Environment and pollution

Study reveals: cigarette filters persist in nature for decades

The research, published Environmental Pollution, was carried out by the Federico II University of Naples

by Davide Madeddu

13 March 2026

3' min read

Translated by AI

Versione italiana

Key points

The study
The Life of Cigarette butts
Ecotoxicity

3' min read

Translated by AI

Versione italiana

Not only smoke. With time also comes microplastics. Because the life of cigarettes, once extinguished, continues in the filter, which does not disappear even after ten years. With effects on the environment, on the soil or in the water. Reconstructing the picture, drawingthe life of the cigarette butt over a period of 120 months is the research carried out with the contribution of various laboratories of the Federico II University (coordinated by Professor Giuliano Bonanomi, Department of Agriculture) and the CNR in which the

chemical, microbiological and toxicological transformations of filters in the soil. With the result that cellulose acetate filters do not biodegrade, but instead progressively fragment into persistent microplastics.

"In a context where sustainability implies products designed to be reused, recycled or truly biodegradable, the cigarette filter is at the opposite end of the spectrum," says Luigi di Costanzo, university lecturer in the Department of Agricultural Sciences at the Federico II University of Naples, "a disposable object with an environmental permanence that can extend over many years.

The Studio

The study, also published in Environmental Pollution, followed the decomposition of filters under controlled conditions and in the field, simulating urban environments, sandy soils, and soils rich in organic matter. 'Contrary to what we think,' the lecturer argues, 'the data show that the butts do not disappear in a few months: in an urban environment, after ten years, up to half of the filter can still be in the soil.

Everything is related to the composition in cellulose acetate, a plastic derived from natural cellulose but chemically modified to increase its strength and stability. 'After ten years, the loss of mass varies significantly depending on the environment,' he adds. In the absence of soil, a condition that mimics urban surfaces or environments poor in biological activity, the loss stops at around 52%. It means that about half of the initial material is still present after a decade'.

The life of a cigarette butt

The figure is different when it comes to sandy soils, as degradation increases to between 66 and 76 per cent. 'In grassland soils, which are richer in organic matter, the mass loss can be as high as 84 per cent,' the professor adds. Even in this case, however, complete mineralisation into carbon dioxide and mineral compounds is not observed: a residual portion remains in the system. The degradation is therefore slow and highly dependent on the presence of nutrients and active microorganisms in the soil'.

In more fertile soils, the material is progressively colonised by microorganisms and shows more signs of biological reworking than in urban or sandy environments. "Transformation, however, does not equate to complete biodegradation".

L’ecotossicità

In addition to physical degradation, the study evaluated the ecotoxicity of the leachate from the butts. Result: "Fresh butts show high toxicity. Leachate concentrations of less than 7 per cent are sufficient to produce a 50 per cent effect on a sensitive marine bacterium, Aliivibrio fischeri, an organism commonly used in environmental toxicity tests,' the expert adds. 'As time passes, toxicity decreases, in parallel with the loss of the more easily soluble substances. In the first few years, a significant decrease in biological effects is observed. However, the dynamic is not linear. Around five years there is an intermediate increase in the biological response in some tests, followed by a new attenuation'.

And although toxicity is reduced after ten years, it is still not completely absent. "This," concludes Luigi di Costanzo, "means that the residues cannot be considered biologically inert even in the long term". With the result that "the cigarette filter represents a single-use object with an environmental permanence that is measured in years, sometimes decades. It does not disappear quickly: it transforms and remains in the system'.