Microplastic Fiber Release by Hand-Washing 8 and Estimated Emissions in China

: 23 Microplastic fibers (MPFs) shed during textile washing is one of the most common 24 sources of microplastics in the aquatic environment. There have been many studies on 25 MPF release by machine washing of textiles. However, traditional hand-washing remains 26 very common in many regions around the world, especially in developing countries. 27 Fiber release from hand-washing remains unquantified, which imparts difficulties to 28 accurately estimating the total fiber release from domestic laundering. We conducted such 29 a study by using two types of synthetic textiles, and examined the effects of various 30 washing factors. Results showed that MPF emission factor of polyester fabric was 0.040 31 mg MPF / g or 329 fibers / g textile during hand washing by adding powder detergent and 32 0.037 mg MPF / g or 353 fibers / g textile by adding liquid detergent under the routine 33 conditions; MPF release was significantly correlated with the use of a detergent or brush, 34 and the soaking time ( P < 0.05). Moreover, we also calculated approximate MPF 35 emissions and discharged into the water environment per year in China. Differences in 36 the geographical distribution of MPF emissions in China mainly depended on the 37 population density at the provincial and grid (1 km × 1 km) scale. Based on the results of 38 this study, several relevant policy recommendations are proposed that will help reduce the 39 discharge of MPFs into the water environment. 40