Hazardous chemicals have to be classified and labelled based on their properties, such as their flammability, in order to ensure their safe use. Which chemicals are to be labelled in what way is regulated by a globally harmonized system. Despite this, chemicals may still be classified differently in different countries. A team of BAM from the Department Chemical Safety Engineering and PTB (Physikalisch-Technische Bundesanstalt) has investigated how a globally consistent assessment could be achieved. The team of authors has published first results in the paper "UN-GHS – Physical hazard classifications of chemicals: A critical review of combinations of hazard classes". This article now ranks among the most downloaded articles of the renowned Journal of Chemical Health & Safety since more than two months.
Dr. Cordula Wilrich, your publication has a somewhat "cumbersome" title – Who does that apply to?
This is about labelling of hazardous chemicals and thus concerns all of us, i.e. the manufacturer, who has to label chemicals and the user who has to understand the label. Probably everyone has already seen pictograms on chemicals, such as a flame in a red diamond on a deospray. Classification and labelling of chemicals is prescribed by an international system, the "Globally Harmonized System of Classification and Labelling of Chemicals" or "UN-GHS", which is developed by a Committee at the United Nations.
And how are you involved in this?
I am a member of the German delegation to the respective GHS-Committee and as such represent BAM's expertise in the area of physical hazards. We step in whenever fire and explosion hazards of chemicals are concerned.
What is the intent of your publication?
Although there is globally harmonized system of criteria for the classification of chemicals, that does not mean that chemicals are classified and labelled in the same way all over the world. Even in countries which have implemented the UN-GHS, i.e. they have "ratified" it, there can be differences for many different reasons. And this may have unwanted or even dangerous consequences: On the one hand, a deviating classification and labelling of one and the same chemical can impede safe handling and use because inappropriate protective measures might be taken. And on the other hand, it complicates trade, because every time a chemical is exported, the exporter has to clarify which regulations and "interpretations" of the UN-GHS are applicable in the respective country.
Diverging „Interpretations“ of the criteria means…?
The UN-GHS distinguishes hazards according to their "nature" and assigns hazard classes based on specified criteria. Overall, the GHS consists of 29 hazard classes, 17 concern our area of expertise, namely fire and explosion hazards of chemicals. And in this area, there is still a diverging understanding which of the 17 physical hazard classes may be assigned simultaneously to a chemical. Can and should e.g. an explosive additionally be classified as flammable solid? And this question arises for all combinations of all 17 physical hazard classes.
Why are rules for combining hazard classes important?
For one thing, the classification of chemicals should be feasible with reasonable efforts by every company. Streamlining of the system can be of enormous help to that regard. In addition to that, also safety aspects play an important role: Test methods for the classification of physical hazards can also be the cause of hazards, if a "wrong" substance is tested. In our above example, dangerous reactions might occur when an explosive is tested for its burning rate which is applicable to flammable solids. Hence, it would be desirable if such combinations were excluded to begin with.
That sounds like a lot of experiments and considerations…
A systematic investigation of all 17 physical hazard classes with regard to their mutual compatibility requires in-depth knowledge of all criteria and experience with the applicable test methods. Therefore, experts from the different divisions of BAM's Department Chemical Safety Engineering as well as an expert from PTB were involved. Jointly, we have expertise regarding all physical hazard classes of the UN-GHS and discussed them comprehensively in a scientific paper. The scope of the Journal of Chemical Health & Safety has proven to perfectly match our subject and intent … and that so well that our article ranks 2nd in the list of most downloaded articles since months.
What was the result of your investigations?
We have summarized the results in a cross-table of all combinations of the 17 physical hazard classes. The investigation has shown that only a minority of the combinations are relevant and applicable in a meaningful way; these are highlighted in green in the cross-table. The majority of combinations are not relevant or might even be counterproductive. These are shown in red and orange in the cross-table.
And what is next?
We hope that this issue will be discussed in the GHS-Committee at the United Nations and that finally a common understanding of "legitimate" and "illicit" combinations of physical hazard classes is developed. For this purpose, we have presented the issue and our publication during the last meeting of the GHS-Committee and are requested to follow-up on the issue. At the end of this tedious process, we hope for an amendment of the UN-GHS giving clear information for the classification of chemicals with regard to their physical hazards. And we hope that an improved harmonization of labelling of chemicals, in turn, helps companies who place chemicals on the market as well as users of chemicals.
UN GHS ‒ Physical hazard classifications of chemicals: A critical review of combinations of hazard classes
Cordula Wilrich, Elisabeth Brandes, Heike Michael-Schulz, Volkmar Schröder, Silke Schwarz, Klaus-Dieter Wehrstedt
Journal of Chemical Health & Safety, Volume 24, Issue 6, November–December 2017, Pages 15-28
BAM Department Chemical Safety Engineering