# An Exploratory Review of Microplastic Pollution, Associated Microbiomes and Pathogens in Water
## 3 Results and Discussion  
### Microplastics in Surface Waters  
**Asia:** In the case of Asia, 55 publications regarding the presence of MP in water were selected (Figure 1). The highest countrywide mean value was reported in Japan at the level of \(\sim\)28,728 particles/m\({}^{3}\) (Figure 1, Supplementary File S1--Asia). The highest levels of MP were found in the rivers Awano (\(\sim\)124,000 particles/m\({}^{3}\)), Ayaragi (\(\sim\)117,000 particles/m\({}^{3}\)), Asia (\(\sim\)129,500 particles/m\({}^{3}\)) and Majime (\(\sim\)580,000 particles/m\({}^{3}\)) [Supplementary File S1--Asia]. Another criterion taken into account during the analysis was water body type. The results of this analysis showed that both rivers and coastal regions have accumulated similar concentrations of MP (-28,827 particles/m\({}^{3}\) and -27,077 particles/m\({}^{3}\), respectively) (Supplementary File S1--Asia). Further studies from 2021 provided additional insights. For instance, a study analyzing surface waters in Japanese rivers reported microplastic concentrations ranging from 300 to 1240 particles/m\({}^{3}\)[26]. In Southeast Asia, the Chao Phraya River in Thailand exhibited mean concentrations of -80 particles/m\({}^{3}\) in urban zones and -48 particles/m\({}^{3}\) in estuary zones [27]. The Saigon River in Vietnam showed 68-20 particles/m\({}^{3}\) in urban areas and -42 particles/m\({}^{3}\) near its estuary [28]. In contrast, the Citarum River in Indonesia had significantly lower concentrations, with -12 particles/m\({}^{3}\) in urban zones and approximately 0.08 \(\pm\) 0 particles/m\({}^{3}\) in estuarine areas [29]. High levels of MP were also found in Southern Korea, where the average detected concentration in surface waters was -22,280 particles/m\({}^{3}\). A higher amount was found in Jinhae Bay---88,000 particles/m\({}^{3}\)[30]. On the other hand, the lowest concentration was found on the coast of Geoje Island, where the average content was \(\sim\)1 particles/m\({}^{3}\)[31]. The mean content of MP, depending on the type of reservoir, showed that coastal areas were characterized by higher concentrations in comparison to rivers (respectively: \(\sim\)699 and -32,751 particles/m\({}^{3}\)) (Supplementary File S1--Asia). The most frequently studied country in terms of the occurrence of MP in surface waters was China (n = 20; Figure 2), where the average was -7260 particles/m\({}^{3}\). The highest levels were found in the Pearl River Estuary of Guangzhou waters--42,100 particles/m\({}^{3}\)[32]. In turn, the lowest occurred in the Yellow Sea and East Chinese Sea waters---130 and -170 particles/m\({}^{3}\), respectively [33; 34]. In the case of China, the lowest mean MP levels were found in the coastal areas, and the highest in the lakes (\(\sim\)2328 and -13,903 particles/m\({}^{3}\), respectively). In the regions of Thailand and India, the average MP level in the waters was similar, at -715 and -710 particles/m\({}^{3}\), respectively. In the case of Thailand, the lowest level was found in the Inner Gulf of Thailand---10 particles/m\({}^{3}\)[35]. In India, the lowest level was found in the areas of the Ganges/Ballia, Ganges/Patna, Ganges/Bhagalpur, Ganges/Farakka, and Ganges/Diamond Harbor rivers, where it ranged from -0.38-0.684 particles/m\({}^{3}\)[36]. Additionally, in the case of India, MPs were absent in some parts of the Munnar and Chenai rivers [37]. On the other hand, in terms of the water body type (Table 1), the lowest MP level in India was found in lakes (-27 particles/m\({}^{3}\)), while in Thailand, the average level was quite  
Figure 1: Sampling sites for detection of MPs—China. similar in rivers and coasts (about 692 and 605 particles/m\({}^{3}\)). Taiwan, on the other hand had the lowest number of available publications regarding the topic (n = 3). The analysis carried out showed that the mean MP content in surface water was about \(\sim\)16 particles/m\({}^{3}\).