http://www.cbsnews.com/news/isis-using-chlorine-gas-iraq-says/
http://www.cnn.com/2015/07/19/middleeast/isis-chemical-weapons/index.html
Easy enough for ISIS or other militias to use chlorine and other chemicals seized when they had control of water treatment and other industrial sites
Duelfer Report on Chemical Weapons in Iraq
The Secret Casualties of Iraqs Abandoned Chemical Weapons
Yeah, I know. FAKE NEWS from a decade agao......