Video Abstract

Video Abstract

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OBJECTIVES

We assessed awareness and perceptions of, information sources about, and engagement in modifying electronic nicotine delivery systems (ENDS) among adolescents and young adults (AYAs).

METHODS

AYAs (N = 1018) endorsing past-month ENDS use completed a survey on awareness and use of the following modifications: (1) refilling rechargeable cartridges/pods or (2) disposable pods, (3) rewicking or (4) recharging disposable pods, (5) modifying nicotine e-liquids (eg, changing propylene glycol/vegetable glycerin, nicotine), (6) combining nicotine and cannabis for simultaneous vaping, and (7) putting cannabis in ENDS designed for nicotine vaping. Logistic regression assessed how sources of information (eg, friends, social media, nonsocial media Web sites, vape shops) about and perceptions of ENDS modifications associated with ENDS modifications.

RESULTS

Refilling (69.0% heard, 40.1% tried) and recharging the battery (66.4% heard, 35.8% tried) of disposable pods were most common. Friends (64.4%) and social media (46.7%) were the most common sources of information. Notable significant associations between information sources and modifications were: 1. nonsocial media Web sites and vape shops with rewicking and recharging disposable devices and modifying nicotine e-liquid; 2. nonsocial media Web sites with refilling rechargeable cartridges/pods and disposable pods; and 3. social media with recharging disposable devices and mixing nicotine and cannabis liquids. Perceptions of reduced harm and “coolness” were associated with various modifications.

DISCUSSION

AYAs are aware of and modify ENDS for purposes unintended by manufacturers. ENDS policies should consider unintended ENDS use to safeguard public health. Prevention efforts should communicate about the potential harms of ENDS modifications.

What’s Known on This Subject:

Adolescents and young adults (AYAs) find the ability to modify or ‘hack’ electronic nicotine delivery systems (ENDS) appealing. However, scientific knowledge of awareness and perceptions of, sources of information about, and actual engagement in ENDS modifications among AYAs is lacking.

What this Study Adds:

AYAs learn about modifying ENDS through various sources such as friends and digital media, and are aware of and engage in ENDS modifications. Perceptions of reduced harm and “coolness” were associated with modifying ENDS.

Adolescents and young adults (AYAs) are the primary users of electronic nicotine delivery systems (ENDS), with 10.0% of US high school-aged adolescents reporting current use (ie, past-month ENDS),1 and 11.0% of US young adults (aged 18–24 years) reporting ENDS use on “some days” or “every day.”2 Understanding the appeal of ENDS is important for preventing AYA use. Despite mounting evidence that the ability to “hack” or modify ENDS products appeals to youth,3,4 there is lack of scientific understanding regarding AYAs’ awareness, perceptions, sources of information, and engagement in ENDS modifications.

AYAs’ device preferences have evolved over time. Initially, there was a preference for customizable devices (eg, mods),5 but this evolved toward devices not designed for modification, such as pod mods. Pod mod brand JUUL became the most-used ENDS brand among youth by 2019.6,7 In 2022, the most commonly used devices among youth were disposable pods (46%), followed by prefilled or refillable pods or cartridges (22%), and tanks or mods (10%).8 The rising popularity of disposable pods raises concerns because of increased nicotine concentrations, larger volumes (eg, thousands of puffs included in a device), and affordability.9,10 

Little is known about the potential manipulation of these nonmodifiable devices by AYAs. Digital media, including social media platforms and nonsocial media Web sites (eg, retailer Web sites, search engines like Google, informational Web sites) commonly feature tutorials on ENDS modifications.11–13 Given AYAs’ interest in ENDS customization3 and the abundance of digital media content showcasing ENDS “hacking” and unintended uses,11–13 a closer examination of ENDS modifications is warranted. Modifications may include refilling a disposable pod or a rechargeable cartridge/pod that is not designed to be refilled; rewicking a disposable pod/cartridge; recharging the battery of a disposable device that is not designed to be recharged; mixing, creating, or changing nicotine e-liquids; mixing nicotine and cannabis liquids; and vaping exclusively cannabis/tetrahydrocannabinol liquid in devices designed to vape nicotine.13 Understanding modifications to ENDS is crucial, because these behaviors can expose AYAs to additional harm through increased risk of burns from devices exploding,14 lung injury because of e-liquid contaminants,15 and exposure to substances like cannabis.16 Modifications may also undermine any policies regarding these products. For instance, policies restricting certain flavors may be undermined if individuals are mixing their own e-liquid solutions and hacking the devices to use restricted flavors to bypass flavor restrictions.

Reasons for ENDS modifications include altering e-liquid flavors and nicotine concentrations, saving money, extending device life, and incorporating cannabis products for perceived health benefits and/or discreet use.13,17 However, limited knowledge exists on how AYAs learn about, perceive, and engage in these modifications. Identifying information sources (eg, friends, social media, nonsocial media Web sites, vape shops) is important for informing ENDS prevention and regulation efforts. Understanding AYA perceptions of ENDS modifications (eg, cool, harmful) is important, because these perceptions are determinants of use behaviors.3,4,18 Thus, we assessed sources of information, awareness, engagement, and perceptions of ENDS modifications, and associations with engagement. Additionally, we assessed age-related differences (<21 or ≥21 years [the legal age to purchase ENDS in the United States]) to understand the potential differential risk of engaging in ENDS modifications.

