title: Variability over 1 week in the urinary concentrations of metabolites of diethyl phthalate and di(2-ethylhexyl) phthalate among eight adults: an observational study.
abstract: BACKGROUND
  Phthalates are metabolized and eliminated in urine within hours after exposure. Several reports suggest that concentrations of phthalate metabolites in a spot urine sample can provide a reliable estimation of exposure to phthalates for up to several months.
  
  
  OBJECTIVE
  We examined inter- and intraperson and inter- and intraday variability in the concentrations of monoethyl phthalate (MEP), the major metabolite of diethyl phthalate, commonly used in personal care products, and mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), a polyvinyl chloride plasticizer of which diet is the principal exposure source, among eight adults who collected all urine voids (average, 7.6 samples/person/day) for 1 week.
  
  
  METHODS
  We analyzed the urine samples using online solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry.
  
  
  RESULTS
  Regardless of the type of void (spot, first morning, 24-hr collection), for MEP, interperson variability in concentrations accounted for > 75% of the total variance. By contrast, for MEHHP, within-person variability was the main contributor (69-83%) of the total variance. Furthermore, we observed considerable intraday variability in the concentrations of spot samples for MEHHP (51%) and MEP (21%).
  
  
  CONCLUSIONS
  MEP and MEHHP urinary concentrations varied considerably during 1 week, but the main contributors to the total variance differed (interday variability, MEHHP; interperson variability, MEP) regardless of the sampling strategy (spot, first morning, 24-hr collection). The nature of the exposure (diet vs. other lifestyle factors) and timing of urine sampling to evaluate exposure to phthalates should be considered. For DEHP and phthalates to which people are mostly exposed through diet, collecting 24-hr voids for only 1 day may not be advantageous compared with multiple spot collections. When collecting multiple spot urine samples, changing the time of collection may provide the most complete approach to assess exposure to diverse phthalates.
authors.affiliation: National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia 30341, USA.
authors.forename: James L
authors.initials: JL
authors.lastname: Preau
authors.forename: Lee-Yang
authors.initials: LY
authors.lastname: Wong
authors.forename: Manori J
authors.initials: MJ
authors.lastname: Silva
authors.forename: Larry L
authors.initials: LL
authors.lastname: Needham
authors.forename: Antonia M
authors.initials: AM
authors.lastname: Calafat
mesh_terms: D000328:Adult; D004051:Diethylhexyl Phthalate / Q000652:urine*; D004781:Environmental Exposure / Q000032:analysis; D004785:Environmental Pollutants / Q000652:urine*; D006801:Humans; D019370:Observation; D015588:Observer Variation; D010795:Phthalic Acids / Q000652:urine*; D010968:Plasticizers / Q000378:metabolism*; D013995:Time
chemical_list: D004785:Environmental Pollutants; D010795:Phthalic Acids; D010968:Plasticizers; C479069:mono(2-ethyl-5-hydroxyhexyl) phthalate; D004051:Diethylhexyl Phthalate; C007379:diethyl phthalate
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