1. Introduction
Cigarette butt contamination poses a significant challenge to urban waste management [
1,
2]. Today, cigarette usage is dominant in several countries, especially among youth [
3,
4]. In some countries, this number has grown to several hundred billion cigarettes a year [
5,
6]. Over the past 70 years, the popularity of filtered cigarettes has led to the creation of a new type of waste consisting of filter leftovers, wrappings, and unused tobacco [
4]. Even though they are small, cigarette butts are a major source of litter around the world, and users often do not care about them, causing problems with accumulation [
7,
8]. Waste collection agencies are facing significant challenges due to the widespread distribution of cigarette butts caused by smokers. Cigarette butts are considered long-lasting garbage in urban and public areas; collecting them is expensive because the collection equipment is ineffective and the butts are small [
9]. Problems related to cigarette butts include their large quantities, their possible widespread dispersion, and the existence of various toxins within the butts that may periodically leach into the environment. Cigarette butts contain thousands of compounds, hundreds of which are known to cause cancer and genetic mutations. Consequently, potential harm to the ecosystem and other forms of life is a major issue with cigarette butts [
10]. Cigarette butts have been found to contain significant amounts of metals, including lead, cadmium, copper, nickel, zinc, and chromium [
11]. Cigarette butts include a wide variety of contaminants, from these metals to organic chemicals to PAHs to nicotine [
12]. These harmful contaminants escape from abandoned cigarette butts and contaminate the ecosystem [
13,
14,
15]. Cigarette butt poisonous contents infiltrate into both soil and water [
16,
17]. Cigarette butt leakage can contaminate water sources, raise the concentration of contaminants in waste from municipal dumps, and produce leachate [
18]. Other potential effects of littering with cigarette butts include the risk of fire and the potential for animals and young children to choke on the butts [
19]. The reduction in cigarette butt pollution necessitates an approach that incorporates several different strategies, including infrastructure improvement, community involvement, regulatory enforcement, and public education. These types of initiatives are critical to encouraging appropriate disposal methods and reducing harm to the environment. There is a big gap in the research on measuring metal emissions and comparing different ways to handle them. Filling this gap is critical for making effective policy decisions and reducing the global environmental impact of cigarette butt waste. This research had the following objectives: (1) to estimate the metal concentration from different brands of littered and newly smoked cigarette butts; and (2) to evaluate various scenarios in order to determine the total quantity of metals released by cigarette butts. Several strong factors make this research highly relevant to an international audience. It will assess the environmental impact of littered and recently smoked cigarette butts. Examining various scenarios to determine the metal emissions from cigarette butts illuminates the extent of metal pollution this waste type generates, which offers a valuable insight for global policymakers, environmental organizations, and public health officials. This study highlights the importance of implementing appropriate mitigation methods and public awareness campaigns worldwide by revealing the full level of metal contamination in cigarette butt litter. It also adds to our scientific knowledge of environmental pollution.
3. Results and Discussions
The study compiled and easily accessed the results of determining the concentrations of five different metals in the cigarette butts connected to seven popular high-consumption cigarette brands (N = 200 per sample) available in the Chinese market, as shown in
Table 3. Statistical analysis values are presented in
Table 4 and
Figure 2, where correlation and pair-panel plots are shown.
