People, animals and the environment can be exposed to multiple chemicals from a variety of sources. EFSA has already developed some approaches for assessing combined exposure to multiple pesticides and contaminants in humans and multiple pesticides in bees. Our scientists are developing new approaches and tools for harmonising how we assess risks to humans and the environment from multiple chemicals in the food chain: “chemical mixtures” and their “cocktail effects”.
Jan 2019 EFSA’s Scientific Committee addressed how to assess the genotoxicity of substances in chemical mixtures. Genotoxicity refers to a chemical’s ability to harm DNA. Our top scientific experts explain how to deal with mixtures containing known genotoxic substances, and also what to do when “unidentified” substances present in mixtures need assessing for genotoxicity.
This work complements EFSA’s guidance on genotoxicity testing strategies from 2011 and also the broader guidance on assessing combined exposure to multiple chemicals, which is called “MixTox”. The draft MixTox guidance underwent a public consultation in 2018 and following up on the high volume of comments we received has put back publication to early-mid 2019. The statement on genotoxicity of mixtures was also subject to public consultation in 2018.
EFSA’s Scientific Committee set up a working group of experts to develop guidance on combined exposure to multiple chemicals. This initiative is called MixTox.
EFSA is undertaking or supporting several research activities to contribute to the development of this guidance:
- Data collection and analysis of combined toxicity of multiple chemicals of relevance to EFSA in the area of human, animal and environmental toxicology.
- Development of tools for modelling (tiered approaches, population dynamics, human variability) for human and ecological risk assessment for single and multiple chemicals.
2019 Finalisation of “MixTox” guidance on assessing combined exposure to multiple chemicals.
2019 First two pilot assessments on cumulative effects of exposure to pesticides in food on the human nervous and thyroid systems.
2018 EFSA sets a new deadline for completion of two pilot assessments on the risks posed to humans by residues of multiple pesticides in food.
2018 EFSA publicly consults on its “draft guidance on harmonised methodologies for human health, animal health and ecological risk assessment of combined exposure to multiple chemicals” and a second draft document on how to address the genotoxicity of chemical mixtures.
2018 EFSA’s partners the Dutch National Institute for Public Health and the Environment (RIVM) and Wageningen University, publish data model for probabilistic cumulative dietary exposure assessments of pesticides.
2017 Step-by-step approaches for human and ecological risk assessment of chemical mixtures using OpenFoodTox data provide alternatives to animal testing in toxicological assessments.
2017 Launch of “OpenFoodTox” database reporting summary chemical hazards information and linking to the OECD eChemPortal.
2016 Public consultation on proposed MixTox scope and objectives.
2016 Joint EFSA and Dutch National Institute for Public Health and the Environment (RIVM) symposium on the future of risk assessment and toxicity testing for chemical mixtures.
2016 An RIVM-EFSA pilot study tests the Monte Carlo Risk Assessment software tool for carrying out exposure assessments of multiple pesticides.
2015 Finalisation of data collection on toxicokinetic and toxicodynamic interactions of chemical mixtures for human risk assessment and combined toxicity of multiple chemicals for animal health and ecological risk assessment.
2014 EFSA hosts scientific colloquium on harmonisation of human and ecological risk assessment of combined exposure to multiple chemicals, in Edinburgh.
2013 EFSA presents cumulative assessment group methodology for pesticides.
2013 Scientific report on international frameworks dealing with human risk assessment of combined exposure to multiple chemicals, reviewing current approaches and setting out future priorities.
2008 Evaluation of existing methodologies for identification of new approaches to assess cumulative and synergistic risks from pesticides to human health.
2006 Scientific colloquium on cumulative risk assessment of pesticides to human health.
EFSA’s Scientific Committee develops harmonised risk assessment methodologies on cross-cutting scientific matters in EFSA's areas of activities where EU-wide approaches are not already defined. The Scientific Committee considers development of guidance for harmonised methodologies for combined exposure to multiple chemicals a priority for EFSA.
EFSA reviewed available international frameworks dealing with human risk assessment of combined exposure to multiple chemicals, and consulted its expert Panels and staff on on-going activities at EFSA. The Scientific Committee recommended several follow up activities to feed into a future guidance document on this topic.
EFSA’s Panel on Plant Protection Products and their Residues is responsible for the general methodology for classifying pesticides into cumulative assessment groups. The methodology developed by the Panel uses broad criteria for inclusion of pesticides in groups to maximise consumer protection.
1. How do scientists assess chemical mixtures?
For a single chemical, scientists review available toxicity data to set a safe level for human health or the environment. They compare this with exposure (for example through food) to predict potential risks. For multiple chemicals, scientists have developed methods which use the same principles. They assess the toxicity of the group of chemicals identifying how these substances are metabolised in the body and how they might express their toxicity, often referred to as “mode of action”. Then, the toxicity information is combined with exposure information to assess potential health risks using assumptions about the combined toxicity. The most common assumptions are dose addition, response addition and interaction.
2. What is dose addition?
Dose addition means that the individual chemicals in the mixture have a similar toxicity and the doses are added up and combined with exposure for the risk assessment.
3. What is response addition?
For response addition, scientists consider the independent toxic effects of each substance in the mixture and include these together when carrying out the risk assessment.
4. What is meant by interactions? What are “synergistic” and “antagonistic” effects?
Interactions are more complex. Some chemicals can become more toxic when combined. This is called “synergism”. On the other hand, other chemicals when combined can be less toxic when combined, which is known as “antagonism”. The mechanisms behind synergism and antagonism are complex. Two important ones are: an increase or decrease in the body’s ability to detoxify and eliminate the compounds, and an increase or decrease in toxicity of the chemical(s). If there is evidence of such interactions, scientists collect the information to take these effects into account in the risk assessment.