New studies reveal a link between glyphosate exposure in mice and signs of neuroinflammation, along with accelerated Alzheimer’s disease-like damage. This research monitors glyphosate’s byproducts in the brain long after exposure has stopped, indicating a range of lasting, harmful effects on brain health. The results imply that the brain might be more vulnerable to the harmful impacts of this herbicide than previously understood. Glyphosate is one of the most widely used herbicides in the U.S. and around the globe.
The human brain has remarkable adaptability, often capable of recovery even after severe injury. However, fresh research indicates that even short-term exposure to a common herbicide can result in long-lasting brain damage, continuing well past the end of exposure.
In an innovative study, Ramon Velazquez from Arizona State University and his team at the Translational Genomics Research Institute (TGen), part of City of Hope, found that mice subjected to glyphosate exposure experience notable brain inflammation, which is linked to neurodegenerative diseases. This research suggests that the brain may be more vulnerable to the herbicide’s harmful effects than previously recognized. Glyphosate is among the most common herbicides in use across the U.S. and globally.
The findings, published today in the Journal of Neuroinflammation, highlight a correlation between glyphosate exposure in mice and symptoms indicative of neuroinflammation, as well as accelerated Alzheimer’s disease-like pathology. The research traces the presence and effects of glyphosate’s breakdown products in the brain even after exposure has ceased, revealing various persistent and damaging consequences for brain health.
Mice exposed to glyphosate also exhibited premature deaths and anxiety-related behaviors, aligning with previous findings from other studies examining glyphosate’s effects in rodents. Moreover, the researchers noted that these symptoms continued even after a recovery period of six months during which the exposure was stopped.
Furthermore, the study found that a glyphosate byproduct, aminomethylphosphonic acid, accumulated in brain tissue, raising significant safety concerns regarding the chemical’s impact on human health.
“Our research adds to the growing body of evidence illustrating the brain’s susceptibility to glyphosate,” Velazquez explains. “Given the increasing rates of cognitive decline in the older population, especially in rural areas with higher glyphosate exposure due to large agricultural operations, there is a pressing need for further foundational research on the effects of this herbicide.”
Velazquez is affiliated with the ASU-Banner Neurodegenerative Disease Research Center at the ASU Biodesign Institute and serves as an assistant professor at the School of Life Sciences. He is supported by first author Samantha K. Bartholomew, a PhD candidate in the Velazquez Lab, as well as other ASU colleagues and co-senior author Patrick Pirrotte, who is an associate professor at TGen and a researcher at the City of Hope Comprehensive Cancer Center in California.
According to the Centers for Disease Research, agricultural workers and those in landscaping are more likely to experience glyphosate exposure, either through inhalation or skin contact. Additionally, the new study indicates that consuming food with residual glyphosate, which has been sprayed with the herbicide, can pose health risks. Most individuals in the U.S. have encountered glyphosate at some point in their lives.
“Our hope is that our findings prompt more research into the effects of glyphosate exposure, which could lead to a reevaluation of its long-term safety and stimulate discussions about other widespread toxins in our environment affecting brain health,” says Bartholomew.
The team’s results build on earlier ASU studies that establish a connection between glyphosate exposure and an increased risk of neurodegenerative disorders.
Previous research showed glyphosate can cross the blood-brain barrier, which usually protects the brain from potentially harmful substances. Once inside, glyphosate interacts with brain tissues and appears to contribute to neuroinflammation and other adverse effects on neural function.
The EPA claims certain levels of glyphosate exposure are safe for humans, suggesting the chemical is minimally absorbed and mostly expelled unchanged from the body. However, recent research, including this study, indicates that glyphosate and its major metabolite, aminomethylphosphonic acid, can persist and accumulate in brain tissue over time, raising concerns about the adequacy of current safety standards and the overall safety of glyphosate use.
Herbicide may affect more than just weeds
Glyphosate is the most widely used herbicide globally, prevalent on crops such as corn, soybeans, sugar beets, alfalfa, cotton, and wheat. Since the release of glyphosate-tolerant crops in 1996, its usage has soared, predominantly in agricultural settings.
The U.S. Geological Survey indicates that around 300 million pounds of glyphosate are used annually in the United States. Although glyphosate levels on imported food are regulated, enforcement and specific limits vary. Its widespread application has led to glyphosate’s presence throughout the food chain, and it can be found in air, soil, surface water, and groundwater.
Even though the EPA regards glyphosate as safe, the International Agency for Research on Cancer has classified it as “possibly carcinogenic to humans.” Emerging studies, including this one, indicate its potential role in exacerbating neurodegenerative diseases through contributing to pathologies, such as those observed in Alzheimer’s disease.
The chemical operates by blocking a specific enzyme pathway in plants necessary for producing vital amino acids. However, its effects extend beyond plants, negatively impacting mammalian biological systems, as evidenced by its persistence in brain tissue and involvement in inflammatory processes.
“Herbicides are used extensively and consistently worldwide,” states Pirrotte, an associate professor in TGen’s Early Detection and Prevention Division, director of the Integrated Mass Spectrometry Shared Resource at TGen, and City of Hope, and the main author of the study. “These findings underline that many chemicals we commonly encounter, previously deemed safe, could present potential health hazards. Nonetheless, more research is necessary to fully evaluate the public health implications and identify safer alternatives.”
Is glyphosate actually safe to use?
The researchers predicted that glyphosate exposure would lead to neuroinflammation in normal mice and aggravate neuroinflammation in Alzheimer’s model mice, resulting in increased Amyloid-β and tau pathology and impaired spatial cognition after recovery. Amyloid-β and tau proteins are key components of plaques and tangles, classic indicators of Alzheimer’s disease. These plaques and tangles disrupt normal neural activities and contribute to memory decline and cognitive impairment.
The study was conducted over 13 weeks, followed by a six-month recovery phase. The primary metabolite, aminomethylphosphonic acid, was found in the brains of both standard and transgenic mice with Alzheimer’s-like symptoms. Transgenic mice are genetically manipulated to develop Alzheimer’s-like characteristics as they age, allowing researchers to explore disease progression and effects in a controlled laboratory environment.
The researchers examined two glyphosate exposure levels: a high dose similar to previous studies and a lower dose that is nearly at the limit considered acceptable for humans.
Even the lower dosage resulted in harmful outcomes in the brains of mice, persisting months after exposure stopped. Although reports indicate that most Americans encounter glyphosate daily, these findings reveal that even brief exposure could lead to neurological damage.
Glyphosate triggered a prolonged increase in inflammatory markers in both the brain and blood, continuing even after the recovery period, suggesting that this persistent inflammation could accelerate neurodegenerative disease progression, including Alzheimer’s. It indicates that even short-term glyphosate exposure may lead to long-lasting inflammatory processes affecting brain health.
The data suggest that glyphosate exposure could be a significant health concern for humans. The researchers emphasize the need for ongoing monitoring and thorough research on the neurological and other long-term adverse health effects of glyphosate.
“Our objective is to identify environmental elements contributing to the rising incidence of cognitive decline and neurodegenerative diseases in our communities,” Velazquez states. “By uncovering these factors, we can create strategies to reduce exposure, thereby enhancing the quality of life for our aging population.”
This study was funded by the National Institutes on Aging, National Cancer Institute of the National Institutes of Health, and the ASU Biodesign Institute.