In this table, we can see a breakdown of the elements of seven distinct brands, with an emphasis on Cr, Ni, Cu, Zn, and Pb. B3 stands out with the highest Ni content at 3.63 µg/g, while B4 has the lowest Cr content at 1.13 µg/g. Cu content varies considerably, with B3 leading at 15.89 µg/g and B2 trailing at 10.36 µg/g. Zn content is highest in B7 at 28.5 µg/g and lowest in B3 at 18.85 µg/g. Additionally, B2 exhibits the highest Pb content at 1.39 µg/g, while B1 has the lowest at 1.05 µg/g. Concerns about the possible effects on human and environmental health are driving interest in the metal concentrations, especially those of Ni, Cu, and Pb. At 3.63 µg/g for Ni and 15.89 µg/g for Cu, B3 possesses the highest concentrations of these elements. Given the environmental impacts and potential health risks, further investigation into elevated levels of specific metals may be necessary. On the other hand, Pb concentrations across all brands are generally low, with B2 recording the highest at 1.39 µg/g. Any lead presence is concerning, so it is important to keep an eye on these numbers even though they are lower than usual health recommendations. All brands’ elemental composition can be measured against these averages. Cr and Ni have mean values of 1.77 µg/g and 2.88 µg/g, respectively, suggesting a relatively consistent presence across the brands. Cu exhibits a higher mean at 12.93 µg/g, indicating a generally elevated copper content in the dataset. Zn and Pb also show higher mean values at 24.25 µg/g and 1.77 µg/g, respectively, underscoring the importance of considering these elements collectively in any assessment. Looking at the highest and minimum values reveals the range of variability, providing a better understanding of the dataset’s extremes. Cr varies from 1.13 µg/g to 2.25 µg/g, Ni from 2.39 µg/g to 3.63 µg/g, Cu from 10.36 µg/g to 15.89 µg/g, Zn from 18.85 µg/g to 28.5 µg/g, and Pb from 1.05 µg/g to 2.25 µg/g. Because different cigarette brands have different elemental compositions, it is important to conduct individualized evaluations based on specific application requirements or government regulations. While metal analysis raises health and environmental issues, distinct patterns reveal individual brands’ strengths and weaknesses. One way to evaluate dataset diversity is to use variability ranges, while mean values can provide a central reference. With this summary, industry and regulators may better understand product composition, make decisions about quality control, and manage the environment. The results show that even when exposed to the same environmental circumstances, cigarette butt concentrations can vary significantly across brands.
Furthermore,
Table 5 demonstrates the widely recognized large variations in the metal content of samples collected under varied environmental conditions. We found that the metal content was lowest under long-persistent and wet conditions, and highest under short-persistent and bright sunlight.
Across the 15-day timeframe, Cr, Ni, and Cu consistently displayed declining concentrations, indicative of potential chemical transformations or leaching mechanisms at play. Notably, rainy conditions appeared to amplify this reduction, suggesting a stronger environmental influence during precipitation events. This suggests a different response to temporal aging or environmental influences, highlighting the complexity of metal behavior in cigarette litter. Pb concentrations, in contrast, displayed noticeable fluctuations. The fluctuating pattern was evident under both sunny and rainy conditions, emphasizing the intricate interactions between atmospheric components and this particular metal. The statistical analysis for
Table 5 is given in
Figure 3. The temporal trends collectively underscore a general reduction in metal concentrations over time, aligning with expectations of potential leaching or alterations within the discarded cigarette butts. Rainfall’s influence, particularly in accelerating the decline of certain metals, adds an environmental dimension to the observed dynamics. In summary, the nuanced temporal and environmental variations in metal concentrations within discarded cigarette butts emphasize the need for a comprehensive understanding of both aging processes and external factors in waste management considerations. The intricate nature of these interactions underscores the importance of developing effective strategies for mitigating environmental and public health risks associated with discarded cigarette litter. The concentrations of metals in littered cigarette butts are given below in
Table 6. Comparing the two tables, the concentrations of metals exhibit variations in response to different environmental conditions and temporal intervals. In
Table 5, metal concentrations after 15 days generally displayed a decreasing trend, with slight fluctuations.
Contrarily,
Table 6, reflecting conditions after 15 sunny days and 48 h of rainy weather, unveils nuanced patterns. In this table, concentrations often align with or slightly exceed previous levels, indicating potential influences of seasonal changes and pollution levels. Cr, Ni, and Zn concentrations, in particular, show distinctive trends in response to varying conditions. These comparisons underscore the dynamic nature of metal behavior, emphasizing the importance of considering both temporal evolution and environmental factors for a comprehensive understanding in environmental studies.
The research concluded that cigarette butts, which contain high levels of metals and many other toxins and poisons, are hazardous waste products that can pollute water and kill species [
3,
10,
27]. Because they contain a lot of metals, cigarette butts are considered hazardous waste [
10,
27]. Additionally, cigarette butts can harm plant growth if they are in the air [
28]. Cigarette butts produce this toxic material by releasing chemicals into the environment [
15]. Humid environments facilitate the release of tobacco filter pollutants more readily. In damp environments, cigarette butts exhibit lower metal concentrations as a result of increased leaking. Despite the fact that cigarette butts do not change significantly over time, they do release pollutants at different rates, which leads to a decrease in the amount of metal that is present in the environment. Examining cigarette butts for metals proves that they are a known metal-release source, but determining precise levels due to environmental variables and structural variations in cigarettes is difficult. Metal discharges from cigarette butts in the Chinese environment can vary between 844.97 kg and 2129.31 kg per year, according to the scenarios evaluated in the present research (
Figure 4).
