Roundup Weed Killer Linked to Cancer

Roundup (glyphosate) is a non-selective herbicide manufactured by agricultural giant Monsanto (now Bayer). It is used by farmers, gardeners, landscapers and agricultural workers in the United States and around the world as an all-purpose weed killer.

Since it first entered the market in the 1970s, Monsanto has marketed Roundup as safe and effective. One advertisement characterized Roundup as “safer than table salt.” Studies have shown, however, that Roundup can cause cancer and a myriad of other serious health problems.

In March 2015, the World Health Organization’s International Agency for Research on Cancer (IARC) surveyed the research on glyphosate, the active ingredient in Roundup. IARC concluded the blockbuster herbicide is “probably carcinogenic to humans,” and the cancer most associated with glyphosate exposure is non-Hodgkin lymphoma (NHL).

Evidence presented in the first lawsuits against Monsanto to proceed to trial indicate that Monsanto knew Roundup was carcinogenic for several decades. Rather than informing the public, Monsanto buried the risks as sales of Roundup continued to skyrocket around the world.

Outraged by Monsanto’s deception, thousands of farmers, agricultural workers, gardeners, landscapers, and their families have sued Monsanto alleging that Roundup caused them to develop cancer.

The following cancers have been linked to Roundup exposure:

  • Non-Hodgkin Lymphoma
  • Colon Cancer
  • Liver Cancer
  • Pancreatic Cancer
  • Kidney Cancer
  • Melanoma
  • Thyroid Cancer,
  • Bone Cancer
  • Breast Cancer

First Three Monsanto Trials Result in $2.424 Billion in Combined Jury Verdicts

The first three Roundup cancer lawsuits to proceed to trial resulted in a combined $2.424 billion in jury verdicts. The law firm of Baum Hedlund Aristei & Goldman is one of the leading law firms in the country representing individuals who allege exposure to Monsanto’s Roundup weed killer caused them to develop non-Hodgkin lymphoma (NHL). Learn more about the firm’s work on these cases in the links below.

Pilliod et al. v. Monsanto Co. – $2.055 Billion Jury Verdict

Johnson v. Monsanto Co. – $289.2 Million Jury Verdict

Hardeman v. Monsanto Co. — $80 Million Jury Verdict

What is Roundup?

Roundup is a non-selective herbicide used to kill weeds that compete with crops. Glyphosate, the active ingredient in Roundup, works by inhibiting a specific enzyme required for plant growth.

Roundup weed killer was first discovered by Monsanto in the 1970s. Public awareness about the toxic effects of pesticides and herbicides was at an all-time high then, and Monsanto was at the heart of the controversy. Monsanto’s blockbuster pesticide dichlorodiphenyltrichloroethane (DDT), which became a mainstay in American agriculture throughout the early 1900s, was shown to be toxic to humans, leading to DDT being banned in the U.S. in 1972.

Between 1961 and 1971, Monsanto was the key developer and supplier of Agent Orange to the military during the Vietnam War. In the late 1970s, after veterans returned from the war, Agent Orange was shown to cause serious health conditions, including increased rates of cancer, and nerve, digestive, skin, and respiratory disorders, higher rates of leukemia, Hodgkin’s lymphoma and non-Hodgkin lymphoma, throat cancer, prostate cancer, lung cancer, colon cancer, soft tissue sarcoma and liver cancer. It was in the aftermath of the DDT and Agent Orange fiascos that Monsanto first launched glyphosate as an all-purpose Roundup weed killer in 1974.

Roundup Ready Crops (GMOs)

Use of Roundup herbicide skyrocketed in the 1990s when Monsanto introduced Roundup Ready crops. Roundup Ready crops come from genetically modified seeds (GMOs) that were specifically engineered by Monsanto to be resistant to Roundup weed killer.

According to Monsanto, Roundup Ready crops substantially improve a farmer’s ability to control weeds, since Roundup can be sprayed on plants during the growing season without harming the crop. Monsanto’s Roundup Ready marketing was extremely effective, with an estimated 70% of corn and cotton and 90% of soybean production being genetically-modified Roundup Ready crops.

In 2001, Roundup became the most-used active ingredient in American agriculture, with an estimated 85-90 million pounds used each year. By 2007, that number ballooned reached 185 million pounds annually. Today, Roundup remains the most widely used herbicide in the United States and worldwide; one has to go to great lengths to avoid it.

