Cigarette butts, the remains of cigarettes after smoking are tiny and tend to be neglected but are a form of non-biodegradable litter (Araújo & Costa, 2019). Cigarette butts are often discarded on streets which find their way to drains, and eventually to the water bodies. According to WHO, ‘Cigarette butts account for 30–40% of all items collected in coastal and urban clean-ups’ (WHO, 2017). Even if the residues of cigarettes seem small, they are generated in large amounts. It has been estimated that nearly 6 trillion cigarettes are smoked every year worldwide and about 4.5 trillion cigarettes are littered in the environment which makes, Cigarette butts the most common form of litter in the world (Araújo & Costa, 2019).
According to WHO, ‘Tobacco waste contains over 7000 toxic chemicals that poison the environment, including human carcinogens’ (WHO, 2017). Smoking cigarettes can be a root cause of several health problems such as Cancer, heart attack and strokes, lung diseases, etc. (WHO, 2017). People getting exposed to secondhand smoke (also called environmental tobacco smoke, involuntary smoking, and passive smoking) can directly affect a person’s heart (with an estimated increased risk of 25–30% of developing heart disease) and blood vessels along with inflamed airways (Logue et al., 2017). According to a scientific report published in the journal Environmental Science and Technology, ‘a person smoking a pack of 20 cigarettes per day for 50 years is responsible for 1.4 million liters of water depletion’ (Dunning & Wilson, 2018). The tobacco industry can cause severe impacts on the environment as nearly 600 million trees are chopped down each year along with annual production of about 64 million metric tons of carbon dioxide globally (Tobacco Free Life, 2016a). The toxic chemicals from cigarettes pose a serious health threat to humans, wildlife, and aquatic organisms (Kurmus & Mohajerani, 2020). One of the studies showed how organic compounds (like nicotine, and PAH) along with metalloids from cigarette butts leach into aquatic ecosystems, which are toxic to aquatic creatures (Akhbarizadeh et al., 2021; Green et al., 2014).
This study aims to bring attention to the severity of the pollution caused by littering cigarette butts and to understand its impact on humans and the environment. The review of the paper includes the components and toxicity of cigarette butts along with the potential impacts on humans, the environment, and the economy.
Study Background:
1.1 Components of Cigarette filters
Owing to the widespread nature and the magnitude of cigarette butts released into the environment, it is important to understand the composition of cigarette butts in order to evaluate their potential impacts on nature. A cigarette filter along with cigarette paper, capsules, and adhesives is a part of the cigarette that was introduced in the early 1950s and specially designed to absorb vapors and accumulate particulate smoke components (In Wikipedia). Filters come with advantages like preventing tobacco from passing into the smoker’s mouth along with a medium as a mouthpiece that will not crumble as the cigarette is smoked. Cigarette filters look like white cotton but are actually made of plastic fibers of cellulose acetate which makes them non-biodegradable as it takes nearly 10 years to decompose (In Wikipedia). Cigarette contains more than 4000 toxic chemicals such as polycyclic aromatic hydrocarbons, formaldehyde, etc. The cigarette butts contain pyrolysis and distillation products along with primary contaminants which eventually leach into the environment (Poppendieck et al., 2016).
1.2 Toxicity of Cigarette Butts
Cigarette butts are one of the most abundant forms of waste in the world, with thousands of chemicals along with micro- and nanoparticles that have a critical consequential impact on the health of humans, wildlife, and aquatic organisms (Kurmus & Mohajerani, 2020; Moroz et al., 2021). Cigarette butts are ubiquitous to terrestrial life which in due course make their way to freshwater and marine life, leaching various toxic chemicals that can remain for as long as 10 years (Kurmus & Mohajerani, 2020). The main toxic agents include polycyclic aromatic hydrocarbons, formaldehyde, argon, carbon monoxide, nitrogen oxides, benzene, hydrocarbons, etc. (Soleimani et al., 2022).
1.2.1 Nicotine contamination
Cigarette butts contain nicotine which along with its metabolites, such as cotinine and trans-3’- hydroxyl cotinine make their passage to wastewater streams as they are littered (Benotti & Brownawell, 2007). Other means of transit to the environment are through cigarette production cigarette combustion and cigarette butts disposal. Nicotine has been found to increase oxidative damage, nicotine-mediated inhibition of nuclear factor erythroid, and elevated cortisol that may promote central obesity, PCOS, endothelial dysfunction, vascular inflammation, and many more (Rehman et al., 2021).