These estimates are based on the consumption of 2.4 trillion cigarettes in China every year, assuming that 80 percent of the cigarette butts produced end up in landfills. Even when we dispose of cigarette butts through the proper channels, there remains a potential for the indirect release of metals into the environment. This is an extremely important fact to acknowledge. Because cigarette butts are present in dumped urban garbage, the concentration of such metals in drainage is significantly higher. The discharge of contaminants like metals from cigarette butts poses a concern for public health since these metals have negative impacts on human health and spread to soil and water sources, increasing the likelihood of sickness in society [
16,
29].
Figure 5 presents a comprehensive overview of the metal concentration ratio across five distinct scenarios. Each scenario represents a specific set of conditions or factors that influence the concentration levels of these metals. In the first scenario, Cr stands out with a concentration ratio of 3.38%, while Zn dominates with an exceptionally high concentration ratio of 61.13%. The second scenario exhibits a lower concentration ratio of Cr and Ni but a substantial increase in Cu and Zn, indicating a shift in the distribution of these metals. The third scenario introduces a moderate increase in Cr and Ni concentration ratios, with a slight decrease in Cu and Zn. Interestingly, Pb experiences a significant decline. Moving to the fourth scenario, there is a slight increase in the Cr and Cu concentration ratios, while Ni and Zn maintain relatively stable levels. Pb also sees a minor increase. The fifth scenario presents a significant shift in metal concentration ratios, particularly in Cu and Zn, with values soaring to 58.32% and 27.32%, respectively. Cr and Ni exhibit marginal increases, while Pb remains relatively stable. Comparing the scenarios reveals intriguing patterns in the distribution of metals. Notably, Zn appears to be a pivotal metal, displaying substantial variations across the scenarios. Scenario three shows a balance in metal concentrations, while scenario five accentuates the dominance of Cu and Zn. Cr and Ni, although displaying some fluctuations, maintain relatively consistent levels. Pb, on the other hand, demonstrates subtle changes, reflecting the scenario-specific dynamics. This comprehensive analysis underscores the complexity of metal distribution and highlights the importance of considering various scenarios and their unique environmental conditions. Understanding these variations is crucial for developing effective environmental management strategies, especially in contexts where metal contamination poses potential risks to ecosystems and public health. For this kind of observation, the impact of cigarette butts that are present in various ecosystems is a key consideration. Because most cigarette butts remain in place until the next day’s clean-up and weather conditions vary from day to day, the amount of metal that leaks out of them varies in urban contexts [
7]. Contaminating a wide variety of organisms, cigarette butts deplete water and soil resources and pose a serious threat to human health. There are significant concerns over the possibility of cigarette butt contamination [
3]. Factors such as the effectiveness of municipal amenities and maintenance, as well as the existence of areas with limited accessibility, affect the overall duration that scattered cigarette butts persist in the environment [
7]. Some claim that different parts of Madrid have varying cleaning standards, leading to a higher concentration of littered cigarette butts in certain regions due to their prolonged persistence [
30]. According to the study’s authors, cigarette butts absorb more metal when stored in inconvenient places like water ditches and bike racks. It is not possible to completely remedy the problem by simply collecting butts or appropriately disposing of them, because doing so may result in the discharge of toxins. We must reduce the generation of butts through cessation programs, provide education to promote safe disposal, and make technological developments to decrease contaminants. This requires a multidisciplinary approach. The development of eco-friendly alternatives and the implementation of pre-landfill extraction procedures achieve the goal of minimizing environmental harm and reducing pollutants in landfills. Controlling the leakage of contaminants, including metals, from cigarette butts is another vital aspect of environmental protection. Improved waste management systems, coupled with stringent regulations, can help prevent the escape of harmful substances from discarded cigarette butts, safeguarding the surrounding environment.
