# Microplastic Pollution on the Beaches of the Black Sea in Romania and Bulgaria
## 4 Discussion
In sand from the Anatolian area of Istanbul, a maximum abundance of 135 microplastic particles/kg was recorded during the summer season for particles ranging between 1 and 5 mm, indicating lower pollution compared to other urban regions [44]. Microplastics were identified in beach sand samples from Romania and Bulgaria. The presence of microplastics in beach sand can be attributed to the geographical characteristics of a region. Consequently, plastic waste and microplastics may be transported by rivers, such as the Danube, from inland areas and accumulate on nearby beaches in Romania. These findings are similar to those of [PERSON] et al. [45] and [PERSON] et al. [46]. In Table 1, the chemical structures and sources of the most common plastic polymer types found in the sand samples are presented. \begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Abbrev.** & **Synthetic Polymers** & **Chemical Formula** & **Chemical Structures** & **Source/Origin [47]** \\ \hline PET & Polyethylene & (C\({}_{10}\)H\({}_{8}\)O\({}_{4}\))\({}_{n}\) & & Drink bottles, car tires, facial cleansing products, cosmetic products, industrial sources, mariculture activities, tertiary industry, domestic sources, agriculture. \\ PA6 & Polyamide (Nylon PA6) & (C\({}_{6}\)H\({}_{11}\)NO)\({}_{n}\) & & Drink bottles, car tires, facial cleansing products, cosmetic products, industrial sources, mariculture activities, tertiary industry, domestic sources, agriculture. \\ PP & Polypropylene & (C\({}_{3}\)H\({}_{6}\))\({}_{n}\) & & \\ PE & Polyethylene & (C\({}_{2}\)H\({}_{4}\))\({}_{n}\) & & \\ PE & Polyurethane & (C\({}_{2}\)H\({}_{4}\))\({}_{n}\) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical structures and sources of the most common plastic polymer types found in sand. Microplastics have emerged as a significant environmental and health concern due to their widespread presence in ecosystems and potential toxic effects on living organisms [48]. Concerning their general toxicity, exposure to microplastics has been linked to various adverse health effects, including neurological disorders such as cognitive dysfunction and neuroinflammation, respiratory complications, and allergic reactions [49]. These particles may cause impaired reproduction [50], malnutrition [50], and physical irritation to the gastrointestinal tract [51], leading to changes in the intestinal microbiome [51]. Furthermore, microplastics can deposit in the lungs, where they may interfere with respiratory function and affect cell viability [51]. As vectors for various contaminants, especially heavy metals, microplastics contribute to the exacerbation of reproduction issues, impaired growth, and weakened immune systems [51]. Their chronic presence has been linked to vascular disease, chronic inflammation, and immune system-related disorders [49], further highlighting their damaging impact on human and animal health. Moreover, evidence suggests that microplastics can inflict harmful effects on the brain and nervous system [49], underscoring their broad and dangerous influence over various biological systems. Table 2 presents data regarding the ecological and environmental impacts of synthetic polymers on beaches, shallow coastal waters, and sand. The biodegradability of microplastics is influenced by various factors, with degradation rates in marine environments varying significantly depending on the type of polymer. For instance, common plastic polymers such as LDPE, HDPE, PP, and PET have been estimated to degrade at rates ranging from 0 to 37 \(\upmu\)m per year [55]. Notably, [PERSON] et al. [54] have reported substantially higher surface degradation rates for polycaprolactone