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Specific Considerations Regarding the Classification of GHS Mixtures

Posted Date:2023/1/13

I. Introduction

Work on the global harmonization system began with the work of the OECD Task Force on Harmonization of classification and labelling on health and environmental hazards and the work of the Expert Committee on the Transport of Dangerous Goods/ILO Working Group on the classification of physical hazards.

Why the Uniform System is currently the most scientific and advanced classification system in the world, please refer to the following requirements of the OECD Task Force on Uniform Classification and Labelling:

1. Comprehensively analyze the current classification system, including the scientific basis, reasons and application instructions of the system and its standards. The OECD Task Force on Uniform Classification and Labelling prepared step 1 documents on the following hazard categories and modified them as needed after discussion: eye irritation/severe eye injury, skin irritation/corrosion, allergenic substances, germ cell mutagenicity, reproductive toxicity, specific target organ toxicity and chemical mixtures;

2. Propose a unified classification system and standards for each hazard type and category. The OECD Task Force on Uniform Classification and Labelling prepares a Step 2 document and changes it as needed after discussion;

3. The task force reached consensus on the second step of the revision; Or if consensus cannot be reached, identify specific items that are "not agreed upon" as alternatives in the revised Step 2 proposal for further discussion and resolution;

4. Final recommendations will be submitted for approval to the joint meeting of the OECD Committee on Chemicals and the Task Force on Chemicals, Pesticides and Biotechnology, and subsequently to the Harmonized Chemical Classification System Coordination Group of the Programme on Chemicals for inclusion in the global harmonized system.

Conclusion: GHS system is a classification standard that combines all the current classification systems in the world with the integration of relevant professional personnel of the United Nations.

II. The concept of "classification"

The GHS uses the term "hazard classification" to indicate that it considers only the intrinsic hazard properties of a substance or mixture.

(a) Data relating to the hazard of the substance or mixture;

(b) Then review the data to identify the hazards associated with the substance or mixture; and

(c) To compare the data with agreed hazard classification criteria to determine whether to classify the substance or mixture as hazardous and, as the case may be, to determine the extent of the hazard.

III. The specific consideration of mixture classification

1. The explanation of some professional attributives

1) Substance: chemical elements and their compounds obtained in their natural state or through any production process, including any additives necessary to maintain the stability of the product and any impurities derived from the process used, but excluding any solvent that can be separated without affecting the stability of the substance or altering its composition.

2) Mixture: a mixture or solution consisting of two or more substances that do not react.

3) Alloy: Alloy is a kind of metal material, macroscopic homogenous, composed of two or more elements, but mechanical means can not easily separate them. Alloys are considered mixtures for classification purposes under the global Uniform System.

2. Use of critical value/concentration limit value

1) For untested mixtures, in classifying them according to the hazard of their components, some of the GHS hazard classes classify mixtures using the generic threshold/concentration limits of the classified components of the mixture. The threshold/concentration limit values used are sufficient to determine the hazard of most mixtures, but some mixtures may also contain hazardous ingredients at concentrations below the uniform threshold/concentration limit and still cause some identifiable hazard. It may also be the case that the uniform threshold/concentration limit is significantly lower than would be expected based on the non-hazardous level of a component that has been determined.

In general, generic threshold/concentration limits adopted in the Global System should be uniformly applied to all jurisdictions and all sectors. However, if the classifier has information indicating that the hazard of an ingredient becomes apparent below the generic threshold/concentration limit, then mixtures containing such ingredient should be classified accordingly.

In some cases, conclusive data may show that the hazard of an ingredient does not become apparent above the generic threshold/concentration limit of the Global System. In this case, the mixture can be classified according to these data. The data should rule out the possibility that the ingredients act in the mixture in such a way that the hazard is higher than that of the pure substance. In addition, the mixture should not contain ingredients that might influence such classification decisions.

To sum up: Most of the components in the mixture can be classified according to the GHS threshold value/concentration limit value for the whole product. However, in some special cases, the concentration limit value of some special chemical substances will be far lower than the hazard classification threshold value in the GHS system. At this time, attention should be paid to the classification according to the specific limit value of the substance.