27
Feb
Glyphosate Weed Killer Contaminates Stem Cells, Is Linked to Blood Cancers and DNA Damage, Study Finds
(Beyond Pesticides, February 27, 2025) In analyzing current scientific literature and data on glyphosate-based herbicides (GBHs), a research article in Environmental Sciences Europe finds that glyphosate (GLY) persists in bones before reentering the bloodstream. The mechanisms in which GLY interacts with important cells for development, called hematopoietic stem cells (HSCs), and breaks and rearranges DNA offer a possible explanation for the heightened risk of cancer, specifically blood cancers like non-Hodgkin lymphoma (NHL), myeloma, and leukemia.
“Existing data on GLY/GBH metabolism and genotoxicity provide critical insights into how exposures may be contributing to blood cancers,†according to the study’s author, Charles Benbrook, PhD. Dr. Benbrook continues: “A significant portion of GLY reaching blood moves quickly into bone marrow and then bone, where it can bioaccumulate and persist… Data reviewed herein suggest that a portion of the GLY excreted by most people on a daily basis can be traced to the shedding of calcium-GLY complexes in bone back into the blood supply.â€
This allows for near-constant contact between glyphosate molecules and hematopoietic stem cells, which are immature cells that can develop into any type of blood cell. Mutations in hematopoietic stem cells can cause blood cancers to emerge. Those at disproportionate risk with GLY exposure, such as farmworkers and pesticide applicators, likely have “hundreds of million, if not billions of GLY molecules in bone marrow for every hematopoietic stem cell,†Dr. Benbrook states, highlighting the connection between GLY exposure and blood cancer risk.
There is a wide body of science on pesticide-induced diseases, with a multitude of studies focusing on GLY/GBH exposure. (See more coverage from Beyond Pesticides here and stay tuned for an in-depth analysis on recent research connecting agrichemical mixtures and pediatric cancer.) These studies confirm that products containing glyphosate can trigger oxidative stress, impair DNA, and increase cancer risk. (See previous Beyond Pesticides coverage here, here, here, and here.) The mechanisms behind these effects are not fully understood, but research, including Dr. Benbrook’s article, showcases potential pathophysiologic bases (combining pathology and physiology) for better understanding the extent to which GLY impacts organisms down to the molecular level.
History of Glyphosate
As the review highlights, GLY is “the most heavily applied pesticide ever brought to market… No other pesticide in history has come close to such extensive worldwide use.†The widespread utilization of this pesticide endangers not only pesticide applicators, but farmers, farmworkers, and their families, those who live near agricultural land, and the general public that consumes food and beverages containing GLY residues.
With its wide use, glyphosate exposure raises concern for all organisms and the environment. As Dr. Benbrook says, “Excessive reliance on GLY has brought on several problems. These include the emergence and spread of resistant weeds, loss of terrestrial biodiversity, water contamination, and declining soil health.â€
GLY exposure, and subsequent research, span many decades. The debate over the carcinogenicity of GLY has persisted for over 40 years, but regulatory agencies such as the U.S. Environmental Protection Agency (EPA) and the European Food Safety Authority (EFSA) “are among several regulatory authorities that have concluded that dietary exposure to active substance glyphosate is unlikely to pose cancer risk.†Dr. Benbrook continues in saying, “But substantial data show that applicators of formulated glyphosate-based herbicides are often exposed dermally to much higher levels of GLY and that repeated dermal exposure episodes over many years heightens cancer risk.†(See studies here, here, here, and here.)
There are many regulatory deficiencies, and dermal exposure to GLY is just one of them. As the review shares: “The Office of Pesticide Programs (OPP) in the U.S. EPA has largely ignored dermal exposures to GBHs in the still ongoing reregistration review cycle… [T]he OPP concluded that applicator and occupational exposure and risk assessments were not necessary. This OPP judgement, and the 0.1 mg/kg occupational exposure threshold, are not based on studies capable of detecting the impacts of GLY/GBH on hematopoietic stem cells.â€
In a previous article by Dr. Benbrook, he analyzes independent research reviewed by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) and reports “~ 80% produced some evidence supportive of an association between GLY/GBHs and DNA damage.†Despite this finding, EPA has continued its registration of GLY. “The OPP relied on mostly negative genotox/mechanistic studies on glyphosate technical carried out by GBH registrants, and the agency dismissed or ignored multiple in vivo studies reporting evidence of genotoxicity and/or oxidative stress following exposure to GBHs, including some studies in exposed human populations,†Dr. Benbrook notes.
Additional independent research (see here and here) of GBHs highlights evidence linking GBH exposures to cancer outcomes. More specifically, as Dr. Benbrook states, “Papers published since the completion of the EPA and IARC reviews have enhanced the weight-of-evidence supporting a linkage between GBH exposures and some hematopoietic cancers.†(See studies here and here.)
