Liquid Chromatography-Tandem Mass Spectrometry Analysis of Biomarkers of Exposure to Phosphorus Flame Retardants in Wastewater to Monitor Community-Wide Exposure. 
Phosphorus flame retardants and plasticizers (PFRs) are increasingly used in consumer goods, from which they can leach and pose potential threats to human health.  Monitoring human exposure to these compounds is thus highly relevant.  Current assessment of exposure through analysis of biological matrices is, however, tedious as well as logistically and financially demanding.  Analysis of selected biomarkers of exposure to PFRs in wastewater could be a simple and complementary approach to monitoring, over space and time, exposure at the population level.  An analytical procedure, based on solid-phase extraction (SPE) and liquid chromatography coupled to tandem mass spectrometry, was developed and validated to monitor the occurrence in wastewater of human exposure biomarkers of 2-ethylhexyldiphenyl phosphate (EHDPHP), tris(2-butoxyethyl) phosphate (TBOEP), triphenyl phosphate (TPHP), tris(2-chloroisopropyl) phosphate (TCIPP), and tris(2-chloroethyl) phosphate (TCEP).  Various SPE sorbents and extraction protocols were evaluated, and for the optimized method, absolute extraction recoveries ranged between 46% and 100%.  Accuracy and precision were satisfactory for the selected compounds.  Method detection limits ranged from 1.6 to 19 ng L-1.  Biomarkers of exposure to PFRs were measured for the first time in influent wastewater.  Concentrations in samples collected in Belgium ranged from below the limit of quantitation to 1072 ng L-1, with 2-ethylhexyl phenyl phosphate (EHPHP) and TCEP being the most abundant.  Per capita loads of target biomarkers varied greatly, suggesting potential differences in exposure between the investigated communities.  The developed method allowed implementation of the concepts of human biomonitoring at the community scale, opening the possibility to assess population-wide exposure to PFRs.