Since the mass production of plastic in 1940, contamination of marine environment by plastics particularly micro plastics has been a growing problem. Micro plastics are little plastic particles, fibers and granules which have been defined in different sizes such as diameter less than 10, 5, 2 and 1 mm. The micro plastics that are made in microscopic size and are used in cleaner and cosmetic materials, are called primary micro plastics and secondary micro plastics are derived from larger particles. Micro plastics are directly transmitted to rivers and then sea via wastewater influent or leachates from refuse sites. Micro plastics are found throughout the water column and due to their small size, micro plastics are considered bioavailable for organisms. Their composition and relatively large surface area make them prone for adhering waterborne organic pollutants such as PAHs, PCBs and DDT. Micro plastics consumption by marine organisms have been shown by environmental and laboratory studies. Although adverse health effects via micro plastics are not obvious alone, but the transition of chemical materials from Microplastics to organisms throughout the food-chain is a significant concern. In this article, micro plastics properties, micro plastics production resources, their entering effects on environment have been considered.

Background: Microplastics, as emerging and persistent pollutants, are ubiquitous in different environmental compartments and could be considered an ecological threat to wildlife and humans. Materials and Methods: In the present review article, the existing studies on the presence of Microplastics in water, sediments, and aquatic organisms of the Persian Gulf were reviewed with regard to different sampling techniques, samples preparation, and identification methods. Results: The results indicated that the contributions of various countries to Microplastics pollution of the Persian Gulf were different. The findings from the Iranian side of the Persian Gulf (especially for coastal sediments) showed higher pollution than its Arabian side. Blue and black fibers were the most predominant types of Microplastics in the Persian Gulf. Based on the results, low density Microplastics were more dominant in the water column, while high-density plastics were mostly found in sediments. The predominant types of Microplastics in marine organisms were related to their habitats. Conclusion: Microplastics contamination is a severe threat to the Persian Gulf’, s environment. However, the lack of harmonized procedure for Microplastics sampling, preparation, analysis, and report makes the comparison of different studies challenging. For instance, four studies reported the level of Microplastics in seawater of the Persian Gulf with three different units. Hence, we suggest all studies use the same methodologies in the Persian Gulf to increase the comparability of the results.