A serious concern in the recycling of used CBs is that they may be contaminated with bacteria or viruses from contact with people or the environment. Consequently, this study undertook two pilot investigations to determine whether the tested species of bacteria were present and if these bacteria posed a health risk to the waste collection and processing personnel.
The first pilot investigation focused on determining whether any of several common bacteria were present on either the used or unused cigarette filters. The purpose of this investigation was to determine if it was plausible that bacteria could be present and survive on discarded CBs. The second pilot investigation provided further results where additional species of bacteria were tested. The second test was conducted on used, unused (control), and dried CBs, as well as CBs that were in contact with two naphthalene balls (mothballs).
6.2.1. Pilot Investigation 1
This investigation consisted of two samples and one control group: Control group (unused CBs); Sample 1—Used CBs, seven-day old sample; and, Sample 2—Used CBs, collected on the day sample.
The control group for the study consisted of generic cigarettes, which were bought and cut down to a length consisting of the filter plus 1.5 cm (for a total length of 3.5 cm). This was to ensure that the tobacco content of the control group closely resembled that of a smoked cigarette. A previous study has shown that some Pseudomonas
spp. can thrive on the nicotine in solid tobacco waste (Wang et al. 2004). As a result of this finding, it was essential to ensure that similar volumes of tobacco were present in all of the samples (Figure 8
The CBs used for this investigation were collected from the tops of bins around Victoria’s Melbourne Central Station. Collecting CBs from the bins increased the chances that the samples were fresh. Melbourne Central Station is a central hub for travel in Melbourne’s CBD and, therefore, it provides reasonably representative samples (i.e., people from many areas and socio-economic backgrounds travel through this area).
In this preliminary bacteriological investigation, the presence of Salmonella spp., Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Coagulase + ve Staphylococcus spp., and Streptococcus spp. were investigated.
live naturally in the intestinal tract of humans and animals and, in most cases, is harmless [51
]. However, some E. coli
are pathogenic and they can cause diarrhoea or other illnesses [51
]. Although the most vulnerable include the elderly and young children, anyone can be infected. The bacteria can be spread through contact with unclean surfaces that are contaminated with faecal matter, such as human hands or door handles [51
], and infections start when this bacteria is consumed. As a result, it is possible that E. coli
can be spread to CBs from unwashed hands that have encountered contaminated surfaces, or they may even be present within the mouth when contaminated food is consumed. Thus, the presence of E. coli
spp. commonly causes gastro, and it is spread through the ingestion of improperly cooked food, water, or through hands that have encountered animal faeces [52
]. As a result, it is plausible that Salmonella
spp. could be present on used CBs if smokers have not washed their hands after coming into contact with animals, another infected person, or a contaminated material, such as improperly cooked food. As this bacterium enters the body through the consumption of contaminated food, it is also possible that it is present within the mouth.
is primarily responsible for the infection of humans by Pseudomonas
strains of bacteria. Healthy people who are infected generally only present mild symptoms, but those with a weak immune system (such as those who are already sick) can suffer severe infections that can be fatal. Pseudomonas aeruginosa
can cause ear infections, eye infections, and skin rashes in healthy people, whilst people with a weak immune system may contract blood infections and pneumonia [53
]. It is primarily spread by hand or from contact with contaminated equipment. Pseudomonas aeruginosa
thrives in moist environments.
species are not pathogenic and they are naturally found in the intestinal tract of humans and animals. However, some strains, including Enterococcus faecalis
, are known pathogens that can cause several illnesses, including urinary tract infections and infections of open wounds. Enterococcus
species are difficult to kill, because they have developed a resistance to antibiotics, including penicillin [54
]. From the intestinal tract, Enterococcus
species could spread to surfaces, and hands, resulting in contamination, where it can be distributed through direct contact (WA n.d.). It is entirely possible that these bacteria could be spread to the surface of CBs through contaminated hands, hence it was investigated.
bacteria are found naturally on the skin and in/around the nose (Healthdirect 2018). It is estimated that around one-third of humans carry Staphylococcus
]. In most cases these bacteria cause no harm, but can become pathogenic if they enter the body. Its population growth can result in an infection. Serious issues include skin impetigo, wound infection, cellulitis, pneumonia, septic arthritis, sepsis, and endocarditis [56
]. Some strains are particularly dangerous, as they are resistant to antibiotics. It is likely that contact with the skin around the mouth or the hands of people that have touched their nose could result in the contamination of CBs by Staphylococcus
bacteria. As contaminated food enters the body, Staphylococcus
bacteria may also be present in the mouth, which may be transferred to CBs.
bacteria are found in the upper respiratory tract and skin of humans. There are two types, Group A and Group B. Group A can cause the common ‘strep throat’, in addition to other illnesses, such as scarlet fever, impetigo, and cellulitis. Group B can cause blood infections, pneumonia, and meningitis [57
]. The bacteria can be spread from person-to-person through sneezing and contact with contaminated surfaces. As a result, it was determined that these bacteria could be present on used CBs.
