title: Estimation of background serum 2,3,7,8-TCDD concentrations by using quantile regression in the UMDES and NHANES populations.
abstract: BACKGROUND
  The goal of the present study was to quantify the population-based background serum concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by using data from the reference population of the 2005 University of Michigan Dioxin Exposure Study (UMDES) and the 2003-2004 National Health and Nutrition Examination Survey (NHANES).
  
  
  METHODS
  Multiple imputation was used to impute the serum TCDD concentrations below the limit of detection by combining the 2 data sources. The background mean, quartiles, and 95th percentile serum TCDD concentrations were estimated by age and sex by using linear and quantile regressions for complex survey data.
  
  
  RESULTS
  Any age- and sex-specific mean, quartiles, and 95th percentiles of background serum TCDD concentrations of study participants between ages 18 and 85 years can be estimated from the regressions for the UMDES reference population and the NHANES non-Hispanic white population. For example, for a 50-year-old man in the reference population of UMDES, the mean, quartiles, and 95th percentile serum TCDD concentrations are estimated to be 1.1, 0.6, 1.1, 1.8, and 3.3 parts per trillion, respectively. The study also shows that the UMDES reference population is a valid reference population for serum TCDD concentrations for other predominantly white populations in Michigan.
  
  
  CONCLUSIONS
  The serum TCDD concentrations increased with age and increased more over age in women than in men, and hence estimation of background concentrations must be adjusted for age and sex. The methods and results discussed in this article have wide application in studies of the concentrations of chemicals in human serum and in environmental samples.
authors.affiliation: Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY, USA. qc2138@columbia.edu
authors.forename: Qixuan
authors.initials: Q
authors.lastname: Chen
authors.forename: David H
authors.initials: DH
authors.lastname: Garabrant
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hedgeman
authors.forename: Roderick J A
authors.initials: RJ
authors.lastname: Little
authors.forename: Michael R
authors.initials: MR
authors.lastname: Elliott
authors.forename: Brenda
authors.initials: B
authors.lastname: Gillespie
authors.forename: Biling
authors.initials: B
authors.lastname: Hong
authors.forename: Shih-Yuan
authors.initials: SY
authors.lastname: Lee
authors.forename: James M
authors.initials: JM
authors.lastname: Lepkowski
authors.forename: Alfred
authors.initials: A
authors.lastname: Franzblau
authors.forename: Peter
authors.initials: P
authors.lastname: Adriaens
authors.forename: Avery H
authors.initials: AH
authors.lastname: Demond
authors.forename: Donald G
authors.initials: DG
authors.lastname: Patterson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004781:Environmental Exposure / Q000032:analysis; D004785:Environmental Pollutants / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008824:Michigan; D008875:Middle Aged; D009749:Nutrition Surveys; D000072317:Polychlorinated Dibenzodioxins / Q000097:blood*; D012016:Reference Values; D012044:Regression Analysis; D055815:Young Adult
chemical_list: D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins