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.

The New Lede — in a collaboration with The Guardian — published a story that examines what Syngenta knew about the evolving science linking the pesticide to the disease.