The MRC questionnaire has been tested in a variety of
different conditions and has been shown to be a reproducible
and accurate way of collecting such information.
Questionnaires were administered face-to-face and consisted
of three parts, including: (1) personal and work
characteristics; (2) respiratory health symptoms, which
included items such as symptoms of dyspnea, cough,
phlegm, eye symptoms, time-of-onset of symptoms, duration
of symptoms, relation of symptoms to work, i.e.,
whether they were worse at work or at home or whether they
only arose exclusively at work, whether treatment had been
received for the symptoms (3) smoking habits. A trained
interviewer interviewed each worker during working time.