A review of occurrence and concentrations of cellulose acetate and other artificial cellulose microfibers in aquatic environmental matrices: an indicator of cigarette butts’ contamination?

• Cellulose acetate (CA) is one of frequent microfibers in the aquatic environment. • CA can be a suitable indicator of dumped cigarette butts (CBs) in environment. • Contaminants loading and hydrodynamic properties are important in CA level in waters. • Higher accumulation of released CA via CBs in sediment and benthic biota than waters. • Benthic invertebrate can serve as effective bioindicators for detecting CA presence. Despite the apparent non-toxicity of cellulose acetate (CA) particles, their insoluble hydrophobic nature and partial degradability due to acetate groups can make CA a potential public concern, especially in water sources that are heavily contaminated. However, there is a lack of comprehensive knowledge to explain the occurrence of CA microfibers (MFs) and their association with potential sources. In this sense, the present study conducted a literature review assessing the prevalence of CA MFs in different environmental compartments, including freshwater and marine water, sediment, and aquatic biota. The compiled data illustrate that CA is one of the most frequently detected MFs in the marine environment (4-42 % of total microplastics (MPs)). The presence of CA in water could be related to the loading of contaminants and the hydrodynamic characteristics of receiving waters. Besides the protective effects of sediment against degradation, the higher specific density of CA increased its frequency in the higher depths. Therefore, the potential accumulation of released CA from different sources especially cigarette butts (CBs), as over 90 % of their components are composed of these fibers, may increase through interactions with biota. Considering the higher density of CA and the close relationship between CA occurrence in aquatic organisms and patterns of habitat use by different biota, benthic invertebrate species may be utilized as a bioindicator for CA and indirectly for CBs as the main source of CA in aquatic habitats. Similarly, anthropogenic cellulose in biota was most likely associated with CBs dumping in the drained streams to water sources. However, there is a knowledge gap regarding the apportionment source of CA and its bioaccumulation in the food chain, thereby, further studies are essential to determine apportionment of the effective sources, especially CBs. Furthermore, toxicological studies are suggested to assess the hazard quotient associated with contaminated food consumption.