1. bookTom 30 (2021): Zeszyt 3 (July 2021)
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A Cross-Sectional Study of Electronic Cigarette Use Among Chinese Adult Populations in Four Cities of China. Part II. Puffing Topography

Data publikacji: 01 Oct 2021
Tom & Zeszyt: Tom 30 (2021) - Zeszyt 3 (July 2021)
Zakres stron: 149 - 157
Otrzymano: 07 May 2020
Przyjęty: 30 Aug 2021
Informacje o czasopiśmie
License
Format
Czasopismo
eISSN
2719-9509
Pierwsze wydanie
01 Jan 1992
Częstotliwość wydawania
4 razy w roku
Języki
Angielski
INTRODUCTION

As an alternative product to conventional cigarettes, consumption of E-cigarettes (ECs) has increased exponentially over the past few years among young people and adults. The popularity of ECs may in part be due to their variety of delivery types, appearances and tastes. Another reason could be the way it can be used as a support to quit smoking (1,2,3,4,5). Already many published articles have reported that the emissions of harmful compounds in ECs’ aerosol are significantly lower than that of mainstream smoke of conventional cigarettes (6,7,8). But the results based on the ISO smoking regime (9) (puff volume 55 mL, puff duration 3 s, puff interval 30 s) are less convincing due to their great deviation to the puffing parameters obtained from actual users (puff volume 45–148 mL, puff duration 1.8–5.29 s, puff interval 10–118 s) (10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27). Furthermore, due to the absence of rigorous regulation of the EC products, e.g., on the concentration of nicotine, the additives in the liquid, the electronic components etc., ECs may vary greatly among the different products, which may pose potential exposure risks to the users. Thus the risk assessment of ECs has gradually become an important factor in public opinion. As a useful tool to establish baseline smoking parameters for regulatory protocols and help to improve the risk assessment of ECs, studies on EC consumers’ puffing topography are essential and have attracted a great deal of attention in recent years.

Puffing topography involves the measurement of puff volume, duration, flow rate and interval. For conventional cigarettes, a lot of scientific work has been carried out and published (28,29,30,31), while for ECs, relevant research is still very limited, which may be due to reasons such as their newness on the market, diversity of product appearance and a lack of suitable and consistent measurement methods. Until present, mainly three methods have been applied to study the puffing topography of ECs, including video recording (10,11,12,13), use of chip-connected eVic ECs (a special kind of product that can automatically record the users’ puffing parameters) (14,15,16), and topography measurement systems (17,18,19,20,21,22,23,24,25,26,27). The video-recording method can only record puff duration and IPI, whereas the accuracy of time parameter recording is often doubtable. The connected ECs can record the time of activation of each puff as well as puff numbers, duration and time of each puff in their internal memory, but they provide no information on puff volume. By comparison, the topography measurement systems are more efficient and can completely record all puffing topography parameters. Behar et al. (17) evaluated the vaping topography of 20 EC users during 10 min ad libitum using of two types of ECs by utilizing the CReSS device. Concentrations of nicotine in the EC liquid were 16 and 18 mg/mL. The results showed that the average puff volume, puff duration and IPI of the two ECs were 51 ± 21 mL, 2.65 ± 0.98 s and 17.9 ± 7.5 s, respectively. It showed the vaping topography was different between the two ECs and different users. Cunningham et al. (21) recruited 60 EC users to evaluate the puffing topography with the modified SA-7 system device. Consumers were provided with rechargeable “cig-a-likes” or larger button-activated ECs to use ad libitum in two sessions. The results showed that user's mean puff duration was similar with both types of ECs (2.0 s and 2.2 s), but mean puff volumes (52.2 mL and 83.0 mL) and IPI (23.2 s and 29.3 s) differed significantly. Other researchers including Robinson et al. (23), Lee et al. (19), Goniewicz et al. (20), and Spindle et al. (26, 27) have also studied the puffing topography of EC users under different conditions. Coresta (32) also published a recommended method for machine-smoking of ECs in 2015. Their recommended machine-puffing parameters are 55 mL, 3 s, and 30 s for puff volume, puff duration, and IPI, respectively. There were significant differences between the various studies, for example, the average puff volume ranged from 51 to 148 mL and the average puff duration ranged from 1.8 to 5.29 s. These large differences might be ascribed to different EC types, nicotine concentrations in liquids, testing instruments and experimental designs, as well as the participants’ numbers (from 11 to 60 participants) and different populations in the various studies.

To better understand the puffing topography of EC users, much research covering more participants, different EC products and different populations are urgently required. Although ECs were first invented in China and Chinese users also increased greatly recently no puffing topography studies have been reported yet. In our study, a cross-sectional epidemiological investigation on puffing topography of 511 EC consumers in four cities of China (Beijing, Shanghai, Guangzhou and Shenzhen) was conducted in January 2018. The relationship between topography and nicotine concentration in EC liquid, as well as product type and smoking status were also studied. The results may help to better understand the puffing topography of EC users, and also may help to provide useful data for the development of smoking machine parameters of EC.

METHODS
Participants

Through the EC users’ geographical distribution and the city ranking of the Baidu Search Index (39), four cities including Beijing, Shanghai, Guangzhou and Shenzhen were chosen as the typical EC users areas in China. The study was reviewed by and received ethics clearance from the Public Health Institute of Zhengzhou University. Voluntary informed consent, confidentiality, rigorousness and authenticity were followed throughout the investigation.

In this study, 18,970 EC users were invited through both online advertisements and local EC stores. Finally, 511 users agreed to participate in this study and the final groups consisted of 82, 123, 149, and 157 volunteers from Beijing, Shanghai, Guangzhou and Shenzhen, respectively.

Eligible subjects were healthy adult EC consumers aged 18–55 who had used ECs at least on 3 days per week for more than 3 months. Exclusion criteria were: a) illicit drug abuse; b) severe depression or other psychiatric disorders; c) severe cardiovascular diseases, chronic obstructive pulmonary disease, lung cancer and other cancers. Women were excluded if they were breastfeeding or pregnant. Participants were asked to sign informed consent before being included in the study.

Method for recording the smoking behavior

The CReSS Pocket device (Version 1.0.1.2001, Borgwaldt KC Inc., Richmond, VA, USA) was used to record vaping topography.

CReSS was originally designed for measuring puffing topography when smoking cigarettes. Due to the various tank and cartomizer systems, ECs may not always be compatible to the CReSS Pocket. Thus a connector made of a silicone tube was developed to fit the different ECs. The calibration method and accuracy validation was developed in our previous work (33).

Participants attended the clinical study at the designed time to complete the computerized questionnaires, and then made at least 15 puffs with their own EC that had been connected to the CReSS Pocket. The process was video-recorded in order to verify compliance and ensure that the data had been correctly recorded. About 10% of the participants were randomly selected to verify the number of puffs recording. To mimic real-world EC use, the staff chatted with the participants before and during the topography recording process to make them relax and use ECs as usual.

