Most cigarettes end up in the environment after smoking and often find their way into ponds, streams and lakes. The numerous pollutants then dissolve in the water from the cigarette filter and thus endanger fish and other aquatic life. But that’s not all: Cigarette butts also promote toxic algae blooms by inhibiting the blue-green algae’s predators, as biologists have now discovered. This makes the stubs even more dangerous to aquatic life than they already are.
Around 4.5 trillion cigarette butts end up in the environment every year worldwide. There, the more than 7,000 pollutants they contain – especially nicotine – affect animals and plants. It becomes particularly critical when the stubs get wet. When it rains, half of all toxic substances are released from the filter and sleeve within just 30 minutes. A single cigarette butt can theoretically contaminate 1,000 liters of water with nicotine and thereby poison large and small aquatic creatures. Aquatic ecosystems are therefore particularly threatened by discarded cigarettes.
Nicotine harms in two waves
But the pollutants could also become dangerous to ponds, lakes and streams in a second “wave of attacks”, as researchers led by Nele Guttmann from the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) have now found out. The team examined the interactions between parasites and their hosts using chytrid fungi and certain cyanobacteria – better known as blue-green algae. By killing the cyanobacteria, the fungi keep their population in check. And that’s a good thing, because if blue-green algae multiply too much, a so-called algae bloom occurs, in which large amounts of toxins are often released into the water. As a result, many of the animals living in the water and those who drink the water die.
But as Guttmann and her colleagues discovered, the pollutants from cigarette butts disrupt the interactions between algae and fungi. The toxic substances from the cigarette filter, including metals and nicotine, damage the fungi and thus inhibit their ability to attack the blue-green algae. “This inhibition in turn indirectly promotes the growth of cyanobacteria and thus shows previously unknown ecological effects of cigarette waste on the aquatic environment,” explains senior author Erika Martinez-Ruiz from the IGB.
See ecosystems as a whole
The residents of affected bodies of water not only have to deal with the pollutants from cigarettes, but in the long term also with the poison from algae blooms, which is likely to further harm their populations. Guttmann and her colleagues are therefore calling for indirect effects of pollutants to be taken more into account in ecotoxicity tests in the future. To date, these have often only focused on the effects of individual pollutants on individual species, ignoring the fact that pollutants usually occur in mixtures and affect a complex system of different organisms.
Source: Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB); Specialist article: Ecotoxicology and Environmental Safety, doi: 10.1016/j.ecoenv.2024.117149)