Short term temporal variability of selected organophosphate esters among healthy adults living in the National Capital Region of Canada

Organophosphate esters (OPEs) are used primarily as flame-retardants and plasticizers. OPEs are commonly detected in various environmental matrices, food and drinking water, and their metabolites are frequently found and quantified in urine. Potential adverse impacts on human health, including carcinogenicity, neurotoxicity, developmental and reproductive toxicity have been well documented. Urinary concentration of OPE metabolites can vary in the same individual, depending on the sampling time, thus introducing significant uncertainty in exposure assessment. The current study focusses on the assessment of short term temporal variability in adult men and women residing in Canada's Capital Region. Fifteen OPE metabolites were analyzed in 562 daily urine samples, collected every three days for five weeks from 11 volunteers. Sample extraction procedure was performed on an automated SPE and extracts analyzed using UPLC-MS/MS. In spot urine samples as well as first morning void (FMV), the detection frequency was greater than 50% for bis (2-chloroethyl) hydrogen phosphate (BCEP), bis (1-chloro-2-propyl) phosphate (BCIPP), bis (1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPHP) and bis(2,4-ditert-butylphenyl) hydrogen phosphate (B2,4DtBPP). Significant difference was observed in males and females for BCEP and BCIPP. Intra-class correlation coefficient (ICC) for creatinine corrected data for the spot urine samples ranged from 0.37 to 0.69. Good reproducibility was observed for creatinine corrected DPHP and BCIPP in both spot urine and FMV samples. More variation was observed between study participants in the spot urine samples when compared to the FMV samples. However, when considering diurnal difference there was a considerable inter-day variation in the FMV samples compared to the spot samples. The strength of the study is that the participants belonged to the same geographical location and working in the same facility, hence spatial variability did not influence the outcome of the results.