Subjective questionnaires

Content of the questionnaire mainly includes three sections. The first one is on demographics and personal information, including age, gender, education, etc. The second one shows the consuming behavior of the users, including product type, nicotine content in the EC liquid, battery power, etc. The third one states their current smoking status, which was mainly used for investigating whether participants also smoked cigarettes at the same time.

Data analysis

The data was analyzed by SPSS 22.0 Demo software (SSPS Inc., Chicago, IL, USA). Tukey's test method was used to eliminate outlier values in the sample. Mean value, standard deviation (SD) and 95%-CIs of puff topography parameters were calculated. Comparison of the parameters was performed by using One Way ANOVA. The level of significance was set at p < 0.05. When the variance was homogeneous, the Least Significant Difference (LSD) method was used for the multiple comparisons between groups. In case of heterogeneity, the Dunnett's T3 was used for the multiple comparisons between groups.

RESULTS
Participant′s characteristics

In total, 511 experienced EC users were recruited in the four cities. Information on the participants is shown in Table 1. Most participants were male (90.6%) with only minor difference between the four cities. The age of the participants ranged from 18 to 62 years. 48% of them were between 19 and 29 years old, the average age was 31 years. In the city of Shenzhen, the average age was only 26 years.

Characteristics of the participants.

Characteristics Average Beijing Shanghai Guangzhou Shenzhen
Gender Male 90.6% 92.7% 84.6% 87.9% 96.8%
Gender Female 9.4% 7.3% 5.4% 12.1% 3.2%
Age Years 31 32 33 35 26

Education/degree Doctoral 0.2% 1.2% 0.0% 0.0% 0.0%
Master 1.2% 6.1% 0.8% 0.0% 0.0%
Bachelor 45.2% 67.1% 61.8% 45.6% 20.4%
Associate degree 36.0% 15.9% 29.3% 38.3% 49.7%
High school 16.8% 9.8% 8.1% 14.8% 29.3%
Other 0.6% 15.9% 29.3% 38.3% 49.7%
Vaping status

The questionnaire results (Table 2) shows that some participants had been using ECs for more than 5 years, while the shortest interval was 3 months. The majority of participants (65.3%) had used ECs for approximately 6 months to 2 years.

Consuming behavior of the participants.

Behavior Ratio (%)
Using time 3–6 months 15.7
6–12 months 30.5
1–2 years 34.8
2–3 years 11.2
3–5 years 4.7
≥5 years 3.1

EC type Cartomizer 2.9
Tank 96.1
Disposable 1.0

Nicotine concentration None 17.2
low (1–5 mg/mL) 58.3
mid (6–11 mg/mL) 15.3
high (12–20 mg/mL) 2.7
ultra high (> 20 mg/mL) 0.4
not stated 6.1

Battery power (w) 0–25 21.2
26–50 38.3
51–75 13.8
76–100 16.3
101–150 3.1
> 151 7.3

In our study, EC products can be classified into three types: a) tank ECs that are designed to be refilled with liquid by the user; b) disposable ECs; c) cartomizer ECs that are operated with prefilled cartridges which need to be replaced once emptied. The results show that most of the users (96.1%) chose the new generation of ECs that are tank systems.

The concentrations of nicotine in EC liquids were divided into 5 levels according to the product survey. These were nicotine-free (0 mg/mL), low-level (1–5 mg/mL), mid-level (6–11 mg/mL), high-level (12–20 mg/mL) and ultra high-level (> 20 mg/mL). The results in the study showed that consumers preferred ECs with low nicotine concentrations (N = 298, 58.3%), and then ECs with no nicotine (N = 88, 17.2%) and mid-nicotine (N = 78, 15.3%). Products with high nicotine levels were rarely used (N = 14, 2.7%). The average and median values of battery power of the ECs used by the consumers were 97.5 W and 80.0 W, respectively. Most consumers preferred a battery power lower than 100 W.

Smoking status

To find out whether the consumers also smoked cigarettes, the participants’ smoking status was investigated. Exclusive EC users were defined as those who used only ECs within one month before the begin of this study. Dual users are those who used ECs and cigarettes at the same time.

The findings (Table 3) show that EC users were mainly dual users, accounting for about 73.2%, and exclusive EC users were only about 26.8%. Among the exclusive EC users, 80.3% were ex-smokers, 54.6% of them ex-smokers who had quit smoking conventional cigarettes within six months past. Among the dual users, 88.2% had smoked cigarettes before using ECs, the others had never smoked before using ECs.

Smoking status of the participants.

Item Ratio (%)
Exclusive EC users 26.8
Dual EC users 73.2
Ex-smokers among exclusive EC users 80.3
No smoking before EC use among exclusive EC users 19.7
Smokers before EC using among dual EC users 88.2
No smoking before EC use among dual EC users 11.8
Puffing topography

The results of the puffing topography measurements obtained from the CReSS are shown in Table 4. In the machine-smoking protocols, parameters of puff volume, duration and IPI are mainly focused on. As opposed to cigarettes, there is no smoldering process with ECs, and the influence of smoking intervals on the aerosol delivery is slightly lower, thus puff volume and duration were our main focuses in the study.

Average puffing topography parameters of the participants.

Puffing topography (average, SD) Total Beijing Shanghai Guangzhou Shenzhen
Volume (mL) 87.2 (50.1) 67.5 (38.2) 78.5 (41.2) 91.4 (53.9) 100.4 (54.0)
Average flow (mL/s) 47.3 (19.2) 43.9 (17.8) 44.2 (19.2) 48.6 (19.6) 50.5 (18.8)
Peak flow (mL/s) 68.7 (27.6) 66.9 (26.6) 63.6 (27.9) 69.7 (28.5) 72.8 (26.3)
Duration (s) 1.97 (0.73) 1.77 (0.78) 1.92 (0.62) 1.99 (0.75) 2.09 (0.75)
IPI (s) 22.0 (79.1) 21.3 (11.7) 11.8 (6.7) 21.9 (32.8) 30.5 (11.0)
Time of peak flow (s) 0.87 (0.43) 0.7 (0.45) 0.8 (0.34) 0.9 (0.46) 1.0 (0.42)

In general, the average and median puff volume of EC users were 87.2 and 75.4 mL, respectively. The distribution of participants’ puff volumes is shown in Figure 1.

Figure 1

Distribution of puff volume of participants.

The percentages of puff volume of < 30, 30 ≤ V < 60, 60 ≤ V < 90, 90 ≤ V< 120, and ≥ 120 mL were 6.5%, 27.4%, 28.0%, 18.0% and 20.1%, respectively. Overall, puff volume of 73.4% participants was in the range of 30–120 mL.

