Microplastic contamination and accumulation in municipal solid waste: A global review of sources, pathways, and impacts

Background: One of the most serious environmental challenges is pollution caused by microplastics. They are found in many parts of the environment, but most research has focused on aquatic environments. Municipal solid waste is the main source of microplastics on land, which has been largely ignored. The sources of microplastics in solid waste can be landfills, sludge, compost, and food waste. Landfills pose a threat to soil and groundwater pollution. Addition of sludge or compost to the soil for fertility poses a threat to the entry of microplastics into the human food chain. Therefore, it is essential to comprehend the behavior of microplastics in various types of solid waste. Methods: We conducted a literature search, screened the articles, and selected the relevant articles. The search was performed in 3 main databases: PubMed, Scopus, and Web of Science. This study evaluated the characteristics of microplastics in landfills, sewage sludge, compost, and food waste, their fate, and their entry into the human body. Finally, methods of biological removal are mentioned. Results: A total of 335 articles were retrieved from three databases; after removing duplicates, 195 articles remained. By screening and removing reviews, notes, books, and irrelevant articles, we identified 74 articles focused on microplastics in municipal solid waste. Conclusion: Municipal solid waste is a source of microplastics, which includes landfill waste, sludge, compost, and food waste. The results of this study will pave the way for future researchers to gain a deeper understanding of the behavior of this pollutant in solid waste.