In vitro particle size distributions in electronic and conventional cigarette aerosols suggest comparable deposition patterns

WITHDRAWN: Patients with lung cancer: Are electronic cigarettes harmful, useful?

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Particle doses in the pulmonary lobes of electronic and conventional cigarette users

The main aim of the present study was to estimate size segregated doses from e-cigarette aerosols as a function of the airway generation number in lung lobes. After a 2-second puff, 7.7 × 10(10) particles (DTot) with a surface area of 3.6 × 10(3) mm(2) (STot), and 3.3 × 10(10) particles with a surface area of 4.2 × 10(3) mm(2) were deposited in the respiratory system for the electronic and conventional cigarettes, respectively. Alveolar and tracheobronchial deposited doses were compared to the ones received by non-smoking individuals in Western countries, showing a similar order of magnitude. Total regional doses (D(R)), in head and lobar tracheobronchial and alveolar regions, ranged from 2.7 × 10(9) to 1.3 × 10(10) particles and 1.1 × 10(9) to 5.3 × 10(10) particles, for the electronic and conventional cigarettes, respectively. D(R) in the right-upper lung lobe was about twice that found in left-upper lobe and 20% greater in right-lower lobe than the left-lower lobe.

Adolescent Use of Electronic Cigarettes: An Emergent Health Concern for Pediatric Nurses

Recent statistics show an increasing trend of electronic cigarette usage among adolescents. Despite common misconceptions, electronic cigarette use does not reduce cigarette use among adolescents and can potentially increase cigarette dependence via nicotine addiction and modeling of smoking behaviors. Pediatric nurses and health care providers should be aware of the popularity and safety concerns of electronic cigarettes so that they can properly provide education regarding the possible negative health effects of adolescent electronic cigarette use, raise awareness of this public health concern, and impact policies in their communities.

Electronic cigarettes for smoking cessation

Electronic cigarettes (e-cigarettes) are novel vaporising devices that, similar to nicotine replacement treatments, deliver nicotine but in lower amounts and less swiftly than tobacco smoking. However, they enjoy far greater popularity than these medications due in part to their behaviour replacement characteristics. Evidence for their efficacy as cessation aids, based on several randomised trials of now obsolete e-cigarettes, suggests a modest effect equivalent to nicotine patch. E-cigarettes are almost certainly far less harmful than tobacco smoking, but the health effects of long-term use are as yet unknown. Dual use is common and almost as harmful as usual smoking unless it leads to quitting. Population effects, such as re-normalising smoking behaviour, are a concern. Clinicians should be knowledgeable about these products. If patients who smoke are unwilling to quit or cannot succeed using evidence-based approaches, e-cigarettes may be an option to be considered after discussing the limitations of current knowledge.

A role for lung retention in the sense of retronasal smell

In olfaction, odors typically engage the lungs on the way to the nose to evoke retronasal smell. This is most notable when the lung has a first pass effect during smoking/vaping, but also upon exhaling after sniffing an odor. The lungs act as a sink for odors, which can both reduce the retronasal odor concentration and the odor mixture makeup. Lung retention is a simple measure that quantifies the effectiveness of the sink. Lung retention has been studied in the context of environmental toxicology and is known for many volatile organic compounds. Available data on human lung retention suggests that the lungs may have a large impact on odor perception, and that this may depend heavily on the specifics of active sampling such as sniffing, smoking and vaping. Suggestions are included for transient measures and models of lung retention.

The effects of electronic cigarette emissions on systemic cotinine levels, weight and postnatal lung growth in neonatal mice

Background/Objective

Electronic cigarette (E-cigarettes) emissions present a potentially new hazard to neonates through inhalation, dermal and oral contact. Exposure to nicotine containing E-cigarettes may cause significant systemic absorption in neonates due to the potential for multi-route exposure. Systemic absorption of nicotine and constituents of E-cigarette emissions may adversely impact weight and lung development in the neonate. To address these questions we exposed neonatal mice to E-cigarette emissions and measured systemic cotinine levels and alveolar lung growth.