The average puff duration was 1.97 s (0.20–4.56 s), and the median was 1.9 s. The distribution of the puff duration for the ranges of 0.2–1.0, 1.01–2.0, 2.01–3.0, 3.01–4.0 and > 4.01 s was about 7.8%, 48.2%, 34.2%, 8.8% and 1.0%, respectively. Overall, puff duration time of most participants was in the range of 2.0–4.0 s (82.4%).

Means +/− SD for IPI, average flow rate, peak flow rate and peak time were 22.0 ± 79.1 s, 47.3 ± 19.2 mL/s, 68.7 ± 27.6 mL/s and 0.87 ± 0.43 s (mean ± SD), respectively.

Data analysis showed that the two parameters (puff volume and puff duration) were significantly different when comparing Beijing to either Guangzhou or Shenzhen. For the puff volume the significance was p = 0.001 for Beijing/Guangzhou and p = 0.000 for Beijing/Shenzhen; for the puff duration the significance was p = 0.031 and p = 0.001, respectivley.

DISCUSSION
Consumption behavior of Chinese EC users

Though the EC was invented in China in 2003 (40), EC using became popular not before 2008. Our findings showed that EC consumers in the four cities were mainly young males with a bachelor's degree. The reason may be that younger consumers with higher education levels pay more attention to health, which is consistent with the low-risk claims of ECs. In terms of EC product types, most consumers preferred tank systems, which was consistent with the results of ETTER's study (34). The reason may be attributed to the fact that along with the power of the battery, the flavor of the EC liquid can be conveniently adjusted according to satisfy their individual tastes and their desire to blow smoke rings. The variety of the appearance may be another reason for the consumption for fashionable reasons. The most popular concentration of nicotine in refill liquid was found to be low among the participating EC users (1–5 mg/mL), very different from that of European and American EC consumers (7–16 mg/mL) (35). During the survey, it was found that many users initially turned to ECs due to the intention of quitting smoking and decreasing the risk of cigarette smoking. In their perception, low nicotine concentrations in the EC's liquid meant low health risk as well as low risk of addiction. This perception may be a reason that they preferred the low nicotine concentrations in the liquid.

The evaluation of the questionnaires showed that 73.2% of the participating users in the study were dual-users. It is speculated that ECs might not fully satisfy the consumer, which may be resulting from their nicotine dependence, but this would need to be proved. Among the exclusive and dual EC users, about 80.3% and 88.2%, respectively, were ex-smokers, showing that most EC users were former cigarette users, and that some consumers were able to quit smoking via the use of EC. Based on the data that showed that 19.7% consumers did not smoke cigarettes prior to start using ECs, it should be noted that ECs could also attract nonsmokers. The result showed that 11.8% of dual users had not smoked cigarettes before using ECs. This finding requires verification in future studies. In particular, the question should be addressed how many adolescent non-smokers start using ECs and then become dual users.

Puffing topography of EC consumers

In previous literature reports (17,18,19,20,21,22,23,24,25,26,27), the average puff volume, puff duration and IPI ranged from 51–148 mL, 1.8–5.29 s and 10–118 s, respectively. Contrarily, in our study the average puff volume, puff duration and IPI were found to be 87.2 mL, 1.97 s and 22.0 s, respectively. Overall, our observed values were within the reported levels. These dissimilarities may have been caused by differences in populations, experimental conditions, EC types, nicotine concentrations in the liquid, and EC battery power. As the participants were using products of their own preference, the individual differences observed in our study were relatively large.

To find out what factors may have played a role in the puffing topography of ECs, the possible influence of parameters such as product type, nicotine concentration in the EC liquid and the power of the battery for the tank ECs were analyzed. The puffing parameters for the different EC product types are given in Table 5.

The influence of EC type on the puff parameters.

Puffing topography Mean value Tank Cartomizer Disposable
Volume (mL) Average 88.6 57.5 57.4
SD 50.5 22.9 19.9

Average flow (mL/s) Average 48.0 29.5 32.2
SD 19.2 10.1 18.8

Peak flow (mL/s) Average 69.7 39.8 46.3
SD 27.6 16.1 30.2

Duration (s) Average 1.97 1.91 1.97
SD 0.74 0.57 0.75

IPI (s) Average 22.5 10.4 10.5
SD 80.6 6.2 7.5

Time of peak flow (s) Average 0.87 0.84 1.04
SD 0.43 0.43 0.63

For the different EC product systems, the results showed that participants using disposable and cartomizer systems took puff volumes of 57.4 ± 19.9 mL and 57.5 ± 22.9 mL, respectively, whereas participants using tank systems took larger puffs of 88.6 ± 50.5 mL. The results were very similar to those of Cunningham et al. (21) with puff volumes of 52.2 mL among cartomizer users and 83.0 mL among tank users. The puff durations were in the range of 1.91–1.97 s, and there were no significant differences between the three types. The average IPI of the participants with disposable and cartomizer system types were 10.5 s and 10.4 s, while for users with tank system types it was 22.5 s. The difference among the parameters needs to be readressed in a future study which should feature a higher number of users of disposable and cartomizer system types. One unambigious finding in previous investigations was that there is a substantial difference in topography patterns between experienced and naïve EC users (11, 14). In this study with experienced EC users, the influence of using time on the puffing topography was also studied (Figure 2). The average puff volumes were 85.0, 90.2, 89.9, 88.9, 62.7 and 69.9 mL for consumers using ECs for the time span of 3–6 months, 6–12 months, 1–2 years, 2–3 years, 3–5 years and above 5 years, respectively.

Figure 2

The effect of using time on the puff volume of EC consumers.

Overall, with the increase of the time span the participants used ECs, the puff volume first increased slowly, then remained stable and finally decreased notably. The results showed that there were significant differences between the puff volumes of longtime consumers of ECs of e.g., 3–5 years and and those who used ECs for shorter periods of time as e.g., 6–12 months 1–2 years, 2–3 years (p = 0.01, 0.01 and 0.03, respectively). The reason of this finding is still unclear. Puff duration did not vary with duration of use, with the average values of 2.02, 1.98, 1.96, 1.94, 1.85, 1.88 s, respectively, for users with 3–6 months, 6–12 months, 1–2 years, 2–3 years, 3–5 years and above 5 years use time.

In previous studies (36, 37), participants who switched from cigarettes with high “tar” levels to cigarettes with low “tar” levels were found to always increase their puff intensity to get the amount of nicotine they crave. In this study, the influence of nicotine concentration in EC liquid on the puffing topography was studied. Since the number of participants of ultra-high nicotine levels was too small, the participants in this group were not included in the evaluation. The results showed that participants who chose nicotine-free liquid had the highest puff volumes of 93.9 ± 59.6 mL, while the puff volumes of participants with low, medium and high nicotine levels were 90.3 ± 49.8, 76.4 ± 43.4, 65.6 ± 28.9 mL, respectively (Table 6). Data analysis results showed significant differences between the participants in the nicotine-free group and those in the medium or high nicotine groups (p = 0.025 or 0.049, respectively). The higher the concentration of nicotine in EC liquid, the smaller the users’ puff volume, which was consistent with the results of Lopez et al. (25). The puff duration and IPI were not affected by the concentration of nicotine in the liquid.

