INTRODUCTION
Consumption and sales of electronic cigarettes (e-cigarettes) have risen dramatically worldwide1,2. Sixty million e-cigarettes and refills are sold annually, and one-third of these are designed for single-use in the United States3. The global market value was estimated to grow from US$ 14.53 billion in 2017 to US$ 48.9 billion by 20254. E-cigarettes are highly popular among youth and young adults1,3. Contradictory and confusing information exists concerning public health risks and benefits of e-cigarettes2. For example, their growing popularity can partly be attributed to e-cigarettes being marketed to the public as ‘healthier alternatives’ and ‘eco-friendly’ compared to conventional cigarettes2,3. However, several scientific studies suggest that e-cigarettes may have short- and long-term health effects2.
E-cigarettes are the most common electronic nicotine delivery systems (ENDS)1,2. These electronic battery-powered devices heat liquid (e-liquid) generally containing nicotine and flavoring agents to become aerosols inhaled by the user1-3. Some e-cigarettes are reusable, which means that batteries, capsules, and atomizers can be replaced, while others are only single-use1. Although e-cigarettes provide users with the sensation of smoking known as vaping, they are promoted as being tobacco-free and do not require burning for consumption2,3.
Although information exists about the direct impact of e-cigarettes on health, very little scientific evidence exists concerning the environmental impact of the life cycle of these products and their potential indirect health harm1-9. From their manufacturing processes to their use and disposal, the environmental impact of e-cigarettes presents a novel public health concern that needs to be urgently investigated5. An example is that e-cigarettes are a growing waste management concern because, despite their small size, they are consumed and discarded much more quickly than typical electronics1-9.
General e-waste can contain precious metals like gold, copper, and nickel, as well as rare materials like indium and palladium6,7. According to the Basel, Rotterdam, and Stockholm Conventions, the presence of toxic materials, such as mercury, lead, or brominated flame retardants, justifies classifying e-waste as ‘hazardous’6,7. Furthermore, e-waste is the fastest-growing hazardous waste stream8,9. In 2019, 53.2 million metric tons (Mt) of e-waste was generated worldwide and is expected to reach 74.7 million Mt by 20308,9.
Tobacco companies, including e-cigarette industries, recognize that they need to address novel environmental impacts caused by their growing use of batteries and other electronics in e-cigarettes5. Yet, despite recognition of the potential hazards, eco-friendly claims are often used as a marketing strategy by the tobacco industry5,10. If these claims are shown to be false, then ‘greenwashing’ needs to be called out to avoid misinformation being used as a tool to unethically drive consumer demand. Hence, there is a need to evaluate the environmental impacts of e-cigarettes and to expand the publicly accessible literature documenting such evidence11. For these reasons, a scoping review was conducted to systematically review available studies to identify the environmental impacts of e-cigarettes. Underlying this approach was the fundamental aim of promoting expanded knowledge and awareness on this overlooked issue, so that comprehensive response policies and strategies may be initiated to mitigate observed and projected health and environmental consequences.
METHODS
This scoping review of peer-reviewed and grey literature was prepared according to the framework of the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA)12 guidelines.
Two databases including PubMed and Web of Science were searched from inception to 21 March 2023 to identify relevant literature. Grey literature was searched using Google Scholar and the first 100 search results sorted by relevance were compared against the inclusion criteria. Moreover, reference lists of publications included in the scoping review were screened manually for additional relevant publications. At this stage, no language restriction was applied.
The search for the relevant literature was conducted using the following keywords in the title and abstract of the literature: e-cigarettes, vaping, climate, environment, planet, and waste. The final search results were exported into an Excel spreadsheet, and duplicates were removed.
Publications were included if they satisfied the following eligibility criteria: 1) all types of scientific publications such as articles, editorials, viewpoints, guidelines, etc.; and 2) English-language publications that focused on the potential impacts of e-cigarettes on the environment.
The selection of relevant publications was conducted in three stages: 1) screening of the title and abstract conducted by two authors; 2) full-text screening completed independently by two authors and raised discrepancies resolved through discussion until consensus was reached; and 3) data extraction and collation. These stages are summarized in the PRISMA flow diagram (Figure 1).
Eligible publications were reviewed by two authors independently and relevant details were extracted which related to the potential impact of e-cigarettes on the environment: namely their components, their chemical contaminants, their waste issues, and pollution (Figure 1). Discrepancies were resolved through discussion until a consensus was reached.