Methods/Main Results

Neonatal mice were exposed to E-cigarettes for the first 10 days of life. E-cigarette cartridges contained either 1.8% nicotine in propylene glycol (PG) or PG vehicle alone. Daily weights, plasma and urine cotinine levels and lung growth using the alveolar mean linear intercept (MLI) method were measured at 10 days of life and compared to room air controls. Mice exposed to 1.8% nicotine/PG had a 13.3% decrease in total body weight compared to room air controls. Plasma cotinine levels were found to be elevated in neonatal mice exposed to 1.8% nicotine/PG E-cigarettes (mean 62.34± 3.3 ng/ml). After adjusting for sex and weight, the nicotine exposed mice were found to have modestly impaired lung growth by MLI compared to room air control mice (p<.054 trial 1; p<.006 trial 2). These studies indicate that exposure to E-cigarette emissions during the neonatal period can adversely impact weight gain. In addition exposure to nicotine containing E-cigarettes can cause detectable levels of systemic cotinine, diminished alveolar cell proliferation and a modest impairment in postnatal lung growth.

Electronic cigarettes: product characterisation and design considerations

Objective

To review the available evidence regarding electronic cigarette (e-cigarette) product characterisation and design features in order to understand their potential impact on individual users and on public health.

Methods

Systematic literature searches in 10 reference databases were conducted through October 2013. A total of 14 articles and documents and 16 patents were included in this analysis.

Results

Numerous disposable and reusable e-cigarette product options exist, representing wide variation in product configuration and component functionality. Common e-cigarette components include an aerosol generator, a flow sensor, a battery and a nicotine-containing solution storage area. e-cigarettes currently include many interchangeable parts, enabling users to modify the character of the delivered aerosol and, therefore, the product's ‘effectiveness’ as a nicotine delivery product. Materials in e-cigarettes may include metals, rubber and ceramics. Some materials may be aerosolised and have adverse health effects. Several studies have described significant performance variability across and within e-cigarette brands. Patent applications include novel product features designed to influence aerosol properties and e-cigarette efficiency at delivering nicotine.

Conclusions

Although e-cigarettes share a basic design, engineering variations and user modifications result in differences in nicotine delivery and potential product risks. e-cigarette aerosols may include harmful and potentially harmful constituents. Battery explosions and the risks of exposure to the e-liquid (especially for children) are also concerns. Additional research will enhance the current understanding of basic e-cigarette design and operation, aerosol production and processing, and functionality. A standardised e-cigarette testing regime should be developed to allow product comparisons.

A Real-Time Fast-Flow Tube Study of VOC and Particulate Emissions from Electronic, Potentially Reduced-Harm, Conventional, and Reference Cigarettes

Tobacco-free electronic cigarettes (e-cigarettes), which are currently not regulated by the FDA, have become widespread as a "safe" form of smoking. One approach to evaluate the potential toxicity of e-cigarettes and other types of potentially "reduced-harm" cigarettes is to compare their emissions of volatile organic compounds (VOCs), including reactive organic electrophillic compounds such as acrolein, and particulate matter to those of conventional and reference cigarettes. Our newly designed fast-flow tube system enabled us to analyze VOC composition and particle number concentration in real-time by promptly diluting puffs of mainstream smoke obtained from different brands of combustion cigarettes and e-cigarettes. A proton transfer reaction time-of-flight mass spectrometer (PTRMS) was used to analyze real-time cigarette VOC emissions with a 1 s time resolution. Particles were detected with a condensation particle counter (CPC). This technique offers real-time analysis of VOCs and particles in each puff without sample aging and does not require any sample pretreatment or extra handling. Several important determining factors in VOC and particle concentration were investigated: (1) puff frequency; (2) puff number; (3) tar content; (4) filter type. Results indicate that electronic cigarettes are not free from acrolein and acetaldehyde emissions and produce comparable particle number concentrations to those of combustion cigarettes, more specifically to the 1R5F reference cigarette. Unlike conventional cigarettes, which emit different amounts of particles and VOCs each puff, there was no significant puff dependence in the e-cigarette emissions. Charcoal filter cigarettes did not fully prevent the emission of acrolein and other VOCs.

Counseling patients on the use of electronic cigarettes

Electronic cigarettes (e-cigarettes) have substantially increased in popularity. Clear evidence about the safety of e-cigarettes is lacking, and laboratory experiments and case reports suggest these products may be associated with potential adverse health consequences. The effectiveness of e-cigarettes for smoking cessation is modest and appears to be comparable to the nicotine patch combined with minimal behavioral support. Although a role for e-cigarettes in the treatment of tobacco dependence may emerge in the future, the potential risk of e-cigarettes outweighs their known benefit as a recommended tobacco treatment strategy by clinicians. Patients should be counseled on the known efficacy and potential risks of e-cigarettes.