The influence of nicotine concentrations on the puff parameters.

Nicotine-free Low 1–5 mg/mL Medium 6–11 mg/mL High 12–20 mg/mL
Volume (mL) 93.9 90.3 76.4 65.6
Average flow (mL/s) 47.5 49.6 42.4 34.6
Peak flow (mL/s) 67.5 72.8 61.2 46.7
Duration (s) 2.02 1.97 1.83 2.08
IPI (s) 22.5 25.2 14.4 16.3
Time of peak flow (s) 0.82 0.87 0.87 1.11

In our study, most participants were dual, i.e., EC and cigarette, users. To investigate whether smoking would affect their vaping behavior with ECs, the puffing topographies of the exclusive and dual EC users were compared. The results showed that exclusive EC users took average puff volumes of 84.7 ± 53.3 mL, similar to that of dual-users 88.1 ± 49.0 mL (p = 0.172). Puff duration and IPI for the exclusive EC users were 1.96 s and 17.5 s, respectively. The values for the dual users were 1.9 s and 23.7 s, respectively. These differences between the two groups were statistically not significant (p = 0.824 and p = 0.353, respectively).

Based on the participant's self-reporting on the power of their used batteries, the relationship between the power of the tank-type ECs and the puffing topography parameters was also studied. The results are shown in Figure 3.

Figure 3

The effect of battery power on the puff volume of EC consumers.

No influence of the battery power on the vaping topography was observed. Farsalinos et al. found that changing the power settings of an EC device would change the puffing topography of the consumers (38). In our study, the information on the battery power of the ECs were obtained via the questionnaire, whether battery power is comparable among different products needs to be investigated in future research.

In summary, we found that EC product type and nicotine concentration in EC liquids were the main factors that affected the puffing topography of the users. A participants’ prior experience with ECs might also have played a role in the puffing topography. Thus in the future, when adjusting the smoking regime of the machine, puff volumes should be classified by EC types.

CONCLUSIONS

A puffing topography study of 511 EC consumers in four cities of China has been carried out. Behavior data were assessed by making use of a questionnaire and a CReSS smoking behavior recorder. The results show that most EC users were young males with a high education level who preferred tank-type ECs with zero or low nicotine concentrations in the liquid. Most of the EC users smoked cigarettes at the same time (dual users). As to puffing topography, the average puff volume, puff duration and IPI were 87.2 mL, 1.97 s and 22.0 s, respectively. Some factors, such as nicotine concentration of liquid and EC type significantly influenced puffing topography. Puff volumes were inversely related to nicotine concentration in the liquid. Consumers of tank-system ECs took larger puff volumes than users of disposable and cartomizer ECs. These results suggest that the EC type and the concentration of nicotine in the liquid needs to be focused on when setting the smoking regime of the machine.

Figure 1

Distribution of puff volume of participants.
Distribution of puff volume of participants.

Figure 2

The effect of using time on the puff volume of EC consumers.
The effect of using time on the puff volume of EC consumers.

Figure 3

The effect of battery power on the puff volume of EC consumers.
The effect of battery power on the puff volume of EC consumers.

Consuming behavior of the participants.

Behavior Ratio (%)
Using time 3–6 months 15.7
6–12 months 30.5
1–2 years 34.8
2–3 years 11.2
3–5 years 4.7
≥5 years 3.1

EC type Cartomizer 2.9
Tank 96.1
Disposable 1.0

Nicotine concentration None 17.2
low (1–5 mg/mL) 58.3
mid (6–11 mg/mL) 15.3
high (12–20 mg/mL) 2.7
ultra high (> 20 mg/mL) 0.4
not stated 6.1

Battery power (w) 0–25 21.2
26–50 38.3
51–75 13.8
76–100 16.3
101–150 3.1
> 151 7.3

The influence of EC type on the puff parameters.

Puffing topography Mean value Tank Cartomizer Disposable
Volume (mL) Average 88.6 57.5 57.4
SD 50.5 22.9 19.9

Average flow (mL/s) Average 48.0 29.5 32.2
SD 19.2 10.1 18.8

Peak flow (mL/s) Average 69.7 39.8 46.3
SD 27.6 16.1 30.2

Duration (s) Average 1.97 1.91 1.97
SD 0.74 0.57 0.75

IPI (s) Average 22.5 10.4 10.5
SD 80.6 6.2 7.5

Time of peak flow (s) Average 0.87 0.84 1.04
SD 0.43 0.43 0.63

Smoking status of the participants.

Item Ratio (%)
Exclusive EC users 26.8
Dual EC users 73.2
Ex-smokers among exclusive EC users 80.3
No smoking before EC use among exclusive EC users 19.7
Smokers before EC using among dual EC users 88.2
No smoking before EC use among dual EC users 11.8

The influence of nicotine concentrations on the puff parameters.

Nicotine-free Low 1–5 mg/mL Medium 6–11 mg/mL High 12–20 mg/mL
Volume (mL) 93.9 90.3 76.4 65.6
Average flow (mL/s) 47.5 49.6 42.4 34.6
Peak flow (mL/s) 67.5 72.8 61.2 46.7
Duration (s) 2.02 1.97 1.83 2.08
IPI (s) 22.5 25.2 14.4 16.3
Time of peak flow (s) 0.82 0.87 0.87 1.11

Average puffing topography parameters of the participants.

Puffing topography (average, SD) Total Beijing Shanghai Guangzhou Shenzhen
Volume (mL) 87.2 (50.1) 67.5 (38.2) 78.5 (41.2) 91.4 (53.9) 100.4 (54.0)
Average flow (mL/s) 47.3 (19.2) 43.9 (17.8) 44.2 (19.2) 48.6 (19.6) 50.5 (18.8)
Peak flow (mL/s) 68.7 (27.6) 66.9 (26.6) 63.6 (27.9) 69.7 (28.5) 72.8 (26.3)
Duration (s) 1.97 (0.73) 1.77 (0.78) 1.92 (0.62) 1.99 (0.75) 2.09 (0.75)
IPI (s) 22.0 (79.1) 21.3 (11.7) 11.8 (6.7) 21.9 (32.8) 30.5 (11.0)
Time of peak flow (s) 0.87 (0.43) 0.7 (0.45) 0.8 (0.34) 0.9 (0.46) 1.0 (0.42)

Characteristics of the participants.

