A public sector agency that holds personal information must not use the information for a purpose other than that for which it was collected unless--
(a) the individual to whom the information relates has consented to the use of the information for that other purpose, or
(b) the other purpose for which the information is used is directly related to the purpose for which the information was collected, or
(c) the use of the information for that other purpose is necessary to prevent or lessen a serious and imminent threat to the life or health of the individual to whom the information relates or of another person.