title: Statistical modeling of occupational chlorinated solvent exposures for case-control studies using a literature-based database.
abstract: OBJECTIVE
  Occupational exposure assessment for population-based case-control studies is challenging due to the wide variety of industries and occupations encountered by study participants. We developed and evaluated statistical models to estimate the intensity of exposure to three chlorinated solvents-methylene chloride, 1,1,1-trichloroethane, and trichloroethylene-using a database of air measurement data and associated exposure determinants.
  
  
  METHODS
  A measurement database was developed after an extensive review of the published industrial hygiene literature. The database of nearly 3000 measurements or summary measurements included sample size, measurement characteristics (year, duration, and type), and several potential exposure determinants associated with the measurements: mechanism of release (e.g. evaporation), process condition, temperature, usage rate, type of ventilation, location, presence of a confined space, and proximity to the source. The natural log-transformed measurement levels in the exposure database were modeled as a function of the measurement characteristics and exposure determinants using maximum likelihood methods. Assuming a single lognormal distribution of the measurements, an arithmetic mean exposure intensity level was estimated for each unique combination of exposure determinants and decade.
  
  
  RESULTS
  The proportions of variability in the measurement data explained by the modeled measurement characteristics and exposure determinants were 36, 38, and 54% for methylene chloride, 1,1,1-trichloroethane, and trichloroethylene, respectively. Model parameter estimates for the exposure determinants were in the anticipated direction. Exposure intensity estimates were plausible and exhibited internal consistency, but the ability to evaluate validity was limited.
  
  
  CONCLUSIONS
  These prediction models can be used to estimate chlorinated solvent exposure intensity for jobs reported by population-based case-control study participants that have sufficiently detailed information regarding the exposure determinants.
authors.affiliation: Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, OH 45226, USA. mhein@cdc.gov
authors.forename: Misty J
authors.initials: MJ
authors.lastname: Hein
authors.forename: Martha A
authors.initials: MA
authors.lastname: Waters
authors.forename: Avima M
authors.initials: AM
authors.lastname: Ruder
authors.forename: Mark R
authors.initials: MR
authors.lastname: Stenzel
authors.forename: Aaron
authors.initials: A
authors.lastname: Blair
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Stewart
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D016022:Case-Control Studies; D019992:Databases as Topic; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000032:analysis*; D019570:Inhalation Exposure / Q000706:statistics & numerical data; D008956:Models, Chemical; D016273:Occupational Exposure / Q000032:analysis / Q000706:statistics & numerical data*; D009790:Occupations / Q000706:statistics & numerical data; D012044:Regression Analysis; D012307:Risk Factors; D012997:Solvents / Q000032:analysis*; D013696:Temperature; D013997:Time Factors; D014691:Ventilation / Q000379:methods; D017132:Workplace / Q000706:statistics & numerical data
chemical_list: D000395:Air Pollutants, Occupational; D006843:Hydrocarbons, Chlorinated; D012997:Solvents