Toxic threat

According to a recent New York Times report, two bunkers at a ruined former chemical weapons production facility in Al Muthanna, near Baghdad, could hold leftover stores of sarin and mustard gas in the form of grenades and warheads.

The problem? Some of the areas where these toxins are stored, or at least suspected of being stored, are now in the hands of the terrorist militia "Islamic State" ("IS"). Chemical weapons experts point out that while it's unlikely that "IS" fighters will be able to use the munitions waste as they were first intended - the stores date almost exclusively from the 1980s - they are nonetheless still dangerous.

Highly toxic

Toxicologist Ralf Trapp, who was on the scientific advisory board of the Organisation for the Prohibition of Chemical Weapons from 1998 to 2006, told DW that it was important to distinguish between the two types of poison gas: mustard gas and sarin.

"The Iraqis have always had difficulties making sarin stable," he said. "We know that the contents of the weapons, when exposed to the [desert] heat, begin to disintegrate after a relatively short period of time. The toxic agents are thus destroyed."

What remains, however, is still quite lethal and can cause serious injury. And even though these old sarin weapons are no longer that useful as chemical warfare, mustard gas grenades remain quite dangerous.

"The sulfur mustard in these old weapons is probably still very active," said Trapp. "We know from the experience of World War I that this chemical is very stable. And even if it begins to deteriorate, the decomposed products are still highly toxic."

Regarding mustard gas, should the terrorists come across gas grenades, they could theoretically still make use of the weapons. But they would themselves be facing a significant risk. As mustard gas goes through certain decomposition processes, high pressure builds up inside the weapon. As a result, the poisonous gas could escape and hurt those handling the grenade.

Difficult to handle, hard to identify

If terrorists decide to accept this risk they could, for example, build a dirty bomb, causing the chemical weapon to explode with a conventional explosive. "These improvised weapons are not likely to be as effective as those found in the military," said Trapp. "But they should still be taken seriously, especially when dealing with unprotected and poorly equipped people."

"Iraq has not identified all of its chemical weapons in accordance with the internationally accepted conventions. And some of these weapons are so old that labels have been lost, due to rust and damage," said Oliver Meier, an international security expert at the German Institute for International and Security Affairs (SWP) in Berlin. "I'm not sure whether, if 'IS' terrorists have a chemical weapon grenade in hand, they would actually realize what it is they are holding."

One possible scenario, according to Belgian security researcher Jean Pascal Zanders, is that "some of the mustard gas grenades lie undetected among many other conventional missiles, and could be fired with the standard artillery. Then we would not be dealing with a deliberate act, but with an erroneous use of poison gas."

These weapons are indeed dangerous - but because they would not be used systematically, their toxic effect would be localized, said Zanders. "Mustard gas is not so deadly. It causes complicated injuries, but to die from it you would need to be exposed to a large amount."

In another scenario, Zanders described how militants could incorporate a poison gas grenade into a booby trap. The New York Times article documented at least one such case in Iraq. "But it's not clear whether the terrorists were really aware that their booby traps were not only explosive, but also toxic," said SWP's Meier. In this particular case, although the US soldiers defusing and removing the explosive device were injured, no one was killed in the attack.

'IS' a threat even without chemical weapons

The conclusion: Though terrorists could use mustard gas grenades to seriously injure or even kill individual victims, they would not be appropriate as weapons of mass destruction. "What we have in Iraq is dangerous for individuals, but not an actual military threat," said Zanders.

"The real danger comes from the recklessness with which 'Islamic State' jihadists build up their regime," he added. "They will probably try to capture more conventional weapons." And with this, continue to spread fear and terror.