Unexpectedly High Concentrations of a Newly Identified Organophosphate Ester, Tris(2,4-di-tert-butylphenyl) Phosphate, in Indoor Dust from Canada

Organophosphate esters (OPEs) represent a group of additives with significant levels of production and significant application to various household and industrial products. Given their potential adverse effects on human health, accurate analysis of novel OPEs in indoor dust is crucial. In this study, the novel tris(2,4-di- tert-butylphenyl) phosphate (AO168═O) and six well-known OPEs were investigated. The seven target OPEs were detected in 100% of the office and home dust samples, with ∑OPEs (sum of the OPE concentrations) ranging from 2.92 to 124 μg/g [geometric mean (GM) of 12.3 μg/g]. Surprisingly, the novel AO168═O (0.10-11.1 μg/g, GM of 1.97 μg/g) was among the highest-concentration congeners, contributing 1.36-65.5% to ∑OPEs (mean of 20.7%). AO168═O was the dominant congener in the home dust samples, indicating it is an important OPE congener overlooked previously. AO168═O was also detected in Standard Reference Material 2585 (indoor dust) at an elevated concentration of 10.9 μg/g, which was significantly higher than the concentrations of the other target OPEs (0.38-2.17 μg/g). Despite the high concentrations measured in this study, no industrial production or application could be identified for AO168═O. The precursor of AO168═O, tris(2,4-di- tert-butylphenyl) phosphite, was detected in 50% of the dust samples, with a GM concentration of 1.48 ng/g. This study demonstrates that human OPE exposure in indoor environments is greater than was previously reported. This is the first report of the occurrence of AO168═O, its precursor, and its hydrolysis products in the environment.