Court-ordered internal documents reveal that Syngenta, the manufacturer of Paraquat, was aware of the link between its herbicide and health problems since at least the 1950s. The documents also suggest that the company was aware of research that showed an association between Paraquat and Parkinson’s disease (PD) since 2001.

A late 2022 collaborative investigative journalism effort by The Guardian and The New Lede, dubbed the “Paraquat Papers,” summarize Syngenta’s internal records, which a judge ordered the company to provide to lawyers representing thousands of plaintiffs who allege that long-term use of the herbicide caused them to develop Parkinson’s, a disorder of the central nervous system that has no cure and typically causes tremors, loss of balance, stiffness and slow movement. 

The internal documents included emails from Syngenta scientists and executives, memos, and internal presentations.  

A predecessor of Syngenta, a Swiss-based chemical company, created Paraquat in the 1950s. The formula for Paraquat was sold under different brand names, including Gramoxone in the 1960s. 

A 2010 research study published in Cell Death and Differentiation states, “Several studies have suggested that pesticide exposure and life in rural areas are significant risk factors for PD. Among other pesticides, paraquat (PQ) has been linked to PD by epidemiological studies and experimental work in rodents.” 

The co-published report, obtained through the Paraquat lawsuit discovery process, shows that Syngenta was aware of problems with Paraquat decades before the health risks were made public and made a concerted effort to keep those alleged health risks hidden, including attempts to prevent scientists critical of the herbicide from landing advisory committee roles with the U.S. Environmental Protection Agency (EPA), which renewed Paraquat’s approval as an herbicide in 2021. 

As early as 1975, internal documents suggest that Syngenta executives expressed concern over litigation the company could face over Paraquat. In 2001, an internal presentation at Syngenta showed that the company was aware of research studies that suggested an association between Paraquat and Parkinson’s disease. In 2003, Syngenta launched a branding strategy that included efforts to influence researchers, regulators and non-governmental organizations (NGOs), the internal documents show. 

To date, approximately 2,000 Paraquat lawsuits have been filed, mostly by agricultural workers. The first trial was set for last year but is now expected to begin in July. Federal Paraquat lawsuits have been consolidated in multidistrict litigation (MDL). The MDL is presided over by U.S. District Judge Nancy Rosenstengel in the Southern District of Illinois.