The Impact of Cigarette Filters on Aquatic Ecosystems Using Daphnids as Model Organisms

Cigarettes are the most littered item in the world. 4.5 trillion are discarded annually, and their filters can introduce toxic chemicals and plastics into waterbodies. Therefore, the assessment of the ecotoxicological effects of smoked and non-smoked cigarette filters is necessary. With the freshwater organism, Daphnia, this study analyses the toxicity and sublethal effects caused by these two types of filters with New Approach Methodologies, such as effect-based bioassays and enzymatic biomarkers. Toxicity was assessed by measuring mortality following exposure to increasing concentrations of filters. The study also analysed the survival and growth rate, and quantified enzyme activities.

After 48 hours, only smoked cigarette filters were toxic from 100 ml extract/L with an EC₅₀ value of 397 ml/L. In contrast, exposure of 21 days reduced survival at lower concentrations, with smoked filters decreasing median survival to 4 days at 200 ml/L, corresponding to 4 filters per litre of water. Daphnids’ growth rate was most affected after 7 days of exposure from concentrations of 5-70 ml/L. Size changes observed at 7 days, were reduced at 14 and 21 days of exposure, suggesting possible acclimation. Enzymatic activity was also altered after 21 days from concentrations of 15-45 ml/L, with significant increases in acid phosphatase and decreases in alkaline phosphatase, peptidase, and β-galactosidase.

Given the observed effects in Daphnia, cigarette filters may potentially impact other freshwater organisms. Past literature has shown that daphnids can have similar responses as vertebrae models to other psychoactive substances. Furthermore, negative effects on these primary consumers may lead to cascading effects on higher trophic levels and loss of biodiversity. Lastly, the limited availability of data on environmentally relevant concentrations of filters also underscores the importance of this study, highlighting the need to consider this emerging contaminant in environmental risk assessment frameworks.