Multi-class plastic additives in outdoor particulate matter at schools across the Pearl River Delta: descriptive geographic contrasts, mixture profiles, and modeled external particle-bound inhalation intake

Airborne plastic additives (PAs) occur as complex mixtures, yet their regional distribution and exposure relevance remain poorly characterized in school-associated outdoor air. We characterized 168 PAs in particulate matter from 98 schools across six cities in the Pearl River Delta (PRD), China, using summer PM 2.5 , winter PM 2.5 , and winter PM 1 datasets. Phthalate diesters dominated each dataset, with dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) among the most abundant compounds. Because sampling configurations differed among campaigns, the three datasets were treated as separate descriptive datasets and were not used to infer seasonal or particle-size effects. Descriptive geographic contrasts were evaluated without spatial-autocorrelation analysis or formal spatial inference, showing substantial overlap in total PA distributions and more apparent differences in class-level profiles. Air-mass trajectories indicated broad regional airflow patterns associated with the South China Sea, South China, and East Coast sectors, while exploratory class-level networks showed extensive within-dataset co-occurrence. Temperature associations were heterogeneous across classes and compounds, with no uniform mixture-wide pattern. DBP and DEHP were the main contributors to modeled external particle-bound outdoor inhalation intake, with the highest EDIs estimated for children aged 3–6 years under the applied IR/BW framework. DBP and DEHP also ranked highly in the HQ-based screening. HQs based on derived or predicted benchmarks were interpreted as screening-level estimates. These findings provide a descriptive multi-dataset survey of particle-bound PA mixtures across schools in the PRD and identify compounds and mixture features relevant to future monitoring and prioritization.