An ingredient in Monsanto MON +0.32%’s Roundup weed-killer – glyphosate – is “probably carcinogenic,” according to a new decision by the World Health Organization yesterday. The decision was laid out in a study in The Lancet Oncology, and published on the WHO’s International Agency for Research on Cancer (IARC) website. The study is based on a new look at the existing research on the chemical exposure in people and lab animals. Though it’s sure to raise consumer concerns, some – like Monsanto – say it’s unwarranted since no new data are included in the research, and previous studies have all deemed glyphosate relatively safe in the doses humans take it in. Consumers’ ears are certainly pricked at this new decision – but how convincing is it?

The report determines that there is “limited evidence” that the chemical can cause non-Hodgkin’s lymphoma and lung cancer in humans. It says there is, however, “convincing evidence” that it can cause cancer in laboratory animals. Among people who work with the herbicide, who generally have traces of the compound in their blood and urine, there appears to be a slightly increased risk of non-Hodgkin lymphoma, according to the report: “Case-control studies of occupational exposure in the USA, Canada, and Sweden reported increased risks for non-Hodgkin lymphoma that persisted after adjustment for other pesticides.”

(Photo by Max Whittaker/Prime for The Washington Post via Getty Images)

Monsanto of course points out that the new report doesn’t include any new evidence – it’s based on data that have previously been analyzed. “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,” said Philip Miller, Monsanto’s Vice President Global Regulatory Affairs.

He’s right at least about the WHO’s departure from earlier decisions from agencies across the globe. Previously, glyphosate had not been considered, by the U.S. or European Union, to pose much, if any, risk to humans in the doses we’d be exposed to. In 2011, a review by the American Council on Science and Health (ACSH) pointed out that that “The World Health Organization, the Environmental Protection Agency, and the European Union have extensively reviewed the full range of toxicological information about glyphosate, pronouncing it of extremely low toxicity and thus nil risk when exposure is factored in.” The EPA has also previously concluded that glyphosate has “low acute toxicity.”

Because of the now conflicting opinions, Monsanto is demanding another look at the data. “We have issued an urgent request,” said Miller, “for appropriate personnel of the WHO to sit down with the global glyphosate taskforces and other regulatory agencies to account for the scientific studies used in their analysis and, equally as important, to account for those scientific studies that were disregarded.”

Some people, however, aren’t at all surprised by the WHO’s new decision, and feel it a small step in the right direction. Author and food industry analyst,Robyn O’Brien says that given the science that’s already there, the new development isn’t totally unexpected, even by Monsanto itself. “In October 2014,” says O’Brien, “Monsanto officials said during their earnings’ report, ‘the Roundup business is expected to soften in 2015’ due to increasing headwinds.  This week’s World Health Organization announcement adds to those headwinds.”

O’Brien hopes the new study will at least spark more scientific inquiry into what these types of compounds to do both humans and the ecosystems into which it’s spread. “Scientists around the world continue to ask why,” she says. “Why do case-control studies of occupational exposure to glyphosate in the USA, Canada and Sweden now show increased risks for non-Hodgkin’s lymphoma? What is this doing to farmers? Why is it being applied in record amounts?”