I know of studies that show the long-term toxicity of cigarette butts, specifically on snails. But I don't know of any research on remediation. If you're interested in the question of specific characteristics of toxicity that would have to be remediated, see: Booth, D. J., Gribben, P., & Parkinson, K. (2015). Impact of cigarette butt leachate on tidepool snails. Marine pollution bulletin, 95(1), 362-364. Gill, H., Rogers, K., Rehman, B., Moynihan, J., & Bergey, E. A. (2018). Cigarette butts may have low toxicity to soil-dwelling invertebrates: Evidence from a land snail. Science of The Total Environment, 628, 556-561. Kander, M. (2017). Bioaccumulation of Metals (As, Cd, Cr, Cu, Ni, Pb, Se, and Zn) from Smoked Cigarette Litter in Fish (Rainbow Trout) and Shellfish (Mediterranean Mussels) (Doctoral dissertation, San Diego State University). And a review: Araújo, Maria Christina B., and Monica F. Costa. "A critical review of the issue of cigarette butt pollution in coastal environments." Environmental research (2019).

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