RESULTS
A total of 693 publications were identified by the search (of the above-mentioned databases and additional publications through manual search). Duplicated records (n=327) were removed. Based on the eligibility criteria, the titles and abstracts of 361 publications were assessed for their relevance, resulting in 33 publications being retained. The full texts of the remaining 33 publications were obtained, and after applying the eligibility criteria, a total of 9 publications met the criteria and were included in this scoping review (Figure 1)1,2,3,5,11,13-16. Characteristics of the included publications are shown in Table 1.
Table 1
Characteristics of nine studies, included in the scoping review from inception until 21 March 2023, reporting the environmental impacts of e-cigarettes
| Authors | Year | Methods | Assessment | Conclusions |
|---|---|---|---|---|
| Chang11 | 2014 | Systematic review | Gaps in research related to the environmental impact of e-cigarettes | Little is known about the environmental impact of e-cigarettes life cycle |
| Krause and Townsend14 | 2015 | Quantitative | Testing e-cigarettes with Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET) to assess the potential of e-cigarettes to be a hazardous waste in the USA | Some e-cigarettes should be classified as hazardous waste for lead leaching |
| Lerner et al.16 | 2015 | Semi-quantitative | Testing the presence of oxidants/ROS in ENDS products (e-cigarettes) | Data on dichloro- fluorescein (DCF) is indicative of oxidant presence but not an accurate measurement of ROS levels |
| Lee et al.13 | 2017 | Quantitative | Assess the content of e-cigarettes emissions using e-cigarette aerosol generation, sampling system, chromatographic and spectroscopic methods | E-cigarettes contain some pollutants |
| Hendlin5 | 2018 | N/A | Information on e-waste | N/A |
| Marcham and Springston2 | 2019 | Review of the literature | E-cigarettes in the indoor environment | E-cigarettes should be considered a source of aerosols, VOCs, and particulates in the indoor environment |
| Papaefstathiou et al.3 | 2019 | Review of the literature | Main and side effects of e-cigarettes | E-cigarettes are non-combustible products, and when heated, they produce aerosols that might be toxic |
| Beutel et al.1 | 2021 | Review of the literature | A review of the environmental pollution of e-cigarettes and cigarettes | E-waste may be a pollutant source |
| Pourchez et al.15 | 2022 | N/A | E-cigarettes as a new environmental threat | N/A |
All publications included were published between 2014 and 2022. Four publications presented reviews of the literature1-3,11, 2 publications quantitative13,14, and 1 publication semi-quantitative methods16 (Table 1).
The publications under review aimed to: assess the research gaps related to the environmental impacts of e-cigarettes due to their manufacture, use and disposal11, assess the potential of e-cigarettes to be classified as hazardous waste14, test the presence of oxidants/reactive oxygen species (ROS) in ENDS products16, assess the content of e-cigarette emissions13, provide information on e-cigarette disposal5, investigate the potential exposures and risks from the use of e-cigarettes, particularly for bystanders, in the indoor environment2, investigate the potential health, safety and environmental effects of e-cigarettes3, discuss the cigarette and e-cigarette contamination in the context of environmental sources and impacts1, and discuss e-cigarettes as a new environmental threat15 (Table 1).
All the publications under review stated that studies on the environmental impact of e-cigarettes are limited. However, all the publications shared one common concern, which is the environmental threat of e-cigarettes. Limited scientific information on the environmental impacts of e-cigarette life cycle11, classifying some e-cigarettes as hazardous waste for lead leaching14, raising concerns regarding the safety of e-cigarettes use and the disposal of e-cigarette waste products into the environment due to the presence of oxidants/ROS, nanoparticles, and copper metals associated with the e-cigarette aerosols intended for inhalation16, the presence of toxic compounds including nicotine, fine and nanoparticles, carbonyls, and some toxic volatile organic compounds (VOCs) such as benzene and toluene in e-cigarettes aerosols13, considering e-cigarettes as a source of aerosols, VOCs, and particulates in the indoor environment2, considering the fact that e-cigarettes are non-combustible products, and when heated, they produce aerosols that might be toxic3, and considering e-cigarette use and disposal as a pollutant source1, were stated as the main outcomes of the publications (Table 1).
