2. Materials and methods
2.1. Participants
Two hundred and thirty-one mine workers (89% response rate) completed questionnaires during the preshift period on-site. The average age of workers was 37.11 years [standard deviation (SD) = 10.40 years] and they had been working in the mining industry (average) for 6.5 years (SD = 7.90 years). Table 1 shows the demographic characteristics of the study sample.