**3. Impact of increasing microplastic burden on seawater utilization and the water use cycle**

An increasing microplastic burden not only has implications for the costs and efficiency of the sea water utilization process, but also for the marine ecosystem and, as a consequence, also for humankind (**Figure 4**).

Bonded in microplastics, pollutants like, for example, dichlorodiphenyltrichloroethane (DDT), dioxins, or heavy metals can be transported and accumulated in organisms via ingested food [28]. Due to the manufacturing process, most polymer blends also contain harmful substances like softening agents or monomers, which in return can be released upon ingestion of the particles via food and exert a direct influence on the organism, since these substances are mostly classified as potentially harmful and/or carcinogenic [29]. It has already been shown in laboratory experiments that microplastics smaller than 150 μm can, after ingestion via food, enter the surrounding tissues, the bloodstream and, through these, the internal organs and also the brain [30]. There is then the risk of the formation of lesions and inflammations. Furthermore, oxidative stress, necrosis, and damage to DNA can be triggered, which again increases the risk of cancer. Neurological behavioral disorders are also possible [31]. Thus, there is a potential risk to human health from microplastics.

**Figure 4.**  *Microplastics in the marine water cycle [27].* 

#### *Plastics in the Environment*

In addition to the decrease in improper disposal, the search for replacement substances and the prohibition of microplastics as a product addition for everyday products, ensuring that the aquiferous processes are free of microplastics also represents a chance to reduce the degree of contamination due to microplastics in the water cycle. Besides the implementation of new technologies for the purification of wastewater in sewage treatment plants, this also includes the conceptual and technical development of new add-on technologies in seawater utilization processes in order to filter microplastics out of the inflowing seawater and eliminate it prior to the seawater utilization processes.
