Comparative Toxicity of Leachates from Menthol and Charcoal Cigarette Filter Microplastics on Caenorhabditis elegans

Abstract

Cigarette filters represent the most abundant form of litter worldwide. Composed primarily of cellulose acetate, these filters degrade into microfibers and microplastics (MPs) under environmental weathering, persisting for over a decade and posing considerable ecological risks. Beyond physical contamination, various chemical additives may leach from these MPs and cause environmental toxicity. This study evaluated the acute toxicity of MPs milled from both non-smoked cigarette filters (NCF) and smoked cigarette filters (SCF) using Caenorhabditis elegans (C. elegans) as a model organism. Charcoal-based and menthol-flavored cigarette filters were compared to assess their differential toxic effects, with leachate characterization performed using non-targeted liquid chromatography–mass spectrometry (LC-MS). Fourier-transform infrared spectroscopy confirmed that milled MPs were composed of cellulose acetate, while scanning electron microscopy revealed microfiber-like structures mimicking environmental degradation forms. Non-targeted LC-MS analysis tentatively identified several concerning compounds in leachates from both NCF and SCF MPs, including nicotine, nornicotine, lenacil, myosmine, and 3-hydroxypyridine. Pyrolysis–gas chromatography–MS detected levomenthol exclusively in menthol-flavored NCF and SCF MPs, consistent with its use as a cigarette flavoring agent. The semi-volatile and hydrophobic properties of levomenthol facilitate its partitioning into water, contributing to aquatic toxicity. Toxicity assays revealed that 48-hour exposure to 10 g/L of menthol-flavored NCF and SCF MPs increased C. elegans mortality rates to 20.75% and 24.53%, respectively, compared to 19.68% and 15.70% for charcoal-based NCF and SCF MPs at the same concentration. These findings demonstrate that both NCF and SCF MPs cause acute toxicity, with menthol-flavored filters exhibiting greater toxic effects than charcoal-based alternatives. This study highlights the significant environmental risk posed by cigarette filter MPs and underscores the need for improved waste management strategies and the development of biodegradable filter alternatives.