Study on water quality criteria and ecological risk assessment of microplastics in China's surface waters

Microplastics (MPs) are widely present in aquatic environments, causing harm to aquatic organisms and posing a threat to human health. MP risk assessment has therefore attracted increasing attention; yet few studies have been conducted on the water quality criteria (WQC) of MPs in the surface waters of China. Herein, data on the toxicity of MPs in aquatic species were reviewed, and the species sensitivity distribution (SSD) method was employed to determine the WQC for the protection of aquatic organisms against MP pollution. Criteria included the maximum concentration (CMC) and the continuous concentration (CCC). In addition, the ecological risk posed by MPs in China's main aquatic systems was assessed using a probabilistic method. The CMC and CCC were estimated at 59.42 mu g/L (1.67 x 10(7) particles/M-3) and 93.94 mu g/L (2.90 x 10(5) particles/M-3), respectively. The ecological risk levels of MP pollution across the seven aquatic systems in China were as follows: Yangtze, Pearl, Yellow, SongHua, LiaoHe, HaiHe, and HuaiHe Rivers. Although the average concentrations of seven rivers are all far lower than the CCC and CMC values obtained in this study, MP pollution might have harmful effects on aquatic organisms in some regions, necessitating tighter water quality management with regard to MPs in the future.