An interdisciplinary approach to understanding cigarette butt littering: spatial distribution, ecological impacts, and human perceptions

Cigarette butts (CBs) are among the most ubiquitous forms of anthropogenic litter worldwide. With over six trillion cigarettes produced annually, an estimated 4.5 trillion are improperly discarded each year, many ultimately entering natural environments. Aquatic ecosystems are particularly vulnerable, as wind, rainfall, and stormwater runoff transport CBs from streets and public spaces into rivers, lakes, and coastal waters. Once in these habitats, CBs release both microplastics and a complex mixture of toxic chemicals, posing a multifaceted pollution threat.Tackling such a complex and socially embedded pollutant demands an interdisciplinary approach that captures its spatial prevalence, ecological consequences, and human behavioural drivers. This thesis combines geospatial analysis (GIS), ecological impact assessment, and social science to provide an integrated understanding of CB littering in the UK. The work addresses eight research questions grouped into four main studies.This paragraph has been redacted due to confidential nature of the dataset.Second, a freshwater mesocosm experiment tested the impacts of smoked CB leachate on the great pond snail (Lymnaea stagnalis). Exposure to increasing concentrations (0.25, 0.5, 1 CB L⁻¹) over four weeks resulted in elevated mortality, reduced feeding, inhibited growth, and substantial declines in reproductive output and egg viability. A subsequent recovery phase showed partial to full reversal of these effects once exposure ceased, indicating that CB pollution can cause substantial but potentially reversible impacts on freshwater invertebrates if inputs are reduced or eliminated.Third, marine mesocosm experiments examined the effects of CB-derived leachate and microplastic filter fragments on the common periwinkle (Littorina littorea). Both stressors induced negative responses at higher concentrations, including reduced feeding rates and increased mortality. Chemical leachate exerted stronger and more consistent effects than microplastic fragments, additionally impairing body condition at sub-lethal concentrations. These findings demonstrate that CBs function as both chemical and physical stressors in marine systems, capable of rapidly degrading organism performance.Finally, focus groups investigated public perceptions of CB litter compared to other common litter types. Participants frequently underestimated CB prevalence and rarely recognised them as plastic items, despite strong awareness of plastic pollution more broadly. Cigarette waste was predominantly framed through health-related narratives rather than ecological ones, with limited spontaneous recognition of microplastic release or chemical toxicity. While cigarette butts were often ranked as highly harmful when participants were prompted to compare litter types directly, they were not consistently perceived as the most common form of litter, particularly when contrasted with larger and more visible plastic items such as bags and bottles. These findings reveal a disconnect between the documented environmental impacts of CBs and public understanding, shaped by visibility, material misrecognition, and entrenched health-focused messaging.By linking spatial distribution patterns, ecological impacts, and social perception data, this thesis demonstrates that cigarette butt litter is both environmentally harmful and systematically under-recognised as a pollution threat. The findings indicate that effective mitigation must extend beyond reactive clean-ups and infrastructure provision, instead targeting the socio-spatial contexts, misperceptions, and social norms that sustain CB littering. This work highlights the value of integrating ecological, geospatial, and social sciences in addressing persistent anthropogenic pollution.