Occupational Exposure Assessment
Information on lifetime occupational history was obtained using
a structured interviewer-led questionnaire. The job title, type of
industry, a description of work tasks, and starting and ending years
were recorded for all jobs held for at least 3 consecutive months
and more than 8 hours per week. Jobs were coded using the
International Standard Classification of Occupations 1988 (ISCO-
88) system [20] and the codes were linked to a general population
job exposure matrix [21,22], with which each individual job was
classified into none, low, or high exposure to biological dust,
mineral dust, and gases/fumes. Cumulative lifetime exposure to
each of the 3 agents was determined using the total number of
years the individual had worked in jobs with high exposure.