Airborne Microplastic Pollution in a Highly Urbanized City: Occurrence, Characteristics, Human Exposure and Potential Risks

The potential threat of airborne microplastics to human health has attracted widespread attention, especially in large cities with high concentrations of these particles. This study performed a preliminary investigation to uncover the occurrence, potential sources and risks of airborne microplastics in Guangzhou, a highly urbanized megacity of South China. The results suggested that the concentrations of airborne microplastics in Guangzhou ranged from 0.5 to 6.7 particles/m3, with an average of 2.5 ± 1.4 particles/m3. The concentrations of atmospheric microplastics at the sampling site near the heavy traffic area (mean: 3.7 ± 1.7 particles/m3) were significantly higher than at other sampling sites (p < 0.05). Temporally, the atmospheric microplastic concentrations were lowest in the morning (mean: 1.9 ± 1.2 particles/m3), indicating the impact of human activities and air temperatures. Four shapes (including fiber, fragment, foam and film) of microplastics were observed, among which fiber was the main shape and most of them were in the range of 50–300 µm. Rayon and polyethylene terephthalate were the predominant polymer types in fibrous microplastics, indicating that such microplastics primarily originated from synthetic textiles. Human exposure to airborne microplastics via inhalation was estimated to be 4.1 × 103–12.18 × 103 particles/yr. The ecological risk level of fibrous microplastic polymers in the atmosphere of Guangzhou was classified as hazard level II. The findings of the study are helpful for understanding the pollution status and potential risks of airborne microplastics in megacities, and highlight the necessity of long-term monitoring of urban atmospheric microplastic pollution.