Sources and fate of organophosphate esters in urban air of Indonesia: Insights from partitioning models and implications for inhalation exposure.

Across Surabaya (SB), Jakarta (JT), and Yogyakarta (YG), Indonesia, we quantified total OPE levels in the gas and PM2.5 phase, identified likely sources, and examined their gas-particle distribution. Total OPEs in the gas phase ranged from 2.25 to 11.56 ng/m³ (5.60 ± 2.75 ng/m³) at SB, 2.03-14.31 ng/m³ (5.94 ± 4.09 ng/m³) at JT, and 1.76-8.88 ng/m³ (5.73 ± 1.94 ng/m³) at YG. In contrast, PM2.5 phase totals were 0.51-1.53 ng/m³ (0.88 ± 0.37 ng/m³), 0.47-1.32 ng/m³ (0.71 ± 0.26 ng/m³), and 0.17-0.71 ng/m³ (0.42 ± 0.15 ng/m³), respectively. Gaseous profiles at all sites were dominated by tris(1-chloro-2-propyl) phosphate (TCIPP) and tris(1,3-dichloro-2-propyl) phosphate (TDCPP). In particles, TCIPP together with tri-n-butyl phosphate (TBP) predominated at SB and JT, whereas TCIPP and tris(2-chloroethyl) phosphate (TCEP) were most abundant at YG. Positive Matrix Factorization (PMF) resolved contributions from construction materials, indoor emissions, traffic, polymer products and coatings, flame-retardant uses (notably in furniture foam, plastics, and textiles), and other building-related sources. Gas-particle partitioning was predicted using the Harner-Bidleman and Li-Ma-Yang models, with the Li-Ma-Yang model showing superior predictive precision. Estimated inhalation exposures indicated low risk to both children and adults at SB, JT, and YG. Overall, this study provides the first baseline characterization of atmospheric OPEs in Indonesian urban air and helps fill a critical geographic gap in global OPE monitoring, supporting future regional assessments of sources, atmospheric processes, and human exposure in tropical megacity environments.