New Scientist has the current issue all about mild exposures to chemical weapons. By and large it isn't pretty. It apparently damages the part of the brain that regulates anger. It can also cause uncontrollable fatigue and many other problem. The Gulf War Syndrome is now thought to be due to very mild exposure to serin when a weapons depot was blown up during the Gulf War.

Any soldiers (or civilians) exposed to chemical weapons will probably be permanently mentally disabled in the sense of having severe problems.

I'd link to the articles, but they are on the subscriber only section.