A chemical found in the world’s most widely used weedkiller can have disrupting effects on sexual development, genes and beneficial gut bacteria at doses considered safe, according to a wide-ranging pilot study in rats.
Glyphosate is the core ingredient in Monsanto’s Roundup herbicide and levels found in the human bloodstream have spiked by more than a 1,000% in the last two decades.
The substance was recently relicensed for a shortened five-year lease by the EU. But scientists involved in the new glyphosate study say their results show that it poses “a significant public health concern”.
One of the report’s authors, Daniele Mandrioli, at the Ramazzini Institute in Bologna, Italy, said significant and potentially detrimental effects from glyphosate had been detected in the gut bacteria of rat pups born to mothers, who appeared to have been unaffected themselves.
“It shouldn’t be happening and it is quite remarkable that it is,” Mandrioli said. “Disruption of the microbiome has been associated with a number of negative health outcomes, such as obsesity, diabetes and immunological problems.”
Prof Philip J Landrigan, of New York’s Icahn School of Medicine, and also one of the research team, said: “These early warnings must be further investigated in a comprehensive long-term study.” He added that serious health effects from the chemical might manifest as long-term cancer risk: “That might affect a huge number of people, given the planet-wide use of the glyphosate-based herbicides.”
Controversy has raged around glyphosate since a World Health Organisation agency – the International Agency for Research on Cancer (IARC) – judged it to be a “probable human carcinogen” in 2015.
However, US and European regulators subsequently deemed it acceptable for use, a move campaigners condemned because of regulators’ use of secret industry papers and experts with alleged ties to Monsanto.
The US firm, which recently merged with Bayer in a deal worth more than $60bn, argues that it is being unfairly targeted by activist scientists with ulterior motives.
Scott Partridge, Monsanto’s VP for global strategy told the Guardian: “The Ramazzini Institute is an activist organisation with an agenda that they have not disclosed as part of their crowdfunding efforts. They wish to support a ban on glyphosate and they have a long history of rendering opinions not supported by regulatory testing agencies.”
“This is not about genuine research,” he added. “All the research to date has demonstrated that there is no link between glyphosate and cancer.”
In 2017, the Ramazinni Institute was criticised by members of the US Congress, which has provided it with funding. US congress members have also probed funding for the IARC.
The new crowdfunded pilot study which the Ramazzini Institute compiled with Bologna University, the Italian National Health Institute, George Washington State University and the Icahn School of Medicine observed the health effects of glyphosate on Sprague Dawley rats, which had been dosed with the US EPA-determined safe limit of 1.75 micrograms per kilo of body weight.
Two-thirds of known carcinogens had been discovered using the Sprague Dawley rat species, Mandrioli said, although further investigation would be needed to establish long-term risks to human health.
The pilot research did not focus on cancer but it did find evidence of glyphosate bioaccumulation in rats– and changes to reproductive health.
“We saw an increase in ano-genital distance in the formulation that is of specific importance for reproductive health,” Mandrioli said. “It might indicate a disruption of the normal level of sexual hormones.”
The study’s three peer-reviewed papers will be published in Environmental Health later in May, ahead of a €5m follow-up study that will compare the safe level against multiple other doses.