture itself and for its components. Principles that have been developed for the classification of mixtures, drawing on existing systems such as the European Union (EU) system for classification of preparations laid down in Directive 1999/45/EC. The process for the classification of mixtures is based on the following steps:
Testing requirements.
The GHS document does not include testing requirements for substances or mixtures. In fact, one of the main goals of the GHS is to reduce the need for animal testing. The GHS criteria for determining health and environmental hazards are test method neutral, allowing different approaches as long as they are scientifically sound and validated according to international procedures and criteria already referred to in existing systems. Test data already generated for the classification of chemicals under existing systems should be accepted when classifying these chemicals under the GHS, thereby avoiding duplicative testing and the unnecessary use of test animals. The GHS physical hazard criteria are linked to specific UN test methods. It is assumed that mixtures will be tested for physical hazards.
Hazard communication.
Per GHS, hazards need to be communicated:
Comprehensibility is challenging for a single culture and language, so global harmonization is complex. The GHS Purple Book includes a comprehensibility-testing instrument in Annex 6. Factors that were considered in developing the GHS communication tools include:
GHS label elements.
The standardized label elements included in the GHS are:
The additional label elements included in the GHS are:
GHS label format.
The GHS includes directions for application of the hazard communication elements on the label. In particular, it specifies for each hazard, and for each class within the hazard, what signal word, pictogram, and hazard statement should be used. The GHS hazard pictograms, signal words and hazard statements should be located together on the label. The actual label format or layout is not specified in the GHS. National authorities may choose to specify where information should appear on the label or allow supplier discretion. There has been discussion about the size of GHS pictograms and that a GHS pictogram might be confused with a transport pictogram or "diamond". Transport pictograms are different in appearance than the GHS pictograms. Annex 7 of the Purple Book explains how the GHS pictograms are expected to be proportional to the size of the label text so that generally the GHS pictograms would be smaller than the transport pictograms.
Safety data sheet.
The safety data sheet or SDS (The GHS dropped the word "material" from material safety data sheet in its final revisions) is specifically aimed at use in the workplace. It should provide comprehensive information about the chemical product that allows employers and workers to obtain concise, relevant and accurate information in perspective to the hazards, uses and risk management of the chemical product in the workplace. While there were some differences in existing industry recommendations and country specific requirements, there was agreement on a 16 section SDS to include the following headings in the order specified:
The primary difference between the GHS and the international industry recommendations is that sections 2 and 3 have been reversed in order. The GHS SDS headings, sequence and content are similar to the ISO, European Union and ANSI MSDS/SDS requirements. The SDS should provide a clear description of the data used to identify the hazards. A table comparing the content and format of a MSDS/SDS versus the GHS SDS is provided in Appendix A of the U.S. Occupational Safety and Health Administration (OSHA) GHS guidance.
Training.
Current training procedures for Hazard Communication in the United States are more detailed than the GHS training recommendations. Educating employees on the updated chemical and product classifications and related pictograms, signal words, hazard statements and precautionary measures at the level of detail by the national authority represents the greatest training challenge. Training will be a key component of the overall GHS approach and should incorporate information as it is introduced into the workplace. Employees and emergency responders will need to be trained on all new program elements, from hazard statements to pictograms. Bear in mind, if the importation of products using only GHS labeling is permitted prior to its adoption in the United States and Canada, employers may need to begin employee training earlier than expected.
Implementation.
The United Nations goal was broad international adoption, and as of 2017, GHS has been adopted to varying degrees in nearly all major countries. 
GHS adoption by country: