Long-term intake of the Monsanto’s most popular Roundup herbicide, even in very small amounts lower than permissible in US water, may lead to kidney and liver damage, a new study claims.

The research, conducted by an international group of scientists from the UK, Italy and France, studied the effects of prolonged exposure to small amounts of the Roundup herbicide and one of its main components – glyphosate.

In their study, published in Environmental Health on August 25, the scientists particularly focused on the influence of Monsanto’s Roundup on gene expression in the kidneys and liver.

In the new two-year study, which extended the findings from one conducted in 2012, the team added tiny amounts of Roundup to water that was given to rats in doses much smaller than allowed in US drinking water.

Scientists say that some of the rats experienced “25 percent body weight loss, presence of tumors over 25 percent bodyweight, hemorrhagic bleeding, or prostration.”

The study’s conclusions indicate that there is an association between wide-scale alterations in liver and kidney gene expression and the consumption of small quantities of Roundup, even at admissible glyphosate-equivalent concentrations. As the dose used is “environmentally relevant in terms of human, domesticated animals and wildlife levels of exposure,” the results potentially have significant health implications for animal and human populations, the study warned.

“There were more than 4,000 genes in the liver and kidneys [of the rats that were fed Roundup] whose levels of expression had changed,” the study’s leading scientist, Michael Antoniou, head of the Gene Expression and Therapy Group at King’s College London, said, as quoted by the Environmental Health News.

“Given even very low levels of exposure, Roundup can potentially result in organ damage when it comes to liver and kidney function,” he added. “The severity we don’t know, but our data say there will be harm given enough time.”

The results of the study have received mixed reviews in the scientific community, although many scientists have expressed their concern about possible negative health effects from Roundup use.

Taking into account that the team “used very low dose levels in drinking water <…> this study should have some kind of public health influence,” said Nichelle Harriott, the science and regulatory director at Beyond Pesticides, a Washington, DC based nonprofit organization, as quoted by the Environmental Health News.

“We don’t know what to make of such changes, they may be meaningful and may not,” said Bruce Blumberg, a professor from the University of California, who did not take part in the study.

“They can’t say which caused what, but what you have is an association – the group treated with a little Roundup had a lot of organ damage and the gene expression findings supported that,” he added.

Key ingredient in #Monsanto's Roundup found 'safe' despite WHO claims – report http://t.co/xDeSMgOCjopic.twitter.com/TJKQpRbdPU — RT America (@RT_America) July 15, 2015

Meanwhile, according to the New England Journal of Medicine, the use of glyphosate in herbicides has increased by more than 250 times in the United States in the last 40 years.

Research conducted in 2014 and published in the International Journal of Environmental Research and Public Health linked the use of Monsanto’s Roundup to widespread chronic kidney disease that took the form of an epidemic in Sri Lanka. Another study showed that Monsanto agrochemicals may have caused cellular and genetic diseases in Brazilian soybean workers.

Additionally, the World Health Organization’s International Agency for Research on Cancer has recently determined that Roundup’s glyphosate is ‘number one’ among carcinogens, “possibly” causing cancer.

WHO labels Dow herbicide ‘possibly’ cancer causing http://t.co/p7ilsr1MvJpic.twitter.com/rJ5Nl6Gaml — RT America (@RT_America) June 23, 2015

However, Monsanto has continuously and consistently insisted that its products are safe, citing other research supporting their claims. The latest such study was conducted by the German Federal Institute for Risk Assessments (BfR) and deemed that Monsanto’s Roundup was safe.

So far, Monsanto has made no comment concerning the research conducted by the group led by Michael Antoniou.