Characteristics Average Beijing Shanghai Guangzhou Shenzhen
Gender Male 90.6% 92.7% 84.6% 87.9% 96.8%
Gender Female 9.4% 7.3% 5.4% 12.1% 3.2%
Age Years 31 32 33 35 26

Education/degree Doctoral 0.2% 1.2% 0.0% 0.0% 0.0%
Master 1.2% 6.1% 0.8% 0.0% 0.0%
Bachelor 45.2% 67.1% 61.8% 45.6% 20.4%
Associate degree 36.0% 15.9% 29.3% 38.3% 49.7%
High school 16.8% 9.8% 8.1% 14.8% 29.3%
Other 0.6% 15.9% 29.3% 38.3% 49.7%

Hajek, P., J.F. Etter, N. Benowitz, T. Eissenberg, and H. McRobbie: Electronic Cigarettes: Review of Use, Content, Safety, Effects on Smokers and Potential for Harm and Benefit; Addiction 109 (2014) 1801–1810. DOI: 10.1111/add.12659 HajekP. EtterJ.F. BenowitzN. EissenbergT. McRobbieH. Electronic Cigarettes: Review of Use, Content, Safety, Effects on Smokers and Potential for Harm and Benefit Addiction 109 2014 1801 1810 10.1111/add.12659448778525078252 Otwórz DOISearch in Google Scholar

Corey, C., B.G. Wang, S.E. Johnson, B. Apelberg, C. Husten, B.A. King, T.A. McAfee, R. Bunnell, R.A. Arrazola, and S.R. Dube: Electronic Cigarette Use Among Middle and High School Students - United States, 2011–2012. Morb. Mortal. Wkly. Rep. 62 (2013) 729–730. CoreyC. WangB.G. JohnsonS.E. ApelbergB. HustenC. KingB.A. McAfeeT.A. BunnellR. ArrazolaR.A. DubeS.R. Electronic Cigarette Use Among Middle and High School Students - United States, 2011–2012 Morb. Mortal. Wkly. Rep. 62 2013 729 730 Search in Google Scholar

King, B.A., S. Alam, G. Promoff, R.A. Arrazola, and S.R. Dube: Awareness and Ever-Use of Electronic Cigarettes Among U.S. Adults, 2010–2011; Nicotine Tob. Res.15 (2013) 1623–1627. DOI: 10.1093/ntr/ntt013 KingB.A. AlamS. PromoffG. ArrazolaR.A. DubeS.R. Awareness and Ever-Use of Electronic Cigarettes Among U.S. Adults, 2010–2011 Nicotine Tob. Res. 15 2013 1623 1627 10.1093/ntr/ntt013457056123449421 Otwórz DOISearch in Google Scholar

Zhu, S.H., Y.L. Zhuang, S. Wong, S.E. Cummins, and G.J. Tedeschi: E-Cigarette Use and Associated Changes in Population Smoking Cessation: Evidence from U.S. Current Population Surveys; BMJ 358 (2017) j3262. DOI: 10.1136/bmj.j3262 ZhuS.H. ZhuangY.L. WongS. CumminsS.E. TedeschiG.J. E-Cigarette Use and Associated Changes in Population Smoking Cessation: Evidence from U.S. Current Population Surveys BMJ 358 2017 j3262 10.1136/bmj.j3262 552604628747333 Otwórz DOISearch in Google Scholar

Levy, D.T., Z. Yuan, Y. Luo, and D.B. Abrams: The Relationship of E-Cigarette Use to Cigarette Quit Attempts and Cessation: Insights From a Large, Nationally Representative U.S. Survey; Nicotine Tob. Res. 20 (2018) 931–939. DOI: 10.1093/ntr/ntx166 LevyD.T. YuanZ. LuoY. AbramsD.B. The Relationship of E-Cigarette Use to Cigarette Quit Attempts and Cessation: Insights From a Large, Nationally Representative U.S. Survey Nicotine Tob. Res. 20 2018 931 939 10.1093/ntr/ntx166 603710629059341 Otwórz DOISearch in Google Scholar

Tayyarah, R. and G.A. Long: Comparison of Select Analytes in Aerosol From E-Cigarettes With Smoke From Conventional Cigarettes and With Ambient Air; Regul. Toxicol. Pharmacol. 70 (2014) 704–710. DOI: 10.1016/j.yrtph.2014.10.010 TayyarahR. LongG.A. Comparison of Select Analytes in Aerosol From E-Cigarettes With Smoke From Conventional Cigarettes and With Ambient Air Regul. Toxicol. Pharmacol. 70 2014 704 710 10.1016/j.yrtph.2014.10.010 25444997 Otwórz DOISearch in Google Scholar

Goniewicz, M.L., J. Knysak, M. Gawron, L. Kosmider, A. Sobczak, J. Kurek, A. Prokopowicz, M. Jablonska-Czapla, C. Rosik-Dulewska, C. Havel, P. Jacob III, and N. Benowitz: Levels of Selected Carcinogens and Toxicants in Vapour From Electronic Cigarettes; Tob. Control 23 (2014) 133–139. DOI: 10.1136/tobaccocontrol-2012-050859 GoniewiczM.L. KnysakJ. GawronM. KosmiderL. SobczakA. KurekJ. ProkopowiczA. Jablonska-CzaplaM. Rosik-DulewskaC. HavelC. JacobP.III BenowitzN. Levels of Selected Carcinogens and Toxicants in Vapour From Electronic Cigarettes Tob. Control 23 2014 133 139 10.1136/tobaccocontrol-2012-050859 415447323467656 Otwórz DOISearch in Google Scholar

Gualano, M.R, S. Passi, F. Bert, G. La Torre, G. Scaioli, and R. Siliquini: Electronic Cigarettes: Assessing the Efficacy and the Adverse Effects Through a Systematic Review of Published Studies; J. Public Health. 37 (2015) 488–497. DOI: 10.1093/pubmed/fdu055 GualanoM.R PassiS. BertF. La TorreG. ScaioliG. SiliquiniR. Electronic Cigarettes: Assessing the Efficacy and the Adverse Effects Through a Systematic Review of Published Studies J. Public Health. 37 2015 488 497 10.1093/pubmed/fdu055 25108741 Otwórz DOISearch in Google Scholar

International Organization for Standardization (ISO): ISO 20768:2018 Vapour Products – Routine Analytical Vaping Machine – Definitions and Standard Conditions; ISO, Geneva, Switzerland, 2018. Available at: https://www.iso.org/standard/69019.html International Organization for Standardization (ISO) ISO 20768:2018 Vapour Products – Routine Analytical Vaping Machine – Definitions and Standard Conditions ISO Geneva, Switzerland 2018 Available at: https://www.iso.org/standard/69019.html Search in Google Scholar

Hua, M., H. Yip, and P. Talbot: Mining Data on Usage of Electronic Nicotine Delivery Systems (ENDS) From YouTube Videos; Tob. Control 22 (2013) 103–106. DOI: 10.1136/tobaccocontrol-2011-050226 HuaM. YipH. TalbotP. Mining Data on Usage of Electronic Nicotine Delivery Systems (ENDS) From YouTube Videos Tob. Control 22 2013 103 106 10.1136/tobaccocontrol-2011-050226 22116832 Otwórz DOISearch in Google Scholar

