title: Implications of common and special variation for occupational health: examples from beryllium manufacturing.
abstract: OBJECTIVE
  Common variation is a statistical process-control term for variability associated with usual operating conditions. Special variation occurs when usual operating conditions are disrupted. The objective was to explore the implications for preventive occupational medicine practice of common and special variation in air-level exposure.
  
  
  METHODS
  Illustrations are derived from US and UK beryllium facility databases.
  
  
  RESULTS
  Special variation may be missed in finite sampling sets, giving a very inaccurate indication of the highest air levels experienced on the job. Depending on the toxicologic model, failure to assess special variation influences the meaningfulness of aspects of occupational prevention, from medical surveillance through risk management.
  
  
  CONCLUSIONS
  Jobs and tasks should be characterized for special variation in addition to traditional air sampling. Both special variation and common variation should be considered in occupational medicine preventive practice.
authors.affiliation: Materion Brush, Inc, Elmore, Ohio 43416, USA. david.deubner@materion.com
authors.forename: David C
authors.initials: DC
authors.lastname: Deubner
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D001607:Berylliosis / Q000517:prevention & control; D001608:Beryllium / Q000032:analysis*; D016208:Databases, Factual; D004784:Environmental Monitoring / Q000379:methods*; D006801:Humans; D007221:Industry; D015233:Models, Statistical; D016273:Occupational Exposure / Q000032:analysis* / Q000706:statistics & numerical data; D016272:Occupational Health; D011159:Population Surveillance; D015203:Reproducibility of Results; D018570:Risk Assessment; D012308:Risk Management; D006113:United Kingdom; D014481:United States
chemical_list: D000395:Air Pollutants, Occupational; D001608:Beryllium