05
Jun
Cross-Sectional Study Finds Connection Between Pesticide Exposure and Alzheimer’s Disease
(Beyond Pesticides, June 5, 2024) Individuals living near chemical-intensive agricultural environments have heightened risk of Alzheimer’s disease relative to the general population, according to a study published earlier this year in Psychiatry Research. This finding builds on existing peer-reviewed studies that document the relationship between chronic pesticide exposure and elevated risk of neurodegenerative disorders including Alzheimer’s disease, as well as Parkinson’s disease, dementia, multiple sclerosis (MS), and Huntington’s disease. In light of the mountains of scientific evidence, advocates continue to demand for a wholesale transformation of agricultural and land management systems to one based in organic principles in alignment with the U.S. National Organic Program.
Study Analysis
This study was published online on May 1, 2024 with the full entry to be published in July 2024. The researchers are physicians, health professionals, and professors at the University of Almeria in southern Spain, specifically working in the Health Research Center and the Department of Nursing, Physiotherapy and Medicine. There is also a researcher, Cristofer Ruiz-González, who works at the Torrecárdenas University Hospital also located in Almeria, Spain. Researchers gathered case information from over 40,000 patients between 2000 and 2021 living in demarcated health care districts with high and low levels of pesticide usage. The acreage of high-use districts, measured by the size of greenhouse space in hectares, make up 93.2% of the total surface area in the region of focus for this study.
The pesticides identified in this region include:
Insecticides
- organophosphates (chlorpyrifos, chlorpyrifosmethyl, dimethoate, pyrimifos-metyl)
- n-methylcarbamates (methomyl, oxamyl)
- macrocyclic lactones (abamectin, spinosad)
- neonicotinoids (imidacloprid, acetamiprid)
- pyrethroids (cypermethrin, deltamethrin)
- miscellaneous insecticides (amitraz, formetanate, indoxacarb, azadirachtin, spiromesifen, Bacillus thuringiensis, endosulfan).
Fungicides
- (di)thiocarbamates (zineb, mancozeb, maneb, thiram)
- conazoles (tebuconazole, triadimenol, myclobutanil, prochloraz)
- dicarboximide (procymidone, iprodione, vinclozolin)
- anilino-pyrimidines (cyprodinil, mepanipyrim, pyrimethanil)
- copper salts (copper oxychloride)
- miscellaneous fungicides (cymoxanil, metalaxyl, fosetyl, thiophanate methyl, fluopicolide, chlorthalonil, propamocarb, dimethomorph, azoxystrobin)
Herbicides
- bipyridyl (paraquat, diquat)
- organophosphates (glyphosate, glufosinate)
- chlorotriazine (atrazine, simazine, terbuthylazine, cyanazine)
- phenylurea (isoproturon, linuron, diuron, monuron)
The researchers determined that there is “a positive association between pesticide exposure and the risk of developing [Alzheimer’s Disease] in individuals residing in the southern region of Spain.” Female participants were more likely to develop Alzheimer’s relative to male participants, despite the former group being more likely to work in agricultural operations for longer periods of time. This finding is consistent with other studies that indicate distinctions in hormonal and biological pathways of pesticides based on sex. Further research is recommended in this arena as outlined in the Discussion section.
