Apparently during the big home boom from 2001-2007 drywall manufactures imported drywall from China because there was such a high demand for it. Little did they know that the drywall was highly toxic.
If you have experienced numerous air condition coil failures, your copper electrical ground wire have turned black, and you are suffering from upper respiratory issues, nose bleeds, unexplained rashes, or severe allergy type symptoms, your house may contain toxic imported Chinese Drywall. This means if your house was built or remodeled during that time.
You can go to the links below to get more information.