I don't know if it's really relevant to your question, but I distinctly recall that, back when they were gassing Iranians in 1984 or 1985, Saddam Hussein said that were just spraying them with pesticide.
Back then the media reported the tactic as chemical warfare. I suppose, though, that pesticide doesn't quite qualify as a "weapon of mass destruction" in today's context.
The curious thing is, perhaps he was telling the truth. Do we have any evidence the mass Iranian casualties were caused by Sarin or VX rather than TEPP?