Osmium tetroxide, molecular model. This chemical is used as a catalyst and a stain. It has also been implicated as a possible component of terrorist bombs. A plot to detonate a bomb containing osmium tetroxide in London, UK, was foiled by police and security services in early April 2004. Osmium tetroxide (OsO4) comprises four oxygen atoms (red/blue) arranged tetrahedrally around a central atom of the metal osmium (purple/yellow). It is toxic to humans, causing blindness and lung damage. It is also corrosive to the skin. However, it is not ideal for use in chemical warfare as it breaks down easily and is extremely expensive.