Lastly, establishing designated areas for the disposal of cigarette butts can contribute to better waste management practices. By implementing regulations that confine the littering of cigarette butts to specific locations, authorities can exert greater control over the environmental impact of these pollutants, ensuring proper containment and disposal. In conclusion, addressing the environmental challenges posed by cigarette butts requires a holistic approach encompassing reduced generation, responsible disposal, pollutant reduction, advanced waste management, and regulatory measures. Only through a concerted effort in these areas can we hope to mitigate the adverse effects of cigarettes on our environment.
We accept various limitations in our models for calculating metal concentrations from cigarette butts and evaluating overall metal emissions, considering the goals stated and the data supplied. The heterogeneity in sampling, which results from different locations and collection techniques, casts doubt on the data’s representativeness. Because analytical techniques have inherent limitations, calibrating efforts may not always produce precise results. Environmental factors such as weather and pollution sources hampered accurately calculating metal deposition and redistribution. Human activity and degradation impact the temporal fluctuation in metal release rates, further complicating predictions. Our findings are further complicated by modeling assumptions regarding the behavior of littering. Furthermore, poor data quality and availability limit the model’s robustness. A refinement of techniques, sensitivity analysis, and validation against empirical data are necessary to address these shortcomings. We can enhance the model’s accuracy and deepen our understanding of the metal pollution stemming from cigarette butt litter by incorporating validation studies and field data. Despite these difficulties, our research offers insightful information about the effects on the ecosystem and emphasizes the necessity of sophisticated strategies for successfully reducing metal pollution.
4. Conclusions
This study has examined seven different brands and five different metals. With a Ni value of 3.63 µg/g, B3 is the most notable, whereas B4 has the lowest Cr content (1.13 µg/g). With B3 leading at 15.89 µg/g and B2 behind at 10.36 µg/g, the Cu content varies significantly. B7 has the highest zinc content (28.5 g/g), whereas B3 has the lowest (18.85 g/g). Furthermore, B2 has the greatest Pb concentration (1.39 µg/g) compared to B1’s lowest (1.05 µg/g). Concerns about potential impacts on human and environmental health, particularly those of Ni, Cu, and Pb, fuel interest in the metal concentrations. With concentrations of 3.63 µg/g for Ni and 15.89 µg/g for Cu, B3 has the highest concentration of these metals. Further research into elevated levels of specific metals may be necessary, given the environmental consequences and possible health risks. Conversely, Pb values are generally modest for all brands, with B2 having the highest concentration at 1.39 µg/g. Even though these values are lower than the standard health recommendations, any presence of lead is cause for concern, so it is crucial to monitor them. Any brand’s elemental content can be compared to this average. With mean levels of 1.77 µg/g and 2.88 µg/g, respectively, Cr and Ni appear to be present in most brands in a fairly consistent amount. Cu has a greater mean of 12.93 µg/g, suggesting that the dataset has a usually higher copper concentration. Higher mean values for zinc and lead (at 24.25 µg/g and 1.77 µg/g, respectively) further highlight the significance of taking these components into account in any assessment. Examining the greatest and lowest values improves our understanding of the dataset’s range of variability and its extremes. The ranges for Cr, Ni, Cu, Zn, and Pb are, 1.13 g/g to 2.25 g/g, 2.39 g/g to 3.63 g/g, 10.36 g/g to 15.89 g/g, and 18.85 g/g to 28.5 g/g, and 1.05 g/g to 2.25 g/g respectively. Because the elemental compositions of different brands of cigarettes vary, it is critical to carry out customized assessments based on application needs or legal restrictions. Metal analysis raises health and environmental concerns, while specific patterns highlight the advantages and disadvantages of particular brands. While mean values can serve as a core reference, variability ranges are one method of assessing dataset diversity. This overview can help industry and regulators make better decisions about quality control, environmental management, and product composition. The results demonstrate that cigarette butt concentrations can differ dramatically between brands even when exposed to identical environmental conditions. Metal leakage accelerates when cigarette butts remain in the atmosphere for extended periods and humidity levels rise. It was estimated that the annual emission of metals from cigarette butts into the Chinese environment is 844.97–2129.31 kg/year. Cigarette butts release contaminants like metals, which can have harmful effects on organisms. To mitigate this, there should be effective ways to clean and recycle cigarette butts, decrease littering by smokers, and decrease the amount of harmful substances in cigarette butts.