Some chemicals and drugs selectively destroy pancreatic cells. Pyrinuron (Vacor), a rodenticide introduced in the United States in 1976, selectively destroys pancreatic beta cells, resulting in type 1 diabetes after accidental poisoning. Pyrinuron was withdrawn from the U. S. market in 1979 and it is not approved by the Environmental Protection Agency for use in the U. S. Streptozotocin (Zanosar), an antineoplastic agent, is selectively toxic to the beta cells of the pancreatic islets. It is used in research for inducing type 1 diabetes on rodents and for treating metastatic cancer of the pancreatic islet cells in patients whose cancer cannot be removed by surgery. Other pancreatic problems, including trauma, pancreatitis, or tumors (either malignant or benign) can also lead to loss of insulin production.