Does Roundup Cause Cancer?

For decades, scientific studies have shown a causal association between Monsanto Roundup and an increased risk of various forms of cancer. There is mounting evidence that glyphosate in isolation is linked to a host of serious health conditions, including cancer. When glyphosate is combined with other ingredients in Roundup, the toxicity only increases.

In 1985, the Environmental Protection Agency (EPA) classified glyphosate as a Group C chemical, determining that glyphosate was probably carcinogenic to humans. This finding was based on early animal studies, which showed increased incidence of cancer in mice exposed to glyphosate.

In 1991, however, after heavy lobbying by Monsanto, the EPA re-evaluated the animal data and re-classified glyphosate as a Group E chemical, indicating that there was no evidence that glyphosate was carcinogenic in humans. This re-classification occurred shortly before Monsanto’s launch of Roundup Ready seeds and set the stage for what would become a $6 billion a year product for Monsanto.

Notably, on two separate occasions, the EPA determined that laboratories hired by Monsanto to study the toxicity of Roundup committed fraud. In the early 1970s, Monsanto hired Industrial Bio-Test Laboratories (IBT) to study Roundup’s toxicity. IBT conducted 30 separate tests on Roundup, including 9 of the original 15 studies done to register glyphosate with the EPA.

In 1976, the U.S. Food and Drug Administration (FDA) performed an inspection of IBT and discovered discrepancies between the raw data obtained in the studies and final reporting of the toxicological effects of glyphosate to the EPA. This led to an EPA audit of all IBT data and a finding that numerous toxicology studies of glyphosate were invalid. One EPA reviewer commented as part of the audit that there was “routine falsification of data” and that it was “hard to believe the scientific integrity of the studies[.]” As a direct result of this audit, in 1983, three top executives at IBT were convicted of fraud.

In 1991, Monsanto hired Craven Laboratories to perform various pesticide and herbicide studies, including studies for Roundup. Later that year, the owner of Craven laboratories and three of its employees were indicted for fraudulent laboratory practices.

In 1996, the New York Attorney General filed a lawsuit against Monsanto for falsely advertising Roundup as being “safer than table salt” and “practically non-toxic” to mammals, birds, and fish.  The New York Attorney General alleged that Monsanto was falsely telling farmers and agricultural workers that Roundup was non-toxic. This lawsuit led to an agreement between Monsanto and the New York Attorney General, whereby Monsanto agreed to stop falsely adverting Roundup as safe within the state of New York. Unfortunately, the agreement was limited to New York, and Monsanto continued to falsely market Roundup as being non-toxic in other states.

IARC Links Roundup to Cancer

Over the last 30 years, there have been numerous studies conducted by independent researchers showing a link between glyphosate and various forms of cancer and other serious health risks.

In 2015, IARC conducted an exhaustive analysis on the toxicity of glyphosate. IARC convened a panel of 17 international scientists from 11 countries to conduct a systematic review of all publically available information about glyphosate. The year-long review resulted in the publication of an IARC Monograph—the authoritative standard for cancer hazard assessment around the world.

IARC typically categorizes agents into four categories: Group 1 (known human carcinogens), Group 2A (probable human carcinogens), Group 2B (possible human carcinogens), and Group 3 (not classified). After its comprehensive evaluation of glyphosate, IARC concluded, among other things, that glyphosate is probably a human carcinogen (Group 2A). As a result of IARC’s study of glyphosate, the State of California’s Office of Environmental Health Hazard Assessment (OEHHA) determined to list glyphosate as an agent “known to the state to cause cancer” pursuant to Proposition 65.

How Does Glyphosate Cause Cancer?

Numerous studies, including a glyphosate residue study published in the Journal of Environmental & Analytical Toxicology in 2014, indicate that “chronically ill humans showed significantly higher glyphosate residues in urine than healthy population.” Glyphosate has been detected in the blood and urine of agricultural workers, indicating that agricultural use of Roundup leads to its absorption.

The IARC Monograph specifically evaluated farm workers in the United States, and found that, within days following the application of Roundup to a crop, approximately 60% of farm workers tested positive for glyphosate in the urine. In fact, in 1995, the Northwest Coalition for Alternatives to Pesticides reported that glyphosate was the third-most reported cause of pesticide illness among agricultural workers in California, which has the most comprehensive program for reporting pesticide-caused illness.