Review of Study Data
To explore his hypotheses regarding how GLY storage occurs in bones and how the prolonged interaction with hematopoietic stem cells heightens the risk of blood cancers, Dr. Benbrook critiques animal bioassays and epidemiologic studies that “link GLY/GBH exposure to heightened risk of blood cancers, and possibly other pathologies.â€
The research he reviews shows adverse impacts on both human and animal health, including non-Hodgkin lymphoma, leukemia, DNA damage, reduced birth weight, dysbiosis in gut microbiota, impaired development in children, and more. Additional areas of concern highlighted by studies involve surfactants in pesticide formulations, as well as the metabolites (breakdown products) of GLY. The implications of these finding are enormous since many biomonitoring studies focused on GLY “show that a majority of people, usually 70–90% or more of individuals tested, have detectable levels of GLY and/or its primary metabolite aminomethylphosphonic acid (AMPA) in their urine or blood,†Dr. Benbrook shares. (See studies here, here, here, here, and here, as well as previous Daily News coverage on GLY contributing to body burden here and here.)
He continues: “[D]ietary exposures and risk assessments should, but often do not, include data on levels of AMPA in food and beverages. This is because once sprayed on a food crop, the GLY in a GBH breaks down to AMPA incrementally over time. Many epidemiological studies report stronger associations between AMPA levels in human biofluids and adverse health outcomes, compared to associations between GLY and the same adverse outcome.â€
Dr. Benbrook also states: “[T]he impact of GLY and AMPA on the etiology of cancer must be evaluated taking into account the impacts of other chemicals. Exposures to complex mixtures can augment oxidative stress, disrupt the repair of damaged DNA, and trigger other adverse genetic and epigenetic effects that, in turn, alter the impacts of GLY and AMPA on cancer and other health outcomes. Moreover, such effects can occur at doses well-below current safety thresholds.â€
Results noted in the review article include:
- “An analysis of GLY/GBH genotoxicity studies published since the completion of the 2015 OPP and IARC GLY oncogenicity reviews found that 24 of 33 assays on technical GLY were positive, and 58 of 61 were positive in assays testing GBHs (overall, 82 positives out of 94 assays, or 87%).â€
- An “in-depth quality analyses of genotoxicity and endocrine disruption revealed strong and consistent positive findings… [GBHs] elicited a stronger effect in both human and animal systems when compared to glyphosate alone…the highest quality studies in humans and human cells consistently revealed strong evidence of genotoxicity.â€
- A Monsanto-commissioned GLY and GBH dermal penetration study “tested penetration rates through rat skin for pure GLY and a formulated GBH and reported that almost ninefold more GLY in the formulated product moved through rat skin compared to pure GLY.â€
- “Substantial GLY metabolism data show that within minutes of entering the bloodstream, GLY moves into bone marrow, and then laterally through bone tissue and back into general circulation.â€
- GLY lingers longer in bones than in blood and other tissue. In four rat metabolism studies, “the largest percentage of the delivered dose of GLY at study termination is retained in bone… The results highlight the degree to which bone is the tissue in which GLY bioaccumulates and where it remains for an extended period of time.â€
- An unpublished Monsanto study in 1983 “demonstrates that over time GLY remains at significantly higher levels in bone marrow compared to blood plasma… These pharmacokinetic findings are consistent with insights gained from [more recent] rat metabolism studies.â€
HSCs and Risk of Blood Cancers
This review focuses on understanding the mechanisms by which exposure to GLY contributes to the risk of hematopoietic cancers based on the current scientific literature. The metabolism data regarding GLY shows its propensity to bind to calcium and become immobilized within bones before reentering the blood stream. This occurs through chelation (a type of bonding), allowing GLY molecules to remain in the body for an extended period of time.Â
In identifying GLY as a genotoxic threat that lingers in bones, Dr. Benbrook’s hypothesis connects the compound with heightened blood cancer risks. “An extensive literature exists on the specific genetic abnormalities typically associated with the etiology of blood cancers,†the review states. “This literature, coupled with published studies on the genotoxicity of GLY and GBHs, helps explain where and how GLY and the coformulants in GBHs can come into contact with HSCs and possibly trigger damage to DNA.â€
Dr. Benbrook continues: “Importantly, GLY has been shown to induce double-strand DNA breaks in human lymphocytes at low doses. Double-strand breaks result in the sort of gene rearrangement and genetic changes typically seen in human NHL… Damage to the DNA in HSCs and progenitor B cells can also lead to several subtypes of leukemia.†Additional studies corroborate this, such as the Agricultural Health Study (AHS), which finds greater leukemia incidence associated with GLY exposure. (See studies here, here, and here.)
Organic Solution
The science showing adverse health effects to humans and wildlife with pesticide exposure is vast, as is data supporting organic alternatives for land management. While current pesticide registration processes are lacking, as highlighted above (and in previous coverage here, here, here, and here), it is more concerning that they do not consider substitutive methods that mitigate threats to all organisms and ecosystems.
Organic agriculture, without the use of GLY/GBHs and other harmful chemicals, provides health and environmental benefits while combatting current crises of biodiversity and climate change in a holistic manner. Help support Beyond Pesticides’ mission of transitioning to a world free from toxic pesticides and synthetic fertilizers by becoming a member today. Stay up to date with the latest science and policy developments with the Daily News Blog and sign up to receive Action of the Week and Weekly News Updates straight to your inbox here.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Benbrook, C. (2025) Hypothesis: glyphosate-based herbicides can increase risk of hematopoietic malignancies through extended persistence in bone, Environmental Sciences Europe. Available at: https://enveurope.springeropen.com/articles/10.1186/s12302-025-01057-1.
