How Cigarette Waste Is Changing Aquatic Ecosystems

Around 90 % (4.5 trillion) of cigarettes consumed globally are improperly discarded, making cigarette butts one of the most common waste types. They contain harmful chemicals such as metals, nicotine, and polycyclic aromatic hydrocarbons, which leach into water and threaten aquatic life. Nicotine dissolves readily in water, with approximately half leaching out from cigarette butts within 30 minutes of rain.

Martínez-Ruiz and colleagues, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany, have measured nicotine levels in local waters, including lakes, ponds, canals, and streams. Post-rainfall, nicotine concentrations surged, particularly in sewer-connected canals, with average levels increasing 16-fold. While median nicotine concentrations across all waterbodies were 28 ng/L, post-rainfall levels averaged 148 ng/L, peaking at 1,470 ng/L in the Teltow Canal. Such levels, though often below the predicted no-effect concentration (PNEC) of 400 ng/L for short-term exposure, can harm aquatic organisms by affecting survival, growth, and reproduction.

The researchers also found that compounds leached from cigarette butts, such as nicotine and various metals, have an unexpected effect on cyanobacteria (Planktothrix agardhii) by suppressing infections from parasitic chytrid fungi (Rhizophydium megarrhizum). Chytrid fungi are known to regulate cyanobacteria populations by infecting and killing their cells. Normally, these fungi help control the growth of cyanobacteria, which can form harmful algal blooms in aquatic ecosystems. As a result, the suppression of chytrid infections allowed the cyanobacteria to thrive and grow more rapidly. Toxic cyanobacteria can harm water quality, impacting drinking water production and recreational use.

Conventional ecotoxicity tests typically examine the effects of individual pollutants on single species. However, the researchers recommend accounting for pollutant mixtures and their impact on multi-species systems, as this approach better reflects real-world conditions and provides deeper insights into the effects of pollutants on aquatic ecosystems.