Skip to Content
No Fees Unless We Win 855-948-5098

Five Facts About IARC and the Glyphosate Debate That You Should Know


Feb. 23, 2018 – Washington D.C. – – On Feb. 6, 2018, the U.S. House of Representatives Committee on Science, Space and Technology held a hearing to scrutinize the International Agency for Research on Cancer (IARC) and its evaluation of glyphosate, the active ingredient in Monsanto’s Roundup weed killer as a probable human carcinogen, which has spurred lawsuits across the country.

The committee heard testimony from four witnesses, three of whom are aligned with Monsanto and the chemical industry. The lone witness testifying in defense of IARC was Jennifer Sass of the National Resources Defense Council (NRDC).

In her testimony, Dr. Sass articulated IARC’s important role in helping to shape public health decision making in the U.S. and around the world. She also outlined the dangers of glyphosate and Monsanto’s efforts to subvert IARC’s finding that glyphosate is a probable human carcinogen.

Monsanto Pushes Myths Instead of Facts About IARC and Glyphosate Safety

Weeks after her testimony, Dr. Sass wrote an insightful blog for the NRDC unpacking some of the false claims about IARC and glyphosate overheard at the Science Committee hearing. Below you will find five facts about IARC and glyphosate to serve as a rebuttal for these false claims.

Fact – IARC Does Not Claim Everything Causes Cancer

The chemical industry and its interests often make the claim that IARC is an extreme organization trumpeting alarmist claims that everything causes cancer. This is false. Only about 20 percent of the substances reviewed by IARC are classified as probable or known carcinogens.

As of February 2018, IARC has evaluated 1,003 chemicals, substances, or other agents in its Monograph program, all of which had enough cancer data to support a nomination for possible evaluation.

Out of 1,003 evaluations, only 120 are classified as known human carcinogens, and only 81 are classified as probable human carcinogens. More than half of the substances evaluated did not have enough data for classification (‘Not classifiable as to its carcinogenicity to humans’). This should actually be of grave concern to members of the House Science Committee because many of the substances in this category are used in everyday commercial products, and yet there is not enough data to know whether or not they are carcinogenic.

Fact – The Two Major Articles Touting Glyphosate Safety Were Funded by Monsanto

The two review articles Greim (2015) and Kier & Kirkland (2013) are often cited by Monsanto and the chemical industry to demonstrate glyphosate’s safety. According to IARC, at the time of the glyphosate meetings in 2015, neither of the review papers reported enough details on the studies they used “for an independent evaluation of the conclusions reached by the Monsanto scientist and other authors.” As noted in the monograph preamble, IARC policy is to only review published, peer-reviewed research in the public domain.

In his testimony before the House Science Committee, Robert Tarone, an industry consultant and one of three Republican majority witnesses, claimed that if IARC had reviewed the data from Greim, glyphosate would have been exonerated. However, an independent analysis of Greim conducted by Dr. Christopher Portier found many more tumors in animal studies than the authors reported. In his report, Dr. Portier identified an excessively high number of malignant lymphomas and hemangiosarcomas in male mice (see page 37).

It is also noteworthy that a hearing on scientific integrity touted a study by Dr. Helmut Greim, who is something of a controversial figure. Dr. Greim once sat on a ‘scientific panel’ funded by car manufacturers to counter an IARC report that diesel exhaust is a known human carcinogen.

The panel conducted studies in which monkeys in a chamber were exposed to diesel exhaust. However, the cars producing the exhaust were rigged with defeat devices (now infamous as a result of the recent Volkswagen scandal) that produced pollution levels far less harmful in the laboratory than on the road. Put simply, the results were deliberately manipulated and the study is now known as ‘Monkeygate,’ which was never published.

Fact – The IARC Working Group Extensively Reviewed All Available Glyphosate Studies That Met Necessary Criteria

Reuters writer Kate Kelland has reported and others (including members of the House Science Committee) have repeated that IARC did not consider the Agricultural Health Study (AHS), which is evidence that IARC’s conclusions on glyphosate are wrong. This is not true. IARC performed a rigorous review of the AHS, as noted by Dr. Charles Jameson, a member of the IARC Working Group responsible for the glyphosate monograph (see page 114).

Also noteworthy, the 2017 AHS update found some evidence of a possible association between glyphosate exposure and acute myeloid leukemia (AML), an aggressive blood cancer. The authors of the study warned: “Given the prevalence of use of this herbicide worldwide, expeditious efforts to replicate these findings are warranted.”

In 2016, a Monsanto-funded review and meta-analysis of epidemiological studies that included the AHS concluded that glyphosate exposure carries a statistically significant risk of non-Hodgkin lymphoma (NHL), which strengthened IARC’s conclusions.

The AHS also has a number of flaws that are never addressed by those who tout the study’s findings. In a January 2018 court deposition, Dr. Jameson stated that the AHS was “seriously” and “fatally” flawed.

Fact – Poison is Poison, Regardless of Dose

“The dose makes the poison” is a common chemical industry mantra. The line was repeated by Dr. Timothy Pastoor, another majority witness at the House Science Committee hearing with ties to industry. Dr. Pastoor, who worked for Syngenta, noted that consideration of hazard without “context” (dose) is outdated.

Quantifying exposure with dosage is important when evaluating the risk of a substance. Nevertheless, numerous other factors, including genetics, co-exposures to other substances, types of exposure, the health of those exposed, and the age of the exposed, among countless other variables, can impact whether adverse health effects are likely to occur. The importance of these variables with regard to evaluating low-dose toxicity of chemicals was cited in a 2017 National Academies of Sciences, Engineering and Medicine report.

Fact – EPA and EFSA Were Influenced by Monsanto While Evaluating Glyphosate

According to court documents, both the EPA and EFSA assessed glyphosate’s carcinogenicity using methods championed by Monsanto. As reported by the Guardian, EFSA’s glyphosate assessment came directly from a draft provided by Monsanto.

For its glyphosate assessment, the EPA’s Office of Pesticide Programs used a systematic review process that came from the EPA’s Office of Chemical Safety and Pollution Prevention, an office run by a former chemical lobbyist.

This method, which has not been scrutinized by the public or via peer review, benefits industry in the following ways:

  • Preferential reliance on Guideline studies conducted by the regulated industry to support the approval of its products. The issue with Guideline studies is that they focus solely on major health endpoints, so they will not predict or indicate early-warnings of potential toxicity that could cause other adverse health events. They are also not designed to consider low-dose exposures, endocrine or hormonal effects, immunotoxicity, cardiotoxicity, learning or behavioral effects, or ‘upstream’ effects like reduced sperm count. Please post in a larger font.
  • Preferential reliance on studies following so-called Good Laboratory Practices (GLP), which are required by industry product-testing labs to prevent malfeasance and misconduct. Industry promotes GLP studies as being higher quality and more reliable because it allows them to champion their own studies over those conducted by independent laboratories, which are not subjected to the same standards. While GLP standards help prevent commercial laboratories from committing outright fraud, they do not ensure that studies are high quality. Please post in larger font.

According to an internal EPA memo, if the Office of Pesticide Programs followed the EPA’s own Cancer Guidelines, its conclusions on glyphosate may have been more in line with IARC.



  • Please enter your first name.
  • Please enter your last name.
  • Please enter your phone number.
    This isn't a valid phone number.
  • Please enter your email address.
    This isn't a valid email address.
  • Please enter your city.
  • Please enter your state.
  • Please make a selection.
  • Please make a selection.
  • Please enter a message.