Organophosphate Flame Retardants in Shanghai Indoor Dust: A 2016 Historical Baseline of Seasonal Variability, Microenvironmental Profiles, and Human Exposure

Organophosphate flame retardants (OPFRs) are additive chemicals that migrate from indoor materials and accumulate in settled dust. This study retrospectively characterized eight OPFRs in floor dust collected in Shanghai during 2016 to establish a seasonally resolved historical reference. A total of 136 residential dust samples were obtained from a convenience panel of 26 homes sampled at approximately two-month intervals; five office and four dormitory composite samples were included only for exploratory microenvironmental comparisons. Sampling, extraction, and LC-MS/MS determination were all completed in 2016. OPFRs were detected in all samples. Median (mean) Σ8OPFR concentrations were 1.51 × 103 (4.35 × 103), 2.48 × 103 (3.36 × 103), and 673 (963) ng·g−1 in residential, office, and dormitory dust, respectively, and chlorinated OPFRs—particularly tris(2-chloroisopropyl) phosphate and tris(2-chloroethyl) phosphate—dominated. Mixed-effects models accounting for repeated sampling confirmed significant season effects for Σ8OPFRs and all frequently detected congeners, with autumn generally lower than spring or winter. Under the mean 2016 concentration scenario, uptake-adjusted total estimated daily intakes were 3.3 ng·kg−1·day−1 for infants and 0.65 ng·kg−1·day−1 for adults. Oral administered-dose screening values did not exceed the selected non-cancer or cancer benchmarks. These measurements do not represent current exposure but provide a historical benchmark for method-matched follow-up monitoring.