Presentation Abstract

Session: SVOC Sources & Fate
Friday, Jun 10, 2011, 8:00 AM -10:05 AM
Presentation: 35 - Indoor Residential Fate Model Of Phthalate Plasticizers
Pres. Time: Friday, Jun 10, 2011, 8:00 AM -10:05 AM
Location: 18A
Keyword 1: three-compartment model
Keyword 2: phthalates
Keyword 3: sorption
Author(s): Yirui Liang; Ying Xu
Abstract: ABSTRACT: A three-compartment model is extended to estimate the fate and transport of DEHP in a realistic residential environment. The model considered eight environmental media (i.e. air, particulate matter with six size fractions, vinyl flooring, carpet, furniture, dust, wall and ceiling). Particle movement (deposition and resuspension), dust removal (vacuuming), indoor cooking, and adsorption/absorption on indoor surfaces are included. The predicted airborne DEHP concentrations at steady state are within 0.1 μg/m3 to 0.2 μg/m3, which are similar to those measured in field studies. After vinyl flooring (the primary source) is removed, it takes 5 years for the indoor airborne DEHP level to reduce to below 0.01 μg/m3, and the time doubles when carpet present. The results indicate that carpets as well as other interior surfaces may be important phthalate sinks and if the only removal mechanism is ventilation, strongly sorbing phthalate may persist for years. Phthalate amount in dust is strongly influenced by the deposition surface. The concentration of DEHP presents10 times higher in dust on the source (vinyl flooring) than on the sink (furniture), and it takes more than a year for DEHP to reach equilibrium between bulk air and dust. The domestic activity of cooking is then included in the model and it shows that suspended particle concentration has a substantial impact on gas-phase DEHP level indoors, while the influence of ventilation is only to some extent. Finally, exposure to DEHP via inhalation, dermal absorption, and oral ingestion of dust is evaluated. RELEVANCE: Phthalate plasticizers have been recognized as major indoor pollutants. Exposure to phthalates may result in profound and irreversible changes in the development of the reproductive tract. A recent report by the National Academies urgently recommends that the most important sources of phthalate exposure be identified. The model clarifies the mechanisms that govern the release of DEHP from vinyl flooring and the subsequent interactions with interior surfaces and particles. It elucidates exposure pathways for phthalates, and can most likely be adapted to predict emissions and transport of other SVOCs indoors. UNCERTAINTY: We adopted a simple Monte Carlo analysis to account for uncertainty associated with the model parameters, as well as natural variability.



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