The reputation of Roundup, whose active ingredient is the world's most widely used weed killer, took a hit on Tuesday when a federal court unsealed documents raising questions about its safety and the research practices of its manufacturer, the chemical giant Monsanto. Monsanto's internal emails and email traffic between the company and federal regulators ... suggested that Monsanto had ghostwritten research that was later attributed to academics and indicated that a senior official at the Environmental Protection Agency had worked to quash a review of Roundup's main ingredient, glyphosate, that was to have been conducted by the United States Department of Health and Human Services. The files were unsealed by Judge Vince Chhabria, who is presiding over litigation brought by people who claim to have developed non-Hodgkin's lymphoma as a result of exposure to glyphosate. The litigation was touched off by a determination made nearly two years ago by the International Agency for Research on Cancer, a branch of the World Health Organization, that glyphosate was a probable carcinogen. Court records show that Monsanto was tipped off to the determination by a deputy division director at the E.P.A., Jess Rowland, months beforehand. That led the company to prepare a public relations assault on the finding well in advance of its publication. Last year, a review by The New York Times showed how the [chemical] industry can manipulate academic research or misstate findings.