All the publications under review reported several reasons and potential impacts of e-cigarettes on the environment, which can be categorized into three main areas: production, use, and disposal. The impacts on air quality, water, land use, and animals, due to the production, use and disposal of e-cigarettes1-3,5,11,13-15, water and energy usage, with associated environmental impacts, required for manufacturing e-cigarette components1,2,5,11,14,16, increased pollution and emissions due to greater e-cigarette production11, having harmful components like e-liquid (e.g. nicotine), batteries, toxic chemical (e.g. VOC, PM, lead)1,5,11,13,15, creating pollution and waste issues1-3,5,11,13-15, and global environmental impacts due to manufacturing and importing ingredients and components of e-cigarettes from low- and middle-income countries5,11, were reported by the publications under review as the environmental impacts of e-cigarettes (Table 2).
Table 2
Potential impacts of e-cigarettes on the environment reported by the publications under the scoping review from inception until 21 March 2023
| Impacts | Chang11 | Krause and Townsend14 | Lerner et al.16 | Lee et al.13 | Hendlin15 | Marcham and Springston2 | Papaefstathiou et al.3 | Beutel et al.1 | Pourchez et al.15 |
|---|---|---|---|---|---|---|---|---|---|
| Impacts on the air, water, land use quality, animals | x | x | x | x | x | x | x | x | |
| Production of e-cigarette components requires energy and water | x | x | x | x | x | x | |||
| Larger factories of e-cigarettes generate greater emissions in the environment | x | ||||||||
| E-cigarettes contain harmful components like e-liquid (e.g. nicotine), batteries, toxic chemical (e.g. VOC, PM, lead) | x | x | x | x | x | ||||
| E-cigarettes create pollution and waste issues | x | x | x | x | x | x | x | x | |
| Global environmental impacts because e-cigarette components and ingredients are imported, and wastes are shipped to developing countries | x | x |
DISCUSSION
This study selectively reviewed the available literature to identify the environmental impacts of e-cigarettes. The results of the present study indicate that air quality, water, land use, and animals, are threatened due to the production, use, and disposal of e-cigarettes1-3,5,11,13-15. Still, evidence remains limited regarding the environmental impacts of e-cigarettes1-3,5,11,13-16. Furthermore, no studies have formally evaluated the environmental impacts of the life cycle of e-cigarettes1,9. It is also unclear how the environmental impacts of e-cigarettes compare to those of conventional cigarettes11. For instance, it could be informative to compare the life cycle pollution from production to disposal between traditional cigarettes and e-cigarettes. Despite the absence of supporting data or environmental impact studies, eco-friendly claims have been used by manufacturers as a marketing strategy to promote e-cigarettes to consumers3,11.
Production
In regard to production, it is worth noting that e-cigarettes contain a battery, a heating element, an atomizer (aerosolization chamber), a cartridge, an e-liquid, and a mouthpiece2,5,11,14,16. Manufacturing the product is an energy-consuming process with associated environmental impacts1,2,5,11,14,16. For example, extraction and purification of nicotine from the tobacco plant requires a large amount of water and generates non-recyclable halogenated waste and pollution1,2,5. Also, as a result of e-cigarette marketing, the demand for tobacco crops could potentially increase, which would present a potential alteration in land use11. Greater e-cigarette production demand drives increased pollution (e.g. greenhouse gas emissions), therefore contributing to processes that may lead to climate change11. Due to a lack of regulations in countries like the US, data on pollutant contamination of water, land, and air may not be obtained from manufacturing sites11. However, global environmental impacts are important to consider because ingredients and components of e-cigarettes are manufactured and imported from low- and middle-income countries including India5,11.
Use
In addition to environmental harms from production, understanding the potential environmental impact of the use of e-cigarettes is important. Beside the direct harm experienced by users, e-cigarette vapors are potent sources of air pollution such as aldehydes, carbon monoxide, particulate matter (PM), VOCs, heavy metals, and nicotine1,3,13. Compared to smoke from conventional cigarettes, the amount of PM and heavy metal emissions from e-cigarette vapor were found to be similar or greater2,13. The potential risks of passive e-cigarette exposure among bystanders needs to be considered2. Because e-cigarette emissions contain measurable amounts of toxic chemicals, further investigation should be conducted to better understand the full scope of the environmental implications2,13.
Disposal
The disposal of e-cigarettes should also be considered when studying their environmental impacts. E-waste is a major environmental problem, with a 2017 estimate suggesting that up to 45 billion kg of e-waste are discarded annually5. Increased use of e-cigarettes has led to a rise in the release of e-cigarette waste and related contaminants into the environment1.