Alzheimer’s Disease Literature Breakdown
Advocates envision a transformational shift to organic agriculture and land management following substantial, peer-reviewed scientific research on the linkage between Alzheimer’s disease and pesticide exposure. A Consumer Reports analysis from last month indicates the health risks associated with low-level pesticide exposure, including elevated risk of neurological impacts such as dementia and Alzheimer’s. Particular classes of pesticides, including organophosphate compounds such as Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), disrupt lysosomal proteins which has been linked to the development of Alzheimer’s disease, according to findings in a 2024 study published in Heliyon. A different pesticide, the legacy insecticide DDT, was found to increase the risk of developing Alzheimer’s after researchers used numerous models demonstrating the effects of DDT on toxic protein production in the brain, based on findings in a 2022 study published in Environmental Health Perspectives. A 2014 study in JAMA Neurology, building on research gathered at Emory University (Georgia) and University of Texas Southwestern Medical School, reached a similar conclusion on linkage to DDT and associated metabolite exposure—even at low levels—to heightened risk of Alzheimer’s. In 2022, researchers at Arizona State University built on existing studies detecting the infamous weedkiller glyphosate in various animals’ brain tissues, finding that glyphosate crosses the blood-brain barrier in both in vitro (artificial environments) and in vivo (living organisms) studies, posing an increased risk of neurological diseases, including Alzheimer’s. Yet another study, published in 2016 in Nature Communications, found that the strobilurin class of fungicides produce genetic changes in mice that are consistent with human neurodegenerative diseases including Alzheimer’s. Be it exposure to herbicides, fungicides, or insecticides, experts from various research institutions conclude relationships between pesticide exposure and elevated risk of Alzheimer’s disease.
Huntington’s Disease and Dementia
Chronic and low-level pesticide exposure also leads to other neurodevelopmental disorders such as Huntington’s disease and dementia. Regarding Huntington’s disease, a 2023 case report published in Frontier in Public Health finds that inhalation of 1,3-dichloropropene (1,3-D or Telone) in workplace settings results in various adverse health effects, including brain edema/neuroinflammation, which can elevate risk of neurodegenerative diseases including Huntington’s, Alzheimer’s, and Parkinson’s. Studies focused on dementia arrive at similar conclusions. Organophosphate exposure has been linked to the onset of major health crises, including dementia, according to the accumulation of population-based research in a literature review published in Science of The Total Environment in 2024.
Parkinson’s Disease
The link between Parkinson’s disease and pesticides is notable given that a miniscule proportion of cases result from genetic inheritance; in other words, most Parkinson’s cases are borne from environmental or other confounding factors. In 2023, a study published in Parkinsonism and Related Disorders determined household exposure to readily accessible pesticides can double the risk of developing Parkinson’s. This phenomenon goes beyond household settings. After combining Parkinson’s Environment and Genes data with the California Pesticide Use Report system, researchers from University of California, Los Angeles found that Central Valley farmworkers had elevated instances of genetic mutations in genes associated with Parkinson’s disease after decades of exposure to organoarsenic pesticides, organophosphorus pesticides, and n-methyl carbamates. There has been growing movement by advocates to ban the use of paraquat in California because of sprawling scientific literature that indicates a relationship between Parkinson’s disease and paraquat exposure. The California bill AB 1963 introduced by Assemblymember Laura Friedman (D-Burbank), would ban the use of paraquat in agriculture and non-agricultural settings by the end of 2025. The California Assembly passed the bill on May 23 and it is currently being deliberated in the state Senate. This move does not surprise advocates after a Science of The Total Environment study published in 2024 found pesticide bans would be economically beneficial when considering long-term health savings. There are numerous additional studies that advocates point to regarding pesticide exposure and Parkinson’s Disease (here, here, and here) as well as in the Pesticide-Induced Disease Database entry on Parkinson’s disease that lists further peer-reviewed science on Parkinson’s.
Call To Action
Advocates continue to invest their time and energy in mobilizing diverse communities of concerned citizens, physicians, farmers, farmworkers, businesses, environmentalists, and elected officials to demand transformational change to food system practices. Rather than relying on a product substitution framework that permits the replacement of toxic pesticides for “less-toxic” pesticides, forward-thinking advocates demand a wholesale transformation toward models rooted in organic land management principles. See Action of The Week to stay informed of opportunities to mobilize your community to make the change you wish to see in eliminating the use of toxic petrochemical pesticides that ultimately enable the cascading crises of public health fragility, biodiversity collapse, and the climate emergency.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Psychiatry Research
