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Objectives Microplastics are released into the aquatic environment through multiple pathways including runoff, atmospheric sedimentation, aquaculture, and fishing and pose a hazard to organisms. Public concerns regarding microplastics are raising as microplastic pollution increases. A lot of studies have been evaluated the behavior of microplastics in the environment, suggesting that microplastics remain a prolonged period in the environment due to their persistence and can interact with other contaminants. Microplastics as carriers of coexisting contaminants may pose a more severe toxicity to organisms than microplastics alone. In this study, we investigated the behavior of microplastics as carriers of environmental contaminants and introduced a potential ecotoxicity of microplastics carrying other contaminants. Methods The behavior of microplastics as carriers of contaminants were classified as adsorption mechanisms. Research literature regarding ecological risk of microplastics carrying contaminants was reviewed in papers published between October 2003 and August 2023. Results and Discussion Adsorption of contaminants onto microplastics are mainly involved in hydrophobic interaction, electrostatic interaction, hydrogen bond, and Van der Waals forces. The co-exposure of microplastics with contaminants to organisms can induce oxidative stress and bioaccumulation and reduce the survival and reproduction rates, chlorophyll content, and photosynthetic efficiency. On the other hand, a few studies reported that the co-exposure of microplastics with contaminants can decrease the toxicity to organisms. Conclusion This paper provides basic information regarding the adsorption interactions of microplastics with diverse contaminants and their ecological effects on organisms. The contents will help to understand a potential function of microplastics as a carrier of coexisting contaminants in aquatic environment and their biological risk.

Objectives Microplastics, known as pieces of polymer debris less than 5 mm, result from plastic particles originally manufactured to small size or fragmentation from larger plastic items. Due to the persistence, microplastics can remain and accumulate in land and ocean for a prolonged period. Microplastics enter ecosystems and cause various problems. Trophic transfer of microplastics can be occurred in food chain, accordingly humans also can ingest microplastics. The accumulation of microplastics raises concerns regarding impacts on human health and terrestrial and aquatic ecosystems. Here, we discuss the source and route of microplastics found in environments, and ecological effects of microplastics on organisms. Methods We explore how microplastics enter terrestrial, atmospheric, and aquatic environments and influence individual animals, plants, and microorganisms living in diverse ecosystems. Research literature is reviewed microplastics in terms of ecological risk published between 2010s and June 2022. Results and Discussion Diverse human activities (e.g., industrial and agricultural activity) accelerate the production of microplastics and result in a release of microplastics to surrounding ecosystems. The microplastics can circulate among the terrestrial, atmospheric, and aquatic environments. The exposure of microplastics can induce oxidative stress, damage of intestinal cells, and reduce the body size in animals. In plants, length of root, biomass, and chlorophyll content are decreased upon exposure to microplastics. In addition, microplastics inhibit the growth of microalgae by reducing algal chlorophyll contents and cause oxidative stress. Conclusion This paper includes basic information regarding the occurrence and accumulation of microplastics and their ecological effects on organisms. The contents will help to understand behavior of microplastics in diverse environments and to further evaluate ecological impacts of microplastics.