Farsalinos, K.E, G. Romagna, D.S. Kyrzopoulos, D. Tsiapras, and V. Voudris: Evaluation of Electronic Cigarette Use (Vaping) Topography and Estimation of Liquid Consumption: Implications for Research Protocol Standards Definition and for Public Health Authorities’ Regulation; Int. J. Environ. Res. Public Health 10 (2013) 2500–2514. DOI: 10.3390/ijerph10062500 FarsalinosK.E RomagnaG. KyrzopoulosD.S. TsiaprasD. VoudrisV. Evaluation of Electronic Cigarette Use (Vaping) Topography and Estimation of Liquid Consumption: Implications for Research Protocol Standards Definition and for Public Health Authorities’ Regulation Int. J. Environ. Res. Public Health 10 2013 2500 2514 10.3390/ijerph10062500 371774923778060 Otwórz DOISearch in Google Scholar

Strasser, A.A., V. Souprountchouk, A. Kaufmann, S. Blazekovic, F. Leone, N.L. Benowitz, and R.A Schnoll: Nicotine Replacement, Topography, and Smoking Phenotypes of E-Cigarettes; Tob. Regul. Sci. 2 (2016) 352–362. DOI: 10.18001/TRS.2.4.7 StrasserA.A. SouprountchoukV. KaufmannA. BlazekovicS. LeoneF. BenowitzN.L. SchnollR.A Nicotine Replacement, Topography, and Smoking Phenotypes of E-Cigarettes Tob. Regul. Sci. 2 2016 352 362 10.18001/TRS.2.4.7 514262627942543 Otwórz DOISearch in Google Scholar

St.Helen, G., K.C. Ross, D.A. Dempsey, C.M. Havel, P. Jacob III, and N.L. Benowitz: Nicotine Delivery and Vaping Behavior During ad Libitum E-Cigarette Access; Tob. Regul. Sci. 2 (2016) 363–376. DOI: 10.18001/TRS.2.4.8. St.HelenG. RossK.C. DempseyD.A. HavelC.M. JacobP.III BenowitzN.L. Nicotine Delivery and Vaping Behavior During ad Libitum E-Cigarette Access Tob. Regul. Sci. 2 2016 363 376 10.18001/TRS.2.4.8 538182128393086 Otwórz DOISearch in Google Scholar

Farsalinos, K.E., A. Spyrou, C. Stefopoulos, K. Tsimopoulou, P. Kourkoveli, D. Tsiapras, S. Kyrzopoulos, K. Poulas, and V. Voudris: Nicotine Absorption From Electronic Cigarette Use: Comparison Between Experienced Consumers (Vapers) and Naïve Users (Smokers); Sci. Rep. 5 (2015) 11269. DOI:10.1038/srep11269 FarsalinosK.E. SpyrouA. StefopoulosC. TsimopoulouK. KourkoveliP. TsiaprasD. KyrzopoulosS. PoulasK. VoudrisV. Nicotine Absorption From Electronic Cigarette Use: Comparison Between Experienced Consumers (Vapers) and Naïve Users (Smokers) Sci. Rep. 5 2015 11269 10.1038/srep11269 446996626082330 Otwórz DOISearch in Google Scholar

Dawkins, L.E, C.F. Kimber, M. Doig, C. Feyerabend, and O. Corcoran: Self-Titration by Experienced E-Cigarette Users: Blood Nicotine Delivery and Subjective Effects; Psychopharmacology 233 (2016) 2933–2941. DOI: 10.1007/s00213-016-4338-2 DawkinsL.E KimberC.F. DoigM. FeyerabendC. CorcoranO. Self-Titration by Experienced E-Cigarette Users: Blood Nicotine Delivery and Subjective Effects Psychopharmacology 233 2016 2933 2941 10.1007/s00213-016-4338-2 27235016 Otwórz DOISearch in Google Scholar

Dautzenberg, B. and D. Bricard: Real-Time Characterization of E-Cigarettes Use: The 1 Million Puffs Study; J. Addict. Res. Ther. 6 (2015) 229–234. DOI: 10.4172/2155-6105.1000229 DautzenbergB. BricardD. Real-Time Characterization of E-Cigarettes Use: The 1 Million Puffs Study J. Addict. Res. Ther. 6 2015 229 234 10.4172/2155-6105.1000229 Otwórz DOISearch in Google Scholar

Behar, R.Z., M. Hua, and P. Talbot: Puffing Topography and Nicotine Intake of Electronic Cigarette Users; PLoS ONE 10 (2015) e0117222. DOI: 10.1371/journal.pone.0117222 BeharR.Z. HuaM. TalbotP. Puffing Topography and Nicotine Intake of Electronic Cigarette Users PLoS ONE 10 2015 e0117222 10.1371/journal.pone.0117222 432184125664463 Otwórz DOISearch in Google Scholar

Norton, K.J., K.M. June, and R.J. O’Connor: Initial Puffing Behaviors and Subjective Responses Differ Between an Electronic Nicotine Delivery System and Traditional Cigarettes; Tob. Induc. Dis. 12 (2014) 17. DOI: 10.1186/1617-9625-12-17 NortonK.J. JuneK.M. O’ConnorR.J. Initial Puffing Behaviors and Subjective Responses Differ Between an Electronic Nicotine Delivery System and Traditional Cigarettes Tob. Induc. Dis. 12 2014 17 10.1186/1617-9625-12-17 419945825324711 Otwórz DOISearch in Google Scholar

Lee, Y.H., M. Gawron, and M,L. Goniewicz: Changes in Puffing Behavior Among Smokers who Switched From Tobacco to Electronic Cigarettes; Addict. Behav. 48 (2015) 1–4. DOI: 10.1016/j.addbeh.2015.04.003 LeeY.H. GawronM. GoniewiczM,L. Changes in Puffing Behavior Among Smokers who Switched From Tobacco to Electronic Cigarettes Addict. Behav. 48 2015 1 4 10.1016/j.addbeh.2015.04.003 445760825930009 Otwórz DOISearch in Google Scholar

Goniewicz, M.L., T. Kuma, M. Gawron, J. Knysak, and L. Kosmider: Nicotine Levels in Electronic Cigarettes; Nicotine Tob. Res. 15 (2013) 158–166. DOI: 10.1093/ntr/nts103 GoniewiczM.L. KumaT. GawronM. KnysakJ. KosmiderL. Nicotine Levels in Electronic Cigarettes Nicotine Tob. Res. 15 2013 158 166 10.1093/ntr/nts103 22529223 Otwórz DOISearch in Google Scholar

