In December 2018, a man in California who claimed the herbicide glyphosate in Roundup led to his cancer received $289 million in damages from a California jury, although the amount has since been reduced to approximately $87 million. (1). This was the first lawsuit to go to trial that alleged there is a link between glyphosate and cancer.
What The Ruling Said
Jurors in the case found that Monsanto’s weedkillers contributed substantially to the malignant non-Hodgkin’s lymphoma he contracted in 2014. His attorneys said he regularly used a type of RangerPro while he was a groundskeeper in Benicia, California. The ruling said the possible risks of the herbicide were known to the scientific community, and that Monsanto had failed to warn about the danger. Jurors also found that the company had acted with malice, and there should have been a warning label about the possible health hazards.
Is there an actual link between cancer and glyphosate?
Glyphosate Cancer Study Overview
There have been several studies that have looked into the possibility of the active herbicide ingredient glyphosate causing cancer in humans, including non-Hodgkins’ lymphoma. Some of the primary studies are highlighted below, which generally do not support a link between exposure to glyphosate and various forms of cancer.
Epidemiologic Studies of Glyphosate and Cancer: A review – Pamela J. Mink, Jack S. Mandel. Bonnielin K. Sceurman, Jessica I. Lundin. (2).
The EPA and other regulatory agencies around the world have registered glyphosate as a herbicide that can be used on various food and non-food use crops. Glyphosate is widely regarded by regulatory authorities to have no carcinogenic potential. This is based primarily on the results of several carcinogenicity studies of rats and mice.
To examine possible cancer risks in humans, the researchers reviewed epidemiologic literature to see whether exposure to the chemical is associated casually with a risk of cancer in humans. The researchers also examined relevant methodological and biomonitoring studies of glyphosate. Seven cohort studies and fourteen case-control studies looked at the association between glyphosate and one or more cancer results.
Their review found no consistent pattern of positive associations indicating a causal relationship between total cancer and site-specific cancer and exposure to glyphosate. Data from biomonitoring studies highlighted the importance of exposure assessment in epidemiological studies. They indicate that studies should incorporate the duration and frequency of the use of the pesticide but also its formulation.
The researchers reviewed epidemiologic studies of glyphosate and cancer outcomes; identified seven cohort studies and 14 case-control studies. Their review found no consistent pattern of positive associations with any cancer.
II. Differences in the Carcinogenic Evaluation of Glyphosate Between the International Agency for Research on Cancer (IARC) and the European Safety Authority (EFSA) (2).
The International Agency for Research on Cancer (IARC) Monographs Programme is responsible for identifying chemicals, drugs, mixtures, occupational exposures and physical and biological agents that cause cancer in humans. Monographs are written by ad hoc Working Groups (WGs) of international experts over approximately a year. For Monograph 112, 17 expert scientists evaluated the carcinogenic hazard for four insecticides, including glyphosate. The WG concluded that data for glyphosate meet the criteria for the chemical to be classified as a probable human carcinogen.
The European Food Safety Authority (EFSA) is the principal agency of the EU for risk assessments about food safety. In October 2015, EFSA reported on their evaluation of the Renewal Assessment Report (RAR) for glyphosate that was prepared by the Rapporteur Member State, which is the Geerman Federal Institute for Risk Assessment. EFSA concluded that glyphosate is unlikely to pose any carcinogenic hazard to humans, and the evidence does not support any such classification regarding its carcinogenic potential.
This study concludes that because there were severe flaws in the scientific evaluation in the RAR that incorrectly characterize the potential for a carcinogenic hazard for exposure to glyphosate, it was important that these flaws were corrected.
This study also strongly disagreed that data from studies published in peer-reviewed literature should get less weight than guideline studies. Compliance with guidelines and GLPs does not guarantee the validity and relevance of the design of a study, the statistical rigor of the study or attention to sources of biases.
III. Glyphosate Use and Cancer Incidence in the Agricultural Health Study (4).
Glyphosate is the most widely used herbicide in the world, with residential and agricultural uses. In 2015, the IARC classified glyphosate as probably carcinogenic to humans, noting what it called strong mechanistic evidence and positive associations for non-Hodgkin lymphoma in some epidemiological studies. A previous evaluation in the Agricultural Health Study with a follow-up in 2001 found no statistically significant associations with glyphosate use and any cancer at any site.
The AHS is a cohort of licensed pesticide applicators from Iowa and North Carolina. The previous evaluation of glyphosate with cancer incidence from registry linkages was updated through 2012 in North Carolina and 2013 in Iowa. Lifetime days and intensity-weighted lifetime days of glyphosate use were based upon information that was self-reported from enrollment between 1993 and 1997, as well as follow up questionnaires from 1999 to 2005.
Among 54,251 applicators, 44,932 used glyphosate and there were 5779 incident cancer cases. In an unlagged analysis, glyphosate was not statistically significantly associated with cancer at any site. But among applicators in the highest exposure quartile, there was a higher risk of acute myeloid leukemia compared with never users, although this association was not deemed statistically significant.
In conclusion, in this large, prospective cohort study, there was no association apparent between glyphosate and any solid tumors or lymphoid malignancies, including non-Hodgkin’s lymphoma and its various subtypes. There was some evidence of AML among the groups with the highest exposure which requires confirmation.
- (1). Weedkiller Cancer Ruling: What Do We Know About Glyphosate? (2018). Retrieved from https://www.bbc.com/news/world-us-canada-45155788
- (2). Epidemiologic Studies of Glyphosate and Cancer: A review. (2012). Retrieved from https://www.sciencedirect.com/science/article/pii/S0273230012000943
- (3). Differences in the Carcinogenic Evaluation of Glyphosate Between the International Agency for Research on Cancer (IARC) and the European Safety Authority (EFSA). Retrieved from https://jech.bmj.com/content/70/8/741
- (4). Glyphosate Use and Cancer Incidence in the Agricultural Health Study. (May 2018). Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/29136183