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Behind the Numbers Linking Pesticides to Neurological Disorders, the World’s Largest Source of Disability
(Beyond Pesticides, July 29, 2025) Are neurological diseases increasing around the world? Yes and no, according to a report published by The Lancet in 2024 on the global burden of nervous system diseases between 1990 and 2021. About 3 billion—a third of the world’s people—suffer from some nervous system condition. These diseases cause 11 million deaths and 443 million disability-adjusted life years (DALYs), which are a measure of the years lost to illness, disability, or early death. Neurological disorders are now the world’s largest source of disability.
The Lancet report does not include an analysis of the role of pesticides in the burden of neurological disease worldwide, although environmental health research continues to expand the evidence that pesticide exposure is a major contributor to that burden. The Lancet report indicates that DALYs from Parkinson’s disease have increased by 10 percent, and autism spectrum disorder and dementia by 2 percent each. Multiple sclerosis has declined by 11 percent, according to the report. Importantly, most of the improvement has come from medical interventions, not prevention—in other words, people are living longer with the diseases rather than avoiding them altogether. But this is not true globally: The burden of disease, and particularly premature death, rests most heavily on the developing world, where medical interventions are much more scarce. A focus on prevention would be a more equitable approach to the problem. See Beyond Pesticides’ deep archive of the evidence on pesticides and neurological diseases in Pesticide-Induced Diseases: Brain and Nervous System Disorders section. Our Gateway on Pesticide Hazards is also invaluable for information about specific pesticides and their adverse health effects.
The Lancet’s big picture does not demonstrate that the burden of pesticide-induced neurological disease is declining. Such a decline seems a logical impossibility, given that more and more people are chronically exposed to more and more pesticides, and more and more research is establishing both population-level and mechanistic evidence of pesticides’ influence on disease induction and outcome, including neurological disorders.
A recent review by Chinese researchers demonstrates that there is no category of pesticide—not herbicides, not fungicides, not insecticides—that does not contribute to neurological dysfunction. The authors recite numerous examples: the herbicide glyphosate affects both cognitive and motor functions. The fungicides tebuconazole and azoxystrobin are associated with neurodevelopmental and neurodegenerative disorders. Organophosphate insecticides lead to sensory disruption, emotional disturbances, and neurodevelopmental problems. Several “natural” chemicals, including rotenone and the plant growth regulators gibberellic acid and indole-3-butyric acid, affect the expression of some neurologically relevant enzymes. One research group found that the insect repellent DEET applied to rats’ skin killed their neurons.
The review examines studies showing pesticides’ neurological damage relevant to long-term exposures, rather than the usual acute exposures that form the outdated regulatory toxicological approach to pesticide hazards and risks. The studies considered encompass pre-clinical research, including in vivo studies involving both humans and animals—as well as in vitro experiments with molecular processes common to both, along with results from clinical and epidemiological studies.
In all, the authors include 47 preclinical and 40 clinical reports involving about 30 pesticides, singly and in combination, including all the major groups. Their analysis shows that the cellular and molecular mechanisms by which pesticides cause neurotoxicity are many and varied. For example, glyphosate produces high levels of inflammatory cytokines in the brains of mice. Rotenone likely disrupts the blood-brain barrier and causes neurons to commit suicide in rodents and aquatic organisms. The organophosphate insecticide chlorpyrifos and the herbicide atrazine affect neurons in the hippocampus region of the brain, which is important to memory. Deltamethrin, a pyrethroid insecticide, likewise affects the hippocampus by preventing new neurons from forming and distressing neurons’ endoplasmic reticulum (cells’ internal transportation and structural system). The fungicide tebuconazole disturbs the gut-brain axis, affecting learning and memory. The organophosphate malathion produces neuroinflammation, cognitive deficits, and amyloid beta deposition in neurons reminiscent of Alzheimer’s disease. Virtually every neonicotinoid insecticide affects the vital neurotransmitter acetylcholine’s functioning. The review’s recitation of pesticides associated with Parkinson’s disease and dementias is too long to mention here.