Cunningham, A., S. Slayford, C. Vas, J. Gee, S. Costigan, and K. Prasad: Development, Validation and Application of a Device to Measure E-Cigarette Users’ Puffing Topography; Sci. Rep. 6 (2016) 35071. DOI: 10.1038/srep35071 CunninghamA. SlayfordS. VasC. GeeJ. CostiganS. PrasadK. Development, Validation and Application of a Device to Measure E-Cigarette Users’ Puffing Topography Sci. Rep. 6 2016 35071 10.1038/srep35071 505634027721496 Otwórz DOISearch in Google Scholar

Vansickel, A.R., J.S. Edmiston, Q. Liang, C. Duhon, C. Connell, D. Bennett, and M. Sarkar: Characterization of Puffing Topography of a Prototype Electronic Cigarette in Adult Exclusive Cigarette Smokers and Adult Exclusive Electronic Cigarette Users; Regul. Toxicol. Pharmacol. 98 (2018) 250–256. DOI: 10.1016/j.yrtph.2018.07.019 VansickelA.R. EdmistonJ.S. LiangQ. DuhonC. ConnellC. BennettD. SarkarM. Characterization of Puffing Topography of a Prototype Electronic Cigarette in Adult Exclusive Cigarette Smokers and Adult Exclusive Electronic Cigarette Users Regul. Toxicol. Pharmacol. 98 2018 250 256 10.1016/j.yrtph.2018.07.019 30053435 Otwórz DOISearch in Google Scholar

Robinson, R.J., E.C. Hensel, P.N. Morabito, and K.A. Roundtree: Electronic Cigarette Topography in the Natural Environment; PLoS ONE 10 (2015) e0129296. DOI: 10.1371/journal.pone.0129296 RobinsonR.J. HenselE.C. MorabitoP.N. RoundtreeK.A. Electronic Cigarette Topography in the Natural Environment PLoS ONE 10 2015 e0129296 10.1371/journal.pone.0129296 Otwórz DOISearch in Google Scholar

Robinson, R.J., E.C. Hensel, K.A. Roundtree, A.G. Difrancesco, J.M. Nonnemaker, and Y.O. Lee: Week Long Topography Study of Young Adults Using Electronic Cigarettes in Their Natural Environment; PLOS ONE 11 (2016) e0164038. DOI: 10.1371/journal.pone.0164038 RobinsonR.J. HenselE.C. RoundtreeK.A. DifrancescoA.G. NonnemakerJ.M. LeeY.O. Week Long Topography Study of Young Adults Using Electronic Cigarettes in Their Natural Environment PLOS ONE 11 2016 e0164038 10.1371/journal.pone.0164038 Otwórz DOISearch in Google Scholar

Lopez, A.A., M.M. Hiler, E.K. Soule, C.P. Ramôa, N.V. Karaoghlanian, T. Lipato, A.B. Breland, A.L. Shihadeh, and T. Eissenberg: Effects of Electronic Cigarette Liquid Nicotine Concentration on Plasma Nicotine and Puff Topography in Tobacco Cigarette Smokers: A Preliminary Report; Nicotine Tob. Res. 18 (2016) 720–723. DOI: 10.1093/ntr/ntv182 LopezA.A. HilerM.M. SouleE.K. RamôaC.P. KaraoghlanianN.V. LipatoT. BrelandA.B. ShihadehA.L. EissenbergT. Effects of Electronic Cigarette Liquid Nicotine Concentration on Plasma Nicotine and Puff Topography in Tobacco Cigarette Smokers: A Preliminary Report Nicotine Tob. Res. 18 2016 720 723 10.1093/ntr/ntv182 Otwórz DOISearch in Google Scholar

Spindle, T.R., A.B. Breland, N.V. Karaoghlanian, A.L. Shihadeh, and T. Eissenberg: Preliminary Results of an Examination of Electronic Cigarette User Puff Topography: The Effect of a Mouthpiece-Based Topography Measurement Device on Plasma Nicotine and Subjective Effects; Nicotine Tob. Res. 17 (2015) 142–149. DOI: 10.1093/ntr/ntu186 SpindleT.R. BrelandA.B. KaraoghlanianN.V. ShihadehA.L. EissenbergT. Preliminary Results of an Examination of Electronic Cigarette User Puff Topography: The Effect of a Mouthpiece-Based Topography Measurement Device on Plasma Nicotine and Subjective Effects Nicotine Tob. Res. 17 2015 142 149 10.1093/ntr/ntu186 Otwórz DOISearch in Google Scholar

Spindle, T.R, MM. Hiler, A.B. Breland, N.V. Karaoghlanian, A.L. Shihadeh, and T. Eissenberg: The Influence of a Mouthpiece-Based Topography Measurement Device on Electronic Cigarette User's Plasma Nicotine Concentration, Heart Rate, and Subjective Effects Under Directed and ad Libitum Use Conditions; Nicotine Tob. Res. 19 (2017) 469–476. DOI: 10.1093/ntr/ntw174 SpindleT.R HilerMM. BrelandA.B. KaraoghlanianN.V. ShihadehA.L. EissenbergT. The Influence of a Mouthpiece-Based Topography Measurement Device on Electronic Cigarette User's Plasma Nicotine Concentration, Heart Rate, and Subjective Effects Under Directed and ad Libitum Use Conditions Nicotine Tob. Res. 19 2017 469 476 10.1093/ntr/ntw174 Otwórz DOISearch in Google Scholar

Chung, S., S.S. Kim, N. Kini, H.J. Fang, D. Kalman, and D.M. Ziedonis: Smoking Topography in Korean American and White Men: Preliminary Findings; J. Immigr. Minor. Health 17 (2015) 860–866. DOI: 10.1007/s10903-013-9921-6 ChungS. KimS.S. KiniN. FangH.J. KalmanD. ZiedonisD.M. Smoking Topography in Korean American and White Men: Preliminary Findings J. Immigr. Minor. Health 17 2015 860 866 10.1007/s10903-013-9921-6 Otwórz DOISearch in Google Scholar

Perkins, K.A., J.L. Karelitz, G.E. Giedgowd, and C.A. Conklin: The Reliability of Puff Topography and Subjective Responses During ad lib Smoking of a Single Cigarette; Nicotine Tob. Res. 14 (2012) 490–494. DOI: 10.1093/ntr/ntr150 PerkinsK.A. KarelitzJ.L. GiedgowdG.E. ConklinC.A. The Reliability of Puff Topography and Subjective Responses During ad lib Smoking of a Single Cigarette Nicotine Tob. Res. 14 2012 490 494 10.1093/ntr/ntr150 Otwórz DOISearch in Google Scholar

June, K.M., K.J. Norton, V.W. Rees, and R.J. O’Connor: Influence of Measurement Setting and Home Smoking Policy on Smoking Topography; Addict. Behav. 37 (2012) 42–46. DOI: 10.1016/j.addbeh.2011.07.039 JuneK.M. NortonK.J. ReesV.W. O’ConnorR.J. Influence of Measurement Setting and Home Smoking Policy on Smoking Topography Addict. Behav. 37 2012 42 46 10.1016/j.addbeh.2011.07.039 Otwórz DOISearch in Google Scholar

