NIST SP 800-122 — Guide to Protecting the Confidentiality of Personally Identifiable Information (PII)
This document by the National Institute of Standards and Technology (NIST) uses a broad definition of PII in order to identify as many potential PII sources as possible in order to protect this information.
http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-122.pdf