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Urinary Metabolites of Organophosphate Flame Retardants and Their Variability in Pregnant Women

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Urinary Metabolites of Organophosphate Flame Retardants and Their Variability in Pregnant Women

Kate Hoffman et al. Environ Int.

Abstract

Organophosphate flame retardants (OPFRs) are commonly added to consumer products to reduce their flammability. Based on levels of OPFRs in indoor environments, human exposure is likely chronic and ubiquitous. Animal studies suggest that exposure to some OPFRs may result in adverse health impacts, particularly for Tris (1,3-dichloropropyl) phosphate (TDCPP); however, human data on the impacts of exposure to OPFRs are lacking. To design human studies, more information is needed on the stability of measured OPFRs in human samples over time. In this study, we sought to assess the degree of temporal variability of urinary TDCPP and triphenyl phosphate (TPP) metabolites throughout pregnancy in a cohort of women from central North Carolina. Eight pregnant women provided multiple urine samples: 3 during the 18th week of pregnancy, 1 during the 28th week, and 1 shortly after the child's birth. Bis (1,3-dichloropropyl) phosphate (BDCPP) and diphenyl phosphate (DPP), the respective metabolites of TDCPP and TPP, were measured in urine samples using liquid chromatography-tandem mass spectrometry. BDCPP and DPP were each detected in 38 of 39 urine samples and were not normally distributed. Geometric mean BDCPP and DPP concentrations were 1.3ng/mL (interquartile range (IQR): 0.8, 2.7ng/mL) and 1.9ng/mL (IQR: 0.9, 3.5ng/mL), respectively. BDCPP and DPP were moderately to strongly reliable over one week (intraclass correlation coefficient (ICC)=0.5; 95% confidence interval (CI): 0.4, 0.7 and ICC=0.7; 95% CI: 0.5, 0.8, respectively), and over the entire pregnancy (ICC=0.5 95% CI: 0.3, 0.7 and ICC=0.6; 95% CI: 0.4, 0.7, respectively). These data suggest that exposures to TDCPP and TPP are widespread and variable for pregnant women, and that a single measure of BDCPP or DPP, taken in the second trimester, likely captures information on the rank order of exposure throughout pregnancy.

Keywords: BDCPP; CI; DPP; GM; ICC; IQR; MDL; ND; OPFRs; Organophosphate flame retardants (OPFRs); PBDEs; Pregnant women; SG; TDCPP; TPP; Triphenyl phosphate (TPP); Tris (1,3-dichloropropyl) phosphate; Tris (1,3-dichloropropyl) phosphate (TDCPP); Urine; Variability; bis (1,3-dichloropropyl) phosphate; confidence interval; diphenyl phosphate; geometric mean; interquartile range; intraclass correlation coefficient; method detection limit; non-detect; organophosphate flame retardants; polybrominated diphenyl ethers; specific gravity; triphenyl phosphate.

Figures

Figure 1
Figure 1
Concentrations (ng/mL) of metabolites in urine from repeated samples collected from 8 pregnant women in the18th (averaged across three measurements) and 28th weeks of pregnancy and at the time of birth. (A) DPP; (B) BDCPP. Colors represent individual participants. Measured samples are connected with lines to assist in the interpretation of changes over time.

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