On March 19, 2019, the 9th meeting of the United Nations TDG and GHS Expert Committee released the main technical revisions of the 8th revised edition of the United Nations GHS. The 8th revised version of GHS is expected to be officially released around July 2019. Since its introduction in 2003, the United Nations GHS system has gradually been adopted by multiple countries/regions such as the European Union, Japan, the United States, and China, and has been transformed into their respective chemical management systems or standards. Therefore, the revised content of the GHS system will gradually be incorporated into the existing system by various implementing countries.

In this compliance interpretation, the editor will first summarize the main updates on chemical classification in the GHS revision.

1、 Aerosol classification

1. Aerosols belong to a physical hazard in Chapter 2.3 of the GHS system. In this revision, in order to better understand the hazard classification criteria for aerosols, a table has been added to the original Section 2.3.2.1, as shown in Table 1.

Table 1 Classification Criteria for Hazards of Aerosols

2. This revision adds a new product category in Chapter 2.3: Chemicals under pressure. Although pressurized chemicals and aerosols are both flammable, GHS classification is based on the flammability and heat of combustion of the contents. However, the allowable pressure, capacity, and process structure of the containers or packaging for the two products are different. In practical classification, a product can only choose one of the two independent hazard categories, aerosol and pressurized chemistry.

3. Added section 2.3.2, which provides detailed regulations on the definition, classification criteria, labeling elements, and classification logic of pressurized chemicals, as follows:

(1) Definition

Pressurized chemicals refer to gases mixed with liquids or solids (in paste or powder form) in pressure vessels (not aerosol cans), with a pressure of ≥ 200kPa at 20 ℃, and do not meet the definition of high-pressure gases (Chapter 2.5). Under normal circumstances, the content of liquid or solid in pressurized chemicals is ≥ 50%. If the content of gas is ≥ 50%, it is usually classified as high-pressure gas.

(2) Classification criteria

The classification criteria for pressurized chemicals are shown in Table 2

The flammable components in pressurized chemicals mainly include flammable gases, flammable liquids, and flammable solids. Just like aerosols, flammable substances, self heating substances, and substances that release flammable gases when in contact with water cannot be used in pressurized chemicals.

(3) GHS label elements

Table 3 GHS label information for pressurized chemicals

2、 The classification of skin corrosion/irritation has been revised and updated with the schematic diagram of the layered classification of skin corrosion/irritation in Chapter 3.2. The new classification logic is shown in Figure 1:

Figure 1 Schematic diagram of the updated layering method

As shown in Figure 1, this revision will present the principle of hierarchical method more clearly and facilitate practical operation.

(1) Step 1: Highlighting that human skin corrosion/irritation data is the first choice for classification, and standard animal testing mainly recommends OECD Test No. 404, in vivo animal testing.

(2) Step 2: Use in vitro experiments. Here, it is recommended to use four OECD skin corrosion/irritation in vitro experiments, each with its own applicable scope when classified, as shown in Table 4.

Table 4 Scope of Application for In Vitro Experiments

As shown in Table 4, Test 430 can only distinguish whether chemical substances have skin corrosiveness and belong to Class 1, but cannot distinguish molecular categories; Test431 can not only distinguish category 1, but also molecular category 1A, but cannot distinguish molecular categories 1B and 1C; Test435 can completely distinguish three subcategories; Test 439 is mainly aimed at skin irritation, but if the test results show that it does not belong to category 2, it is necessary to combine other test data to determine whether it belongs to category 3.

(3) Step 3: Encourage the use of existing animal skin test data, mainly recommending the following 5 categories, as shown in Table 5.

Table 5: Sources of Other Animal Skin Test Data

When using each type of experimental data to infer skin corrosion/irritation, on the one hand, it is important to note that each type of experimental result has its own shortcomings or incompleteness, such as the acute transdermal toxicity test results of rats (OECD Test 402). Due to the fact that the skin sensitivity of the selected species is not as high as that of rabbits, when evaluating skin corrosion/irritation results using this result, it is necessary to combine evidence weighting.

(4) Step 4: Mainly using the pH value of the test chemical, substances with pH ≤ 2 or ≥ 11.5 can be classified as skin corrosion category 1 without any other information, but sometimes the acid-base buffering capacity also needs to be considered. The pH value and acid-base buffering capacity can be determined according to OECD Test 122.

(5) Step 5: It mainly recommends non testing methods, including SAR, QSAR, cross referencing, and computer expert systems, which have gradually developed in recent years. When using cross referencing, it is necessary to have reliable test results for similar substances and sufficient evidence of similarity between the two substances. In this case, the derived results are more feasible than SAR or QSAR.

(6) Step 6: This is mainly aimed at the risk of lower classification results if the lower level (such as step 4) derivation results are more rigorous than the higher-level (such as step 3) derivation results when using the five steps mentioned above. In this case, the evidence weighting method of step 6 needs to be used for analysis.

3、 Summary

In this compliance interpretation, we have briefly reviewed the main revisions related to the hazard categories of aerosols and skin corrosion/irritation in the 8th revised GHS system. Next time, we will provide a detailed explanation of the new solutions for label use in this revision. Please look forward to it.