Aerosol deposition doses in the human respiratory tree of electronic cigarette smokers

Aerosols from eight e-cigarettes at different nicotine levels and flavoring were characterized as particle number size distributions in the range 5.6-560 nm by FMPS and CPC. Results were used to provided osimetry estimates applying the MMPD model.Particle number concentrations varied between 3.26 x 10(9) and 4.09 x 10(9) part cm(-3) for e-liquids without nicotine and between 5.08 x 10(9) and 5.29 x 10(9) part cm(-3) for e-liquids with nicotine. No flavor effects were detected on particle concentration data. Particle size distributions were unimodal with modes between 107-165 nm and 165-255 nm, for number and volume metrics, respectively. Averagely, 6.25 x 10(10) particles were deposited in respiratory tree after a single puff. Highest deposition densities and mean layer thickness of e-cigarette liquid on the lung epithelium were estimated at lobar bronchi. Our study shows that e-cigarette aerosol is source of high particle dose in respiratory system, from 23%to 35% of the daily dose of a no-smoking individual.

Why public health people are more worried than excited over e-cigarettes

The research field on e-cigarettes is characterized by severe methodological problems, severe conflicts of interest, relatively few and often small studies, inconsistencies and contradictions in results, and a lack of long-term follow-up. Therefore, no firm conclusions can be drawn on the harm of e-cigarettes, but they can hardly be called safe. Experimental studies indicate negative health effects and, amongst others, the major ingredient propylene glycol warrants concern. Growing evidence raises doubt about the efficacy of e-cigarettes as a smoking cessation aid. Unfortunately, it seems that many smokers use e-cigarettes with the intention to quit but switch to long-term use of e-cigarettes or dual use. Use is spreading rapidly to minors, ex-smokers, and never-smokers. It is questionable whether the potential health benefits obtained by some smokers outweigh the potential harm by use of non-smokers, of undermining of complete cessation, smokers' dual use, and of eventual re-normalization of smoking. Even if e-cigarettes are significantly less harmful than conventional cigarettes, the product may have a very negative impact on public health if its use is spread to a large part of the population.

A systematic review of health effects of electronic cigarettes

OBJECTIVE

To provide a systematic review of the existing literature on health consequences of vaporing of electronic cigarettes (ECs).

METHODS

Search in: PubMed, EMBASE and CINAHL.

INCLUSION CRITERIA

Original publications describing a health-related topic, published before 14 August 2014. PRISMA recommendations were followed. We identified 1101 studies; 271 relevant after screening; 94 eligible.

RESULTS

We included 76 studies investigating content of fluid/vapor of ECs, reports on adverse events and human and animal experimental studies. Serious methodological problems were identified. In 34% of the articles the authors had a conflict of interest. Studies found fine/ultrafine particles, harmful metals, carcinogenic tobacco-specific nitrosamines, volatile organic compounds, carcinogenic carbonyls (some in high but most in low/trace concentrations), cytotoxicity and changed gene expression. Of special concern are compounds not found in conventional cigarettes, e.g. propylene glycol. Experimental studies found increased airway resistance after short-term exposure. Reports on short-term adverse events were often flawed by selection bias.

CONCLUSIONS

Due to many methodological problems, severe conflicts of interest, the relatively few and often small studies, the inconsistencies and contradictions in results, and the lack of long-term follow-up no firm conclusions can be drawn on the safety of ECs. However, they can hardly be considered harmless.

NIH electronic cigarette workshop: developing a research agenda

BACKGROUND

Electronic cigarettes (e-cigarettes) represent an emerging public health issue. These devices deliver nicotine along with other constituents, including flavorants, via an inhalable aerosol. Their uptake is rapidly increasing in both adults and youths, primarily among current smokers. Public debate is increasing on how these devices should be regulated and used, yet only limited peer-reviewed research exists. To develop a informed policy for e-cigarettes, their effects on human behavior, physiology, and health need to be understood.

PURPOSE

This paper describes proceedings from a National Institutes of Health-sponsored workshop, which was held in November 2013, to identify research needs related to the effects of e-cigarettes. Discussion topics included e-cigarette risks and abuse potential; the potential role for e-cigarettes in harm reduction and smoking cessation; unintended consequences of e-cigarette use, such as becoming a gateway to conventional cigarettes; and dual use of both e-cigarettes and conventional cigarettes.