It is important to note that many of the pesticides included in the review are no longer registered for use in the United States and other countries (e.g., endosulfan, DDT, carbofuran, maneb), but this is cold comfort, because most of these are so persistent that they continue to expose millions of people long after their discontinuance. This is a problem in indoor environments where organochlorine insecticides like carbofuran and DDT were used in the past. Many old pesticides still linger in soils as well.
But it is also clear that newer pesticides present gross risks to humans and ecosystems. Pesticide use has doubled globally since 1990, according to an analysis by the Food and Agriculture Organization, with the greatest jump—from about a million tons in 1990 to about 2.75 million tons in 2023—in herbicides.
One set of pesticides has received very little attention until recently, when evidence has emerged that these chemicals do indeed have neurological effects: gibberellic acid and indole-3-butyric acid, both derived from natural plant growth regulators. These substances are not technically classed as pesticides, but they remain as residues on plant products.
The review authors cite studies showing that their effects on plants are very different from their effects on animals. Gibberellic acid has been given a pass by EPA since its registration review in 1995. It induces cell division in plants, but a pair of studies found that prenatal exposure to gibberellic acid in rats produces oxidative stress during the development of the cerebellum when the brain requires high amounts of oxygen but has few defense mechanisms against reactive oxygen species. Indole-3-butyric acid exerts effects on the brain through the gut-brain axis and has been shown to affect the neurotransmitter acetylcholine, which is also targeted by organophosphate and carbamate pesticides. EPA considers Indole-3-butyric acid to be essentially nontoxic. In addition, there is some evidence that some indole compounds may actually be protective against dementia, so this is an area in need of much more research.
What this review indicates is that, despite The Lancet’s assessment that the global burden of many neurological diseases is static or declining, there is a serious undertow in the wave of progress in the form of burgeoning pesticide usage. For example, Parkinson’s disease is undoubtedly on the increase worldwide, but the 2024 Lancet report on neurological diseases conflicts with an earlier Lancet report specific to Parkinson’s from 2018. The latter report notes that Parkinson’s is the primary reason for the jump in neurological diseases. The 2024 Lancet report said there was a 10 percent increase in the incidence of Parkinson’s between 1990 and 2021. But the 2018 Parkinson’s report stated DALYs increased from 2.5 million in 1990 to 6.1 million in 2016—a jump of 21 percent. More recent work shows even worse acceleration: according to a 2025 review in Frontiers in Aging Neuroscience, DALYs from Parkinson’s have increased 85 percent since 2000, and deaths have jumped by more than 100 percent. And environmental toxicants, particularly pesticides associated with food, are very strongly implicated in these increases, as detailed in a 2024 review of environmental toxins and Parkinson’s in Science of the Total Environment.
Beyond Pesticides has accumulated overwhelming evidence from scientific studies that Parkinson’s and the other neurodevelopmental and neurodegenerative diseases, including Alzheimer’s, autism spectrum disorder, attention deficits, memory and cognition disorders, and more, are strongly linked to pesticide exposures. While there is no question that therapeutic and palliative practices can reduce some of the suffering victims endure, the more obvious and prudent course would be to work on prevention. Eliminating pesticides from all forms of agriculture, public lands, gardening, municipal landscapes, and the like would go further to protect public health than simply trying to treat the symptoms once a disease has taken hold. Organic and regenerative practices are the key.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
Neurotoxic risks of long-term environmental exposure to pesticides: a review
Yumeng Leng et al
Chemico-Biological Interactions, 5 September 2025
https://www.sciencedirect.com/science/article/abs/pii/S000927972500256X
Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021
GBD 2021 Nervous System Disorders Collaborators
https://www.thelancet.com/action/showPdf?pii=S1474-4422%2824%2900038-3
Global, regional, and national burden of Parkinson’s disease, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016
GBD 2016 Parkinson’s Disease Collaborators
The Lancet Neurology 2018
https://pmc.ncbi.nlm.nih.gov/articles/PMC6191528/
Pesticide-Induced Diseases: Brain and Nervous System Disorders
Beyond Pesticides
https://www.beyondpesticides.org/resources/pesticide-induced-diseases-database/brain-and-nervous-system-disorders
