Comparison of rates of direct and indirect migration of phosphorus flame retardants from flame-retardant-treated polyester curtains to indoor dust

In this study, the pathways for migration of phosphorus flame retardants (PFRs), tris(1,3-dichloroisopropyl) phosphate (TDCPP) and tricresyl phosphate (TCsP) which were detected from curtains often, from flame-retardant-treated polyester curtains to indoor dust were investigated. Two possible migration pathways were compared quantitatively: (1) an indirect pathway in which the PFRs in the curtains first evaporate from the curtains and are then adsorbed onto indoor dust and (2) a direct pathway in which the PFRs are directly transferred to dust placed on the curtains. The contribution of the indirect pathway was evaluated by means of emission cell tests, which showed that the area-specific emission rates from curtains treated with PFRs were 0.044 (TDCPP, Curtain 5), 0.17 (TDCPP, Curtain 8), and 0.060 (TCsP, Curtain 12) mu g m(-2) h(-1) at 20 degrees C (averaged during 24 h). The contribution of the direct pathway was evaluated by measurement of the time dependence of PFR concentrations on the indoor dust placed on the curtains. These measurements indicated that PFR concentrations on the dust increased with time and that the direct migration rates of PFRs from curtains treated with PFRs were 4.4 (TDCPP, Curtain 5), 12 (TDCPP, Curtain 8), and 7.0 (TCsP, Curtain 12) mu g m(-2) h(-1) at 20 degrees C (averaged during 24 h), or 71-120 times the indirect migration rate. This result suggests that the direct pathway can be expected to predominate.