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Zyklon B

Pesticide notorious for its use during the Holocaust

  • 12 min read
  • 5 chapters

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Through Adsorption, Nazi Germany and Cellular respiration

Hydrogen cyanide, a poisonous gas that interferes with cellular respiration, was first used as a pesticide in California in the 1880s. Research at Degesch of Germany led to the development of Zyklon (later known as Zyklon A), a pesticide that released hydrogen cyanide upon exposure to water and heat. It was banned after World War I, because some of its components were used in German chemical weapons. Degussa purchased Degesch in 1922. Their team of chemists, which included Walter Heerdt and Bruno Tesch, devised a method of packaging hydrogen cyanide in sealed canisters along with a cautionary eye irritant and one of several adsorbents such as diatomaceous earth. The new product was also named Zyklon, but it became known as Zyklon B to distinguish it from the earlier version. Uses included delousing clothing and fumigating ships, warehouses, and trains.

The Nazis began using Zyklon B in extermination camps in early 1942 to murder prisoners during the Holocaust. Tesch and his deputy executive, Karl Weinbacher, were executed in 1946 for knowingly selling the product to the SS for use on humans. Hydrogen cyanide is now rarely used as a pesticide but still has industrial applications. Firms in several countries continue to produce Zyklon B under alternative brand names, including Detia-Degesch, the successor to Degesch.

Mode of action

Hydrogen cyanide is a poisonous gas that interferes with cellular respiration. Cyanide poisoning prevents the cell from producing adenosine triphosphate (ATP) by binding to one of the proteins involved in the electron transport chain. This protein, cytochrome c oxidase, contains several subunits and has ligands containing iron groups. The cyanide component of Zyklon B can bind at one of these iron groups, heme a3, forming a more stabilized compound through metal-to-ligand pi bonding. As a result of the formation of this new iron–cyanide complex, the electrons that would situate themselves on the heme a3 group can no longer do so. Instead, these electrons destabilize the compound; thus, the heme group no longer accepts them. Consequently, electron transport is halted, and cells can no longer produce the energy needed to synthesize ATP. Death occurs in a human being weighing 68 kilograms (150 lb) within two minutes of inhaling 70 mg of hydrogen cyanide.

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