Cigarettes contain more than 4 000 toxic substances, while cigarette butts comprise the exact same amounts. The latter often end in water and oceans, causing major environmental issues. In fact, one cigarette butt pollutes up to 500 liters of freshwater. Cigarette remnants, more specifically their filters are composed of a plastic material, the cellulose acetate. Our goal is to use the latter as a substrate by degrading it using E. Coli bacteria.
The aim of these experiments is to evaluate the viability of E.Coli bacteria when exposed to cigarette butts and their toxic components.
Two different testings were conducted, both either under aerobic or anaerobic conditions, i.e. with or without oxygen.
The aim of our first test conducted was to examine the cellulose acetate fibers’ toxicity on E. Coli bacteria. Different amounts of cigarette filters were washed in equal volumes of freshwater, in order to obtain three concentrations, which are 60, 35 and 10 cigarette butts per litre. For comparison purposes, a clean non-smoked filter and a smoked filter that has not been washed were added to the experiment. All cellulose acetate fiber samples were separately introduced to E.Coli bacteria cultures. These cultures were then incubated at an optimal temperature for 1 or 2 days and their growth was regularly measured.
The aim of our second test was to examine the toxicity on bacteria of the washing water, after the filters disgorging step. A specific amount of filters was washed, corresponding to 120 cigarette butts per litre, for one day. The polluted water was then recovered and a range of dilutions was performed. All dilution samples were separately introduced to E.Coli bacteria cultures. These cultures were then incubated at an optimal temperature for 1 or 2 days and their growth was regularly measured.
Both tests led to the conclusion that almost all concentrations containing cigarette butt filters could be introduced to the bacteria without killing them. The exposed bacteria are also able to grow despite the toxicity released by the cigarette butt filters. The results are positive for our project, considering that the toxicity resistance of our bacteria was decisive for the development of our project.
As forecast, the lethal dose of cigarette remnant polluants at which no bacteria remains viable should be defined.