Occurrence of Novel Alternative Phosphorus Flame Retardants on Indoor Dust Collected From Japanese Dwellings and a Kindergarten

Alternative flame retardants, especially those containing phosphorus, have changed over time to meet flammability standards; however, studies on the presence of these alternatives on indoor dust, which is a major exposure carrier to human beings, have been limited. In this study, we measured the concentrations of four novel phosphorus flame retardants (PFRs), including 6-benzylbenzo[c][2,1]benzoxaphosphinine 6-oxide (BzlDOPO), naphthalen-2-yl diphenyl phosphate (NDPhP), (5-ethyl-2-methyl-2-oxido-1,3,2-dioxaphosphorinan-5-yl)methyl methyl methylphosphonate (PMMMP), and bis[(5-ethyl-2-methyl-2-oxido-1,3,2-dioxaphosphinan-5-yl)methyl] methylphosphonate (di-PMMMP), and 13 conventional PFRs on indoor dust collected from 29 dwellings and a kindergarten in Japan. The concentration of the PFRs on indoor dust ranged from 3.0 ng g⁻¹ (TPP [tripropyl phosphate]) to 4,600,000 ng g⁻¹ (TBOEP [tris (2-butoxyethyl) phosphate]). Among the PFRs targeted in this study, TBOEP exhibited the highest median concentration, followed by tris(2-chloroisopropyl) phosphate (TCPP), tris(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPhP), and tris(1,3-dichloro-2-propyl) phosphate (TDCPP). The novel PFRs, PMMMP, di-PMMMP, BzlDOPO, and NDPhP, were detected at 51, 63, 6, and 3 ng g⁻¹, respectively, in dust samples. TBOEP exhibited the lowest margin of exposure (1.5 × 10³ [5%ile]) among the PFRs examined. The results indicate that the novel PFRs are present in indoor environments and that humans are exposed through indoor dust. Further studies are needed to evaluate the toxicity of novel PFRs and assess their potential health risks.