Experts meet to debate chemical mixtures
More than 100 risk assessors, scientists and policymakers from 21 countries gathered in Edinburgh for an open scientific debate on the harmonisation of human and ecological risk assessment of combined exposure to multiple chemicals (chemical mixtures).
Discussions at the EFSA Scientific Colloquium focused on: mechanistic models for hazard assessment; harmonisation of methods for combined exposure assessment; the use of OMICs and in silico methods for risk assessment; and the application of science-based uncertainty factors and approaches in risk characterisation using mechanistic approaches.
Human and ecological risk assessment of combined exposure to multiple chemicals poses a number of 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.
The colloquium identified opportunities and challenges for the harmonisation of these approaches. The discussions will inform the future activity of the Scientific Committee of EFSA in this area.
- EFSA's 21st Scientific Colloquium on Harmonisation of human and ecological risk assessment of combined exposure to multiple chemicals