On May 25, 2021, the European Food Safety Authority announced it was accepting comments on its draft “guidance document on scientific criteria for grouping chemicals into assessment groups for human risk assessment of combined exposure to multiple chemicals.” EFSA is proposing a framework for pragmatically grouping chemicals from across the food system, such as plant protection products or contaminants, to do assessments of chemical mixtures on human health. Hazard information about chemical groups can then be collected and particular groups prioritized for further study. This new guidance document follows-up on the procedures outlined in EFSA’s MixTox framework released in 2019 (FPF reported).

EFSA notes “that it is not feasible to start a risk assessment from the whole universe of chemicals.” Instead, the agency outlines a tiered pathway with which chemicals can be grouped and assessed. Chemical groups are proposed to be formed from three steps considering: 1) mode of action (MoA) – the chemical’s primary triggers to cause an adverse reaction, 2) adverse outcome pathway (AoP) – the sequence of events that take place to cause an adverse reaction, and 3) if the chemicals share a common target organ or bodily system. According to EFSA, international scientific advisory bodies such as the World Health Organization, US Environmental Protection Agency, and the OECD “have developed MoA and AoP frameworks to describe the mechanistic basis of toxicity.”

Priority levels of the groups can then be assessed through exposure metrics by “combining occurrence data of each chemical in different foods with consumption data for the food items.” If a chemical is unlikely to be found in the food system with other chemicals in the group, or if the likely added risk of the chemical is low, that chemical can be assigned a lower priority in order to focus research resources on the most common and potentially hazardous chemicals and groups.

Mixture toxicity, when chemicals act together to cause an effect even if individual chemical concentrations are below a relevant threshold, is well-reported within the scientific literature (FPF reported here and here). The proposed guidance document notes “the appropriateness of threshold values for risk metrics needs to be considered depending on the regulatory context of the assessment (i.e., protection goals), data availability and number of chemicals under consideration.”

EFSA additionally hopes to update assessment procedures to incorporate new testing tools, create open source tools to carry out the prioritization of chemical mixtures, and update the OpenFoodTox database (FPF reported).

Feedback on the draft guidance document, particularly from experts in chemical risk assessment as well as organizations and professionals in the field of chemicals mixtures and food safety, is being accepted through July 10, 2021.



EFSA (May 25, 2021). “Draft EFSA Scientific Committee guidance document on scientific criteria for grouping chemicals into assessment groups for human risk assessment of combined exposure to multiple chemicals.”

Read More

EFSA (May 25, 2021). “Grouping chemicals for joint assessments – have your say!

EFSA (March 25, 2019). “Mixtures methodology equips EFSA for multiple chemicals.”