The role of different remaining parts of cigarette butts in the transfer of phenolic compounds into the aquatic environment and their ecological risk.

Cigarette butts (CBs), the most prevalent waste material globally, have the potential to leach various toxic substances, including phenolic compounds (PhCs), into the environment and aquatic ecosystems. Nevertheless, there is a lack of knowledge concerning the long-term release of PhCs via the different parts of CBs which are littered into the environment. Hence, the present study was designed to investigate the ecological risk as well as the leachate concentrations of PhCs, including phenol, o-cresol, 2,4-dimethylphenol, pentachlorophenol and 2,3,4,6-tetrachlorophenol via different parts of CBs littered into water at several exposure times. Aged CBs collected from the environment, freshly smoked CBs, filter and paper, and remaining tobacco plus ash of freshly smoked CBs were studied to determine the leachate levels of PhCs. Pentachlorophenol and 2,3,4,6-tetrachlorophenol were not detected and quantified in the leachates of all CB types at all exposure times. The combination of filter and paper from freshly smoked CBs exhibited the highest mass-based leachate levels of phenol, o-cresol, and 2,4-dimethylphenol, whereas aged CBs showed the lowest levels. The mean leachate of phenol, o-cresol, and 2,4-dimethylphenol from all four examined CB types were in the ranges of 0.43-639.56, 0.77-58.61, and 0.25-16.58 μg L^-1 per CB, respectively. The ecological risk assessment showed that PhC leachates via all CB types had high risks for algae, Daphnia magna, and fish. The present study elucidated the release behavior of several PhCs and toxic CB-associated contaminants that have been overlooked in the literature.