This is the ValueSet that contains all the codes in Impurity Classification Terminology (http://hl7.org/fhir/us/pq-cmc-fda/ValueSet/pqcmc-impurity-classification-terminology) and Impurity Classification Terminology (http://hl7.org/fhir/us/pq-cmc-fda/ValueSet/pqcmc-impurity-classification-terminology). E.g. what you have to deal with if you get resources containing codes in either of them