23
Apr
Literature Reviews Add to Wide Body of Science Connecting Pesticides to Parkinson’s Disease
(Beyond Pesticides, April 23, 2025) Recent reviews of scientific literature, in both Chemosphere and Reports in Public Health, associate Parkinson’s disease (PD), the second most prevalent neurodegenerative disease globally, with pesticide exposure. “Given the pervasive nature of pesticide residues in everyday food consumption and inadequate monitoring of their long-term toxicological impacts, the role of pesticide exposure as a modifiable risk factor for neurological disorders, including PD, warrants urgent attention,” the researchers state in the article in Chemosphere.
In describing the history of Parkinson’s and previous research, the authors in Reports in Public Health note that while PD etiology is not fully understood, it is a multifactorial disease. “Hereditary factors are present in approximately 10% of diagnosed cases of Parkinson’s disease, presenting early onset; while the other 90% of cases are categorized as idiopathic or sporadic Parkinson’s disease, occurring in older individuals and may be associated with exposure to environmental agents,” the researchers say.
This disease, first described by English physician James Parkinson, M.D. in 1817, involves neurochemical changes that present as “the appearance of cardinal motor symptoms, such as bradykinesia, rigidity, postural instability, and rest tremor, which are essential for the clinical diagnosis of the disease,” the researchers note.
The prevalence of PD, according to a 2021 study, experienced a 155.5% increase between 1990 to 2019, affecting approximately 8.5 million people worldwide. Current estimates say more than 10 million people are living with PD and studies predict this number could exceed 25 million by 2050.
The researchers reviewed observational studies, conducted on humans, for evidence of pesticides’ association with PD. The studies focus on the Brazilian population, as “Brazil is responsible for approximately 20% of the world’s pesticide consumption,” they state. From the review, the authors find that “rotenone, paraquat, and maneb show toxicity mechanisms that have been most elucidated in pre-clinical studies.” (See studies here, here, here, here, and here.)
Additional study results include:
- Pesticides could trigger the development of PD through facilitation of gene or protein expression changes. (See studies here and here.)
- “[O]xidative stress markers were altered in Parkinson’s disease patients exposed to pesticides. Therefore, oxidative stress may be an aggravator in the neurodegenerative progression.”
- Occupational exposure to maneb is associated with Parkinsonian syndrome. (See here.)
- “[B]oth mancozeb and maneb inhibit the mitochondrial respiratory chain, leading to increased reactive oxygen species, motor impairments, and degeneration of nigrostriatal dopaminergic neurons in preclinical studies.” (See studies here and here.)
- “A 54-year-old man, without a familial history of Parkinson’s disease, accidentally sprayed himself with glyphosate, the most commercialized herbicide in Brazil and worldwide. Initially, one month after the acute intoxication, he presented slowness and rigidity in all four limbs, progressing to resting tremors in the left arm and hand and short-term memory deficit one year later.” (See here.)
- “[O]ccupational exposure to pesticides doubled the mortality of patients with Parkinson’s disease when compared to non-exposed patients.”
- “A case-control study carried out at the Mato Grosso State General University Hospital, including 88 Parkinson’s disease patients and 264 control individuals, also showed that direct handling of pesticides in the workplace increased the probability of developing Parkinson’s disease by more than three times.”
- The mechanisms of action of the herbicides 2,4-D and atrazine, and the insecticide malathion, are linked to the pathophysiology of Parkinson’s disease. (See studies here, here, and here.)
- “Risk of developing Parkinson’s disease doubled in individuals exposed to household pesticides for more than 30 days per year at any time during their lifetime.”
These findings are further supported and explained in the Chemosphere article, where the researchers “provide an overview of the molecular pathways impacted by known neurotoxic pesticides and their involvement in the development of PD/parkinsonism.” In exploring the molecular mechanisms of PD development and the key pathways that can be induced by pesticides, such as with exposure to rotenone, paraquat, maneb, and others, the authors are “shedding light on their role in the pathogenesis of PD and highlighting the need for preventative measures and regulatory oversight to mitigate these risks.”
Through the analysis of a multitude of studies, the researchers conclude that pesticides, though they share common neurotoxic mechanisms, exhibit distinct pathways of toxicity and “disrupt mitochondrial and proteasomal functions, impair autophagy, and interfere with dopamine transport and metabolism, contributing to neurodegeneration.”
In describing these mechanisms as they relate to PD and pesticide exposure, the authors include the following:
- Pesticides can cause alpha-synuclein (aSyn) oligomerization, where proteins that play a crucial role in PD and other neurodegenerative disorders within the brain, specifically in nerve terminals, are misfolded. These alterations occur “through oxidative stress, ubiquitin-proteasome inhibition, mitochondria impairment, reactive oxygen species (ROS) accumulation, and altered lipid metabolism.” (See studies here, here, here, and here.)
