The World Health Organization’s cancer agency has declared the world’s most widely used weedkiller as a “probable carcinogen.” This has alarmed the agrochemical industry and amateur gardeners.
Glyphosate is used in herbicides with estimated annual sales of $6bn.
The assessment by the International Agency for Research on Cancer of glyphosate will be of particular concern to Monsanto, the company that brought glyphosate to market under the trade name Roundup in the 1970s.
Monsanto’s current generation of herbicide-resistant genetically modified crops depends on farmers spraying their fields with glyphosate to kill weeds.
The International Agency for Research on Cancer assembled 17 experts to assess five organophosphate pesticides. The panel decided that two of the chemicals were possible carcinogens (class 2B) and three were probable carcinogens (class 2A).
A summary of the assessment was published online on Friday in the journal Lancet Oncology.
The International Agency for Research on Cancer has no regulatory role and its assessments do not immediately lead to bans or marketing restrictions. However, campaigners are expected to use the decisions to put pressure on regulators to take action against products containing glyphosate.
The report points out that 750 products used in agriculture, forestry and domestic gardening contain glyphosate and its use has increased with the development of GM glyphosate-resistant crop varieties.
The report also indicated that glyphosate has been detected in air during spraying, in water and in food.
The study found evidence that glyphosate could also cause cancer in laboratory animals.
The research took evidence from studies from studies published in the U.S., Canada, and Sweden since 2001.
Some academic experts are critical of the findings. Some believe that the 2A classification of glyphosate and malathion demonstrates a variety of laboratory results with a small number of studies in humans of varied quality and mixed conclusions.
In addition, a recent four year evaluation of glyphosate by the German government for the EU found that it was unlikely to pose a carcinogenic risk in humans.