title: Evaluation of occupational exposure: comparison of biological and environmental variabilities using physiologically based toxicokinetic modeling.
abstract: OBJECTIVE
  Few studies compare the variabilities that characterize environmental (EM) and biological monitoring (BM) data. Indeed, comparing their respective variabilities can help to identify the best strategy for evaluating occupational exposure. The objective of this study is to quantify the biological variability associated with 18 bio-indicators currently used in work environments.
  
  
  METHODS
  Intra-individual (BV(intra)), inter-individual (BV(inter)), and total biological variability (BV(total)) were quantified using validated physiologically based toxicokinetic (PBTK) models coupled with Monte Carlo simulations. Two environmental exposure profiles with different levels of variability were considered (GSD of 1.5 and 2.0).
  
  
  RESULTS
  PBTK models coupled with Monte Carlo simulations were successfully used to predict the biological variability of biological exposure indicators. The predicted values follow a lognormal distribution, characterized by GSD ranging from 1.1 to 2.3. Our results show that there is a link between biological variability and the half-life of bio-indicators, since BV(intra) and BV(total) both decrease as the biological indicator half-lives increase. BV(intra) is always lower than the variability in the air concentrations. On an individual basis, this means that the variability associated with the measurement of biological indicators is always lower than the variability characterizing airborne levels of contaminants. For a group of workers, BM is less variable than EM for bio-indicators with half-lives longer than 10-15 h.
  
  
  CONCLUSIONS
  The variability data obtained in the present study can be useful in the development of BM strategies for exposure assessment and can be used to calculate the number of samples required for guiding industrial hygienists or medical doctors in decision-making.
authors.affiliation: Institut de recherche Robert-Sauvé en santé et en sécurité du travail, 505 boul. De Maisonneuve Ouest, Montréal, QC H3A 3C2, Canada. truchon.ginette@irsst.qc.ca
authors.forename: G
authors.initials: G
authors.lastname: Truchon
authors.forename: R
authors.initials: R
authors.lastname: Tardif
authors.forename: G
authors.initials: G
authors.lastname: Charest-Tardif
authors.forename: A
authors.initials: A
authors.lastname: de Batz
authors.forename: P O
authors.initials: PO
authors.lastname: Droz
mesh_terms: D000096:Acetone / Q000493:pharmacokinetics; D000395:Air Pollutants, Occupational / Q000493:pharmacokinetics*; D004784:Environmental Monitoring; D006207:Half-Life; D006586:Hexanes / Q000493:pharmacokinetics; D006801:Humans; D006841:Hydrocarbons, Aromatic / Q000493:pharmacokinetics; D006843:Hydrocarbons, Chlorinated / Q000493:pharmacokinetics; D008954:Models, Biological; D009010:Monte Carlo Method; D016273:Occupational Exposure / Q000032:analysis*; D018709:Statistics, Nonparametric
chemical_list: D000395:Air Pollutants, Occupational; D006586:Hexanes; D006841:Hydrocarbons, Aromatic; D006843:Hydrocarbons, Chlorinated; D000096:Acetone; C026385:n-hexane