Science in Society Archive

Glyphosate ‘Probably Carcinogenic to Humans’ Latest WHO Assessment

The world authority on cancer’s evidence-based assessment is pitched against the Monsanto-led corrupt approvals in US and Europe Dr. Mae-Wan Ho and Dr Nancy Swanson

World authority experts selected free from conflict of interest

The world authority on cancer, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) declared the herbicide glyphosate ‘probably carcinogenic to humans’ in its latest expert assessment [1, 2]. A Working Group of 17 experts from 11 countries met at IARC headquarters 3-10 March 2015 in Lyon, France. The meeting followed almost a year of review and preparation, including a comprehensive review of the latest available scientific evidence. The experts were selected on the basis of their expertise and most importantly, the absence of real or apparent conflicts of interest. The Working Group considered “reports that have been published or accepted for publication in the openly available scientific literature” as well as “data from governmental reports that are publicly available”. They evaluated five organophosphate insecticides and herbicides including glyphosate. The results, announced 20 March were as follows. The herbicide glyphosate and the insecticides malathion and diazinon were classified as probably carcinogenic to humans (Group 2A). The insecticides tetrachlorvinphos and parathion were classified as possibly carcinogenic to humans (Group 2B).

Significance of the assessment

To understand the real significance of the new assessment, some background information is needed. Substances and exposures that can lead to cancer are called carcinogens.

The IARC is part of the WHO, its major goal is to identify causes of cancer, and its classification for carcinogens is the most widely used and accepted in the world [3]. In the past 30 years, the IARC has evaluated the cancer-causing potential of more than 900 likely candidates, placing them into the following categories:

  • Group 1: Carcinogenic to humans
  • Group 2A: Probably carcinogenic to humans
  • Group 2B: Possibly carcinogenic to humans
  • Group 3: Unclassifiable as to carcinogenicity in humans
  • Group 4: Probably not carcinogenic to humans

Commenting on the classification system, the American Cancer Society stated [3]: “Perhaps not surprisingly, based on how hard it can be to test these candidate carcinogen, most are listed as being of probable, possible, or unknown risk. Only a little over 100 are classified as “carcinogenic to humans.””

The Environmental Protection Agency uses a rating system similar to that of IARC [3]:

  • Group A: Carcinogenic to humans
  • Group B: Likely to be carcinogenic to humans
  • Group C: Suggestive evidence of carcinogenic potential
  • Group D: Inadequate information to assess carcinogenic potential
  • Group E: Not likely to be carcinogenic humans

Thus, a classification of 2A in cancer-causing potential for glyphosate on the IARC is almost the highest possible categorization.

As stated in the IARC press release [1]: “Group 2A means that the agent is probably carcinogenic to humans. This category is used when there is limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals.” 

It should also be noted that the two insecticides placed in the lower category (2B) in terms of cancer-causing potential are both in restricted use.  Tetrachlorvinphos is banned in the European Union, but continues to be used in the US; while parathion has been severely restricted since the 1980s, and all authorized uses were cancelled in the European Union and USA by 2003.

Of the organophosphates in Group 2 A, diazinon has been used in agriculture and home and garden insect-control. It has been in low production especially after 2006 due to restrictions in the USA and the EU. Malathion is used in agriculture, public health and residential insect control, and continues to be produced in substantial volumes throughout the world. But it is minor league compared with glyphosate. As highlighted in the assessment [1, 2], glyphosate has the highest global production volume of all herbicides. The agricultural use of glyphosate has increased sharply since the introduction of genetically modified (GM) crops tolerant to glyphosate. The largest use worldwide is in agriculture, but it is also deployed in forestry, urban, and home applications in more than 750 different commercial products. Consequently, glyphosate has been detected in the air during spraying, in water, and in food. The general population is exposed primarily through residence near sprayed areas, home use, and diet.

