When it comes to determining if the herbicide glyphosate causes cancer, experts do not agree. Two different European health organizations have issued contradictory advice about this widely used weedkiller.
Glyphosate has been marketed by Monsanto since the 1970s and is the main ingredient in its Roundup line of herbicides. Last week, the European Food Safety Authority (EFSA) said that glyphosate is "unlikely" to cause cancer, but the International Agency for Research on Cancer (IARC) said in March that it "probably" does.
Both agencies may be right, but only because their findings are not directly comparable.
For one thing, the evidence the two agencies evaluated was not the same. EFSA only assessed glyphosate, while IARC looked at glyphosate alone and at products it is used in. They also used different methods to draw conclusions. They looked at the chemical from different viewpoints: hazard identification versus risk assessment.
One key distinction to understand is the difference between hazard and risk. IARC is part of the World Health Organization (WHO) that lists probable and possible cancer risks, including such risks as high-temperature frying, eating red meat, shift working, and mobile phone use. The agency's job is to highlight anything that might in certain conditions, even very rare conditions, be able to cause cancer in people. Its review of glyphosate was about the assessment of a potential hazard.
EFSA is concerned with real life risks and whether there is evidence to show that, when used in normal conditions, glyphosate poses an unacceptable risk to human health or the environment.
EFSA's purpose is to guide policymaking in the European Union. It describes itself as an independent agency funded by the EU but that operates separately from EU member states. IARC's activities are mainly funded by the regular budget contributions paid by its 25 member states, including the United States, Australia and many European countries.
David Coggon, a professor of occupational and environmental medicine at Britain's University of Southampton, told Reuters Health that "it's important to bear in mind that EFSA and IARC operate within different frameworks."
"The level of precaution that is applied in the face of scientific uncertainty depends on value judgments, and is not a scientific question."