RESULTS AND CONCLUSIONS

The research needs identified by the workshop participants included the following: standards to measure the contents and emissions of e-cigarettes; biomarkers of exposure; physiological effects of e-cigarettes on tissues and organ systems, including pulmonary and cardiovascular; information on e-cigarette users, how the devices are used, and identification of the best tools to assess these measures; factors that drive use and influence patterns of use; and appropriate methods for evaluating a potential role for e-cigarettes in smoking or nicotine cessation. To understand fully the challenges and the opportunities that e-cigarettes represent, expertise will be needed in basic, behavioral, translational, and clinical sciences.

E-cigarette awareness, use, and harm perceptions in Italy: a national representative survey

INTRODUCTION

Only a few studies have provided information on awareness, use, and harm perceptions of e-cigarettes in Europe. We fill the knowledge gap in Italy.

METHODS

We used data from a face-to-face survey conducted in 2013 of a sample of 3,000 individuals, representative of the Italian population aged ≥15 years (51.1 million inhabitants).

RESULTS

Awareness of e-cigarettes was 91.1%; it was lowest among women (87.8%), the elderly (78.4%), those with less education (84.1%), and never-smokers (89.0%). Ever e-cigarette use was 6.8% overall and was inversely related to age, whereas no significant difference was observed according to sex. With regard to smoking status, 2.6% of never-smokers, 7.0% of ex-smokers, and 20.4% of current smokers tried the e-cigarette at least once. Regular e-cigarette use was 1.2% overall, 1.5% among men, and 0.9% among women, and it was highest among young (2.4%) and current smokers (3.7%). Among 36 e-cigarette regular users, 22.0% did not change their smoking habit, 67.7% reduced traditional cigarette consumption, and 10.4% quit smoking.

CONCLUSIONS

After fewer than 3 years from the opening of the first Italian e-cigarette shop, more than 45 million Italians have heard about e-cigarettes, 3.5 million have tried e-cigaretts, and more than 600,000 Italians regularly use e-cigarettes. Three out of 4 e-cigarette users reported to have favorably modified their smoking habit; however, 90% of users did not quit smoking as a consequence of starting vaping e-cigarettes. Almost 900,000 Italian never-smokers, particularly young never-smokers, have tried this new and potentially addictive product at least once.

Electronic nicotine delivery systems ("e-cigarettes"): review of safety and smoking cessation efficacy

BACKGROUND AND OBJECTIVES

Cigarette smoking is common among cancer patients and is associated with negative outcomes. Electronic nicotine delivery systems ("e-cigarettes") are rapidly growing in popularity and use, but there is limited information on their safety or effectiveness in helping individuals quit smoking.

DATA SOURCES

The authors searched PubMed, Web of Science, and additional sources for published empirical data on safety and use of electronic cigarettes as an aid to quit smoking.

REVIEW METHODS

We conducted a structured search of the current literature up to and including November 2013.

RESULTS

E-cigarettes currently vary widely in their contents and are sometimes inconsistent with labeling. Compared to tobacco cigarettes, available evidence suggests that e-cigarettes are often substantially lower in toxic content, cytotoxicity, associated adverse effects, and secondhand toxicity exposure. Data on the use of e-cigarettes for quitting smoking are suggestive but ultimately inconclusive.

CONCLUSIONS

Clinicians are advised to be aware that the use of e-cigarettes, especially among cigarette smokers, is growing rapidly. These devices are unregulated, of unknown safety, and of uncertain benefit in quitting smoking.

IMPLICATIONS FOR PRACTICE

In the absence of further data or regulation, oncologists are advised to discuss the known and unknown safety and efficacy information on e-cigarettes with interested patients and to encourage patients to first try FDA-approved pharmacotherapies for smoking cessation.

Chemical evaluation of electronic cigarettes

OBJECTIVE

To review the available evidence evaluating the chemicals in refill solutions, cartridges, aerosols and environmental emissions of electronic cigarettes (e-cigarettes).

METHODS

Systematic literature searches were conducted to identify research related to e-cigarettes and chemistry using 5 reference databases and 11 search terms. The search date range was January 2007 to September 2013. The search yielded 36 articles, of which 29 were deemed relevant for analysis.

