Are Chemical Weapons Considered Weapons of Mass Destruction?

That's my question of the day. This below report by Fox News says that some of our troops who fought in Iraq have been exposed to and even wounded by chemical weapons which were discovered after the 2003 invasion.

http://www.foxnews.com/politics/2014/10/15/us-troops-wounded-by-decades-old-chemical-weapons-during-iraq-war-report-claims/

"In one case, a wounded soldier who suffered burns and blisters due to mustard gas was presented with a Purple Heart by former Secretary of the Army Peter Geren. Weeks later, he was told that he had been denied the medal because the Army had determined that his wounds had not been suffered in enemy action."

Now I am really confused. If we sent our troops into Iraq over the issue of WMD and some of our troops were infected with WMD (chemical weapons) why no purple heart?

Oh yes. We have learned that there never were any WMD in Iraq.