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Ecotoxicity assessment of aqueous leachates from tobacco products

Gkioka Anastasia

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Summary

Smoking and conventional cigarettes are widespread throughout the world. The high mortality rates, but also the serious environmental impact of this widespread use, raise the need to explore new tobacco alternatives or substitutes. This category includes "heat not burn" products, which are based on heating the tobacco to a lower temperature than that of a conventional cigarette. The main objective of this new technology is to reduce the harmful toxic compounds produced during combustion. However, the impact of these products and the waste produced on the microbial community in ecosystems has not yet been sufficiently addressed by the scientific community. In the context, the main objective of this thesis was to evaluate the ecotoxicity of leachates from used and unused heated tobacco sticks, as well as from the parts of which they are composed (tobacco, filter). Regarding the used tobacco products, a cigarette-smoking machine was used, which was adjusted according to a specific protocol. As a first step, ecotoxicity testing was carried out using biomarkers, namely the bacterium Vibrio fischeri and the fungus Penicillium purpurogenum. The results concerning the bacterium showed that the leachates are not acute toxic towards V. fischeri. The LD50 was recorded only at the lowest dilution of leachates (50%) concerning total used TS, used and unused filters. At the same dilution, however, the smoked filters led to the greatest reduction of V. fischeri population. The presence of total unused TS had no effect on the growth of the bacterium, since the population reduction in almost all dilutions of this sample reached zero levels. The behavior of P. purpurogenum in the presence of leachates of tobacco products was studied over a period of two weeks, and the results showed that in the first week the fungus grew, but its concentration was 2 Logs lower than that of the control sample. The unused tobacco resulted in the greatest reduction of the fungus, while the lowest one occurred when the unused filter was tested. Aftert 14 days, there was a significant increase in the population of the fungus with its concentration being very close to that of the control. However, the used tobacco limited its growth, in contrast to the unused filter which favored it greatly.In the second part of this study, ecotoxicity testing was carried out on two types of soil from different areas in Chania. In particular, the effect of leachates on the bacterial and fungal community of the soils was examined over a period of 60 days. The methods used were those of fungal and bacterial culture and real time PCR to quantify the bacterial population through the detection of the 16S rRNA gene. The results of the first method showed that the unused tobacco in soil A and the used tobacco in soil B had no significant effect on the bacterial population. However, a decrease was observed in the first soil and in the presence of total used TS, while a similar decrease was observed due to the unused tobacco in the second soil. Fungi showed less sensitivity to the leachates compared to the bacteria. In soil A, there was no toxic effect, while in soil B, the used and unused filters caused a slight reduction of their population. The results of the molecular method for soil A showed a decrease in the bacterial population in the presence of the leachates, with the exception of unused tobacco and total used TS, which led to an increase. Regarding the bacteria in soil B, real time PCR showed the leachates to be non-toxic. Furthermore, most of the leachates favored the growth of microorganisms.Concluding, the bacteria seem to be more susceptible than the fungi, regarding their response to the leachates of the tobacco products tested. However, further research is required on the toxicity of these products to organisms of aquatic and terrestrial ecosystems, as the question of their environmental impact remains unanswered.

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