1.2.2 Tobacco- specific Nitrosamines (TSNA)
TSNA, one of the constituents of the complex mixture of chemicals present in cigarette smoke has been found to cause cancers of the lung, pancreas, esophagus, and oral cavity. TSNA has a direct impact on people who use tobacco products along with people who are exposed to secondhand smoke (Konstantinou et al., 2018).
1.2.3 Polycyclic aromatic hydrocarbons (PAHs)
Cigarette butts with partial or incomplete tobacco burning may contain high levels of polycyclic aromatic hydrocarbons (PAHs) (Dobaradaran et al., 2020). The three most abundant PAHs in tobacco smoke Tar are the low molecular weight two-ring naphthalene, and the three-ring PAHs fluorene And phenanthrene. The PAHs are carcinogenic to humans and can remain in the environment for decades if present in higher or accumulated concentrations (Gong et al., 2020).
1.2.4 Carbon Monoxide
Cigarette smoking directly exposes the smoker to carbon monoxide which can increase the preoperative carbon monoxide levels. The estimated preoperative carbon monoxide level in the exhaled breath level may serve as an indicator of the potential risk of perioperative respiratory complications (Ozgunay et al., 2018).
1.3 Impacts on the environment
Cigarette litter is a notable concern to the environment as it contains chemicals such as arsenic (used to kill rats), lead, and heavy metals which seep into soil and water sources making their way into the food chain and thereby pressing the ecotoxicological challenges. Toxic exposure to such chemicals poses a serious threat to aquatic and terrestrial animals (Truth initiative, 2017; Qamar et al., 2020).
1.3.1 Microorganisms
Microorganisms include prokaryotes (bacteria), eukaryotes (fungi and protozoans), symbioses, and viruses. Littered cigarette butts can leach a significant amount of chemicals into the soil which affects the bacterial communities (Koroleva et al., 2021). The leachate constrains nicotine into the environment which can impair aquatic primary producers and hence predators at relevant concentrations (Oropesa et al., 2017). Therefore, population dynamics and food web interactions are affected to a great extent once nicotine enters aquatic systems.
One of the studies demonstrated the impact of CBs on the diversity of microbial communities in the environment where marine sediments were treated with smoked CBs for 96h. The result showed the microbial communities were altered with a decrease in two taxonomic families, Cyanobacteria (involved in primary production through photosynthesis) and Bacteroidetes (involved in organic matter biodegradation) (Quéméneur et al., 2020).
1.2.5 Aquatic organisms
Cigarette butts litter often washes off to aquatic bodies. CBs float for a long time prior to sinking (Dobaradaran et al., 2021). CBs along with their toxic chemicals (mainly nicotine and ethyl phenol– are toxic to marine life) along with metalloids might be ingested by diverse aquatic organisms which can have immunotoxic, morphotoxic, and mutagenic (Montalvão et al., 2019). Fishes, turtles, and seabirds frequently consume cigarette butts by mistaking them for food.
It has been found, at concentrations of one cigarette butt per liter of water, the toxins are lethal to small fish, and to planktonic organisms such as water fleas at one-eighth of this concentration. Several bioassays were tested and they concluded that marine assays were more affected by leachates than freshwater ones (Olivia et al., 2021).
1.3.3 Plants
Leachate of CBs contains nicotine which is one of the reasons for the elevated nicotine levels in plant commodities. Detection of elevated nicotine levels in plant tissues that are not known for endogenous nicotine synthesis, and where nicotine-containing insecticides had not been applied (Selmar et al, 2015; Weidner et al., 2005). High levels of nicotine cause human health risks which are a concern to the market causing economic losses for farmers and distributors (Semar et al., 2018).
Many studies have been conducted to demonstrate the impact of CBs and their associated smoke on the soil and plant processes. Montalvão et al. noted that the leachate of smoked CBs at environmental concentrations (1.9 µg/L of nicotine) had cytotoxic, genotoxic, and mutagenic effects on onion (Allium cepa) roots (Montalvão et al., 2018). Another study showed that discarded CBs reduced the germination success and shoot length after 21 days of both perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) (Green et al., 2019). The studies prove the potential of CB litter in reducing the net primary productivity of terrestrial plants.
