We observed weak and non-statically significant correlations between urinary DPP and BDCPP concentrations which may be explained by differences in the sources of exposure to TDCPP and TPP. While both TDCPP and TPP are used as additive flame retardants in household products, TPP is also used as a plasticizer and lubricant and in hydraulic fluids (van der Veen and de Boer, 2012). Differences in the metabolism and excretion of TDCPP and TPP also provide possible explanations for the weak correlation observed in urinary biomarkers of exposure.