# 2005 British Occupational Hygiene Society Published by Oxford University Press doi:10.1093/annhyg/mei013 Variability in Dust Exposure in a Cement Factory

Tanzania, as part of an epidemiological study assessing chronic respiratory health effects. One hundred and twenty personal ‘total ’ dust samples were collected from 80 randomly selected workers from eight a priori occupational groups (OGs) based on work areas using a 37 mmMillipore sampler. The between-group, within-group and within-worker variances were determined to assess the con-trast in exposure level between the OGs and to estimate the attenuation and standard error of the theoretical exposure–response slope. Using mixed-effect model estimates, the probability of overexposure relative to the occupational exposure limit (OEL) was assessed for each OG. The geometric means of total dust exposure were higher in the cranes (38.64 mg m3), packing (21.30 mg m3) and crusher (13.48 mg m3) than in the cement mill (3.23 mg m3), kiln (2.87 mg m3), raw mill (1.85 mg m3), maintenance (1.16 mg m3) and administration (0.29 mg m3). The a priori grouping scheme seems to be an efficient scheme because of the high contrast in exposure level between the OGs (0.78) and minimal attenuation of the theoretical exposure–response slope (1.0%). When using the reduced mixed-effect model, the probabilities of overexposure (q) relative to the OEL of 10 mg m3 for total cement dust were higher in the crane (96%), packing (88%) and crusher (73%) than in the cement mill (16%), kiln (14%), raw mill (5%), maintenance (2%) and administration (0.01%)