Evidence of glyphosate’s cancer-causing potential including that suppressed by EPA

The assessment cited the main evidence on which the classification of glyphosate as probably carcinogenic to humans is based [1] as follows: 

“For the herbicide glyphosate, there was limited evidence of carcinogenicity in human for non-Hodgkin lymphoma. The evidence in humans is from studies of exposures, mostly agricultural in the US, Canada, and Sweden published since 2001. In addition, there is convincing evidence that glyphosate also can cause cancer in laboratory animals. On the basis of tumours in mice, the United States Environmental Protection Agency (USEPA) originally classified glyphosate as possibly carcinogenic to humans (Group C) in 1985 [equivalent to IARC group 2C]. After a re-evaluation of that mouse study, the US EPA changes its classification to evidence to non-carcinogenicity in humans (Group E) in 1991. The US EPA Scientific Advisory Panel noted that the re-evaluated glyphosate results were still significant using two statistical tests recommended in the IARC Preamble. The IARC Working Group that conducted the evaluation considered the significant findings from the US EPA report and several more recent positive results in concluding that there is sufficient evidence of carcinogenicity in experimental animals. Glyphosate also caused DNA and chromosomal damage in human cells, although it gave negative results in tests using bacteria. One study in community residents reported increases in blood markers of chromosomal damage (micronuclei) after glyphosate formulations were sprayed nearby.”

Note the pointed reference to US EPA evidence that has been suppressed. This happened through a litany of outright fraud committed by testing companies working for the corporations, deception, and half-truths (see [4] Glyphosate and Cancer, SiS  62). It should be seen in the light of EPA’s decision in 2013 to raise the allowable limits of glyphosate contamination in farm-grown food and animal feed [5].  The amount of allowable glyphosate in oilseed crops (except for canola and soy) went up from 20 ppm to 40 ppm, 100 000 times the amount needed to induce breast cancer cells.

Yet more evidence was cited for animal experiments with glyphosate [2]. These included glyphosate induced positive trend in the incidence of a rare renal tubule carcinoma in male CD-1 mice, a positive trend for haemangiosarcoma in male mice, pancreatic islet-cell adenoma in male rats in two studies, and a promotion of skin tumours in an initiation-promotion study in mice [6].

Also pointed out in the assessment [2], glyphosate has been detected in the blood and urine of agricultural workers, indicating absorption into the body. Soil microbes are known to degrade glyphosate to aminomethylphosphoric acid (AMPA). Blood AMPA detection after poisonings therefore suggests intestinal microbial metabolism in humans.

Glyphosate and glyphosate formulations induced DNA and chromosomal damage in mammals, and in human and animal cells in vitro. One study reported increases in blood markers of chromosomal damage (micronuclei) in residents of several communities after spraying of glyphosate formulations. Bacterial mutagenesis tests were negative, but glyphosate, glyphosate formulations, and AMPA induced oxidative stress in rodents and in vitro. Oxidative stress induces reactive oxygen species that can damage DNA [7].

Since our last review on glyphosate and cancer [4], new evidence has emerged. Leah Schinasi and Maria Leon at IARC, Lyon, France carried out a systematic review and a series of meta-analyses of nearly three decades worth of epidemiologic research on the relationship between non-Hodgkin lymphoma (NHL) and occupational exposure to agricultural pesticide active ingredients and chemical groups. Estimates of associations of NHL with 21 pesticides and 80 active ingredients were extracted from 44 papers, all reporting studies conducted in high-income countries (12 countries, majority in Europe or N. America) [8]. Random effects meta-analyses (allowing heterogeneity between studies to contribute to the variance) showed that phenoxyherbicides, carbamate insectices, organophosphorus insecticide and the active ingredient lindane, an organochlorine insecticide, were positively associated with NHL. In addition, in a handful of papers, associations between pesticides and NHL subtypes were reported: B cell lymphoma was positively associated with phenoxy herbicides and glyphosate. Diffuse large B-cell lymphoma was positively associated with phenoxy herbicide exposure.

New evidence has also come from Argentina, where a team of researchers at Universidad Nacional de Rio Cuarto used a recently established method for monitoring genetic damage resulting from chemical exposure by determining the frequency of micronuclei in the cells lining the inside of the mouth [9]. They found that children living within 500 m of spraying areas have over 66 % more cells with micronuclei than those living more than 3 000 m away. In addition, 40 % of the exposed children suffer from persistent conditions that may be associated with chronic pesticide exposure including respiratory symptoms, with and without additional symptoms such skin itching or stains, nose itching or bleeding, lacrimation, eye and ear burning or itching.

