title: Characterization of phthalate exposure among pregnant women assessed by repeat air and urine samples.
abstract: BACKGROUND
  Although urinary concentrations of phthalate metabolites are frequently used as biomarkers in epidemiologic studies, variability during pregnancy has not been characterized.
  
  
  METHODS
  We measured phthalate metabolite concentrations in spot urine samples collected from 246 pregnant Dominican and African-American women. Twenty-eight women had repeat urine samples collected over a 6-week period. We also analyzed 48-hr personal air samples (n = 96 women) and repeated indoor air samples (n = 32 homes) for five phthalate diesters. Mixed-effects models were fit to evaluate reproducibility via intraclass correlation coefficients (ICC). We evaluated the sensitivity and specificity of using a single specimen versus repeat samples to classify a woman's exposure in the low or high category.
  
  
  RESULTS
  Phthalates were detected in 85-100% of air and urine samples. ICCs for the unadjusted urinary metabolite concentrations ranged from 0.30 for mono-ethyl phthalate to 0.66 for monobenzyl phthalate. For indoor air, ICCs ranged from 0.48 [di-2-ethylhexyl phthalate (DEHP)] to 0.83 [butylbenzyl phthalate (BBzP)]. Air levels of phthalate diesters correlated with their respective urinary metabolite concentrations for BBzP (r = 0.71), di-isobutyl phthalate (r = 0.44), and diethyl phthalate (DEP; r = 0.39). In women sampled late in pregnancy, specific gravity appeared to be more effective than creatinine in adjusting for urine dilution.
  
  
  CONCLUSIONS
  Urinary concentrations of DEP and DEHP metabolites in pregnant women showed lower reproducibility than metabolites for di-n-butyl phthalate and BBzP. A single indoor air sample may be sufficient to characterize phthalate exposure in the home, whereas urinary phthalate biomarkers should be sampled longitudinally during pregnancy to minimize exposure misclassification.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Adibi
authors.forename: Robin M
authors.initials: RM
authors.lastname: Whyatt
authors.forename: Paige L
authors.initials: PL
authors.lastname: Williams
authors.forename: Antonia M
authors.initials: AM
authors.lastname: Calafat
authors.forename: David
authors.initials: D
authors.lastname: Camann
authors.forename: Robert
authors.initials: R
authors.lastname: Herrick
authors.forename: Heather
authors.initials: H
authors.lastname: Nelson
authors.forename: Hari K
authors.initials: HK
authors.lastname: Bhat
authors.forename: Frederica P
authors.initials: FP
authors.lastname: Perera
authors.forename: Manori J
authors.initials: MJ
authors.lastname: Silva
authors.forename: Russ
authors.initials: R
authors.lastname: Hauser
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000032:analysis* / Q000652:urine*; D000397:Air Pollution / Q000032:analysis*; D015415:Biomarkers / Q000032:analysis; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D018811:Maternal Exposure; D010795:Phthalic Acids / Q000032:analysis* / Q000652:urine*; D011247:Pregnancy; D012680:Sensitivity and Specificity
chemical_list: D000393:Air Pollutants; D015415:Biomarkers; D010795:Phthalic Acids