such as industry or hospital (22, 23). This information was
used to define four broad occupational categories (dental,
medical, industrial, and nuclear power workers). The same
procedure was used for assigning occupational categories as
in the mortality study (3), except that workers at Atomic
Energy of Canada Limited were assigned to the nuclear
power category rather than to the industrial category. This
was done because of the greater similarity of both the type
of work and the socioeconomic status between nuclear
power workers and Atomic Energy of Canada Limited
workers.