Seasonal co-occurrence and inhalation risks of microplastics and benzotriazole ultraviolet stabilizers in atmospheric PM2.5 from northern Chinese city

Microplastics (MPs) and benzotriazole ultraviolet stabilizers (BUVs) are emerging contaminants in airborne PM_2.5, yet their co-occurrence patterns, seasonal dynamics, and health risks remain poorly understood. We conducted a year-long study (2023-2024) in Shijiazhuang, a northern Chinese city, analyzing PM_2.5 samples (n = 117) for MPs (abundance, size, polymer type) and BUVs (UV-320, UV-327, UV-328) via microscopy, Raman spectroscopy, and UPLC-MS/MS. Correlations with criteria air pollutants (PM_2.5, PM₁₀, NO₂, CO and O₃) and meteorological factors (temperature, humidity and wind scale) were assessed using spearman analysis. Health risks were evaluated via inhalation exposure models. MPs (predominantly PP/PS/PE/PC fragments) and BUVs peaked in winter (MPs: 9.56 N·m^-3; ∑BUVs: 7.10 ng·m^-3) due to low temperatures, weak solar radiation, and stagnant air, contrasting with summer minima (MPs: 6.18 N·m^-3; ∑BUVs: 2.23 ng·m^-3). MPs correlated with PM_2.5 (r = 0.69), PM₁₀ (r = 0.61), CO (r = 0.54) and BUVs (r = 0.58), while BUVs associated with CO (r = 0.74), NO₂ (r = 0.77) and MPs (r = 0.58), suggesting shared emission sources (e.g., plastic waste combustion). Annual inhalation exposure reached 3.86 × 10⁴ MPs/person and ∑BUVs up to 0.82 ng·kg^-1·d^-1 (highest in children). This study highlights the synergistic pollution of MPs and BUVs in PM_2.5, driven by fossil fuel combustion and meteorological conditions. The findings underscore the need to regulate plastic production/waste as well as plastic additives in urban air quality management.