title: Construction of a Job Exposure Matrix to Dust, Fluoride, and Polycyclic Aromatic Hydrocarbons in the Norwegian Aluminum Industry using Prediction Models.
abstract: BACKGROUND
  The Norwegian aluminum industry developed and implemented a protocol for prospective monitoring of employees' exposure using personal samplers. We analyzed these data to develop prediction lines to construct a job exposure matrix (JEM) for the period 1986-1995.
  
  
  METHODS
  The protocol for personal monitoring of exposure was implemented in all seven Norwegian aluminum plants in 1986 and continued until 1995. Personal samplers were used to collect total dust, fluorides, and total polycyclic aromatic hydrocarbons (PAH). In addition, exposure could be categorized according to process, i.e. prebake, Søderberg, and 'other'. We constructed four-dimensional JEMs characterized by: Plant, Job descriptor, Process, and Year. Totally 8074, 6734, and 3524 measurements were available for dust, fluorides, and PAH, respectively. The data were analyzed using linear mixed models with two-way interactions. The models were assessed using the Akaike criterion (AIC) and unadjusted R (2). The significance level was set to 10% (two-sided) for retaining variables in the model.
  
  
  RESULTS
  In 1986, the geometric mean (95% confidence interval in parentheses) for total dust, total fluorides, and PAH were 3.18 (0.46-22.2) mg m(-3), 0.58 (0.085-4.00) mg m(-3), and 33.9 (2.3-504) µg m(-3), respectively. During 10 years of follow-up, the exposure to total dust, fluorides, and PAH decreased by 9.2, 11.7, and 14.9% per year, respectively. Each model encompassed from 49 to 72 significant components of the interaction terms. The interaction components were at least as important as the main effects, and 65 to 91% of the significant components of the interaction terms were time-dependent.
  
  
  CONCLUSIONS
  Our prediction models indicated that exposures were highly time-dependent. We expect that the time-dependent changes in exposure are of major importance for longitudinal studies of health effects in the aluminum industry.
authors.affiliation: 1.Medical Division, Akershus University Hospital, Lørenskog 1478, Norway; 2.Faculty of Medicine, University of Oslo, Oslo 0318, Norway; 3.Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, MS 2800, 1095 Willowdale Road, Morgantown, WV 26505, USA; Vidar.soyseth@medisin.uio.no.
authors.forename: Vidar
authors.initials: V
authors.lastname: Søyseth
authors.affiliation: 3.Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, MS 2800, 1095 Willowdale Road, Morgantown, WV 26505, USA;
authors.forename: Paul
authors.initials: P
authors.lastname: Henneberger
authors.affiliation: 3.Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, MS 2800, 1095 Willowdale Road, Morgantown, WV 26505, USA;
authors.forename: Mohammed Abbas
authors.initials: MA
authors.lastname: Virji
authors.affiliation: 4.Department of Chemical and Biological Work Environment, National Institute of Occupational Health, Oslo 0363, Norway;
authors.forename: Berit
authors.initials: B
authors.lastname: Bakke
authors.affiliation: 2.Faculty of Medicine, University of Oslo, Oslo 0318, Norway; 5.Department of Respiratory Medicine, Rikshospitalet, Oslo University Hospital, Oslo 0372, Norway.
authors.forename: Johny
authors.initials: J
authors.lastname: Kongerud
mesh_terms: D000535:Aluminum; D004391:Dust / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods; D005260:Female; D005459:Fluorides / Q000032:analysis*; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis*; D008297:Male; D008669:Metallurgy; D015233:Models, Statistical; D009664:Norway; D016273:Occupational Exposure / Q000032:analysis*; D052638:Particulate Matter; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D011446:Prospective Studies; D013997:Time Factors
chemical_list: D004391:Dust; D052638:Particulate Matter; D011084:Polycyclic Aromatic Hydrocarbons; D000535:Aluminum; D005459:Fluorides
keywords: aluminium; epidemiology; exposure assessment-mixed models; exposure estimation; measurement strategy; polycyclic aromatic hydrocarbons