The results presented in Table 3
show that Coagulase + ve Staphylococcus
spp. were sufficient in number in sample 2, whilst there were insufficient numbers to be detected in sample 1. The presence of Coagulase + ve Staphylococcus
is shown in Figure 9
This bacterium was not detected in sample 1, which could be an indication that Staphylococcus
bacteria struggle to survive on CBs for an extended period. Alternatively, it could indicate that Staphylococcus
was only present on the CBs of sample 2. Despite the confirmation of the presence of these bacteria, it has been reported that Staphylococcus
requires a colony count exceeding 100,000 to infect humans [58
]. However, it is possible that these bacteria could enter via the mouth or through cuts in the hands of workers, where the colony could flourish to an infectious concentration. Consequently, it is recommended that gloves should be used when handling CBs.
A very small concentration of Enterococcus faecalis was also detected in sample 1, which reinforces the prediction that unclean hands can transfer intestinal bacteria to CBs. It is possible that the original concentration was higher, and the bacteria had slowly died over time. It is also plausible that the original concentration was just as low and the bacteria can effectively survive on the surface of the CBs for a few hours. In either case, the concentration is a negligible one, but it shows that the bacteria are capable of surviving on the surface of used CBs for an unknown period.
6.2.2. Pilot Investigation 2
This investigation consisted of one control group and four additional samples (Figure 10
): Control group (unused CBs); Sample 1—Used CBs, fresh CBs collected the day before the test; Sample 2—Used CBs, older samples; Sample 3—Used CBs, older samples that were dried at 105 degrees for 6 h; and, Sample 4—Used CBs, fresh CBs in contact with mothballs for 24 h.
Similar to the pilot investigation 1, the control group for pilot investigation 2 was prepared while using the same method and preparations. The sample size was approximately double when compared to investigation 1, as more tests were required to investigate the larger variety of bacteria. The control group was prepared a day before the test.
For sample 1, fresh CBs for this investigation were collected from the tops of bins and their tilt trays as well as ashtrays from restaurants/cafes around Melbourne’s CBD. Fresh CBs were collected in this manner in order to reduce the chance of the butts being very old and the chance that the butts encountered the ground. The samples were collected on the day before the testing. For sample 2, old CBs that were a few months old were collected from RMIT University storage. Sample 3 comprised old CBs that were a few months old and collected from RMIT storage; however, these CBs were placed in an oven at 105 degrees for 6 h. Sample 4 were fresh CBs that were collected in the same manner as sample 1, but had been treated with mothballs. The treatment consisted of placing two naphthalene (mothballs) balls inside a bag full of CBs and leaving for 24 h before removing them from the bag for testing. Samples 3 and 4 were two of the tested treatment methods for reducing the bacterium counts.
In this preliminary bacteriological investigation, the previous six bacteria were investigated: Salmonella spp., Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Coagulase + ve Staphylococcus spp., and Streptococcus spp. Furthermore, an additional four types of bacteria were investigated: Listeria spp., Legionella spp., Bacillus spp., and Clostridia spp.
spp. are present in a wide variety of environments, including the soil, in animals, and in areas with water [59
]. Most of the species of this bacteria group are not pathogens; however, there is one pathogen within this species that is harmful to humans, the ‘Listeria monocytogenes
]. This pathogen is harmful, as it can cause listeriosis. Although most healthy people who are infected generally only present mild symptoms, it can prove fatal to people with a weak immune system, the elderly, and can cause pregnant women to undergo a miscarriage [59
]. L. monocytogenes
can exist and grow in food. Through consumption, L. monocytogenes
may exist within the mouth, where it is possible that it may spread to CBs. Therefore, the presence of this species has been investigated.
spp. are naturally present in water sources of the environment. This pathogen is harmful when it grows within artificial water systems, such as pipes, which are common within households [60
spp. can cause two main illnesses—pneumonia and Pontiac fever [60
]. Most healthy people who encounter Legionella
spp. are not affected. Those vulnerable include the elderly, smokers, and people with a weak immune system. Legionella
spp. can enter the body via respiration and aspiration. It is possible that Legionella
spp. may be present in the evaporated water that people can breathe if a colony is large enough and is thriving within an artificial water system [60
]. Though less frequent, people may also get sick when drinking water contaminated with Legionella
spp., as it could accidentally enter the lung [60
]. It is possible that this pathogen is spread to CBs when exposed to a water environment and, thus, the presence of this species has been investigated.
