Occurrence, Sources, and Health Risks of Chlorinated Paraffins and Environmental Persistent Free Radicals in Urban PM _2.5 from the Megacity Shijiazhuang, China

Chlorinated paraffins (CPs) and environmental persistent free radicals (EPFRs) are classes of emerging organic pollutants with adverse health and environmental impacts. In this study, we investigated the occurrence, sources, environmental determinants, and health risks associated with CPs and EPFRs in PM2.5 collected from Shijiazhuang, China. The results demonstrated the ubiquity of both CPs (primarily SCCPs and MCCPs) and EPFRs in PM2.5, with concentrations ranging from 3.48 × 102 to 3.89 × 103 pg/m3 and from 1.03 × 1012 to 6.11 × 1013 spins/m3, respectively. Source apportionment revealed that CPs primarily originated from CP-related products, industrial emissions, and vehicular emissions, whereas EPFRs were mainly attributed to atmospheric oxidation and vehicle emissions. The concentrations of CPs and EPFRs were positively associated with PM10, CO, and NO2 and negatively associated with relative humidity. Health risk assessments indicated that children (<6 years) and adults (≥18 years) exhibited higher inhalation exposure levels to both CPs and EPFRs. Notably, individuals aged 18–59 years showed the highest cigarette equivalent inhalation exposure to EPFRs, with average values of 0.285 (head airway), 0.030 (tracheobronchial region), and 0.063 (alveolar region). These findings provide valuable scientific insights for formulating targeted control strategies and public health interventions to mitigate the health risk of these pollutants globally.