Journal
ENVIRONMENTAL HEALTH
Volume 11, Issue -, Pages -Publisher
BMC
DOI: 10.1186/1476-069X-11-29
Keywords
Biomarker; Endocrine Disruptor; Phenols; Phthalate esters; Pregnancy; Sampling conditions
Funding
- French Agency for Environmental and Occupational Health Safety (ANSES)
- Foundation for medical research (FRM)
- Eden cohort is funded by the Foundation for medical research (FRM), Inserm
- IReSP
- Nestle
- French Ministry of health
- National Research Agency (ANR)
- Univ. Paris-Sud
- Institute of health monitoring (InVS)
- AFSSET
- MGEN
- AFSSA (ANSES)
- ANSES
- Ministry of Health, Ministry of Labor
- ANR
- InVS
- Inserm
- Regional Council of Brittany
- AVENIR grant from Inserm
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Background: Environmental epidemiology and biomonitoring studies typically rely on biological samples to assay the concentration of non-persistent exposure biomarkers. Between-participant variations in sampling conditions of these biological samples constitute a potential source of exposure misclassification. Few studies attempted to correct biomarker levels for this error. We aimed to assess the influence of sampling conditions on concentrations of urinary biomarkers of select phenols and phthalates, two widely-produced families of chemicals, and to standardize biomarker concentrations on sampling conditions. Methods: Urine samples were collected between 2002 and 2006 among 287 pregnant women from Eden and Pelagie cohorts, from which phthalates and phenols metabolites levels were assayed. We applied a 2-step standardization method based on regression residuals. First, the influence of sampling conditions (including sampling hour, duration of storage before freezing) and of creatinine levels on biomarker concentrations were characterized using adjusted linear regression models. In the second step, the model estimates were used to remove the variability in biomarker concentrations due to sampling conditions and to standardize concentrations as if all samples had been collected under the same conditions (e. g., same hour of urine collection). Results: Sampling hour was associated with concentrations of several exposure biomarkers. After standardization for sampling conditions, median concentrations differed by - 38 % for 2,5-dichlorophenol to +80 % for a metabolite of diisodecyl phthalate. However, at the individual level, standardized biomarker levels were strongly correlated (correlation coefficients above 0.80) with unstandardized measures. Conclusions: Sampling conditions, such as sampling hour, should be systematically collected in biomarker-based studies, in particular when the biomarker half-life is short. The 2-step standardization method based on regression residuals that we proposed in order to limit the impact of heterogeneity in sampling conditions could be further tested in studies describing levels of biomarkers or their influence on health.
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