Pickworth, W.B., Z.R. Rosenberry, K.E. O’Grady, and B. Koszowski: Dual Use of Cigarettes, Little Cigars, Cigarillos, and Large Cigars: Smoking Topography and Toxicant Exposure; Tob. Regul. Sci. Suppl 1 (2017) S72–S83. DOI: 10.18001/trs.3.2(suppl1).8 PickworthW.B. RosenberryZ.R. O’GradyK.E. KoszowskiB. Dual Use of Cigarettes, Little Cigars, Cigarillos, and Large Cigars: Smoking Topography and Toxicant Exposure Tob. Regul. Sci. Suppl 1 2017 S72 S83 10.18001/trs.3.2(suppl1).8 Otwórz DOISearch in Google Scholar

Cooperation Center for Scientific Research Relative to Tobacco (CORESTA): CORESTA Recommended Method No. 81: Routine Analytical Machine for E-Cigarette Aerosol Generation and Collection - Definitions and Standard Conditions; (2015). Available at: https://www.coresta.org/routine-analytical-machine-e-cigarette-aerosol-generation-and-collection-definitions-and-standard (accessed July 2021) Cooperation Center for Scientific Research Relative to Tobacco (CORESTA) CORESTA Recommended Method No. 81: Routine Analytical Machine for E-Cigarette Aerosol Generation and Collection - Definitions and Standard Conditions 2015 Available at: https://www.coresta.org/routine-analytical-machine-e-cigarette-aerosol-generation-and-collection-definitions-and-standard (accessed July 2021) Search in Google Scholar

Xu, B.X., G. Zhao, J.W. Zhao, X. Li, H. Wang, L.T. Xu, Y.C. Zhang, S.J. Zheng, G.X. Peng, and F.W. Xie: Method to Determine Puffing Volume Taken by E-Cigarette Consumer; Tob. Sci. Technol. 51 (2018) 70–76. DOI: 10.16135/j.issn 1002-0861.2018.0040 XuB.X. ZhaoG. ZhaoJ.W. LiX. WangH. XuL.T. ZhangY.C. ZhengS.J. PengG.X. XieF.W. Method to Determine Puffing Volume Taken by E-Cigarette Consumer Tob. Sci. Technol. 51 2018 70 76 10.16135/j.issn 1002-0861.2018.0040 Otwórz DOISearch in Google Scholar

Etter, J.F.: Characteristics of Users and Usage of Different Types of Electronic Cigarettes: Findings From an Online Survey; Addiction 111 (2015) 724–733. DOI: 10.1111/add.13240 EtterJ.F. Characteristics of Users and Usage of Different Types of Electronic Cigarettes: Findings From an Online Survey Addiction 111 2015 724 733 10.1111/add.13240 26597453 Otwórz DOISearch in Google Scholar

Farsalinos, K.E., G. Romagna, D. Tsiapras, S. Kyrzopoulos, and V. Voudris: Characteristics, Perceived Side Effects and Benefits of Electronic Cigarette Use: A Worldwide Survey of More than 19,000 Consumers; Int. J. Environ. Res. Public Health 11 (2014) 4356–4373. DOI: 10.3390/ijerph110404356 FarsalinosK.E. RomagnaG. TsiaprasD. KyrzopoulosS. VoudrisV. Characteristics, Perceived Side Effects and Benefits of Electronic Cigarette Use: A Worldwide Survey of More than 19,000 Consumers Int. J. Environ. Res. Public Health 11 2014 4356 4373 10.3390/ijerph110404356 402502424758891 Otwórz DOISearch in Google Scholar

Kozlowski, L.T. and R.J. O’Connor: Cigarette Filter Ventilation is a Defective Design Because of Misleading Taste, Bigger Puffs, and Blocked Vents; Tob. Control 11 (2002) I40–150. DOI: 10.1136/tc.11.suppl_1.i40 KozlowskiL.T. O’ConnorR.J. Cigarette Filter Ventilation is a Defective Design Because of Misleading Taste, Bigger Puffs, and Blocked Vents Tob. Control 11 2002 I40 150 10.1136/tc.11.suppl_1.i40 176606111893814 Otwórz DOISearch in Google Scholar

Sutton, S.R., M.A. Russell, R. Iyer, C. Feyerabend, and Y. Saloojee: Relationship Between Cigarette Yields, Puffing Patterns, and Smoke Intake: Evidence for Tar compensation?; Brit. Med. J. (Clin Res Ed) 285 (1982) 600–603. DOI: 10.1136/bmj.285.6342.600 SuttonS.R. RussellM.A. IyerR. FeyerabendC. SaloojeeY. Relationship Between Cigarette Yields, Puffing Patterns, and Smoke Intake: Evidence for Tar compensation? Brit. Med. J. (Clin Res Ed) 285 1982 600 603 10.1136/bmj.285.6342.600 14994436819031 Otwórz DOISearch in Google Scholar

Farsalinos, K., K. Poulas, and V. Voudris: Changes in Puffing Topography and Nicotine Consumption Depending on the Power Setting of Electronic Cigarettes; Nicotine Tob. Res. 20 (2018) 993–997. DOI: 10.1093/ntr/ntx219 FarsalinosK. PoulasK. VoudrisV. Changes in Puffing Topography and Nicotine Consumption Depending on the Power Setting of Electronic Cigarettes Nicotine Tob. Res. 20 2018 993 997 10.1093/ntr/ntx219 29059377 Otwórz DOISearch in Google Scholar

Vaughan, L. and Y. Chen: Data Mining From Web Search Queries: A Comparison of Google Trends and Baidu Index; J. Assn. Inf. Sci. Tec. 66 (2015) 13–22. DOI: 10.1002/asi.23201 VaughanL. ChenY. Data Mining From Web Search Queries: A Comparison of Google Trends and Baidu Index J. Assn. Inf. Sci. Tec. 66 2015 13 22 10.1002/asi.23201 Otwórz DOISearch in Google Scholar

Cooperation Center for Scientific Research Relative to Tobacco (CORESTA): A Brief Description of History, Operation and Regulation; CORESTA E-Cigarette Task Force, Reference Report, February 2014. Available at: https://www.coresta.org/e-cigarettes-brief-description-history-operation-and-regulation-29234.html (accessed July 2021) Cooperation Center for Scientific Research Relative to Tobacco (CORESTA) A Brief Description of History, Operation and Regulation; CORESTA E-Cigarette Task Force, Reference Report February 2014 Available at: https://www.coresta.org/e-cigarettes-brief-description-history-operation-and-regulation-29234.html (accessed July 2021) Search in Google Scholar

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