Qualtrics Online Sample, a secure market research service operated by Qualtrics, Inc, recruited participants (N = 1018) from their panels who fit the eligibility criteria (ie, individuals between ages 14 and 29 years who had used ENDS at least 1 day in the past month) to complete a 20-minute online survey in November 2022 to February 2023. Quotas were set to ensure representation by sex (∼50% male/female), race and ethnicity based on the US Census, and geographic location in the United States (ie, 30% Northeast, 30% West, 20% South, 20% Midwest).19,20 All participants consented (aged 18–29 years) or assented (aged 14–17 years) before starting the study. To ensure data quality, all participants (N = 1018) successfully passed an attention check question embedded in the survey (386 participants failed the check and were excluded). Qualtrics, Inc directly compensated participants for study participation on the basis of their preestablished arrangements with their panelists (eg, ∼$5 in redeemable points, charitable donations, cash, airline miles). The Yale University institutional review board approved all study procedures (institutional review board #2000033834).

Awareness of ENDS Modifications

Participants reported whether they had ever heard of each modification (yes/no for each):

1. “refilling a vape pod/cartridge that is not designed to be refilled (eg, hacking a JUUL pod);”

2. “refilling a disposable vape like a Puffbar by taking it apart and adding more nicotine or nicotine-free e-liquid (not cannabis);”

3. “rewicking a pod/cartridge that is designed for 1-time use (eg, taking the cotton wick out of a JUUL pod and replacing it with a new cotton wick that you made;”

4. “recharging the battery in a disposable vape that is not designed to be recharged (eg, taking the vape apart and attaching its wires to a different power source like a stripped-down universal serial bus cord to charge it);”

5. “mixing, creating, or changing nicotine e-liquids (eg, changing propylene glycol/vegetable glycerin, flavors, nicotine level);”

6. “mixing, creating, or changing e-liquids to combine nicotine and cannabis;” and

7. “putting cannabis/tetrahydrocannabinol liquid into a vape that originally was designed to vape nicotine not cannabis.”

Sources of Information About and Engagement in ENDS Modification

Participants who reported hearing about a modification reported where they heard about it (“Where did you hear about…” select all that apply: “Friends, social media, Web sites other than social media, vape shop, other”) and whether they had tried the modification (“Did you ever try…” yes/no).

Perceptions of ENDS Modification

Participants reported on perceptions of modifying ENDS in general: “Using a device or e-liquid that has been hacked in ways that are not intended by the manufacturer is…” “unsafe,” “harmful to one's health,” “reckless,” “trendy/cool.” Response ranged from 1 = “strongly disagree” to 5 = “strongly agree.” The harm perception variables (ie, unsafe, harmful to one’s health, reckless) were highly correlated (r[1018] = 0.67 − 0.72, P values < .001), so we averaged these variables to create a composite harm variable.

ENDS Use

We assessed ever trying each ENDS product: Disposable ENDS, cig-a-like, e-hookah, vape pen, JUUL, any pod system other than JUUL, and a mod or an advanced personalized vaporizer (yes/no to each). We also assessed which device participants used most often.

Covariates Included Variables Associated With ENDS Use Among AYAs21,22: Days vaped in the past 30 days (0–30 days), past-month marijuana use (yes/no), age (14–29), sex at birth (male, female), Hispanic ethnicity (yes/no), race (yes/no for Asian American, Black, other, white). Endorsement of American Indian, Native Hawaiian/Pacific Islander, and other were combined into other category because of low endorsement <5%. We also included perceived family financial security, which is a proxy for socioeconomic status (SES) among AYAs,23 to explore whether SES status is associated with ENDS modifications, given that cost is a significant factor influencing ENDS use among AYAs4,24 (“How much money does your family have?” 1 = “not enough to get by,” 2 = “just enough to get by,” 3 = “we only have to worry about money for fun or extras,” and 4 = “we never have to worry about money”).

We conducted descriptive statistics on all study variables. We conducted χ2 tests to assess the association between engaging in each modification by age group (<21 years old versus ≥21 years old). Then, we conducted separate multivariable logistic regression models to assess the association between ever trying each modification (no/yes) with sources of information and perceptions while controlling for covariates (ie, frequency of ENDS use, marijuana use, age, sex, ethnicity, race, SES). When examining behaviors related to modifying a specific device type, we selected participants who reported ever trying that device; behaviors related to modifying disposable pods were analyzed with data from participants who reported ever using disposable pods; behaviors related to modifying rechargeable pod/cartridge devices were analyzed with participants who reported ever using rechargeable pod/cartridge devices; and modifications related to nicotine and/or cannabis liquids were analyzed with the whole sample.

Participants were 55% female, 6.0% Asian American, 16.3% Black, 19.4% Hispanic, 69.6% white, and 21.6 years old (SD 4.57). The most frequently used ENDS in our sample were disposable pods (44.4%) and rechargeable pods/cartridges (27.6%). The median days of ENDS use in the past 30 days was 20 days (interquartile range 21), and 65.6% reported past-month cannabis use (See Table 1 for all sample characteristics).

