They’re not likely to refer to it to today, but in Nov 2016 the NYT reported this:
WASHINGTON — The Islamic State has used chemical weapons, including chlorine and sulfur mustard agents, at least 52 times on the battlefield in Syria and Iraq since it swept to power in 2014, according to a new independent analysis.
More than one-third of those chemical attacks have come in and around Mosul, the Islamic State stronghold in northern Iraq, according to the assessment by the IHS Conflict Monitor, a London-based intelligence collection and analysis service.
