Smokers’ behaviour and the toxicity of cigarette filters to aquatic life: a multidisciplinary study

Abstract Cigarettes are the most littered item in public spaces. Smokers who litter are leaving a trace of toxic waste that adds to the global plastic pollution due to harmful chemicals and semisynthetic microfibres that compose cigarette filters. Here we present a multidisciplinary study aiming to assess i) predictors of cigarette littering, and ii) the toxicity of semisynthetic filters to the freshwater invertebrate Chironomus riparius , including iii) the potential driver of toxicity. Unobtrusive observations of 597 smokers at public places were analysed using logistic regression, which showed that age (negatively) and group setting (positively) are personal predictors, and the number of present ashtrays (negatively) is a contextual predictor of cigarette littering. In addition, we assessed acute and chronic aquatic toxicity of cigarette filters in standardized ecotoxicity tests on several lethal and sublethal effects, using both smoked and unsmoked filters. Following 48-h exposure, concentrations of 2 filters/L from smoked and unsmoked filters caused 36–100% and 75–100% larvae immobility, respectively. We further demonstrated that cigarette filter fibres seem to add to the toxicity of filter leachates. Seven-day exposures that used either contaminated water or sediment (3 weeks leaching time, eq. 1 filter/L water and 1 filter/166.5 ml sediment) showed exposures via sediment caused more frequent and severe effects on the larvae than exposures via water. Larvae exposed to contaminated sediment (smoked and unsmoked filters) exhibited > 20% higher mortality, > 1.5-fold decrease in growth, and > 80% decreased development, compared to larvae in control conditions. Moreover, we found that cigarette filters have the potential to be teratogenic to freshwater invertebrates. Our results could be used to support litter prevention efforts, advisably via integrated educational campaigns. The campaigns could account for the societal and environmental complexity of cigarette littering by being tailored to the determined littering predictors and using ecotoxicity results as content.