Its no secret Iraq had chemical weapons. They used them liberally against Iranian human wave attacks during the Iran Iraq war.
The reason they were hushed up is because they were provided by western countries. You do know the U.S. and Europe backed Saddam in the Iran Iraq war and most probably encouraged the use of chemical weapons against Iranian teenagers right? Iran had a huge population advantage, Iraqi Shias weren't that keen on fighting Iranian Shia, so Iraq needed technology to level the field and the West helped with that edge.
The West was really happy about a lengthy, bloody stalemate in that war bleeding both countries white.