When "privacy" threatens public health

A European directive on privacy may make illegal much life-saving research on cancer in Britain, and the "fundamental principle" (no use of named records without permission of the individuals) could limit statistical work in Canadian cancer registries. Although the intent is to protect individuals from improper administrative use, this hardly applies to statistical aggregates that cannot identify anybody. Abstract position statements have done little to clarify the reasoning. To counter this, the present paper points to actual statistical uses of Canada's mortality database for individual follow-up on an unprecedented scale under conditions of strict confidentiality. The statistics serve to connect earlier causes with later harm. However, confusion still surrounds the question of whether privacy can be fundamentally violated by statistics drawn from personal records. Without wider understanding, real harm to health will compete poorly with imagined harm to privacy.