Monsanto, the Glyphosate Task Force, and the Joint Glyphosate Task Force protest against classification 

Monsanto, whose $15.9 billion of annual sales are closely tied to glyphosate [10], protested that the scientific data did not support the conclusions and called on WHO to hold an urgent meeting to explain the findings [11]. “We don’t know how IARC could reach a conclusion that is such a dramatic departure from the conclusion reached by all regulatory agencies around the globe,” Philip Miller, Monsanto’s vice-president of global regulatory affairs, told the press. Apart from the EPA’s 2013 hike of allowable glyphosate contamination levels [5], the German government completed a four year evaluation of glyphosate for the EU, concluding that it was “unlikely to pose a carcinogenic risk in humans” [12].

The Glyphosate Task Force (GTF) is a consortium of chemical companies, including Monsanto, formed to promote glyphosate in Europe.  The Joint Glyphosate Task Force (JGTF) is the US counterpart.  On the same day that the Lancet article [2] was published, both the GTF and the JGTF published announcements decrying the WHO classification [13].  They accuse the IARC of only taking into account “a narrow selection of studies and was therefore made without the benefit of analyzing the extensive and relevant database on glyphosate relied upon by the world's regulatory authorities...”   They then lauded the German glyphosate re-assessment report (RAR) saying, “As recently as January, the German government completed a four-year study of glyphosate on behalf of the European Union and concluded that glyphosate was unlikely to pose a carcinogenic risk in humans. It is baffling that IARC arrived at such a different conclusion than all these other scientific reviews.” 

Of course they would refer to the RAR.  They wrote it.  The GTF prepared the dossier on glyphosate renewal for the German member state and submitted it to the Federal Institute for Risk Assessment (BfR) in Germany.  The BfR rubber-stamped it and sent it on to the European Food Safety Authority (EFSA), adding only a few comments here and there.

Finally, the GTF accuses the IARC of not taking into account all of the data available, particularly the industry-sponsored studies [14].  “Most peer reviewed literature and other publicly available information such as the evaluations, opinions and conclusions of regulatory competent authorities were also dismissed by IARC.”

Corrupt assessment in the European Union

It is supreme irony for GTF to accuse IARC of not taking into account all of the data available, as the GTF’s assessment on behalf of the German government was most narrowly based on industry studies and others that concurred with the findings from industry.

In the carcinogenicity section of toxicology portion of the RAR, 13 industry-sponsored studies were evaluated.  All were deemed “acceptable” and all found no significant carcinogenetic effects.  Two published studies on rodents were considered.  One found no significant results and the other was “considered by the authors to indicate a tumor promoting potential of glyphosate. However, the formulation Roundup was used in the study and not the active substance glyphosate.” All studies that used an actual product were disqualified because they claim that only the active ingredient, glyphosate, needs to be evaluated [15].   

Twelve peer-reviewed studies, most of which were based on data from a single study (the Agricultural Health Study), found no evidence of carcinogenicity.  These studies were all deemed reliable and used in the evaluation. 

Only six studies finding a link between glyphosate and cancer were included in the RAR but were disqualified and deemed unreliable, mostly because exact exposures to glyphosate could not be identified in the epidemiological studies.  The one lab study (Seralini) was disqualified because they didn't follow OECD guidelines.  And this was only the cancer section. For more details see [15] Scandal of Glyphosate Re-assessment in Europe, SiS 63 and [17].

Glyphosate bans already under consideration

Fortunately, there are non-corrupt regulatory agencies in the world that look at the whole range of evidence on glyphosate toxicity, of which being a probable human carcinogen is just one aspect (see [18] A Roundup of Roundup® Reveals Converging Pattern of Toxicity from Farm to Clinic to Laboratory Studies, SiS 65). Glyphosate and in particular the Monsanto formulations Roundup is a wide-spectrum weed killer with wide-spectrum toxicities on organisms and cells. A number of countries have already imposed bans on the herbicide.

