Multimedia-Based Source Apportionment and Health Implications of Indoor Organophosphate Esters in Various Scenes of Urban Beijing, China

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Studies on source apportionment of indoor OPEs rarely involve multiple media and characteristic source markers on emissions. Herein, we present a novel framework for quantitative and integrative source appointment of indoor OPEs by integrating OPE concentrations in multimedia into equivalent indoor concentrations ( EICs ) and using characteristic source markers on indoor emissions. Utility was demonstrated by applying it to five types of microenvironments where the 13 OPEs were ubiquitous (indoor dust: 993–14000 ng/g; indoor air: 0.549–14.1 ng/m 3 ). The paired dust and air samples were adopted to construct the “Measured-Paired- EICs ” data set for source apportionments via positive matrix factorization (PMF). Moreover, an alternative model method for constructing EIC data sets from single-medium measurements was established to improve the applicability of the framework. Accordingly, “Modeled-Paired- EICs ”, “Dust-Only”, and “Air-Only” data sets were constructed for comparison. The extracted factors exhibited consistent contributions for “Measured-Paired- EICs ” and “Modeled-Paired- EICs ” solutions (RSD: 0.14–5.4%), while the “Air-Only” solution identified incomplete factors and the “Dust-Only” solution showed errors of 40.6–262%. Specifically, PMF analysis resolved seven known sources and other unknown sources. Furthermore, heterogeneities in source identification and source contributions were observed across various exposure scenarios; the probabilistic carcinogenic risk of TCEP (up to 7.19 × 10 –7 ) was close to the acceptable level (1 × 10 –6 ) and demands further attention.