Mixtures in the environment – development of assessment strategies under REACH


Different societal groups are requesting that aspects of simultaneous exposure to different chemicals be more strongly considered in the substance focused chemicals risks assessment. The scientific debate and the development of approaches for the assessment of mixture toxicity has become more intense and relevant also at EU level, in particular in the fields of food safety, biocides and plant protection products.

The EU Commission is obliged to report on the operation of REACH, including In contrast to the continuously increasing number of scientific publications on the topic of mixture toxicity assessment, specific concepts, concrete approaches as well as examples and guidance for practical consideration of the issue in the every-day company practice and at regulatory level are missing.

Aims and work process

This project aims at analysing the options and the feasibility of integrating aspects of mixture toxicity and the simultaneous exposure to different substances in the assessment of environmental risks in the context of the European chemicals regulation REACH. If possible, concrete and pragmatic concepts should be deduced and introduced into the European discussion.

As a first step, the relevance and the necessities for the integration of mixture toxicity assessment under REACH are analysed and compiled.

Existing methods and concepts for the environmental mixture toxicity assessment are analysed with regard to aspects which are scientifically sound and pragmatic and could be appropriate for use at regulatory level. Different scenarios for mixtures in the environment will be developed in order to carry out and test respective approaches at an exemplary level.

Based on the above, it is planned to develop decision criteria for the assessment of mixtures.

Finally, concrete proposals will be developed how (and which aspects of the) risk assessment for mixture could be integrated in the REACH procedures and which policy making steps would be helpful.

The results of the project will be discussed at an expert workshop.

Expected results

The results of the project will be different short reports, which summarize the findings of the different work steps.


The chemical safety report under REACH refers to singel substances. In reality, man and the environment are exposed to different substance, which may act additively or even synergistically.

Different studies show, that the (eco-)toxicity of mixtures can be higher than the sum of the (eco-)toxic hazards of the single components, because of “combined actions”.

Several stakeholders requested that mixture effects should be considered in the regulatory risk assessment. The EU-Commission published a communication in which respective action was announced.


The aim of the project was to identify if and if yes, which aspects of the risks assessment for mixtures could be integrated into the REACH regulation’s procedures. The feasibility of several options for authorities and industry actors should be analysed.


The result of the project is a report discussing different aspects of integrating mixture risk assessment into REACH. These are among others:

    • Discussion of the current responsibilities and obligations of the REACH actors regarding chemical safety assessment and communication
    • Methods for the risk assessment of mixtures; a tiered approach was developed to derive a hazard index
    • Possibilities to prioritise substances and/or mixture for which a mixture risk assessment is regarded as useful or important
    • Description of various options to act for industry actors and authorities and a first, qualitative analysis of their feasibility considering information availability, cost/benefit relation and the regulatory framework 


Antonia Reihlen

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