Assessment of multiple pesticides in food

Dr Yasser Sokeirik

The occurrence of multiple residues of pesticides in food keeps causing concern in the perception of the general public. What is missing though is a generally accepted method for cumulative risk assessment.

The European Food Safety Authority (EFSA) has announced significant advances towards cumulative risk assessment methodology, following the development of a software tool capable of assessing exposure to large groups of pesticides.

The requirement for cumulative risk assessment is stipulated in the legislation governing the approval of active substances and in the setting of Maximum Residue Levels (MRLs). Therefore, decisions on approvals and MRLs should take into account cumulative effects of pesticides when the methods to assess such effects become available.

Using software known as the Monte Carlo Risk Assessment (MCRA) model the EFSA has developed a new approach for grouping pesticides that paves the way for the implementation of cumulative risk assessment – a sophisticated technique to assess the risk posed by exposure to multiple pesticide residues. The general methodology for classifying pesticides into so-called cumulative assessment groups (CAGs) is based on identifying compounds that exhibit similar toxicological properties in a specific organ or system. 

EFSA are conducting two pilot assessments on the risks posed to humans by residues of multiple pesticides in food. The assessments were originally scheduled for publication by the end of 2018 but have been moved back following feedback from stakeholders.

The full risk assessments of the cumulative effects of pesticides on the human nervous and thyroid systems are now expected in June 2019.

If the initial assessments are successful, EFSA hopes to start progressively incorporating tests on cumulative risk assessment into its consumer exposure assessments that are conducted for the EFSA annual report on pesticides residues in food. The experiences gained in these tests will be used for further optimising the tool to ensure its fitness for purpose for taking into account cumulative effects of pesticides for regulatory purposes in future. Until then, there is however still a lot of more work to do, both by risk assessors and risk managers.


The EU regulation on maximum residue levels (MRLs) in food stipulates that decisions on MRLs should take into account cumulative effects of pesticides when the methods to assess such effects become available. In addition, the regulation covering the placing of pesticides on the market stipulates that pesticides should have no harmful effects – including cumulative effects – on humans.

Over the past years the Commission has been working with the EU countries, EFSA and independent scientists on a methodology to take into account these cumulative effects.

The substances to be considered in the assessments of the thyroid and nervous systems were identified by EFSA’s pesticide experts using a methodology specially devised for classifying pesticides into “cumulative assessment groups” (CAGs). Over the coming years, CAGs will be defined for other organs, tissues and systems, such as the liver, kidneys, eyes, and the reproductive and developmental systems.

The methodology rests on the assumption that pesticides causing the same specific effects can produce cumulative toxicity – even if they do not have similar modes of action.