Cigarette butts as a microfiber source with a microplastic level of concern.

Microplastic pollution is a growing environmental concern among the scientific community. These small particles (<5 mm) might come from the fragmentation or direct emission of artificial and synthetic polymers. Among them, the microfibers (MF) are one of the most common types of microplastics identified in the environment. On the other hand, the most encountered type of garbage found in clean-up campaigns is the cigarette butts, which contains the smoked filters (SF) and unsmoked rests of tobacco. SFs are hazardous debris but are usually not properly disposed as such, and are composed of >15,000 strands that can be detached as MFs. This study aims to evaluate the detachment rate, the acute aquatic toxicity, and the aquatic-, thermooxidative-, and photo-degradability of the MFs generated from SFs. In this way, it was found that SFs detach approximately 100 small MFs (<0.2 mm) per day. In a rough estimation, about 0.3 million tons of potential MFs might be annually reaching aquatic environments from this source. Concerning the eco-toxicity, a statistically significant difference was found when MFs are present in the leachate generated by the SFs, where the Daphnia magna EC100 and EC50 were of 0.620 SF/L and 0.017 SF/L, respectively. Finally, the degradability of the SFs was evaluated by applying two methods (ATR-FTIR analysis and gravimetry). In both of them, a low degradability rate was observed. Thus, it may be concluded that MFs from SFs constitute an important source of microplastics, which might partially explain the high concentration of artificial polymers that have been found in the deep-sea sediments. Yet, the correct management of the SFs is an unsolved issue that should receive urgent attention. CAPSULE: This work evaluates the detachment rate, toxicity, and degradability of the microfibers detached from the cigarette butts.