RESULTS

The levels of nicotine, tobacco-specific nitrosamines (TSNAs), aldehydes, metals, volatile organic compounds (VOCs), flavours, solvent carriers and tobacco alkaloids in e-cigarette refill solutions, cartridges, aerosols and environmental emissions vary considerably. The delivery of nicotine and the release of TSNAs, aldehydes and metals are not consistent across products. Furthermore, the nicotine level listed on the labels of e-cigarette cartridges and refill solutions is often significantly different from measured values. Phenolic compounds, polycyclic aromatic hydrocarbons and drugs have also been reported in e-cigarette refill solutions, cartridges and aerosols. Varying results in particle size distributions of particular matter emissions from e-cigarettes across studies have been observed. Methods applied for the generation and chemical analyses of aerosols differ across studies. Performance characteristics of e-cigarette devices also vary across and within brands.

CONCLUSIONS

Additional studies based on knowledge of e-cigarette user behaviours and scientifically validated aerosol generation and chemical analysis methods would be helpful in generating reliable measures of chemical quantities. This would allow comparisons of e-cigarette aerosol and traditional smoke constituent levels and would inform an evaluation of the toxicity potential of e-cigarettes.

Chemical evaluation of electronic cigarettes

OBJECTIVE

To review the available evidence evaluating the chemicals in refill solutions, cartridges, aerosols and environmental emissions of electronic cigarettes (e-cigarettes).

METHODS

Systematic literature searches were conducted to identify research related to e-cigarettes and chemistry using 5 reference databases and 11 search terms. The search date range was January 2007 to September 2013. The search yielded 36 articles, of which 29 were deemed relevant for analysis.

RESULTS

The levels of nicotine, tobacco-specific nitrosamines (TSNAs), aldehydes, metals, volatile organic compounds (VOCs), flavours, solvent carriers and tobacco alkaloids in e-cigarette refill solutions, cartridges, aerosols and environmental emissions vary considerably. The delivery of nicotine and the release of TSNAs, aldehydes and metals are not consistent across products. Furthermore, the nicotine level listed on the labels of e-cigarette cartridges and refill solutions is often significantly different from measured values. Phenolic compounds, polycyclic aromatic hydrocarbons and drugs have also been reported in e-cigarette refill solutions, cartridges and aerosols. Varying results in particle size distributions of particular matter emissions from e-cigarettes across studies have been observed. Methods applied for the generation and chemical analyses of aerosols differ across studies. Performance characteristics of e-cigarette devices also vary across and within brands.

CONCLUSIONS

Additional studies based on knowledge of e-cigarette user behaviours and scientifically validated aerosol generation and chemical analysis methods would be helpful in generating reliable measures of chemical quantities. This would allow comparisons of e-cigarette aerosol and traditional smoke constituent levels and would inform an evaluation of the toxicity potential of e-cigarettes.

Secondhand exposure to vapors from electronic cigarettes

INTRODUCTION

Electronic cigarettes (e-cigarettes) are designed to generate inhalable nicotine aerosol (vapor). When an e-cigarette user takes a puff, the nicotine solution is heated and the vapor is taken into lungs. Although no sidestream vapor is generated between puffs, some of the mainstream vapor is exhaled by e-cigarette user. The aim of this study was to evaluate the secondhand exposure to nicotine and other tobacco-related toxicants from e-cigarettes.

MATERIALS AND METHODS

We measured selected airborne markers of secondhand exposure: nicotine, aerosol particles (PM(2.5)), carbon monoxide, and volatile organic compounds (VOCs) in an exposure chamber. We generated e-cigarette vapor from 3 various brands of e-cigarette using a smoking machine and controlled exposure conditions. We also compared secondhand exposure with e-cigarette vapor and tobacco smoke generated by 5 dual users.

RESULTS

The study showed that e-cigarettes are a source of secondhand exposure to nicotine but not to combustion toxicants. The air concentrations of nicotine emitted by various brands of e-cigarettes ranged from 0.82 to 6.23 µg/m(3). The average concentration of nicotine resulting from smoking tobacco cigarettes was 10 times higher than from e-cigarettes (31.60±6.91 vs. 3.32±2.49 µg/m(3), respectively; p = .0081).

CONCLUSIONS

Using an e-cigarette in indoor environments may involuntarily expose nonusers to nicotine but not to toxic tobacco-specific combustion products. More research is needed to evaluate health consequences of secondhand exposure to nicotine, especially among vulnerable populations, including children, pregnant women, and people with cardiovascular conditions.

