SAN FRANCISCO (CN) – A recently unsealed brief in the nation’s largest lawsuit over whether chemical giant Monsanto’s Roundup causes cancer shows the extent to which the company tried to influence academic literature, and casts doubt on the procedural integrity of the U.S. Environmental Protection Agency.

On March 13, U.S. District Judge Vince Chhabria unsealed several documents in a multidistrict class action against Monsanto over claims that the chemical giant has hidden the fact that its flagship product – the weed killer Roundup – causes non-Hodgkin’s lymphoma.

One of the documents included the plaintiffs’ response to a pretrial order by Chhabria, in which he asked both sides to clarify their arguments over whether the EPA’s and International Agency on Research on Cancer’s conclusions about carcinogenicity of Roundup are relevant to the judge’s consideration of general causation.

The plaintiffs’ submission claims Monsanto ghostwrote and funded two major studies which concluded a lack of evidence that chemicals in Roundup, including the key ingredient glyphosate, are carcinogenic.

“Co-authors with Larry Kier were discussed,” a memo by David Saltmiras, a toxicology manager with Monsanto, sent in July 2012 to executive Christophe Gustin, another researcher at Monsanto, said. “David Kirkland was proposed as a strong candidate for this role.”

Gustin then forwarded the message to several Monsanto executives, discussing the cost of hiring both of the authors to write ostensibly objective academic papers exploring the causal relationship between Roundup and a particular brand of lymphoma, according to the document.

“Adding David Kirkland as a co-author to both review papers would add £14,000 to the project, which split by 25 seems a fair investment,” Gustin wrote in the email, which the plaintiffs included as an exhibit to their submission.

The discussions are particularly troubling, according to the plaintiffs in the case, because Kirkland went on to co-author a 2013 study titled “Review of genotoxicity studies of glyphosate and glyphosate-based formulations,” which ultimately found “that glyphosate and typical GBFs are not genotoxic.”

The EPA issued a paper in September 2016 on the carcinogenic potential of glyphosate, concluding that the chemical compound is “not likely to be carcinogenic” – a fact Monsanto often points to when defending the product’s safety.

But the EPA’s conclusion differs from the one reached by the International Agency for Research on Cancer, which concluded that glyphosate was a “probable carcinogen to humans” in March 2015.

As for the differing agency conclusions, the plaintiffs in the multidistrict litigation point to emails that appear to indicate Monsanto arranged and paid Kirkland for his contributions to one of the papers upon which the EPA grounded its assessment.

Furthermore, the plaintiffs say another paper on which the EPA relied was published in 2015 by Helmut Greim and co-authored by David Saltmiras, the Monsanto employee who also recommended the company hire Kirkland.

“The Greim article, co-authored by a Monsanto employee, offers Monsanto’s opinions related to 13 industry animal studies that have not been subjected to the peer-review process, and was newly submitted to the agency as part of [the Office of Pesticide Programs’] current review of glyphosate,” the plaintiffs said in a brief published March 13.

They claim the study wouldn’t have been accepted by the International Agency for Research on Cancer because the study lacks necessary underlying data to support its conclusion that “there was no evidence of a carcinogenic effect related to glyphosate treatment.”

The plaintiffs also say a 2000 study, which came to similar conclusions about the safety of Roundup – and was referenced repeatedly by authors of the two more current studies and by the EPA in its own paper – was ghostwritten by Monsanto.

“The EPA may be unaware of Monsanto’s deceptive authorship practice and therefore accepted representations about 17 genotox studies reported in the Kier & Kirkland article without having looked at the original reports,” the plaintiffs say in the brief.

However, the recently disclosed documents do reveal there was debate within the EPA about the validity of its September 2016 findings regarding the lack of evidence of a link between Roundup and non-Hodgkin’s lymphoma.

When a separate branch of EPA scientists reviewed the September 2016 paper written by the agency they found “the analysis of the cancer data in the assessment was basically conducted on a study-by-study basis instead of using a more inclusive, systematic approach to provide an integrated analysis of the data.”

However, that paper notes that in discussing the most appropriate way to label glyphosate, “carcinogenic to humans” is not applicable, noting that International Agency for Research on Cancer and other agencies agree. No agency has yet ruled that glyphosate and other chemicals in Roundup conclusively cause cancer.

But they don’t say definitively that Roundup doesn’t cause cancer.

“The positive association (i.e., limited evidence) of carcinogenicity in humans could arguably rule out the last cancer category (“not likely to be carcinogenic”),” the EPA scientists said.

Monsanto did not return a phone call seeking comment for this story.

The lead attorney for plaintiffs is Robin Greenwald of Weitz and Luxenberg in New York.