Glyphosate, one of the world’s most commonly used herbicides, is unlikely to increase the risk of cancer—at least in its pure form—according to an assessment released today by the European Food Safety Authority (EFSA) in Parma, Italy. The report will likely have a major influence on the European Union’s upcoming decision whether to keep glyphosate, the active ingredient in widely used herbicides such as Roundup, on its list of approved chemical substances. Approval for the chemical expires at the end of 2015.
The report sets the first so-called “acute reference dose” for the substance, a recommended limit for food-based intake of the chemical. It also says that there is not sufficient evidence to decide whether commercially available formulations of glyphosate, which include other ingredients, are safe.
The assessment is the latest in a series of conflicting conclusions about the cancer-causing potential of glyphosate. Earlier this year the World Health Organization’s International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans.” But the German Federal Institute for Risk Assessment (BfR), tasked by EFSA to evaluate the available evidence, came to a different conclusion, saying that it was not likely to cause cancer. It said cell-based and animal tests suggest that glyphosate is unlikely to damage DNA. BfR also decided that five mouse studies and nine long-term rat studies do not provide evidence that the chemical causes an increase in tumors.
The difference is in part due to the fact that the EFSA assessment includes several unpublished studies, whereas IARC based its assessment only on published papers. That troubles critics of EFSA’s assessment. “Regulatory decisions on the E.U. shouldn’t be based on unpublished studies,” says Franziska Achterberg of Greenpeace in Brussels. “It’s very worrying that they make such prominent use of these studies.”
The EFSA report also used different statistical methods than the IARC evaluation. The Pesticide Action Network Germany, based in Hamburg, criticized the German agency’s analysis in a report this month, saying that it used improper statistical methods to dismiss data in multiple studies that do indicate an increase in tumors in rats and mice fed glyphosate.
The EFSA report concludes that epidemiological studies don’t suggest an increased risk of cancer after exposure to glyphosate. The report noted that epidemiological studies cited in the IARC report were difficult to assess because they evaluated commercially available herbicides that include glyphosate as well as other ingredients; EFSA’s analysis was limited to glyphosate alone. However, “taking into consideration the weight of evidence,” EFSA concluded that the epidemiological studies did not contradict the conclusion from animal studies “that glyphosate is unlikely to pose a carcinogenic hazard to humans.”
Nevertheless, the agency does set an “acute reference dose” for the chemical—the recommended maximum short-term limit for intake—of 0.5 milligrams per kilogram of body weight. (That means someone who weighs 80 kilos shouldn’t consume more than 40 milligrams of glyphosate per day.) The level, which is based on toxicity studies in rabbits, will allow regulators to better assess levels of glyphosate in food and other sources, the agency says.