Determination of Representative Values of Aerodynamic Diameters of Suspended Particles for Model Predictions of Di (2-Ethylhexyl) Phthalate Concentrations in Indoor Air

Chemical exposures are typically investigated by measuring the actual concentration of exposure. However, due to time and cost constraints, actual exposure concentration measurements are not always possible; hence, there is an increased demand for model estimation. Meanwhile, many semivolatile organic compound model predictions have not accurately reproduced the measured fractions of gas- and particle-phase concentrations in air. In this study, in order to improve the reproducibility of the fraction of phase concentration in air by the exposure model, the suspended particle diameter, which is one of the parameters affecting the particle-phase concentration, was optimized. Our comprehensive literature research on the interaction between gaseous di (2-ethylhexyl) phthalate and the suspended particle found that the representative value of aerodynamic diameters of PM10 for the particle-phase concentration were 0.375μm. By optimizing the particle diameter, the estimated fraction of gas-phase concentration improved from 58% to 29%, thereby approaching the measured fraction of 10%-20%. Although the Factor value, which denotes the estimation accuracy of total air concentration, shifted by 64% to the safe side from 2.8 to 4.6, the screening accuracy remained adequate. Furthermore, the higher tier assessment accuracy for the estimated concentration of settled dust was maintained.