The glyphosate molecule … Monsanto discovered its herbicide characteristics in the 1970s
(Photo: Wikipedia)

March 27, 2015

The world’s most popular herbicide, glyphosate, has been labelled as “probably carcinogenic to humans” by international researchers after a review of existing studies.

Earlier this month, 17 experts from 11 countries met at the World Health Organisation’s International Agency for Research on Cancer (IARC) in France to assess the carcinogenicity of different organophosphate chemicals used as pesticides or herbicides.

Their findings are summarised in The Lancet medical journal (free text available after registering with website).

The classification that has attracted the most attention is their report on glyphosate, a herbicide discovered by Monsanto which is now used in more than 750 products, both on farms and in home gardens.

The researchers said there was “limited evidence in humans for carcinogenicity” but after examining epidemiological studies, animal studies, and in vitro studies, classified the herbicide as “probably carcinogenic to humans”.

The IARC team reported:

  • The use of glyphosate has risen in agriculture in recent years due to the development of glyphosate-resistant crops
  • Case-control studies of occupational exposure in the USA, Canada and Sweden have reported increased risks for non-Hodgkin lymphoma. However,  a large cohort study of agricultural workers did not show any significantly increased risk
  • Glyphosate has been detected in the blood and urine of agricultural workers, indicating absorption
  • Microbes in the human gut may be able to metabolise glyphosate. Soil microbes degrade glyphosate to aminomethylphosphoric acid (AMPA).  AMPA has been detected in humans after poisonings
  • One study reported increases in blood markers of chromosomal damage in residents of several communities after spraying of glyphosate formulations
  • Some mice studies indicated exposure to glyphosate was linked to different types of tumours (in mice)

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Monsanto – the manufacturer of the popular Roundup glyphosate product – has attacked the classification and labelled it as “junk science” on its website.

“We are outraged with this assessment,”  chief technology officer Dr Robb Fraley said.

“This conclusion is inconsistent with the decades of ongoing comprehensive safety reviews by the leading regulatory authorities around the world that have concluded that all labeled uses of glyphosate are safe for human health.

“This result was reached by selective ‘cherry picking’ of data and is a clear example of agenda-driven bias.”

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[UPDATED with correction]