We should be more worried about the more functional chemical weapons from the Assad regime that IS has access to, but 2,500 old chemical rockets makes for a dangerous stockpile in the hands of the Islamic State.

Many chemical weapons incidents clustered around the ruins of the Muthanna State Establishment, the center of Iraqi chemical agent production in the 1980s.

Since June, the compound has been held by the Islamic State, the world’s most radical and violent jihadist group. In a letter sent to the United Nations this summer, the Iraqi government said that about 2,500 corroded chemical rockets remained on the grounds, and that Iraqi officials had witnessed intruders looting equipment before militants shut down the surveillance cameras.

Soldiers in chemical protection gear, including Sgt. Eric J. Duling and Specialist Andrew T. Goldman, examining suspected chemical munitions at a site near Camp Taji, Iraq, on Aug. 16, 2008.The New York Times

The United States government says the abandoned weapons no longer pose a threat. But nearly a decade of wartime experience showed that old Iraqi chemical munitions often remained dangerous when repurposed for local attacks in makeshift bombs, as insurgents did starting in 2004.

And it is worth noting that these were once secured by American blood.