title: Variability of exposure and estimation of cumulative exposure in a manually operated coal mine.
abstract: This study aims at estimating variability in exposure to respirable dust and assessing whether the a priori grouping by job team is appropriate for an exposure-response study on respiratory effects among workers in a manually operated coal mine in Tanzania. Furthermore, estimated exposure levels were used to calculate cumulative exposure. Full-shift personal respirable dust samples (n = 204) were collected from 141 randomly chosen workers at underground and surface work sites. The geometric mean exposure for respirable dust varied from 0.07 mg m(-3) for office workers to 1.96 mg m(-3) for the development team. The analogous range of respirable quartz exposure was 0.006-0.073 mg m(-3). Variance components were estimated using random effect models. For most job teams the within-worker variance component was considerably higher than the between-worker variance component. For respirable dust the estimated attenuation of the linear exposure-response relationship was low (5.9%) when grouping by job team. Grouping by job team was considered appropriate for studying the association between current dust exposure and respiratory effects. Based on the estimated worker-specific mean exposure in the job teams, the arithmetic mean cumulative exposure for the 299 workers who participated in the epidemiological part of the study was 38.1 mg* yr m(-3) for respirable dust and 2.0 mg* yr m(-3) for quartz.
authors.affiliation: Centre for International Health, University of Bergen, Norway. mamuyasimon@yahoo.com
authors.forename: Simon H D
authors.initials: SH
authors.lastname: Mamuya
authors.forename: Magne
authors.initials: M
authors.lastname: Bråtveit
authors.forename: Julius
authors.initials: J
authors.lastname: Mwaiselage
authors.forename: Bente E
authors.initials: BE
authors.lastname: Moen
mesh_terms: D000328:Adult; D000395:Air Pollutants, Occupational / Q000032:analysis*; D003032:Coal Mining; D004391:Dust / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000032:analysis*; D011791:Quartz / Q000032:analysis
chemical_list: D000395:Air Pollutants, Occupational; D004391:Dust; D011791:Quartz