A holistic assessment of microplastic ubiquitousness: Pathway for source identification in the environment

Microplastic (MP) pollution is increasing and several extensive global studies have demonstrated its ubiquity. Information on the summary of the sources of microplastics in all areas of the environment at the global level is insufficient, thus, the need for this study. Through this study, we aim to find answers to the questions: (1) What are the sources, distribution, and nature of microplastics in the environment from a global perspective? (2) What are the knowledge gaps for future microplastic studies? To achieve these objectives, the PRISMA guidelines for reviews were employed to gather similar but relevant peer-reviewed articles, book chapters, and scientific reports on this topic. The main search engines used were: Google Scholar, ScienceDirect, Web of Science, and PubMed. The study focused on environmental compartments such as the marine environment, soil, and the atmosphere. Two other relevant components including food and drinking water were also considered. Microplastics are found everywhere ranging from remote areas such as deserts and the Arctic Sea to indoor environments. Fragmentation of plastic debris, synthetic textiles, road markings, personal care products, tire wear, indoor furnishes, illegal dumps, and vessels lost at sea remain the ultimate sources of microplastics in the environment. It revealed that studies on this potential deleterious contaminant are concentrated in some regions (e.g., Asia, Europe) with just a few studies in other areas (e.g., Africa, South America). Microplastics will continue to increase as plastic debris enters the environment each day and with the aid of photodegradation, mechanical, thermal, animal predation, microbial degradation, and biochemical mechanisms. Polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polystyrene, and polyester are the major types of polymers reported by studies. Polyethylene, for example, was found in almost all studies on personal care products, which are widely used. We conclude that, although studies on the confirmation of the effects of microplastics on human health are still in the early stages, measures to contain microplastics contamination should be strengthened and adopted globally.