What is cyanide, and why is it in treated lumber?

what is cyanide, which is some type of treated in treated wood. i have been getting ill at work because of me inhaling fumes from treated lumber, which there's no fresh air coming inside the building unless a customer comes through the door..i started off with a dry acking cough back in november of last year, afterward my doctor found out that i had pneumonia..the doctor stated that i had inhale a lot of the fumes coming from the treated lumber....and now i'm ill again with the same illness...what is it that's making me ill?