1.3.4 Animals
The leachate of CBs contains various toxic compounds including nicotine, PAHs, metals, and volatile organic compounds which are known to be toxic to many aquatic organisms mainly zooplankton, frogs, snails, and fishes (Venugopal et al., 2021). The bioaccumulation of nicotine starting with plants and later on passing to animals have a great impact on the environment. The CB pollutants have a potential chronic impact on the growth and behavior of both aquatic and terrestrial animals. The non-biodegradable plastic CBs made of cellulose acetate are frequently consumed by animals which may lead to vomiting and neurological toxicity (Novotny et al., 2011). Cigarettes contain tobacco and it is known to be lethal to various mammals.
1.3.5 Humans
As noted earlier, the CB and its associated smoke contain thousands of chemicals that pose severe health issues to humans. Likewise, exposure to secondhand smoke also has critical impacts. The main components of the environment like water, soil, dust, and plants have been contaminated with tobacco, and water is a significant route to expose tobacco to humans. The bioaccumulation of nicotine in plants and animals presents a possible source for human exposure to nicotine in addition to metals, PAHs, and plastic nanoparticles.
Recent studies suggest that tobacco waste pollution is toxic to humans using mice and human cell-based assays. Bekele and Ashall demonstrated how mice that ingested CB leachate showed negative developmental effects (Bekele, T.T., 2019).
1.4 Waste Management System
Cigarette butts are abundant and widespread non-biodegradable waste in our environment. It is mainly composed of a cellulose acetate-based polymeric structure which makes CB take years to biodegrade and leach its toxic chemicals and heavy metals. Therefore, it is very important to find an appropriate method to recycle useful resources from waste.
Researchers have developed a novel encapsulation technique for CBs where they incorporated bitumen and wax-encapsulated cigarette butts in dense-graded asphalt preparation to recycle the CBs as a construction material (Rahman & Mohajerani, 2021). CBs consist of nicotine and harmine which has been used for the fabrication of N-doped carbon aerogel (NDC) via hydrothermal and carbonization processes (Alhokbany et al., 2020). Cigarette-derived functional carbon (CDFC) materials have been prepared by pyrolysis of CBs which applications in supercapacitors and water contaminant removal (Li et al., 2020). CBs are recycled into fired clay bricks and asphalt production without any pre-processing.
However, methods like absorbent material production, vector control, and use as a biofilm carrier in wastewater treatment need various processing methods (Torkashvand & Farzadkia, 2019). The current waste management system faces challenges and has inferior performance therefore basic strategies like reducing the littering rate and recycling are best for the management of this toxic abundant waste (Ghasemi et al., 2022).
1.5 Cigarette Butt as Potential Pollutant
Cigarette smoking is not just injurious to health but also has a greater overall environmental impact. Cigarettes are made from tobacco and the tobacco industry contributes significantly to global warming along with massive exploitation of human lives, trees, and natural resources (WHO, 2022). Smoke from these tobacco products contains fine particles in their additives and paper, containing over 7000 chemicals which after combustion release carcinogens. Thus, inhaling cigarette smoke through passive smoking has similar effects as active smoking in the form of increased genomic mutations, tumor-inducing inflammations, and epigenetic abnormalities (Kwit, 2022; Zhou, G., 2019). Besides being a major contributor to air pollution, cigarettes have now also become one of the most abundant sources of marine pollution. Their residues in the form of cigarette butts are often thrown about or tossed onto the streets, beaches, etc. from where they sweep into the drains and other water bodies.
These residual cigarette butts being lightweight are easily carried away by rain and get embedded in the water cycle, yielding their harmful effects on our marine ecosystem. Several studies have shown the potential of cigarette butts to pollute water as a more harmful source of pollution than plastic bags imparting their toxicity to aquatic life (Tobacco Free Life, 2016b; Kwit, 2020). Cigarette butts pose a great threat to our environment being the most littered item on the planet leading to catastrophic consequences due to their toxicity and retention which most people are unaware of.