Pesticide companies failed to disclose a series of studies assessing brain toxicity to European regulators, according to new research, despite the same studies having been submitted to US regulators. When the EU authorities were made aware of the studies, between 14 and 21 years after they were conducted, new safety limits were applied in some cases and evaluation is still under way in other cases. The researchers described the omissions as “outrageous”, concluding that “apparently non-disclosure is a problem that is not rare” and that there could be “no reliable safety evaluation of pesticides by EU authorities without full access to all performed toxicity studies”. The new research is the first systematic assessment of non-disclosure and focused only on developmental neurotoxicity (DNT) studies. The researchers found 35 DNT studies submitted to the US Environmental Protection Agency as part of the pesticide approval process but found that nine of these had not been included in dossiers sent to the EU authorities for the same pesticides. Among the findings in the undisclosed studies were changes in brain size, delayed sexual maturation and reduced weight gain in the offspring of laboratory rats exposed to a pesticide when pregnant. The pesticides identified in the new study include the insecticides abamectin, ethoprophos and pyridaben and the fungicide fluazinam. These are, or have been, used on a range of crops including tomatoes, strawberries, potatoes and aubergines. “Brains are unbelievably complex and so central for us being humans, and damage to brain development is immensely costly to societies,” said Dr Axel Mie, at Stockholm University, Sweden, who led the new study. “So it’s really important for us to make sure that the chemical products we use are not damaging the brains of our kids and grandchildren.” Prof Christina Rudén, study co-author and also at Stockholm University, said: “Most important to me is the principle to have to tell the truth, the whole truth and nothing but the truth. It is outrageous, what they’re doing.” Sarah Wiener, a Green party MEP from Austria and the European parliament rapporteur for new EU pesticide regulation proposals, said: “The analysis shows that the pesticide industry is fooling EU authorities. In the end, it is EU citizens who pay the price. Their health is jeopardised when relevant studies are withheld.” “The EU therefore needs to make sure that there are harsh consequences for the withholding of data,” she said. “This could mean that corporations would have to pay considerable fines.” EU regulations state that pesticide dossiers should “include a full and unbiased report of the studies conducted [unless] it is not necessary owing to the nature of the product or its proposed uses, or it is not scientifically necessary. In such a case a justification shall be provided.” A spokesperson for the European Commission said: “There is a clear obligation to submit all available adverse data as part of applications since 2013, and there is an obligation to notify adverse data when they become available since 1991.” The power to penalise companies if they unlawfully fail to disclose toxicity studies in Europe lies with national regulators. But no known penalty has been imposed on any pesticide company to date. The UK pesticides regulator, the Health and Safety Executive, did not answer a request for comment. In correspondence seen by the Guardian, a senior official in the European Commission’s directorate for health and food safety expressed “serious concern” in September 2022 after being made aware of two of the undisclosed studies: “The fact that certain applicants have apparently not provided studies with an unfavourable outcome for certain active substances as part of the application dossiers is a serious concern.” The chemical companies said they had complied with the EU regulations, in some cases arguing they were not legally obliged to submit the studies. They also disagreed with the researchers’ conclusions that some of the studies had led to tighter regulation when the EU authorities had become aware of the studies’ existence, or that they could do so in the future. Previous work estimated that exposure in the EU to organophosphate insecticides, which are now banned and were not part of the new study, caused brain damage costing €146bn a year in lost productivity. The new report said: “For some compounds, it has taken decades from the initial evidence of DNT effects in humans until such hazards became widely recognised.” The study is published in the peer-reviewed journal Environmental Health. It found nine undisclosed DNT studies produced between 2001 and 2007, up to 20 years before the submission of the most recent EU regulatory dossiers. The EU authorities became aware of the studies between 2017 and 2022, the researchers said. Standard DNT tests expose pregnant female rats to a pesticide and assess their offspring for neuropathological and behavioural changes. The tests have been shown to identify chemicals known to cause DNT damage in humans, though in some cases humans are substantially more sensitive than the rodents. Three of the undisclosed DNT studies have already led to regulatory changes, after subsequent evaluation by EU regulatory