# Microbial Life on the Surface of Microlgistics in Natural Waters
## 8 Risk of Microplastic for Animals and Humans  
Role of microplastic in marine life and its impact on marine inhabitants has been intensively studied during recent years, however a restricted amount of research is done to investigate microplastic impact on human health. It was estimated that humans consume several milligrams of microplastic daily, which consist of up to millions of MP particles a year [138]. Drinking water which comes from freshwater natural resources containing microplastic particles is a source of this contaminant in the human diet, because treatment of water with coagulation-floculation processes removes only up to 88% of MPs [139]. Tap water in China contains microplastic particles, mostly polyethylene and polypropylene, from 440 \(\pm\) 275 particles/L [140]. Analysis for microplastic of water taken from different natural water sources showed that its content ranged from 1473 to 3605 particles in 1 L, and MPs content in the treated drinking water varied from 338 to 628 particles in 1 L [139]. PET (polyethyleneerephthalate), PP (polypropylene) and PE (polyethylene) consisted of 70% of the total microplastics amount. Generally, microplastics and nanoplastics can enter the human body by indigestion, inhalation and through contact with skin [25]. It was evaluated that one person consumes between 39,000 and 52,000 particles of microplastic with food annually [141], and the consumption of sea food containing microplastic contributes in these numbers.  
Microplastic is consumed by various marine organisms from zooplankton to higher trophic levels (fish and marine mammals) and from contaminated prey to predators [142; 143]. Trophic transfer, bioaccumulation and biom magnification of microplastic in seafood create a real way for intake of MRs by humans. Plastic debris has been found in fishes, shellfish, mussels and cockles designated for human consumption [144; 145; 146; 147].  
A lot of microplastic is found in sea salt. The authors [149] proposed to consider sea salt to be an indicator of microplastic pollution of the environment and showed the presence of microplastic particles ranging from 0 to 1674 n/kg in 28 sea salt brands from 16 countries/regions on six continents. The microplastic content, mainly polyethylene,erephthalate, polyethylene, and cellophane, in sea salts was from 550 to 681 particles/kg and from 43 to 364 particles in lake salts from supermarkets throughout China [64].  
Effects of microplastic consumption on human health are still not well known and need to be investigated. At the present time there is no scientifically proven data that microplastics impact human health. However, the removal of microplastic from organisms is difficult and MPs particles can be accumulated [149]. It is considered that microplastic being consumed by humans can cause inflammation of the gastrointestinal system and in cases when MPs particles serve as carrier for environmental chemicals it can cause toxic effects and organ damage. The presence of microplastics in a human's body will increase the risk of cancer [82]. However, only microplastics particles with a size of less than 20 \(\upmu\)m are capable of penetrating organs and particles with size less than 10 \(\upmu\)m could access all organs and cross cell membranes [150; 151].