For decades, Swiss chemical giant Syngenta has manufactured and marketed a widely used weed-killing chemical called paraquat, and for much of that time the company has been dealing with external concerns that long-term exposure to the chemical may be a cause of the incurable brain ailment known as Parkinson’s disease.
Syngenta has repeatedly told customers and regulators that scientific research does not prove a connection between its weedkiller and the disease, insisting that the chemical does not readily cross the blood-brain barrier, and does not affect brain cells in ways that cause Parkinson’s.
But a cache of internal corporate documents dating back to the 1950s reviewed by the Guardian suggests that the public narrative put forward by Syngenta and the corporate entities that preceded it has at times contradicted the company’s own research and knowledge.
