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Monsanto attacks World Health Organization's report that calls Roundup a 'probable carcinogen'

Adam Allington | St. Louis Public Radio

St. Louis-based Monsanto lined up its experts for a conference call with reporters on Tuesday, to challenge last week’s determination by a World Health Organization committee that the active ingredient in Monsanto's Roundup weed killer could be dangerous to people with frequent exposure. 

“It contradicts decades of careful and credible research, reviewed by the world’s leading regulatory authorities," said Brett Begemann, Monsanto’s president and COO. “This contradiction has the potential to unnecessarily confuse and alarm parents and consumers, parents and the public at large."   

The determination, made by a team of 17 scientists who reviewed available medical literature, classified glyphosate, the active ingredient in Roundup, as a “probable carcinogen.”

The four possible determinations of risk the committee could have made are:   

Credit Adam Allington | St. Louis Public Radio

  • Group 1  Carcinogenic to humans (116 agents are classified in this group)
  • Group 2A  Probably carcinogenic to humans (73 agents)
  • Group 2B  Possibly carcinogenic to humans (287 agents)
  • Group 3  Not classifiable as to its carcinogenicity in humans (506 agents)
  • Group 4  Probably not carcinogenic to humans (1 agent)

There are 72 agents classified by the International Agency for Research on Cancer (the cancer arm of the WHO) that are listed in the same “probably carcinogenic” category as glyphosate. These include inorganic lead compounds, human papillomavirus and exposure to chemicals while working as a hairdresser.

Glyphosate was developed by Monsanto in the 1970's but has since aged out of its patent; generic versions are now sold by companies around the world. 

Last week’s decision, published in the journal Lancet Oncology, also reviewed four insecticides; Diazinon (2A), Malathion (2A), Parathion (2B) and Tetrachlorvinphos (2B). 

Read previous coverage of WHO’s carcinogen determination from St. Louis Public Radio.

In an interview with St. Louis Public Radio, the chair of the WHO committee that wrote the determination said reliable medical literature shows sufficient evidence that exposure to glyphosate increases the rate of rare cancers in mice. Paired with studies that show limited evidence that glyphosate may have a role in rates of non-Hodgkin’s lymphoma among farmers, the committee assigned it the 2A, or “probable carcinogenic” rating.

“There were enough studies to suggest something was going on, but not enough to be sure that was absolutely happening,” said Dr. Aaron Blair, a cancer epidemiologist and scientist emeritus at the National Institutes of Health in Rockville, Md. 

Monsanto held a press call Tuesday with company officials, a National Corn Growers Association representative and two toxicologists. They outlined a host of criticisms of the report, including: 

  • The report’s determination excluded the Agricultural Health Study, which studied health outcomes of American farmers and their spouses between 1993 and 2014. The brief instead cited three human studies from the National Institutes of Health, Canada, and Sweden.
  • The report cited a WHO study that showed a positive trend in a variety of highly aggressive cancer in male mice, but the researchers from that study concluded overall that the changes were not statistically significant. (Three other mouse studies suggesting a correlation between glyphosate and rare tumors were also cited).
  • A German health regulator, Bundesinstitut für Risikobewertung, had recently reviewed similar medical literature and determined that available evidence did not show glyphosate to have carcinogenic properties. 

Monsanto’s vice president of global regulatory affairs, Phil Miller, said the company would like the IARC to retract their statement and provide an accounting of how they came to their conclusion.

The WHO article was a 2-page brief with 16 footnotes, but a book-sized version of the committee’s findings is due later this year.

Committee chairman Blair declined to comment directly regarding the accusations.

“Any research that you do that has major economic consequences, it is appropriate that all sides of the argument be heard,” Blair said. “On all sides, it should follow normal rules of scientific evaluation. And as long as that happens, the debate is good.” 

The U.S. Environmental Protection Agency is currently re-evaluating glyphosate as part of a scheduled 15-year review.

Follow Durrie Bouscaren on Twitter for more health news: @durrieB

Copyright 2021 St. Louis Public Radio. To see more, visit St. Louis Public Radio.

Durrie Bouscaren was a general assignment reporter with Iowa Public Radio from March 2013 through July 2014.
Durrie Bouscaren
Durrie Bouscaren covers healthcare and medical research throughout the St. Louis metro area. She comes most recently from Iowa Public Radio’s newsroom in Des Moines, where she reported on floods, a propane shortage, and small-town defense contractors. Since catching the radio bug in college, Bouscaren has freelanced and interned at NPR member stations WRVO, WAER and KQED. Her work has aired on All Things Considered, KQED’s The California Report, and Harvest Public Media, a regional reporting collaborative.
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