Tracing High-Risk Traditional and Novel Organophosphate Flame Retardants in Urban PM2.5: Source Contributions and Toxicity Insights

Organophosphate flame retardants (OPFRs), widely used in consumer products as flame retardants and plasticizers, pose significant health risks, yet their high-risk sources in urban PM2.5 are understudied. In this study, we investigated the atmospheric prevalence of 13 traditional and 13 novel OPFRs in Shenzhen, a dynamic urban hub in southern China, using multiseason PM2.5 sampling paired with advanced analytical techniques, including atmospheric pressure gas chromatography mass spectrometry and liquid chromatography-tandem mass spectrometry. Concentrations of traditional and novel OPFRs in PM2.5 were 5062.2 ± 1618.0 pg m–3 (range: 2562.8–9154.7 pg m–3) and 3081.3 ± 1552.8 pg m–3 (range: 663.3–7607.3 pg m–3), respectively. Employing positive matrix factorization with source-specific markers, we identified six emission sources, with plastic processing and waste disposal dominating, contributing 61.0% and 51.6% to traditional and novel OPFRs, respectively, and increasing to 71.9% and 63.0% during the wet season. Although inhalation risks from coexposure to traditional and novel OPFRs in PM2.5 were generally low, chlorinated OPFRs from these sources posed elevated risks. Toxicity prediction further revealed that certain novel aryl-OPFRs, such as isodecyl diphenyl phosphate (IDDPP) and bis(2,4-di-tert-butylphenyl) phosphate (B2,4DtBPP), may induce more severe adverse health effects associated with estrogen receptor disruption and oxidative stress than traditional OPFRs. These findings underscore the urgent need to address high-risk novel OPFRs and their dominant emission sources, offering critical insights for mitigating air pollution and safeguarding public health in rapidly urbanizing regions.