Sri Lanka had originally imposed a total ban based on evidence of glyphosate link to a deadly kidney disease, with prevalence estimated at 15 % affecting a total of 400 000 patients with an estimated death toll of around 20 000. Under pressure from industry, it has now a partial ban in certain districts [19].

El Salvador, stricken with the same lethal kidney disease epidemic, has voted to ban glyphosate along with 52 other chemicals since 2013 [20], though it has yet to be written into law, again under great pressure from industry.

Brazil’s Federal Public Prosecutor has requested the Justice Department to ban glyphosate along with 8 other chemicals [21]. Finally, the Dutch Parliament voted for a ban on non-agricultural uses [22].

To conclude

Individuals, farmers, gardeners, restaurants, shops, local communities should now stop using glyphosate herbicides in defiance of the corrupt approvals given, in order to safeguard the health of people and planet.

Article first published 24/03/15


  1. IARC Monographs Volume 112: evaluation of five organophosphate insecticides and herbicides. International Agency for Research on Cancer World Health Organization 20 March 2015.
  2. Guyton KZ, Loomis D, Grosse Y, El Ghissassi F, Benbrahim-Tallaa L, Ghua N, Scoccianti C, Mattock H, Straif K. Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazion, and glyphosate. The Lancet, 20 March 2014,
  3.  Known and probable human carcinogens Introduction. American Cancer Society, accessed 22 March 2015,
  4. Ho MW. Glyphosate and cancer. Science in Society 62, 12-14, 2014.
  5. Electronic code of federal regulations. eCFR Data is current as of March 20, 2015, US Government Publishing Office,
  6. WHO/FAO. Glyphosate. Pesticides residues in food 2004 Joint FAO/WHO Meeting on Pesticides Residues. Part II Toxicological. IPCS/WHO 2004; 95–162, accessed 12 March 2015,
  7. Cade J and Wagner JR. DNA base damage by reactive oxygen species, oxidizing agents, and UV radiation. Co Spr Harb Persp Biol 2013,5, a012559, 18pp.
  8. Schinasi L and Leon ME. Non-Hodgkin Lymphoma and occupational exposure to agricultural pesticide chemical groups and active ingredients: a systematic review and meta-analysis. Int J Environ Res Pub Health 2014, 11, 4449-4527.
  9. Bernari N, Gile N, Mañas F. Méndez Á, Gorla N and Aiassa D. Assessment of the level of damage to the genetic material of children exposed to pesticides in the province of Córdoba. Arch Argen Pediatr 2015, 113, 126-32.
  10. “Monsanto Weedkiller is ‘probably carcinogenic’ WHO says”, Jack Kaskey, Bloomberg Business, 20 March 2015,
  11.  “New study points to link between weedkiller glyphosate and cancer”, Clive Cookson,, 20 March 2015,
  12.  “Roundup weedkiller ‘probably’ causes cancer says WHO study”, The Guardian, 21 March 2015,
  13. “IARC misclassification of glyphosate as Group 2A probable carcinogen”,, 20 March 2015,
  14. “Statement of the GTF on the recent IARC decision concerning glyphosate”, PR Newswire, 20 March 2015,
  15. Renewal Assessment Report on glyphosate (2014), Bundesinstitut fur Risikobewertung, Germany. Vol. Vol. 1, p. 68
  16. Swanson N and Ho MW. Scandal of glyphosate reassessment in Europe. Science in Society 63, 8-9, 2014.
  17. Swanson N. Glyphosate reassessment in Europe is corrupt: Toxicology.
  18. Sirinathsinghji E. A roundup of Roundup reveals converging patterns of toxicities from farm to clinic to laboratory studies. Science in Society 65, 26-31, 2015.
  19. “Sri Lanka bans pesticides containing 5 chemicals”,, 23 December 2014,
  20. “El Salvador: use of 53 chemicals banned”, Parque Logistico Panama, 3 September 2013,
  21. “Ministerio Publico quer proibir uso do glifosato”, Agrolink, 25 March 2014,, via GMWatch
  22. “Dutch Parliament decides to ban glyphosate use in gardens”, Stop the Crop, 18 March 2014,

