Common pesticide linked to hidden brain damage, scientists warn
A research team at Pennsylvania State University in the United States, in a new study published in Nature Communications, has shown that chronic low-dose exposure to chlorpyrifos — a pesticide still widely used worldwide — causes structural damage to nervous-system cells. The study tracked the effect of 18 weeks of low-dose pesticide exposure in mouse models.
Chlorpyrifos is an organophosphate-class agricultural pesticide; it has long been used on corn, soybeans, citrus, vineyards and for roadside vegetation control. The US Environmental Protection Agency (EPA) banned its use on food crops in 2021, but the ban was rolled back in 2022 under pressure from farm-lobby circles. Litigation and state-level restrictions have continued since.
Lead author Dr Hannah Wilson said: 'Classical toxicology studies measure acute high-dose effects; we tracked the effect of long-term, low-dose, continuous exposure. Our findings provide a molecular basis for long-debated effects on children.' The study showed that even at low doses, chlorpyrifos disrupts mitochondrial function and blocks autophagy processes in neurons.
The observed changes in the mouse models were striking. In mice exposed to a daily dose of 0.5 mg/kg of chlorpyrifos over 18 weeks, the team observed cell loss in the hippocampus, thinning of the myelin sheath covering axons, and a reduction in synaptic transmission capacity. Behavioural tests showed that exposed mice scored 34% worse than controls in maze-solving performance.
The link between chlorpyrifos and human health has been investigated in epidemiological studies since the 2000s. A 2012 study by the Columbia Center for Children's Environmental Health found that children exposed in utero to higher levels of chlorpyrifos had lower scores on memory and attention measures. The Penn State study offers a mechanistic explanation for those epidemiological observations.
'What is particularly striking about this study is that effects appear at doses well below current safety limits,' said Dr Maria Rodriguez, professor of neurological sciences at Stanford University, who was not involved in the work. 'The EPA will need to consider these new mechanistic data in its review process for this pesticide.'
Chlorpyrifos use varies significantly across countries. The European Union did not renew its approval in 2020, and the pesticide is banned from entry into the EU. Use is widespread in China, Brazil and India. In the United States, after the 2021 ban on food crops, states have taken different paths — California has banned agricultural use, but it is still in use in 25 states. In Turkey, the licensed-substances list including this pesticide is revised annually since 2022.
The study authors said these mechanistic data could be important in the EPA's chlorpyrifos re-evaluation, scheduled for autumn 2026. The authors also called for stricter residue testing on crops imported into the United States from Eastern Europe and Latin America.
The research also raises new questions about other organophosphate pesticides beyond chlorpyrifos. Dr Wilson at Penn State said similar toxicology studies should be initiated for other pesticides in the class (malathion, dimethoate). 'Many pesticides use the same acetylcholinesterase inhibition mechanism; we need to systematically investigate whether the effects we see in one class member also appear in others.'
Disclaimer: This article is for information only. If you have occupational pesticide exposure or live near agricultural areas, it is advised to consult an occupational safety specialist or environmental-health department on personal protective equipment, household cleaning protocols and limiting children's exposure.