Researchers who have re-run a key fungicide study on neurotoxicity have come up with vastly different results, and campaigners say the substance should be taken off the market immediately.
In 2005, a study conducted by Huntingdon Life Sciences on behalf of ISK, the manufacturer of fluazinam, on the neurotoxicity of fluazinam in pregnant rats concluded that there were no statistically significant effects on brain development in the rat offspring.
After safety evaluation, the insecticide fluazinam was approved in the EU in 2008. Fluazinam is a Pfas fungicide used to control various soil-borne fungal pathogens in potatoes and apples. In 2024, 340 tons were sold in Germany alone.
As the Guardian previously revealed, the 2005 study was not submitted as part of the evidence in the approval decision, but was used in subsequent discussions.
In a new study (not yet peer-reviewed) using the same statistical methods, researchers at Stockholm University reached a different conclusion, finding six cases where exposure to pesticides had a statistically significant effect on brain development.
Remarkably, they found that exposure to pesticides led to decreased brain weight and width in rat offspring.
“In our opinion, the effects of chemicals on brain weight, width, and morphometry are considered serious, given the lifelong effects that impaired brain development can cause,” the authors write.
The researchers told the Guardian: “It is impossible to correctly arrive at the results of the 2005 report based on the raw data of the 2005 report using the methods specified in the 2005 report. It is impossible to draw any conclusions from the results. We can say that the conclusions of the 2005 report (especially those regarding adult children’s brains) are completely unreasonable and not supported by the results that should be reported.
Antoine Bayeux, a professor of EU law and legal theory at the University of California, Leuven in Belgium, said failure to report statistical significance for developmental neurotoxicity would be a violation of EU pesticide regulations.
Dr Angeliki Rysimachou, head of science and policy at campaign group Pesticide Action Network (Pan) Europe, said the study was “hidden from regulators and shielded from proper scrutiny. When it finally reached the authorities, the warning signs were still overlooked. This is a breach of both legal obligations and scientific integrity, and calls for an urgent investigation, full accountability of those responsible, and the immediate withdrawal of fluazinam from the market.”
Considering the effects of pesticides on brain development, the study authors wrote that the pesticide should not have been approved for use in 2008 because it is impossible to establish safe exposure levels.
Hans-Peter Arp, an environmental chemist at the Norwegian Geotechnical Institute, reviewed the study for the Guardian and agreed that, based on these findings, the pesticide should not have been approved.
Fluazinam is being evaluated for reauthorization in the EU. The fungicide will remain on the UK’s Approved Active Substances Register after Brexit and is approved for use until 2029.
Bayrou said fluazinam should not be renewed without further investigation.
Pan UK’s policy manager Nick Mole said the UK health and safety executive should “revoke the license immediately”.
The study authors wrote that continued use of this pesticide since 2008 may have resulted in “unnecessary and potentially harmful human exposures.” Fluazinum has been detected in a children’s playground in Italy’s South Tyrol region, where the pesticide is used by a nearby farm to treat apple trees.
Dr. Axel Mee, lead author of the study, said animal studies cannot be directly translated to humans. But if a substance adversely affects brain development in rats, one must assume that the same thing could happen in humans, he said.
Christina Ruden, professor of regulatory and ecotoxicology at Stockholm University and co-author of the study, said the current EU pesticide approval system “relies on a conflict of interest” in that the companies that produce pesticides are responsible for producing data on their safety.
The EU faces accusations that it is seeking to further weaken pesticide safeguards by introducing open-ended authorizations.
“These findings send exactly the opposite message. Europe needs stronger law enforcement, greater transparency and independent scrutiny of industry science. When reliable evidence points to risks to children’s neurodevelopment, public health must be prioritized over commercial interests.”
The European Food Safety Authority (EFSA) has announced that the Austrian Agency for Health and Food Safety (AGES) has been requested to review the statistical analysis and basic data for the approval of fluazinam.
A spokesperson said: “This review is independent and follows established EU procedures. EFSA does not act alone. Conclusions are reached jointly with member states through a peer review process. Once AGES has completed its assessment, “The results will be scrutinized in the context of the ongoing risk assessment of fluazinam. We plan to publish our conclusions on fluazinam’s safety, which we have agreed with and jointly developed with all EU Member States, by the first quarter of 2027.”
An Aegis spokesperson said the concerns raised in the study would be subject to “further evaluation to provide a sound basis for a decision to renew fluazinam’s approval.”
An ISK spokesperson said: “We are aware of the allegations regarding the 2005 study but cannot comment further as we have not received the underlying analysis.”
“This study of active substances forms part of a regulatory assessment and has been reviewed by the competent authorities in accordance with applicable procedures. We have confidence in the established regulatory process and emphasize that relevant claims should be carefully scrutinized and substantiated.”
Huntingdon Life Sciences did not respond to requests for comment.
This article was reported in collaboration with Germany’s Bayerischer Radio (BR/ARD), Italy’s FF Südtirol and Sweden’s Sveriges Television (SVT).
