Hiltermann noted that although cyanosis (the medical term for the blue discolorations in question) is etymologically related to cyanide, the former condition indicates only a blood supply deprived of oxygen, and is in no way sufficient to diagnose cyanide poisoning; in fact, "it could just as easily suggest the use of a nerve agent." Furthermore, "Even the proven presence of cyanide gas at Halabja would not necessarily implicate Iran," for two reasons outlined by Hiltermann. Prior to Halabja, Iranian forces made widespread use of amyl nitrite to counter what they repeatedly alleged was Iraqi cyanide gas. If those Iranian claims are accepted, then "By that logic, Iraq could also be implicated in any Halabja deaths by cyanide." However, cyanide evaporates rapidly and tabun—a major part of Iraq's chemical arsenal at the time—contains cyanide as an essential ingredient, factors that rendered it impossible for the UN to confirm any Iraqi use of cyanide gas during the Iran–Iraq war: "Because of its connection to tabun, if hydrocyanide is found in a given environment, it could be either the residual effect of poorly manufactured tabun or a breakdown element when tabun decomposes."