Experiences with task-based exposure assessment in studies of farmers and tunnel workers

Results are described from exposure assessments in two epidemiological studies of farmers and tunnel workers. The inter and intra worker variances of exposure were used as a basis for classification of workers in groups exposed to different levels. The between worker variability of exposure to α-quartz showed that tunnel workers were exposed to different levels (GSDB = 2.7). Classification by job type showed only 39% higher exposure of concrete workers compared to excavation workers. The influence of tasks on exposure to α-quartz among concrete workers was studied further because the between worker variability was large (GSDB = 4.3). Multiple regression of tasks on α-quartz exposure identified two tasks that explained 51% of the total variance (R2 adj). Further classification of concrete workers will depend on identification of workers that use different time on these tasks. As farmers carry out few exposed tasks per day, exposure for each task was measured separately. The between worker variability of exposure to fungal spores among farmers was high (GSDB = 4.4). Classification of measurements into two broad task categories related to plant and livestock production showed that the tasks within each category were relative homogeneously exposed (GSDB = 1.1 and 1.4) and with geometric...