DNA Damage and DNA Strand Breaks

Various studies have shown that exposure to glyphosate can cause DNA damage and DNA strand breaks, which is an important precursor to cancer. Indeed, IARC specifically assessed the genotoxicity of Roundup (the property of chemical agents that damages the genetic information within a cell causing mutations, which may lead to cancer) and concluded that “[t]here is strong evidence that glyphosate causes genotoxicity.”

Oxidative Stress

Studies have also shown that that glyphosate exposure can induce oxidative stress, which is thought to be involved in the development of numerous conditions, including cancer, autism, and Parkinson’s disease. When the IARC evaluated whether glyphosate was associated with oxidative stress, the agency concluded that “strong evidence exists that glyphosate . . . can induce oxidative stress.” This could be an important mechanism by which Roundup causes cancer.

Impaired Gut Health

In addition to DNA damage and oxidative stress, some scientists have suggested Roundup’s association with various serious health conditions is linked to the effect that Roundup has on the digestive system.  Specifically, some scientists believe the same mechanism that makes Roundup toxic to weeds also makes it toxic to the microbes within the human gut. When humans are exposed to Roundup, it leads to a chronic inflammatory state in the gut, as well an impaired gut barrier, which can lead to many long-term health effects, including an increased risk of cancer.

Roundup is Banned or Restricted in Many Places Throughout the World

Due to the mounting scientific evidence indicating that glyphosate is a carcinogen, the following countries have issued outright bans on glyphosate, imposed restrictions or have issued statements of intention to ban or restrict glyphosate-based herbicides, including Roundup:

Costa Rica


Czech RepublicDenmark


El SalvadorFrance
MaltaMexicoNetherlandsNew ZealandOmanPortugalQatar
St. VincentThe GrenadinesSaudi ArabiaScotlandSlovenia




Sri Lanka








United Arab EmiratesUnited KingdomVietnam


Does Roundup Cause Non-Hodgkin Lymphoma?

In the IARC Monograph on glyphosate, the researchers conducted a systematic review of over 15 studies designed to assess whether there was an association between Roundup exposure in agricultural workers and Non-Hodgkin Lymphoma (NHL). The researchers reviewed each study, identified the results and assessed each study’s strengths and weaknesses. After the evaluation, IARC concluded that despite the limited evidence concerning the carcinogenicity of glyphosate in humans, a “positive association has been observed for non-Hodgkin lymphoma.”

In addition to the IARC’s assessment, in 2014, scientists published a systematic review and meta-analysis on the relationship between non-Hodgkin lymphoma and occupational exposure to agricultural pesticides, including glyphosate, in the International Journal of Environmental Research and Public Health. The study showed a statistically significant association between farm workers exposed to Roundup and non-Hodgkin lymphoma. It also confirmed two smaller studies from 2002 and 2008, published in the journal Leukemia & Lymphoma (2002) and the International Journal on Cancer (2008), both of which also showed a statistically significant increase in non-Hodgkin lymphoma among agricultural workers exposed to glyphosate.

Below are links to some of the studies demonstrating the link between Roundup exposure and NHL:

The Monsanto Papers

The Monsanto Papers are documents obtained during the Roundup litigation in discovery (pre-trial civil procedure allowing the parties to obtain evidence from each other). These documents allow people to see what happens “behind the curtain” of secrecy that normally shrouds ongoing litigation. You will find links to internal Monsanto emails, text messages, company reports, studies and other memoranda.

The documents in this chart are categorized as follows:

  • Absorption, Distribution, Metabolism & Excretion
  • Discrediting IARC Kate Kelland Interaction with Monsanto
  • Discrediting Seralini
  • Freedom to Operate
  • Ghostwriting, Peer-Review & Retraction
  • Media and PR Response
  • Prop 65 and OEHHA
  • Regulatory & Government
  • Surfactants, Carcinogenicity & Testing

The Monsanto Papers tell an alarming story of ghostwriting, scientific manipulation, collusion with the EPA and other agencies, and previously undisclosed information about how humans absorb glyphosate. These documents, which Monsanto does not want you to see, provide a deeper understanding of the serious public health consequences surrounding Monsanto’s marketing of Roundup.