MATERIALS AND METHODS
The National Dose Registry of Canada
The National Dose Registry, maintained by the Radiation
Protection Bureau of Health Canada, contains radiation
exposure records for virtually all monitored radiation workers
in Canada since its creation in 1951 (22, 23). Exposure
records cover over 500,000 workers from about 24,000
organizations. Types of exposure include external exposures
to gamma rays, beta rays, x-rays, and neutrons, as well as
internal exposures to tritium and radon progeny. Dose
records in the National Dose Registry include a job classification
code representing a variety of occupations, for example,
construction workers at nuclear power generating stations,
hospital radiologists, or dentists.