Flame retardants (FRs) are either additive or reactive ingredients applied to household and consumer products to reduce the products flammability, and to meet state and federal fire safety standards and regulations. Until recently, the dominant class of FR additives used for household products was polybrominated diphenyl ethers (PBDEs), which are persistent and can accumulate in the environment (de Wit, 2002; Law 2006, Stapleton 2012). Flame retardant formulations containing chlorinated and non-chlorinated organophosphates and products such as Firemaster 550 (FM550) have entered the consumers’ market worldwide as PBDEs have been phased-out in many countries (van der Veen, 2012). We recently developed a method to measure diphenyl phosphate, bis(1,3-dichloro-2-propyl) phosphate), bis(1-chloro-2-propyl) phosphate, bis(2-chloroethyl) phosphate, di-p-cresyl phosphate, di-o-cresyl phosphate, dibutyl phosphate, dibenzyl phosphate, and 2,3,4,5-tetrabromobenzoic acid . These compounds are urinary metabolites of triphenyl phosphate, tris(1,3-dichloro-2-propyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(2-chloroethyl) phosphate, tri-cresyl phosphates, tributyl phosphate, tribenzyl phosphate, and 2-ethylhexyl-2,3,4,5-tetrabromobenzoate, respectively, and can be used as exposure biomarkers for these compounds.
A random 1/3 sample of participants aged 6+ years from NHANES 2013-2014 with stored urine.
Description of Laboratory Methodology
The method uses 0.4 mL urine and is based on enzymatic hydrolysis of urinary conjugates of the target analytes, automated off-line solid phase extraction, reversed phase high-performance liquid chromatography separation, and isotope dilution-electrospray ionization tandem mass spectrometry detection (Jayatilaka 2017).
Laboratory Quality Assurance and Monitoring
The analytical measurements were conducted following strict quality control/quality assurance CLIA guidelines. Along with the study samples, each analytical run included high- and low-concentration quality control materials (QCs) and reagent blanks to assure the accuracy and reliability of the data. The concentrations of the high-concentration QCs and the low-concentration QCs, averaged to obtain one measurement of high-concentration QC and low-concentration QC for each run, were evaluated using standard statistical probability rules (Caudill et al. 2008).
Data Processing and Editing
Data were received after all analyses were complete. The data were not edited. Data Access: All data are publicly available.
The detection limits were constant for all of the analytes in the data set. Two variables are provided for each analyte. The variable name ending in “L” (ex., SSDPHPL) indicates whether the result was below the limit of detection: the value “0” means that the result was at or above the limit of detection, “1” indicates that the result was below the limit of detection. For analytes with analytic results below the limit of detection (ex., SSDPHPL=1), an imputed fill value was placed in the analyte results field. This value is the limit of detection divided by square root of 2 (LOD/√2). The other variable prefixed SS (ex., SSDPHP) provides the analytic result for that analyte.
The limit of detection (LOD, in µg/L) for DPhP, BDCPP, BCPP, BCEtP, DpCP, DoCP, DBuP, DBzP and TBBA:
||Diphenyl phosphate (µg/L)
||Bis(1,3-dichloro-2-propyl) phosphate (µg/L)
||Bis(1-chloro-2-propyl) phosphate (µg/L)
||Bis(2-chloroethyl) phosphate (µg/L)
||Di-p-cresyl phosphate (µg/L)
||Di-o-cresyl phosphate (µg/L)
||Dibutyl phosphate (µg/L)
||Dibenzyl phosphate (µg/L)
||2,3,4,5-tetrabromobenzoic acid (µg/L)
Blanks in an analyte results field represent missing values in cases when the presence of interferences precluded obtaining a valid numeric result for a given analyte.