Cigarette Butt Pollution in Aquatic Ecosystems: Sources, Environmental Fate, Ecotoxicological Impacts and Mitigation...

Cigarette butts (CBs) are one of the most abundant forms of anthropogenic litter worldwide and represent an important source of chemical and microplastic pollution in aquatic ecosystems. An estimated 4.5 trillion CBs are discarded annually, with a substantial proportion entering freshwater, estuarine and marine environments. Cigarette litter contains a complex mixture of hazardous substances, including nicotine, cotinine, polycyclic aromatic hydrocarbons (PAHs), heavy metals, aromatic amines, BTEX compounds, tobacco-specific nitrosamines and cellulose acetate microfibres. Evidence from laboratory and field studies demonstrates that cigarette-butt-derived contaminants adversely affect a wide range of aquatic organisms, including phytoplankton, zooplankton, molluscs, crustaceans, polychaetes, fish and microbial communities. Reported effects include mortality, oxidative stress, neurotoxicity, developmental abnormalities, reproductive impairment, behavioural alterations, histopathological damage and disruption of ecological processes. This review synthesises current knowledge on the occurrence, environmental fate, chemical composition, persistence and ecological impacts of CB pollution in aquatic ecosystems. Several studies have demonstrated the bioaccumulation of nicotine, metals, PAHs and other tobacco-related compounds in aquatic organisms, raising concerns regarding their potential transfer through aquatic food webs. The review also examines the environmental persistence of cellulose acetate filters and their potential role as sources of both chemical pollutants and microplastic fibres. Emerging mitigation approaches, including waste valorisation, bioremediation, behavioural interventions, improved waste management, extended producer responsibility and other policy-based source-reduction strategies, are critically evaluated. The review identifies major knowledge gaps, particularly the limited availability of environmentally realistic, chronic, multi-generational and ecosystem-scale studies, and highlights the need for integrated source-reduction and long-term ecological risk assessment strategies.