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Catherine Seymour- Grossjan Comment left 14th June 2015 05:05:20
I want to thank all of the independent scientists involved in the in the "WHO test studies", I have always known Roundup and many pesticides/ herbicides were bad for us! I never used to have allergies until I moved to Chico, CA. I was exposed to many different pesticides through residential use(abuse!). The one exposure that really affected me enough to see a Dr was when a licensed, bonded pesticide Co came to spray for ants at a mobile home I was renting back in 1995.. He sprayed inside using Tempo, said "it was safe", used in hospitals all the time around patients! He then proceeded to spray my kitchen linoleum around the baseboards12-18" of floor! Whe we were eating! I wanted him to come when we were out! My landlord wanted it done "ASAP"! He was w him! So, he continued to spray my bathroom was the entry point of the ants, he pumped that stuff into my walls! Then he went outside whe central air conditioning was running and sprayed Drione under the house, which had a skirt around it, a stray cat hid under there, was exposed along w her unborn young! (I later discovered!) After I dropped my family members off, I returned home alone, I found my daughters baby rabbit in a great deal of distress! I noticed a smell of pesticides in the air and opened all windows! I called Bidwell nature Ctr to see what to do for my rabbit, the poor rabbit was writhing in pain! It's stomach sounded like a war zone! It finally gave one last cry and died in my arms! I was sitting on my bed in my room! The vet said it was probably pesticide poisoning! I was very disoriented and not able to think clearly ended up falling asleep, a coue days later I show up at my daughters scho looking like death warmed over! I felt sick, thought I had the flu! A kind teacher recognized my symptoms, She came to my home and pointed out that Drione was meant for outdoor use only! 99% of its ingred were " inert" So, they didn't show what they were! However, when used in an aluminum container it was a noxious poison! I moved out of this mobile ASAP! I saw a Dr who diagnosed possible pesticide exposure! I was a sine mom going to College and caring for my 7 year old daughter! This was devastating to my life and health! My stomach pains were horrific! I found that most tests for these types of exposures are inadequate! I was referred to a toxicologist, Dr Jeffrey Andersen with RTCI," response team for the chemically injured". They were the ones equipped to deal with my symptoms! I tested positive, I had new and old exposures to pesticides, I used to live near an orange grove in Fontana Calif.. My Milein lining was worn down! I had a diagnosis of possible carcinogenic exposures! I felt so sick! My liver was enlarged, I was all broken out on my face, I saw another Dr of homeopathic meds, he got me on a cleansing regiment, to detox like the book L Ron Hubbards " Clear body clear mind".. I worked out, lost 15 lbs, I sweated it out in the steam room after 1 hour workouts, and ate raw veggies, organic foods, and took charcoal tablets at intervals, along w mineral oil, all to cleanse my liver, and then took vitamins, nutritious fruit smoothies, I felt great after 6 weeks! Euphoric! It was amazing! I feel for all those who suffer not knowing that they have been poisoned! If they knew how the poison is stored in the fat even in our brains! When we become active it is released kind of like a person who used LSD! Then, it recirculates and you start tripping again! This ought to be a crime! Using pesticides the way they did in my home! Yet, when I told the dept of agriculture a 25 year old guy w a Texas accent told me " Are you kidding me? He can lose his job! ? " (Referring to the pesticide guy!) I retorted; " I could've lost my life!" I got ridiculed! I couldn't find an atty either! Nobody wants to fight big ag! I was harassed, my car broken into, my notebook went missing then reappears! I was afraid for my life! So, now I have finally gotten support, validation for my suffering! Thank you! Respectfully yours, Catherine Seymour- Grossjan 10011 Folsom Blvd # 285 Sacramento, CA 95827

Brett Danson Comment left 30th September 2015 03:03:14
Remove Glyphosate Poison from Water - Global Environmental Legacy Foundation is scaling up technology to remove glyphosate from water. Please follow the link, watch the video. Thanks for your support! Brett Danson / Founder