Some e-cigarettes are designed to be completely disposable, while others are rechargeable2,14. Disposable e-cigarettes and vaping pods, spent e-cigarette capsules or replaceable pods, pose the most significant potential environmental burden5,15. Vaping pods are an example of plastic waste because they are not biodegradable and are poorly recyclable15. Also, they contain similar waste components as reusable e-cigarettes but are used for a shorter time before being discarded5.
Components like batteries and replaceable capsules containing concentrated nicotine residues can leach pollutants into water, air, and soil1. A particularly serious threat of environmental pollution is the littering of e-liquid containers1. They may contain high concentrations of residual nicotine, of known and unknown toxicity, and flavoring additives such as aldehydes1,3.
Therefore, e-cigarettes have different types of waste, including biohazard, plastic, and electronic waste15. We contend that the potential waste load from e-cigarettes exceeds that of traditional cigarettes due to the larger amount of components3. E-cigarette components like nicotine, lithiumion batteries, and electronic circuit boards, are considerable forms of biohazard and electronic waste1,3,5,13-16. On the one hand, the biohazard waste (nicotine, lithium-ion batteries) risk arises when e-cigarettes are improperly discarded and when broken components leach heavy metals (e.g. mercury, lead) and release toxic chemicals into the environment, affecting humans and animals1,3,5,13-16. These products can then bioaccumulate in animals and humans, creating health issues1,3,5,8-11. On the other hand, the electronic waste risk occurs when discarded components like batteries pose an explosion and fire hazard in waste and recycling facilities15. Biohazard and electronic waste should not be discarded in regular trash and instead should be disposed of in specific facilities5,14,15. However, regulation of such requires strengthened legislation and policies to be enacted. The likelihood of universal compliance with such regulation presents an additional and significant challenge for claims of e-cigarettes’ environmental safety.
The Basel, Rotterdam, and Stockholm conventions are science-based, legally binding global treaties aimed at protecting human health and the environment from hazardous chemicals and wastes. However, non-compliance is common as the global transport of waste continues to expand. Most e-waste from Western countries is shipped to developing countries, shifting the dangers and pollution-related risks to settings that are often least able to adequately address and mitigate them5. This rich-to-poor country shift transfers risk and harm whilst further exacerbating global health inequities. Moving forward, e-cigarettes will need to be part of the ongoing conversation on how to better govern and enforce such regulations under the broader aim of reducing the global environmental injustices that practices such as offshoring pollution continue to contribute towards.
Strengths and limitations
The present study’s strength is that it is the first scoping review conducted to identify the environmental impacts of e-cigarettes. However, the limitations of our study need to be considered. One limitation of our study is that only two databases were searched, which might have led to the absence of relevant studies. More databases can be included for future studies. Manual screening of reference lists of publications included in the scoping review was used to add relevant publications that had not been initially identified through database searching.
Although it ensured that the review was exhaustive, some conclusions may have been influenced by this manual search strategy. Despite not restricting the language of publication, only English keywords were searched, which may have led to the exclusion of non-English publications. Another limitation is that only publications written in English were included. Future reviews should include non-English studies to have a better understanding of the situation.
CONCLUSIONS
E-cigarette emissions and waste contain measurable amounts of nicotine and other toxic chemicals, thereby serving as significant sources of environmental pollution. Despite the emphasis on the environmental threat of e-cigarettes, there are limited scientific studies on the environmental impacts of the e-cigarette life cycle (manufacturing, use, and disposal). This life cycle is not studied enough for its impacts on human health associated with environmental pollution. As a result, critical ecosystems providing clean water, air, and food production, can be negatively affected. Although limited data have been reported about the life cycle of e-cigarettes, they may represent a significant long-term environmental threat due to the toxic nature of their composition. E-cigarette environmental impacts can be prevented with improved regulation of their production, use, and disposal. For example, the gradual elimination of disposable e-cigarettes in favor of reusable e-cigarettes and proper recycling and waste management could reduce environmental damage. It is important to note that ‘absence of evidence is not evidence of absence’. Since e-cigarettes are mainly owned by the tobacco industry, it is important to question whether vaping is more eco-friendly than smoking, as companies claim. Given the rapid expansion of e-cigarette manufacture, distribution, use, and disposal globally, a rigorous assessment of their life-cycle environmental burden of the various potential health, environmental, and other consequences is urgently required.
