## 5 Toxicity of MPs
### Human Exposure and Health Impacts of MPs  
The human organism is exposed to MPs through food, water, pharmaceuticals, cosmetic products and airborne dust. The main routes of MP entry into the human body are ingestion into the digestive system, inhalation into the respiratory system and dermal absorption [73] (Figure 5). The estimation of human exposure to MPs varies between 74,000 and 121,000 particles per year, considering consumption and inhalation [74]. The intake of MPs into human organisms is inevitable [75] because MP contamination has become evident in many categories of food products (Figure 6), including those that are consumed frequently and in large quantities [11], namely drinking water [61] and table salt [49; 76; 77]. MP presence has also been reported in fresh and processed seafood [49; 76], honey [78], beer [79], sugar [80], milk [81], eggs [82], tea [76], soft drinks [83], infant formula [84], foods of plant origin (seaweed, rice [25] and various fruits and vegetables from shopping centers, such as carrots, lettuce, broccoli, potatoes, apples and pears [85]), foodstuffs packed in canes [86] and plastic packaging [76], etc. It is estimated that people who order take-out food 4-7 times weekly may intake 12-203 pieces of MPs through containers made of polymer materials [87]. MP content may increase or decrease during food processing or cooking raw food [76], which depends on many factors such as ingredient characteristics, MP types and the process itself (e.g., no significant change in MP content in eggs was observed after cooking [82]). There is a high probability that humans are most exposed to MPs due to the consumption of seafood (shellfish, crabs, fish and seaweed) and products from the sea (table salt). [PERSON] et al. (2018) [49] estimate that MP intake through the consumption of shellfish in Europe is up to 11,000 particles per year per person. Considering that MP particles are less often found in the tissue of marine organisms compared to the digestive tract, it is recommended to thoroughly clean or remove the digestive organs before consumption. In addition, it has been confirmed that washing the digestive system of bivalves significantly reduces the proportion of MPs [76]. The presence of MPs was reported in 128 brands of commercially available table salt from 38 different sources from five continents [77]. The highest concentration of MPs was found in fine sea salt from Croatia (800-19,800 particles per kilogram) [76; 77]. Based on MP concentrations in commercially available salt brands and the recommended daily intake of salt (5 g), [PERSON] et al. (2019) [77] calculated the annual intake of MPs through salt consumption, which is 1460-36,135 particles per year for consumers in Croatia. The presence of MPs in drinking water was first reported in 2017 within a global survey of tap water from six regions on five continents by [PERSON] et al. (2017) [88]. Eighty-three percent of the 159 samples analyzed were found to contain plastic particles. Surface and underground sources of drinking water are polluted by MPs due to inadequate disposal of plastic waste in the environment. It is estimated that individuals who meet the recommended water intake through only bottled sources may be ingesting 90,000 MP annually compared to 4000 MP for those who consume only tap water [74]. The main  
Figure 5: The main routes of microplastic entry into the human body (adapted from [73]). Figure 6: Foods and beverages reported to be contaminated with MPs. source of MPs in bottled drinking water is the packaging and the filling process, which was proven by a comparative analysis of water from the same source packed in plastic and glass bottles [61]. MPs released from plastic bottles or bottle caps into content were also reported for vinegar [89] and white wine [90]. MPs have been detected in human feces, removed intestinal fragments, saliva, bronchial mucus, skin, hair, lymph nodes, livers, spleens, placentas and blood [54, 61, 75, 91]. [PERSON] et al.