authorities, according to Mie and Rudén. For the pesticide abamectin, for example, new health-based safety levels for people were set, they said. For ethoprophos, Mie and Rudén said the DNT study “contributed to” it being banned by EU authorities in 2019. Bayer, the company that commissioned a DNT study on ethoprophos in 2004, denied this. The EU ruling that banned the pesticide said “the risk assessment could not be finalised” for DNT or other areas of concern and also noted a “high acute risk” to birds and soil organisms. Bayer sold ethoprophos to another company in 2010. Another four undisclosed DNT studies could have “a potential effect on toxicological reference values or hazard classification”, based on Mie and Rudén’s assessment of the US EPA’s evaluation of the studies. One DNT did not have any regulatory impact and insufficient information was available to assess the potential regulatory impact of the ninth study. Some of the pesticides have been banned for other reasons since 2018 and overall five of the nine chemicals retain EU approval today. A spokesperson for Syngenta, which commissioned two DNT studies on abamectin in 2005 and 2007, as well as studies on two other pesticides, said: “Syngenta has complied with all EU data requests and provided relevant study data in accordance with regulatory requirements.” The spokesperson said the abamectin DNT studies were not submitted to EU authorities in an application for approval that was completed successfully in 2008 because the studies had been conducted for its US regulatory application and were not a requirement in the EU at the time. He said these studies were not considered to provide any new toxicological information. However, the Efsa spokesperson said: “The [DNT] studies were used to derive health-based safety levels for consumer and operator exposure.” A spokesperson for Bayer said: “At all times, we submitted the necessary studies required by the regulations at the time. For all three active ingredients [cited in the new research], the studies would not have changed the authorities’ risk assessment.” Nissan Chemical Corporation said it had submitted the DNT study for its pesticide pyridaben, completed in 2007, to EU regulatory authorities in February 2023. Mie and Rudén said the study has the potential to impact the regulation of the chemical, which is still approved in the EU. Japanese company ISK said it had submitted a 2005 DNT study on their pesticide fluazinam to EU authorities in 2020 and said it had not been required to do so beforehand. Efsa said the study was now being evaluated as part of the assessment of whether to renew the pesticide’s approval. None of the companies said they had submitted justifications for exemption from the need to submit existing studies, though some said other DNT studies had been submitted. Reforms proposed by Mie and Rudén to ensure all toxicity studies are submitted to EU regulatory authorities include cross-checking datasets with counterparts in other countries, such as the US EPA. “The rules should also be revised to ensure that non-disclosure of toxicity studies carries a significant legal risk for pesticide companies,” they said. Apolline Roger, a lawyer at ClientEarth, contrasted the lack of penalties for non-disclosure of toxicity studies with those imposed for breaches of EU data protection and competition laws, which can lead to fines of significant percentages of a company’s annual turnover. “You don’t have [penalties] like that for this process, even though what is at stake is the dispersion of potentially very harmful substances in the environment, and therefore in our food, water and bodies,” she said. “What does it say about us when we place a higher value on digital data and consumer protection than on health and the environment?” Currently, pesticide safety studies are commissioned and paid for by the companies. Mie and Rudén suggested the studies should be commissioned by regulatory authorities, to prevent conflicts of interest, with the costs being recovered from the companies. “[Mie and Rudén] are really finding the root of the issue when they say studies should not be made by the companies,” said Roger. “It’s the elephant in the room.” The Efsa spokesperson said: “In the EU regulatory system for pesticides, the burden of proof of safety lies with the company that seeks to place their product on the market.” Tougher EU rules on the notification of safety studies became applicable from March 2021, meaning companies now have to notify the authorities of all studies commissioned and cannot withhold studies even if they are considered to have found no adverse findings. However, Angeliki Lysimachou, head of science and policy at Pesticide Action Network Europe, said: “That means that all the pesticides already in the market won’t be examined until their reapproval comes up, which could take 10 or 15 years, sometimes more.” In the meantime, the pesticides remain approved for use, she said. Rudén said: “There’s no reason we are aware of to believe that withholding evidence is limited to DNT studies, or limited to pesticides.” She said the cases of tobacco and PFAS – “forever chemicals” – were previous examples of where companies withheld knowledge about toxicity from the public.