Indirect Emissions from Organophosphite Antioxidants Result in Significant Organophosphate Ester Contamination in China

Abstract

Organophosphite antioxidants (OPAs) have been seriously neglected as potential sources of organophosphate esters (OPEs) in environments. This study utilizes a modeling approach to quantify for the first time national emissions and multimedia distributions of triphenyl phosphate (TPHP)─a well-known flame retardant─and three novel OPEs: tris(2,4-ditert-butylphenyl) phosphate (AO168═O), bis(2,4-ditert-butylphenyl) pentaerythritol diphosphate (AO626═O₂), and trisnonylphenol phosphate (TNPP). Emphasis is on the quantitative assessment of OPA source in China. TPHP has 1.1–9.7 times higher emission (300 Mg/year in 2019 with half from OPA sources) than AO168═O (278 Mg/year), AO626═O₂ (53 Mg/year), and TNPP (32 Mg/year), but AO168═O is predominant in environments (63–79%) except freshwaters. About 72–99% of the studied OPEs are emitted via air, with 88–99% ultimately distributed into soils as the major sink. OPA-source emissions contribute 9.5–57% and 4.7–56% of TPHP masses and concentrations (except in sediments) in different media, respectively. Both AO168═O and AO626═O₂ exhibit high overall persistence ranging between 2 and 11 years. Source emissions and environmental concentrations are elevated in economically developed areas, while persistence is higher in northern areas, where precipitation and temperature are lower. This study shows the significance of the sources of OPA to OPE contamination, which supports chemical management of these substances.