TRGS 600 "Substitution"

Technical Rule for Hazardous Substances (German TRGS)

1. Elaborated by

Committee on Hazardous Substances (AGS), revised 2020

2. Description

According to the German Ordinance on Hazardous Substances (GefStoffV), employers are obliged to identify substitution options, to examine them, to make decisions and to document this. The Committee on Hazardous Substances (AGS) establishes Technical Rules for Hazardous Substances (TRGS), which describe the state of the art, occupational safety and health protection at the workplace as well as industrial hygiene. Further, requirements for the marketing and handling of hazardous substances are taken into account.

The aim of the TRGS on substitution (TRGS 600 and rules on individual substances) is to support employers:

to avoid activities with hazardous substances,
to replace dangerous substances with substances, mixtures or processes that are less dangerous under the given conditions of use,
to replace dangerous processes with less dangerous ones.

The TRGS 600, which is the framework for the specific TRGSs for substitution, indicates information sources in which possible substitution solutions can be found. It describes criteria for technical feasibility, health protection, physicochemical risks of alternatives as well as criteria for substitution decisions in individual company cases.

For assessing a substance at the workplace the following criteria are particularly relevant:

Health hazards:

They can be assessed using the column model in Appendix 2 of the TRGS 600. It differentiates between acute health hazards and chronic health hazards, e.g. carcinogenes, germ cell mutagens or toxic substances for reproduction. The priorities for substitution are ranked within a column (very high -> high -> medium -> low -> negligible).

Physico-chemical hazards:

They can also be assessed using the column model described in Appendix 2 of TRGS 600.
Risks from the release potential are very relevant in the workplace:

High concentration/large amount > low concentration/small amount,
Process with wetting of large areas > Process with wetting of small areas,
Gas > liquid > paste,
Dusting solid > non-dusting solid,
Sublimating solid > non-subliming solid,
Low boiling point (high vapour pressure) > high boiling point (low vapour pressure),
Open process > process with integrated suction > closed process > chambered system (closed process in its own closed room),
Process at high temperature > Process at room temperature,
Process under pressure > pressure less process,
Process with generation of aerosols > aerosol-free processes.
Solvent-based systems > aqueous systems

Technical suitability

Technical suitability is a prerequisite for a substitution solution. It is easier to assess if recognized solutions from TRGS or from industry-related sources are available. Otherwise, the technical suitability needs checking in each individual case. Basic considerations on this are set out in TRGS 600.
When deciding on the implementation of a substitution solution, the technical suitability as well as the health and physicochemical risks are considered in an integrated manner. If relevant, additional aspects, e.g. environment can be included. The employer can also include economic considerations in the decision, although higher costs do not generally exclude substitution. For activities with hazardous substances that are toxic, very toxic, carcinogenic, mutagenic or toxic to reproduction (categories 1 and 2), substitution must be implemented if alternatives are technically feasible and their use reduces the overall risk for workers.

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3. Reliability

Safety data sheets are an important source of information for this method. In various studies carried out across Europe, relevant deficits have been identified in safety data sheets, particularly for classification. Therefore, it may be advisable to check the classifications assigned to substances by using additional sources (see appendix of TRGS 600). However, the implementation of the European Chemicals Regulation (REACH) has improved the amount and quality of information for substances.

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4. Applicability

The focus of TRGS 600 is on the comparison of substances and mixtures with unchanged conditions of use ("drop-in" substitutes). The replacement of dangerous processes or the introduction of less dangerous processes is also accepted as a substitution and can be assessed. The method emphasises that substitution shall decrease the overall risk for workers (not only specific hazard) and that other protected interests shall be respected. Examples in the appendix of the TRGS 600 display these principles.
The methods of TRGS 600 are suitable also for SMEs and users who have no special expertise. The assessment covers chemical hazards, aspects of exposures and risk, and also technical and economic feasibility. The method can be used with qualitative information and needs no quantification of the criteria.

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5. User friendliness

The TRGS 600 method is easy to use even for SMEs and non-specialized users without a specified expertise, provided that safety data sheets are available. It includes all relevant criteria for assessment and decision. A key feature of the method is that it allows a quick assessment of a significant number of possible substitutes.

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6. Limitations

The method is based on the classification of substances. Classification is legally required for all substances that are placed on the market in the EU. However, from safety data sheets is often not obvious why a classification was NOT assigned (due to missing data or inconclusive data or due to data management that there is no danger?). In cases of doubt, classification should be cross-checked with other databases, e.g. ECHA substance database. If uncertainty persists, the TRGS 600 offers default assumptions.

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