- The association between pesticide exposure and PD development is supported by studies highlighting the structural similarities between certain pesticides and neurotoxicants. (See studies here, here, here, and here.)
- “Epidemiologic studies have linked rotenone exposure, either alone or in combination with other pesticides, to an increased risk of developing PD.” (See here.)
- Paraquat is able to cross the blood-brain barrier (BBB), cause prolonged oxidative stress, and alter multiple metabolic pathways that can induce neurotoxicity. (See studies here and here and Daily News here and here.)
- “Both acute and chronic exposure to maneb have been associated with adverse effects in the CNS [central nervous system] among agricultural workers. These effects manifest as Parkinsonism-like motor symptoms, encompassing postural tremor and bradykinesia, alongside complaints of fatigue, memory issues, and drowsiness.” This occurs through mitochondrial dysfunction and oxidative stress. (See here.)
- “Despite the ban on dieldrin many years ago, this insecticide continues to pose a significant threat to the environmental diversity and human health, persisting in soil, rivers, and food samples.” Studies (see here and here) of post-mortem PD brains reveal dieldrin accumulation in the tissue.
- A study shows “alpha-cypermethrin-treated cells exhibited increased expression of several pro-apoptotic [cell death] genes, alongside key autophagy-related genes, as well as increased oxidative stress, characterized by increased nitric oxide levels, lipid peroxidation, and DNA damage.”
- Dichlorvos is shown to selectively induce degeneration of neurons and alter mitochondria morphology through swelling and disintegration. (See studies here and here.)
- Chlorpyrifos induces cell death in cortical neurons, as well as causes aSyn proteins to cluster together. (See here.)
With Parkinson’s disease considered the fastest-growing neurodegenerative disorder worldwide without an effective cure currently available, preventing exposure to environmental contaminants that increase disease risk is imperative. Unfortunately, as the researchers point out, regulatory protocols regarding pesticides “fall short in assessing the full range of their effects on the nervous system. Current guidelines mandate neurotoxicity assessments only if the active ingredient exhibits known neurotoxic properties or shares structural similarities with known neurotoxicants.”
They continue, saying: “This regulatory gap is particularly concerning given the growing body of evidence linking chronic pesticide exposure to PD and other neurodegenerative disorders… [There is a] systemic failure of current regulatory systems, which often underestimate neurotoxicity risks, particularly from chronic low-dose exposures or pesticide mixtures used in real-world agricultural settings. Regulatory frameworks, such as those of EFSA [The European Food Safety Authority] and EPA [U.S. Environmental Protection Agency], continue to prioritize data from short-term, high-dose toxicity studies, which are poorly suited to detect subtle, cumulative damage to dopaminergic neurons [involving dopamine as a neurotransmitter] that can evolve over years or decades.” (See more on EPA failures here.)
Pesticides are intended to target specific pests but are often ineffective and carry unreasonable risks to nontarget organisms and the environment. As the authors state: “[O]ut of the annual 3 billion kilograms of pesticides used globally, only a mere 1% proves effective. This inefficiency has resulted in the widespread, indiscriminate, and often random use of pesticides, leading to environmental contamination and adverse health effects.” (See studies here and here and learn more through the Pesticide-Induced Diseases Database.)
Beyond Pesticides has reported on the association between PD, as well as other brain and nervous system disorders, for many years. (See Parkinson’s Daily News archive here.) Coverage includes Pesticide-Induced Gut Microbiota Composition Alterations Linked to Parkinson’s Disease Prognosis, as well as the alteration of genes with pesticide exposure and how toxicants cause neurodegeneration through inhalation and ingestion pathways.
A Daily News post in February 2024 highlights a study published in Science of The Total Environment, where the researchers find health savings overshadow the cost of banning pesticides linked to Parkinson’s. Despite differing pesticide exposure scenarios, PD risk lowers without pesticide exposure, particularly to those that elicit neurotoxicity, and banning these chemicals is economically beneficial. The study concludes, “[T]he population-level long-term health benefits and health savings would outweigh the financial losses due to the pesticide ban.”
While Parkinson’s disease has no cure, preventive practices, such as organic agriculture and the Parks for a Sustainable Future program, eliminate exposure to toxic PD-inducing pesticides. Learn more about the health and environmental benefits of organic land management here and here. Make The Safer Choice by avoiding hazardous home, garden, community, and food use pesticides and become a member today to help support Beyond Pesticides’ mission of eliminating petrochemical pesticides and synthetic fertilizers by 2032!
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
Amaral, L. et al. (2025) The neurotoxicity of pesticides: Implications for Parkinson’s disease, Chemosphere. Available at: https://www.sciencedirect.com/science/article/pii/S0045653525002905.
Santos, J. et al. (2025) Pesticide exposure and the development of Parkinson disease: a systematic review of Brazilian studies, Reports in Public Health. Available at: https://www.scielosp.org/article/csp/2025.v41n4/e00011424/en/.
