The debate concerning pesticide residues has intensified in recent days, with the environmental association Mouvement Écologique warning about the danger to public health on the basis of a new study by the Pesticide Action Network Europe (PAN Europe), while representatives of the agricultural sector argue that the findings are being overstated. At the heart of the discussion lies a broader issue: what the presence of pesticide residues actually means, how these substances are assessed scientifically, and at what point exposure can genuinely be considered a health risk.
Emma Schymanski, a chemist and researcher in Environmental Cheminformatics at the University of Luxembourg, made it clear from the outset that she sees herself somewhere between the positions defended by the Mouvement Ecologique and representatives of the agricultural sector.
One of Schymanski’s main criticisms of the PAN Europe report, cited by the Mouvement Ecologique, is that it focuses primarily on detection. The report flags the presence of pesticide residues but does not sufficiently address the thresholds at which those residues become problematic, she said.
The chemist further explained that simply detecting a substance does not automatically mean there is a health risk. She described the approach as somewhat exaggerated and even provocative, arguing that it equates detection with danger without providing the necessary toxicological context. This makes it impossible to make scientifically grounded statements based on the study, Schymanski added.
By contrast, she considers the most recent European Food Safety Authority (EFSA) study more appropriate for assessing potential risks, as it identifies cases where legally defined maximum residue levels (MRLs) are actually exceeded. Looking at those results in detail, she noted that the data clearly do not support alarmist claims that everyday consumption of apples poses an immediate threat.
According to the EFSA data, 627 pesticides were analysed in Luxembourg, above the average of 249 substances tested across participating countries. Luxembourg’s level of screening is therefore comparatively high, similar to Germany (717), Belgium (631), and Austria (618).
Out of 13,246 food samples analysed, 246 exceeded the maximum residue level, around 1.9%. For baby food samples, the proportion was approximately 0.6%. In 70% of cases, no detectable pesticide residues were found at all, while in 28% residues were detected but remained below EFSA’s safety thresholds.
Schymanski stressed that these findings also demonstrate how sensitive modern analytical methods have become. She said that laboratories can nowadays identify pesticides and their breakdown products at extremely low concentrations, often long before they reach levels considered harmful. As she explained, analytical testing exists precisely to identify potential risks early, before they become problematic.
At the same time, Schymanski acknowledged that increasing detection inevitably raises questions, adding that something must eventually be done against contamination. She gave the example of Luxembourg and other countries that are working on improving wastewater treatment systems to remove contaminants more effectively, including from drinking water. However, she cautioned against conflating treated wastewater with tap water.
When it comes to food, she emphasised that pesticides are primarily used to prevent mould and fungal contamination, which can, in some cases, be more harmful to humans than trace pesticide residues. Other pesticides target weeds or insects.
Schymanski also pointed out that a healthy immune system is capable of processing such residues. Maintaining good health, she argued, depends largely on a balanced diet rich in fruit and vegetables. She also added that it would require the consumption of “extremely large” quantities of residues before genuine toxicity becomes a concern.
PFAS, or per- and polyfluoroalkyl substances, often referred to as “forever chemicals”, are frequently mentioned in debates about pesticides and are linked to cancer risks.
Schymanski stressed the need for nuance. She explained that while certain PFAS compounds may be present in pesticides, these are not necessarily the long-chain PFAS molecules associated with severe toxic effects, adding that it would be inaccurate to claim that PFAS-based pesticides are automatically more dangerous than other pesticides.
However, Schymanski cautioned that PFAS remain under scrutiny because some degrade into trifluoroacetic acid (TFA), a substance that is difficult to remove from drinking water. The issue, she explained, is complex and involves multiple processes that cannot simply be lumped together.
Schymanski argued that the fact that the EU has banned numerous pesticides in recent years demonstrates that regulatory mechanisms are functioning. She stressed tha EFSA carries out regular evaluations, with member states required to submit monitoring data. According to Schymanski, Luxembourg alone conducted more than 600 pesticide screenings.
While additional testing is always possible, she maintained that oversight is firmly in place.
Ultimately, pesticides represent a delicate “balancing act”, according to Schymanski. They serve to protect crop quality and food security, but robust monitoring is essential to ensure they do not harm human health.
Schymanski also highlighted a broader issue: although she strongly supports the principles of open science, many toxicological studies remain inaccessible. Without full transparency, she said, it can be difficult for researchers to assess the scientific basis for certain safety thresholds.
She explained that, through this lack of transparency, there is not always sufficient data for certain pesticides to determine with certainty how dangerous a given threshold value actually is, or where that limit should be set in order to protect public health without imposing unnecessarily excessive restrictions.
As toxicity testing is extremely expensive, independent replication is often financially unfeasible. Schymanski concluded that greater transparency and legally ensured earlier publication of studies are needed.