Electronic cigarettes and vaping: a new challenge in clinical medicine and public health. A literature review

Electronic cigarette (e-cigarette) use, or vaping, in the United States and worldwide is increasing. Their use is highly controversial from scientific, political, financial, psychological, and sociological ideologies. Given the controversial nature of e-cigarettes and vaping, how should medical care providers advise their patients? To effectively face this new challenge, health care professionals need to become more familiar with the existing literature concerning e-cigarettes and vaping, especially the scientific literature. Thus, the aim of this article is to present a review of the scientific evidence-based primary literature concerning electronic cigarettes and vaping. A search of the most current literature using the pubmed database dating back to 2008, and using electronic cigarette(s) or e-cigarette(s) as key words, yielded a total of 66 highly relevant articles. These articles primarily deal with (1) consumer-based surveys regarding personal views on vaping, (2) chemical analysis of e-cigarette cartridges, solutions, and mist, (3) nicotine content, delivery, and pharmacokinetics, and (4) clinical and physiological studies investigating the effects of acute vaping. When compared to the effects of smoking, the scant available literature suggests that vaping could be a “harm reduction” alternative to smoking and a possible means for smoking cessation, at least to the same degree as other Food and Drug Administration-approved nicotine replacement therapies. However, it is unclear if vaping e-cigarettes will reduce or increase nicotine addiction. It is obvious that more rigorous investigations of the acute and long-term health effects of vaping are required to establish the safety and efficacy of these devices; especially parallel experiments comparing the cardiopulmonary effects of vaping to smoking. Only then will the medical community be able to adequately meet the new challenge e-cigarettes and vaping present to clinical medicine and public health.

[Comparison of the aerosol produced by electronic cigarettes with conventional cigarettes and the shisha]

In previous studies of the smoke from regular cigarettes and water pipes, we measured aerosol particle sizes in three streams; S1, inhaled by the smoker, S2, released by the device itself and S3, exhaled by the smoker. We used an electrostatic low-pressure impactor (ELPI), giving particle size distributions in real time and calculated median diameters, D50, and dispersion (σg). This allowed us to predict airway deposition. In addition, the aerosol particle half-life in the air was used as a measure of the risk to others from passive smoking. With the same equipment, we measured the particle sizes and persistence in air of the liquid aerosol generated by e-cigarettes (Cigarettec®) containing water, propylene glycol and flavorings with or without nicotine. Aerosol generation was triggered by a syringe or by the inspiration of volunteer smokers. The D50 data obtained in S1, were 0.65 μm with nicotine and 0.60 μm without nicotine. Deposition in the airways could then be calculated: 26% of the total would deposit, of which 14% would reach the alveoli. These data are close to those found with regular cigarettes. For S3, D50 data were 0.34 μm and 0.29 μm with or without nicotine. The half-life in air of the S3 stream was 11 seconds due to a rapid evaporation. The-e-cigarette aerosol, as measured here, is made of particles bigger than those of cigarette and water pipe aerosols. Their deposition in the lung depends on their fate in the airways, which is unknown. Contrary to tobacco smoke, which has a half-life in air of 19 to 20 minutes, the risk of passive "smoking" exposure from e-cigarettes is modest.

Lung deposition analyses of inhaled toxic aerosols in conventional and less harmful cigarette smoke: a review

Inhaled toxic aerosols of conventional cigarette smoke may impact not only the health of smokers, but also those exposed to second-stream smoke, especially children. Thus, less harmful cigarettes (LHCs), also called potential reduced exposure products (PREPs), or modified risk tobacco products (MRTP) have been designed by tobacco manufacturers to focus on the reduction of the concentration of carcinogenic components and toxicants in tobacco. However, some studies have pointed out that the new cigarette products may be actually more harmful than the conventional ones due to variations in puffing or post-puffing behavior, different physical and chemical characteristics of inhaled toxic aerosols, and longer exposure conditions. In order to understand the toxicological impact of tobacco smoke, it is essential for scientists, engineers and manufacturers to develop experiments, clinical investigations, and predictive numerical models for tracking the intake and deposition of toxicants of both LHCs and conventional cigarettes. Furthermore, to link inhaled toxicants to lung and other diseases, it is necessary to determine the physical mechanisms and parameters that have significant impacts on droplet/vapor transport and deposition. Complex mechanisms include droplet coagulation, hygroscopic growth, condensation and evaporation, vapor formation and changes in composition. Of interest are also different puffing behavior, smoke inlet conditions, subject geometries, and mass transfer of deposited material into systemic regions. This review article is intended to serve as an overview of contributions mainly published between 2009 and 2013, focusing on the potential health risks of toxicants in cigarette smoke, progress made in different approaches of impact analyses for inhaled toxic aerosols, as well as challenges and future directions.