By Luyi Cheng
Glyphosate, the world’s most widely used weed killer, can reach the brain and cause inflammation associated with neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease, according to new research. These findings add to growing concerns that glyphosate and other pesticides are leaving a damaging impact on human health and the environment.
The results mark the first time scientists have identified glyphosate present in brain tissue, said Ramon Velazquez, an assistant professor studying neurodegenerative diseases at Arizona State University and a senior author of the study
Velazquez and a team of other scientists from Arizona State University, the City of Hope Comprehensive Cancer Center, and the Translational Genomics Research Institute published their work late last month in the Journal of Neuroinflammation.
Health concerns over glyphosate exposure
Glyphosate, also known as the active ingredient in Roundup, is the most used herbicide in the United States. It is popular with farmers who use it in their fields, and is also used in forestry management and for treating weeds in residential lawn and garden settings. A June report by the Centers for Disease Control and Prevention found that over 80 percent of urine samples collected from adults and children in the United States contained detectable levels of glyphosate.
The World Health Organization’s International Agency for Research on Cancer concluded that glyphosate is “probably carcinogenic to humans” in 2015. In 2019, more research tied glyphosate exposure to a 41% higher risk of cancer, specifically non-Hodgkin lymphoma. A series of court trials in the United States have also accused Monsanto of hiding the cancer risks of its Roundup products.
Despite the concerns about the health effects of glyphosate exposure, the Environmental Protection Agency (EPA) still declares that they have found “no risks of concern to human health when glyphosate is used in accordance with its current label” and that “glyphosate is unlikely to be a human carcinogen.”
Potential implications for neurodegenerative diseases
In addition to finding glyphosate in brain tissue, the study authors also found higher levels of an signaling molecule that causes inflammation, called TNFa, in the glyphosate-exposed mice.
While healthy adult brains are expected to have low levels of TNFa, brains with neurodegenerative diseases have much higher levels of TNFa. According to the study, the subsequent elevated levels of TNFa in the brain after glyphosate exposure “may have implications for neurodegenerative disorders such as Alzheimer’s Disease.”
The researchers conducted their study by dosing mice with glyphosate. After 14 days of exposure, they found the herbicide present in their brain tissue. To collect evidence that glyphosate could be connected to neurodegenerative diseases, the research team applied glyphosate to samples of brains cells extracted from the mice. After 24 hours, they found that the glyphosate exposure triggered the cells to increase production of a protein considered a hallmark of Alzheimer’s Disease.
According to Velazquez, it’s important to note that the glyphosate doses tested on the mice in this study (ranging between administering 250 and 500 milligrams of glyphosate per kilogram of mouse body weight per day) are higher than the typical daily exposure to humans. However, the doses are based on other past mice research and are still within the “maximum dose at which there is no significant toxic effect” for mice, initially established by the EPA. According to the study, the results “still hold value” in providing evidence of the potential consequences of glyphosate exposure.
More research is definitely needed, said Velazquez. “I think that this is an important first step: showing that [glyphosate] gets into the brain and induces these changes.”
The research team is continuing to study both the longer-term consequences of glyphosate, as well as human-relevant doses, in mice.