title: Measurement of Total and Free Urinary Phenol and Paraben Concentrations over the Course of Pregnancy: Assessing Reliability and Contamination of Specimens in the Norwegian Mother and Child Cohort Study.
abstract: BACKGROUND
  Exposures to environmental phenols and parabens may be harmful, especially in utero. Prior studies have demonstrated high within-person variability of urinary concentrations across pregnancy.
  
  
  OBJECTIVE
  We sought to measure phenol and paraben biomarker concentrations for the Norwegian Mother and Child Cohort (MoBa) study, assess within-person variability, and investigate any possible external phenol or paraben contamination of specimens.
  
  
  METHODS
  We collected three spot urine samples at approximately 17, 23, and 29 weeks gestation in a hospital setting and added a preservative containing ethyl paraben. We measured urinary concentrations and within-person variability for phenols and parabens in a MoBa sample (n = 45), including a subgroup of 15 participants previously randomly selected for a bisphenol A (BPA) exposure study who had unusually high total BPA concentrations. Additionally, we compared reliability results for total, conjugated, and free concentrations of phenolic compounds.
  
  
  RESULTS
  We detected total and free BPA, butyl paraben, propyl paraben, and methyl paraben in 100% of samples, total benzophenone-3 in 95% of samples, and infrequently detected free benzophenone-3 and total and free 2,4-dichlorophenol and 2,5-dichlorophenol. Intraclass correlation coefficients (ICCs) for total, conjugated, and free concentrations ranged from relatively low for BPA to moderate for propyl paraben. ICCs were generally similar overall and by subgroup.
  
  
  CONCLUSIONS
  Using conjugated concentrations improved reliability estimates only for BPA. Measuring total and free concentrations, an approach that may be useful for future studies, allowed us to identify likely BPA and butyl paraben contamination of archived MoBa urine specimens.
authors.affiliation: Department of Epidemiology, UNC Gillings School of Global Public Health, Chapel Hill, North Carolina, USA.
authors.forename: Virginia T
authors.initials: VT
authors.lastname: Guidry
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Longnecker
authors.forename: Heidi
authors.initials: H
authors.lastname: Aase
authors.forename: Merete
authors.initials: M
authors.lastname: Eggesbø
authors.forename: Pål
authors.initials: P
authors.lastname: Zeiner
authors.forename: Ted
authors.initials: T
authors.lastname: Reichborn-Kjennerud
authors.forename: Gun P
authors.initials: GP
authors.lastname: Knudsen
authors.forename: Randi J
authors.initials: RJ
authors.lastname: Bertelsen
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Ye
authors.forename: Antonia M
authors.initials: AM
authors.lastname: Calafat
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Engel
mesh_terms: D000328:Adult; D001559:Benzhydryl Compounds / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D002733:Chlorophenols / Q000652:urine; D015331:Cohort Studies; D004781:Environmental Exposure / Q000032:analysis; D005260:Female; D006801:Humans; D009664:Norway; D010226:Parabens / Q000032:analysis*; D010636:Phenols / Q000652:urine*; D011247:Pregnancy; D011310:Preservatives, Pharmaceutical / Q000737:chemistry; D015203:Reproducibility of Results; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D015415:Biomarkers; D002733:Chlorophenols; D010226:Parabens; D010636:Phenols; D011310:Preservatives, Pharmaceutical; C006780:bisphenol A; D000098826:Bisphenol A Compounds