spp. are generally present in soil environments [61
]. They are most commonly found in raw vegetables, water, organic matter, dust, and some flora species; however, there have been scenarios where Bacillus
spp. was found in other types of food groups, such as meats and rice, and in hospital environments [61
]. Most of these species are non-pathogenic. When Bacillus
spp. contaminates food, it typically survives the cooking procedure and, as a result, food poisoning is likely to occur upon consumption [62
]. This can be prevented through proper food handling. Gastrointestinal illness can develop if a high quantity of Bacillus
spp. is consumed [62
]. It is possible that Bacillus
spp. could spread to CBs when exposed to soil, contaminated hands, contaminated surfaces, or the mouth, hence the presence of this species was investigated.
spp. are mainly present in soil environments where organic matter exists [63
]. Other locations include the sediments of aquatic environments, and the intestinal tract and normal microbial flora of animals and humans [64
]. Pathogenic species that are harmful to humans include, but are not limited to, C. botulinum
—which can cause food-borne botulism, C. tetani
—which can cause tetanus, C. perfringens
—which can cause wounds, surgical infections, gas gangrene, and food poisoning, and, lastly, C. difficile
—which can cause antibiotic-associated diarrhoea, colitis, and pseudomembranous colitis [64
]. An external method for Clostridia
spp. to enter the body is from the consumption of improperly cooked and stored food, in particular, meat and improperly heated canned food [63
]. It is possible that Clostridia
spp. could spread to CBs when encountering soil, contaminated hands, contaminated surfaces, or the mouth; hence, the presence of this species was investigated.
The results presented in Table 4
show that Salmonella
, Coagulase +ve Staphylococcus
spp., and Legionella
spp. were not found in any of the samples.
The investigation of Coagulase + ve Staphylococcus spp. for sample 1 (the freshest CBs of this investigation) was not present in comparison to pilot investigation 1, where it was present in sample 2 (the fresh CBs of that investigation). This could be, because the sample was slightly fresher or that the bacteria were only present within the sample collected. In this investigation, a small count of Pseudomonas aeruginosa was found in sample 1. As this species of bacteria is primarily spread by hand, its presence may be due to unclean hands that transfer the bacteria to CBs. A small count of Enterococcus faecalis was found in the control sample, which was likely contaminated by the preparation environment, as this bacterium was not present in the control sample of pilot investigation 1.
In sample 2, Listeria
spp. was detected from the older CBs. Listeria
spp. is known to survive in waste water and sewerage sludge for a long period of time [65
]. This sample may have been contaminated by this species of bacteria, where its characteristics of surviving for a long period of time can be observed.
Lastly, for Bacillus
spp., counts of 70,000 cfu/g were found on control sample 1, 39,000 cfu/g were found on sample 2, and 440 cfu/g were found on sample 3 (Figure 11
). These higher quantities are not unusual for soil. As Bacillus
spp. have been recorded to grow on fresh and cured tobacco leaves, this could be a plausible reason for its presence [66
]. When comparing the dried CBs from sample 3 with the other samples, the count of Bacillus
spp. was significantly lower. This indicates that the majority of Bacillus
spp. that were present did not survive the drying process. It was noted that sample 4′s preparation method was easier than sample 3′s and it was almost as effective at eliminating the Bacillus
The workers dealing with cigarette butts should wear the appropriate PPE and follow OH&S procedures to mitigate the potential risk that the pathogens and chemicals in CBs pose. Some of the PPE recommended include wearing long sleeves and gloves and the use of an appropriate mask.
The results of both pilot investigations 1 and 2 should in no way be interpreted as a comprehensive study. Only six types of bacteria were investigated for pilot investigation 1 and 10 types were investigated for pilot investigation 2. In addition, only a small number of cigarettes were tested. About 75 CBs were collected for each sample for pilot investigation 1, and 150 CBs were collected for each sample for pilot investigation 2. This quantity was then divided to investigate each species of bacteria, thus limiting the scope of the findings.
This paper suggests that further investigation be conducted in this area, particularly given the positive confirmation that Enterococcus faecalis, Coagulase + ve Staphylococcus spp., Pseudomonas aeruginosa, Listeria spp., and Bacillus spp. were present in such a small population of CBs.
Attempts at determining a way of investigating the presence of viruses failed, as it is impractical to develop a method to utilise for testing and almost impossible to verify whether the produced results would be accurate, or that the virus presented a viable infectious threat.