Impurities of Resorcinol Bis(diphenyl phosphate) in Plastics and Dust Collected on Electric/Electronic Material

Resorcinol bis(diphenylphosphate) (RDP) is an organophosphorus flame retardant widely used in electric and electronic equipment. It has been detected in house dust of several European countries according to recent literature. Similar to other flame retardants, RDP formulations and products treated with RDP, such as plastics, can contain RDP impurities, byproducts and breakdown products. In this study, we use screening methods based on wide scope solvent extraction and high resolution time-of-flight mass spectrometry for the identification of RDP related compounds in products and in dust. We analyzed both plastics from electrical/electronic equipment that contained RDP and indoor dust collected on and around surfaces of this equipment. A variety of compounds, namely TPHP, hydroxylated TPHP and RDP (meta-HO-TPHP and meta-HO-RDP), dihydroxylated TPHP, RDP with the loss of a phenyl group (RDP-[Phe]) and RDP oligomers were detected in plastics containing high levels of RDP. Regarding dust samples collected on electronics, TPHP meta-HO-TPHP, meta-HO-RDP, RDP-[Phe] and RDP oligomers were detected. High concentrations of meta-HO-TPHP (20–14 227 ng/g), TPHP (222–50 728 ng/g) and RDP (23–29 118 ng/g) were found in many of the dust samples, so that these compounds seem to easily migrate into the environment. These RDP impurities, byproducts and breakdown products are for the first time reported in indoor dust. Meta-HO-TPHP could be relevant for future biomonitoring studies concerning flame retardants

In Vitro Human Metabolism of the Flame Retardant Resorcinol Bis(diphenylphosphate) (RDP)

Resorcinol bis­(diphenylphosphate) (RDP) is widely used as a flame retardant in electrical/electronic products and constitutes a suitable alternative to decabrominated diphenyl ether. Due to its toxicity and its recently reported ubiquity in electronics and house dust, there are increasing concerns about human exposure to this emerging contaminant. With the aim of identifying human-specific biomarkers, the in vitro metabolism of RDP and its oligomers was investigated using human liver microsomes and human liver cytosol. Mono- and dihydroxy-metabolites, together with glucuronidated and sulfated metabolites, were detected. Regarding RDP oligomers, only a hydroxy-metabolite of the dimer could be detected. RDP and its oligomers were also readily hydrolyzed, giving rise to a variety of compounds, such as diphenyl phosphate, <i>para</i>-hydroxy-triphenyl phosphate, and <i>para</i>-hydroxy RDP, which were further metabolized. These degradation products or impurities are possibly of environmental importance in future studies