Long-term cigarette butts’ decomposition over 10 years reveals multi-stage microbial, chemical, and toxicological transformations

: Cigarette butts (CBs) are the most common global waste, posing a long-term environmental hazard due to their slow decomposition and release of toxic substances. This study provides the first comprehensive investigation into the decade-long decomposition of CBs, analyzing mass loss, chemical transformations, microbial dynamics, and ecotoxicity under various environmental conditions. Decomposition follows a multi-stage process: an initial rapid mass loss is succeeded by a prolonged, slow phase due to the recalcitrance of the cellulose acetate filter. However, in nitrogen-rich conditions, CBs achieved significant mass loss, reaching up to 84% over ten years, which was linked to extensive cellulose acetate degradation. Notably, ecotoxicity assessments revealed an initial peak immediately after smoking and a second peak during the mid-decomposition stage, highlighting the persistent ecological risks associated with aged CBs. This research offers crucial insight into the environmental fate and impact of this pervasive pollutant, underscoring the necessity of developing effective mitigation strategies.