Ecotoxicological effects of cellulose acetate nanoplastic derived from cigarette butts on earthworm (Allolobophora caliginosa): Implications for soil health

Plastic pollution from nanoplastics (NPs) poses a growing environmental threat, with cigarette butts (CBs) representing a significant yet often overlooked source of terrestrial contamination. This study investigates the ecotoxicological effects of cellulose acetate nanoplastics (CA-NPs) derived from both smoked (SCB-NPs) and unsmoked (USCB-NPs) on the earthworm Allolobophora caliginosa, using commercially available CA-NPs (CCA-NPs) for comparison. The NPs were characterized and tested for their impact on earthworm endpoints such as mortality, growth, oxidative stress biomarkers, and genotoxicity. SCB-NPs exhibited the most severe toxic effects, leading to increased mortality, growth inhibition, heightened oxidative stress parameters and significant DNA damage. USCB-NPs and CCA-NPs also induced notable adverse effects, though to a lesser extent than SCB-NPs. Markers of oxidative stress were elevated across all NPs exposures, accompanied by suppressed antioxidant enzyme activities and an increase in detoxification enzyme activity. Genotoxicity analysis using the Comet assay confirmed greater DNA damage in earthworms exposed to SCB-NPs. These findings suggest that combustion by products intensify the toxicity of CB-derived NPs, posing a serious risk to soil organisms and ecosystem health. The results emphasize the urgent need for improved cigarette waste management to mitigate the release and impact of toxic nanoparticles in terrestrial environments.