EU-approved pesticide found to have potential effects on brain development

New study on fluazinam’s neurotoxicity comes up with different findings from earlier report based on manufacturer’s data

Researchers who re-ran a crucial fungicide study on neurotoxicity have come up with significantly different findings, and campaigners argue that the substance should now be withdrawn from the market.

In 2005, a study conducted by Huntingdon Life Sciences on behalf of ISK, the manufacturer of fluazinam, on the development of neurotoxicity of fluazinam in pregnant rats concluded there were no statistically significant effects in relation to brain development in the rats’ offspring.

In 2008, after a safety evaluation, the pesticide fluazinam was granted approval in the EU. Fluazinam is a Pfas fungicide that is used to control various soil-borne fungal pathogens in potatoes and apples. In 2024, 340 tonnes of it was sold in Germany alone.

The 2005 study, as the Guardian previously revealed , was not submitted as part of the evidence for the approval decision but was used in subsequent discussion.

In a new study , which has yet to be peer-reviewed, using the same statistical methods, Stockholm University researchers have come to a different conclusion, finding six instances where exposure to the pesticide led to statistically significant impacts on brain development.

Notably, they found that exposure to the pesticide led to decreases in brain weight and width in the rats’ offspring.

“In our opinion, considering the potentially lifelong consequences of brain development deficits, an effect of a chemical on brain weight, width and morphometrics qualifies as severe,” the authors write.

The researchers told the Guardian: “It is impossible to correctly reach the results in the 2005 report based on the raw data in the 2005 report using the methods specified in the 2005 report. Drawing conclusions from results is a more complicated and less straightforward matter. We would say that the conclusions in the 2005 report (specifically those relating to the brains in adult offspring) are entirely unreasonable and not supported by the results that should have been reported.”

Antoine Bailleux, a professor of EU law and legal theory at UCLouvain in Belgium, said that failing to report a statistical significance when it came to developmental neurotoxicity would amount to a breach of the EU pesticide regulations.

Dr Angeliki Lysimachou, the head of science and policy at campaign group Pesticide Action Network (Pan) Europe , said this study was “withheld from regulators and shielded from proper scrutiny. When it finally reached the authorities, the warning signs were still missed. This is a breach of both legal obligations and scientific integrity that demands an urgent investigation, full accountability for those responsible, and the immediate withdrawal of fluazinam from the market.”

Given the pesticide’s effects on brain development, the study authors write that it is not possible to establish a safe level of exposure and therefore they say it should not have been approved for use in 2008.

Having reviewed the study for the Guardian, Hans Peter Arp, an environmental chemist at the Norwegian Geotechnical Institute, agreed that based on these findings, the pesticide should not have been approved.

Fluazinam is being evaluated for re-approval in the EU. The fungicide was carried over into the UK’s approved active substance register after Brexit, where it is approved for use until 2029.

Bailleux said that fluazinam should not be renewed without further investigation.

Nick Mole, a policy manager at Pan UK, said the UK’s Health and Safety Executive should “immediately revoke its authorisation”.

The study authors write that continued use of this pesticide since 2008 may have resulted in “unnecessary and potentially harmful human exposure”. Fluazinam has been detected at children’s playgrounds in the South Tirol region of Italy, where the pesticide is used on nearby farms to treat apple trees.

Dr Axel Mie, the lead author of the study, said animal studies could not be directly extrapolated to humans. However, he said that if a substance harmed brain development in rats, it must be assumed that the same could occur in humans.

Christina Rudén, a professor in regulatory toxicology and ecotoxicology at Stockholm University and a co-author of the study, said the current EU system for approving pesticides “relies on a conflict of interest” in that the company producing the pesticide was responsible for producing data on its safety.

The EU is facing accusations of seeking to further weaken pesticide safeguards by introducing time-unlimited approvals.

Lysimachou said: “These findings send exactly the opposite message: Europe needs stronger enforcement, greater transparency, and more independent scrutiny of industry science. When credible evidence points to risks for children’s neurological development, public health must come before commercial interests.”

The European Food Safety Authority (EFSA) said the Austrian Agency for Health and Food Safety (AGES) had been asked to review the statistical analysis and underlying data for fluazinam’s approval.

A spokesperson said: “This review is independent and follows established EU procedures. EFSA does not act alone: conclusions are reached collectively with member states through the peer review process. Once AGES has completed its assessment, the findings will be scrutinised in the context of the ongoing risk assessment of fluazinam. We expect to publish our conclusions on the safety of fluazinam, agreed and drawn up together with all EU member states, by the first quarter of 2027.”

A spokesperson from Ages said the concerns raised in the study would be subject to “further assessments in order to provide a sound basis for the decision about the renewal of the approval of fluazinam.”

A spokesperson for ISK said: “We are aware of the claims regarding the 2005 study and, as we have not received the underlying analysis, are unable to provide further commentary.

“The study of this active substance forms part of the regulatory assessment and has been reviewed by competent authorities in accordance with applicable procedures. We trust established regulatory processes and emphasise that any related claims should be carefully scrutinised and substantiated.”

Huntingdon Life Sciences has not responded to a request for comment.

This story was reported in collaboration with Bayerischer Rundfunk (BR/ARD) in Germany, FF Südtirol in Italy and Sveriges Television (SVT) in Sweden.