Exploring the discharge characteristics of personal care behaviors for high precision estimation of microplastic emission

Microplastics (MPs) from personal care and cosmetic products (PCCPs) pose a threat to aquatic environment due to the small size and the complexity of composition. Although the habits of personal care behaviors (PCBs) vary from individuals affecting MPs emissions, quantitative research is not sufficient to support high-precision emission estimates and targeted management decisions. Based on a questionnaire survey about PCBs and laboratory experiments on corresponding PCCPs utilization, this study proposed a bottom-up micro-simulation method to quantify MPs emissions combining multinomial logit model and categorized emission coefficients, and identified the impact of individual attributes on the emissions. The results show that the annual PCBs-derived MPs emissions amounted to 2931.8 trillion particles in China, of which teeth brushing, face washing, and bathing behavior accounted for 29%, 36% and 35%, respectively. The residents discharged an average of 2.18 million particles per capita per year with 95% confidence interval of 0.58-4.34 million particles. Gender, age and living region had greater impacts on PCBs-derived MPs emissions. The effect of living region was significantly related to local temperature and humidity. The estimation based on the MPs discharge characteristics of PCBs provides high-precision method regarding the MPs emission from people's daily life and contributes to further understanding the source of MPs and initiating environmental control strategies.