EFSA Scientific Colloquium N°21: Harmonisation of human and ecological risk assessment of combined exposure to multiple chemicals

Edinburgh , 11 September 2014


Human and ecological risk assessment of combined exposure to multiple chemicals (“chemical mixtures”) poses several challenges to scientists, risk assessors and risk managers, particularly because of the large number of chemicals involved, their associated exposure patterns and their toxicological profiles in humans and other species present in the environment. The Scientific Committee of EFSA has identified this area of risk assessment as a priority for guidance development. In principle, methodological frameworks for the risk assessment of combined exposure to multiple chemicals use tiered approaches for exposure assessment, hazard assessment and risk characterisation. These tiered approaches, originally developed by the US-EPA and the WHO, range from qualitative/semi-quantitative tiers to fully probabilistic tiers – the choice of the tier often depending on data availability – and the purpose of the risk assessment. In the human health area, these frameworks have been applied recently to multiple pesticides with a similar and a dissimilar mode of action by EFSA’s Panel on Plant Protection Products and their Residues (PPR) and to multiple contaminants by EFSA’s scientific Panel on Contaminants in the Food Chain. In ecological risk assessment, recent examples include a decision tree developed by the three non-food committees of the European Commission and the methodology for assessing combined toxicity of pesticides in bees proposed by the PPR panel of EFSA.

This colloquium will bring together the human health and the ecological scientific communities to discuss the respective methodologies for risk assessment of multiple chemicals. This will allow the identification of opportunities and challenges for the harmonisation of these approaches. In addition, the discussions will inform the future activity of the Scientific Committee of EFSA in this area.

Objectives of the Colloquium

International experts will gather for an open scientific debate on the harmonisation of human and ecological risk assessment of combined exposure to multiple chemicals (chemical mixtures). Discussions will focus on the following topics of relevance to both human and ecological risk assessment of combined exposure to multiple chemicals: i) mechanistic models for hazard assessment; ii) harmonisation of methods for combined exposure assessment; iii) the use of OMICs and in silico methods for risk assessment; and iv) application of science-based uncertainty factors and approaches for risk characterisation using mechanistic approaches.

Structure of the meeting

Colloquia are not consensus meetings: their objective is to convene leading scientists from Europe and beyond. Rather than offering a series of lectures, this Colloquium will provide ample opportunity for an exchange of expert opinions and scientific debate. Following the opening plenary session with introductory keynote speeches, the meeting will be structured to enable participants to reach conclusions and make recommendations in small groups, focusing the discussions on four specific topics.

The four discussion groups (DGs) will focus on the following themes:

DG 1 – Tiered approaches in hazard assessment of combined exposure to multiple chemicals in human and ecological risk assessment: from default assumptions to mechanistic models
DG 2 – Harmonisation of combined exposure assessment to multiple chemicals in humans and the environment: from environmental fate to internal dose
DG 3 – Applying biologically-based models and in silico tools and OMICs to human and ecological risk assessment of combined exposure to multiple chemicals
DG 4 – Harmonisation of uncertainty factors and risk characterisation for human and ecological risk assessment using mechanistic descriptors

The outcome of the discussion groups will be presented and discussed in a final plenary session to formulate conclusions of the Colloquium and, as appropriate, recommendations.The outcomes of the Colloquium will be summarised in an overall report after the meeting.

Who should attend?

Risk assessors, scientists and policymakers are among those encouraged to attend the event. The Colloquium is also aimed at risk managers working in the area of human health and/or ecological risk assessment of chemicals – particularly those interested in combined exposure to multiple chemicals (chemical mixtures), new mechanistic models and methods for risk assessment (toxicokinetic and/or toxicodynamic modelling, OMICS, in silico methods) as well as uncertainty factors.

The registrations are closed. The registered participants will be informed about their participation during the week of 30th June 2014.

On-line registrants

As soon as possible after closure of registration, applicants will be informed whether they have been selected to participate. Selected participants will be asked to make their own travel arrangements at their own expense. Concerning accommodation, EFSA has made a block-booking for the nights of 10th and 11th September. Selected participants will be requested to make their own reservation when participation is confirmed. There is no fee for participation.

Dates and Venue

The Colloquium will be held in Edinburgh, UK. The meeting will start at 08:30 on 11th September 2014 and will end at 13:30 on 12th September 2014. Further details on the venue and logistics will be communicated to participants upon confirmation of selection.


English will be the official language of the Colloquium. No translation will be provided.


Briefing notes will be published on this page in the next days and will contain reference to relevant background documents to inform about the contents of each discussion group.
The presentations and the conclusions of the meeting will be made available on the EFSA website. EFSA will also publish a summary report of the event in the form of a booklet.


For more information on the Scientific Colloquium, please do not hesitate to contact EFSA at scientific.colloquia@efsa.europa.eu.


Programme (0.3 Mb)

Briefing notes (0.2 Mb)