title: The incidence of work-related asthma-like symptoms and dust exposure in Norwegian smelters.
abstract: BACKGROUND
  The prevalence of respiratory symptoms among employees in smelters is positively associated with dust exposure.
  
  
  OBJECTIVE
  To investigate the association between the incidence of work-related asthma-like symptoms (WASTH) and dust exposure.
  
  
  METHODS
  All the employees were invited to participate in a 5-year longitudinal study. The outcome of WASTH was defined as the combination of dyspnea and wheezing improving on rest days or vacation in an individual who had no asthma previously. Information about smoking and occupational status was obtained from a questionnaire. A job exposure matrix of total dust was developed. Multivariate data analyses were performed using Cox regression.
  
  
  RESULTS
  The total follow-up time of the employees (n = 2,476) was 8,469 years, and the median follow-up time for participants was 4.0 years. During the follow-up, 91 employees developed WASTH, and the corresponding incidence rate for WASTH per 1,000 person-years was 8.9 (7.3-10.9) (95% confidence interval in parentheses). The risk ratio of WASTH increased significantly (P = 0.0001) with dust exposure in the middle and high categories (1.0-2.9 and ≥ 3.0 mg/m(3)). Stratified analyses showed that the effect of current dust exposure varied with both previous exposure (PE) to dust and fumes (P = 0.006) and airflow limitation (AFL) (P = 0.033). The final analyses showed that the risk ratios for WASTH per 1 mg/m(3) increase in current dust exposure were 1.1 (0.93-1.2), 1.4 (1.1-1.8), 1.6 (1.1-2.3), and 1.9 (1.2-3.0) for the categories (PE+/AFL-), (PE-/AFL-), (PE+/AFL+, and (PE-/AFL+).
  
  
  CONCLUSIONS
  In conclusion, dust exposure was associated with an increased incidence of WASTH.
authors.affiliation: Department of Medicine, Akershus University Hospital and Institute of Clinical Medicine, Campus Akershus University Hospital, University of Oslo, Lørenskog, Norway. vidar.soyseth@medisin.uio.no
authors.forename: Vidar
authors.initials: V
authors.lastname: Søyseth
authors.forename: Helle Laier
authors.initials: HL
authors.lastname: Johnsen
authors.forename: Paul K
authors.initials: PK
authors.lastname: Henneberger
authors.forename: Johny
authors.initials: J
authors.lastname: Kongerud
mesh_terms: D000328:Adult; D017677:Age Distribution; D059366:Asthma, Occupational / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D015331:Cohort Studies; D004391:Dust; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D019570:Inhalation Exposure / Q000009:adverse effects / Q000706:statistics & numerical data*; D008137:Longitudinal Studies; D008297:Male; D008669:Metallurgy; D008875:Middle Aged; D015999:Multivariate Analysis; D009664:Norway / Q000453:epidemiology; D016273:Occupational Exposure / Q000009:adverse effects*; D009790:Occupations; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D012972:Sodium Hydroxide; D013147:Spirometry / Q000379:methods; D055815:Young Adult
chemical_list: D004391:Dust; D012972:Sodium Hydroxide