Study indicates “persistent, damaging” effects of glyphosate herbicide exposure on brain health

Exposure to a widely used weed killing chemical could be having “persistent, damaging effects” on brain health, according to a new study.

The study, published Wednesday in the Journal of Neuroinflammation, found that laboratory mice exposed to glyphosate herbicide developed significant brain inflammation, a condition associated with neurodegenerative diseases such as Alzheimer’s. The researchers, many who are associated with a neurodegenerative disease research center at Arizona State University (ASU), said the symptoms continued even long after exposure ended.

“This work is yet another step forward in understanding the impact of this widely used herbicide on the brain,” lead ASU researcher Ramon Velazquez said. “But more research is needed to determine the impact that glyphosate has on the brain since most Americans are exposed to this herbicide on a daily basis.” Velazquez noted that the work is particularly important given the increasing incidence of cognitive decline in the aging population, particularly in rural communities where glyphosate is used in farming. 

Glyphosate is the most commonly used herbicide globally – made popular by Monsanto Co as the active ingredient in its Roundup brand, among others. It has been used so extensively by farmers, homeowners and industrial and municipal users for so long that it is considered ubiquitous – found in food, water and in human urine samples. A 2022 report by a unit of the Centers for Disease Control and Prevention (CDC) said more than 80% of urine samples drawn from children and adults in a US health study contained glyphosate.

Several authors of the new paper were also part of a team that published a prior, related study that examined the impact of glyphosate when it infiltrates the brain.  

In the new study, the dosing of the mice ran for 13 weeks, followed by a six-month recovery period. The research used both normal mice and transgenic mice that had been genetically altered to carry genes that cause them to develop Alzheimer’s symptoms.

Even a low dose, close to the limit used to set acceptable doses for humans, had harmful effects on the mice, the researchers determined.

The authors said the mouse study showed that glyphosate exposure resulted in premature death, “accelerated” Alzheimer’s disease-like pathology and “subsequent anxiety-like behaviors” in the transgenic mice, and caused neuroinflammation in both types of mice, despite months of recovery after the glyphosate dosing. The finding that a byproduct of glyphosate called aminomethylphosphonic acid accumulated in brain tissue raises serious concerns about the chemical’s safety for human populations, according to an ASU press release about the study.

The study was funded by the National Institutes on Aging, the National Cancer Institute of the National Institutes of Health, and the ASU Biodesign Institute.