The highly toxic herbicide and multi-purpose poison arsenic was key to the production of cotton in the United States and Mexico, and in the process sickened and killed a multitude of Black and brown agricultural workers, said Jayson Porter, a PhD candidate in history at Northwestern University. Arsenic “helped build the U.S. empire” and paved the way for the so-called ‘Green Revolution’ and large-scale cash crop farming, as well as the bioweapons used to decimate Vietnamese plant life and people, said Porter.