TABLE 1

Sample Characteristics

Variables%, M (SD), Median (IQR)
Source of information on ENDS modifications (select all that apply)  
 Friends 64.4% 
 Social media 46.7% 
 Nonsocial media Web sites 14.8% 
 Vape shops 11.3% 
 Perceptions of ENDS modificationa  
 Harmful (mean, SD) 3.94 (0.87) 
 Cool (Mean, SD) 2.48 (1.22) 
 Age (14–29 y old) 21.6 (4.57) 
 Sex (female) 55.0% 
Race/ethnicity  
 Asian American 6.0% 
 Black 16.3% 
 Hispanic 19.4% 
 White 69.6% 
 Otherb 16.6% 
Financial securityc 2.48 (8.01) 
Vaping frequency (d/mo; med, IQR) 20 (21) 
ENDS device most used  
 Disposable pod 44.4% 
 Rechargeable pod/cartridge 27.6% 
 Vape pen 12.8% 
 Mod 9.8% 
 Cigalike 3.2% 
 E-hookah 1.5% 
Past-mo cannabis use 65.6% 
Variables%, M (SD), Median (IQR)
Source of information on ENDS modifications (select all that apply)  
 Friends 64.4% 
 Social media 46.7% 
 Nonsocial media Web sites 14.8% 
 Vape shops 11.3% 
 Perceptions of ENDS modificationa  
 Harmful (mean, SD) 3.94 (0.87) 
 Cool (Mean, SD) 2.48 (1.22) 
 Age (14–29 y old) 21.6 (4.57) 
 Sex (female) 55.0% 
Race/ethnicity  
 Asian American 6.0% 
 Black 16.3% 
 Hispanic 19.4% 
 White 69.6% 
 Otherb 16.6% 
Financial securityc 2.48 (8.01) 
Vaping frequency (d/mo; med, IQR) 20 (21) 
ENDS device most used  
 Disposable pod 44.4% 
 Rechargeable pod/cartridge 27.6% 
 Vape pen 12.8% 
 Mod 9.8% 
 Cigalike 3.2% 
 E-hookah 1.5% 
Past-mo cannabis use 65.6% 

IQR, interquartile range; M, mean; med, median.

a

Response options: Strongly disagree = 1 to “strongly agree” = 5.

b

Other race included American Indian (4.2%), Pacific Islander (1.4%), other race (5.4%).

c

Response options: Not enough to get by = 1, just enough to get by = 2, we only have to worry about money for fun or extras = 3, and we never have to worry about money = 4, rated on a 4-point scale.

Participants were most aware of refilling rechargeable pod/cartridge devices (69.0%) and recharging disposable pod devices (66.4%). Similarly, the most tried modifications were refilling rechargeable pod/cartridge devices (40.1%) and recharging disposable pod devices (35.8%). See Fig 1 for rates of awareness and trying different ENDS modifications. We observed differences in ENDS modifications by age group. Participants <21 years old were more likely than participants ≥21 years old to report refilling rechargeable pods/cartridges (P = .03), refilling disposable pod devices (P = .04), and recharging disposable pod devices (P < .01). Participants ≥21 years old were more likely than participants <21 years old to report modifying nicotine e-liquid (P = .01), combining nicotine and cannabis liquids (P < .01), and putting cannabis liquid in devices made/marketed for nicotine use (P < .01; Fig 2). Sources of information about ENDS modifications were friends (64.4%), social media (46.7%), nonsocial media Web sites (14.8%), and vape shops (11.3%). ENDS modifications were generally seen as harmful (mean 3.94, SD 0.87), and perceptions of them being cool/trendy were neutral (mean 2.48, SD 1.22).

FIGURE 1

Awareness of and trying ENDS modifications. The percentages of refilling rechargeable pod/cartridges were derived from participants who reported ever using those devices (n = 827). The percentages of refilling, rewicking, and recharging disposable pods were derived from participants who reported ever using disposable devices (n = 885). Modifications related to nicotine and/or cannabis liquids were derived from the whole sample (N = 1018).

FIGURE 1

Awareness of and trying ENDS modifications. The percentages of refilling rechargeable pod/cartridges were derived from participants who reported ever using those devices (n = 827). The percentages of refilling, rewicking, and recharging disposable pods were derived from participants who reported ever using disposable devices (n = 885). Modifications related to nicotine and/or cannabis liquids were derived from the whole sample (N = 1018).

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FIGURE 2

Trying ENDS modification by age group. The percentages of refilling rechargeable pod/cartridges were derived from participants who reported ever using those devices (n = 827). The percentages of refilling, rewicking, and recharging disposable pods were derived from participants who reported ever using disposable devices (n = 885). Modifications related to nicotine and/or cannabis liquids were derived from the whole sample (N = 1018). Asterisks indicate P ≤ .05.

FIGURE 2

Trying ENDS modification by age group. The percentages of refilling rechargeable pod/cartridges were derived from participants who reported ever using those devices (n = 827). The percentages of refilling, rewicking, and recharging disposable pods were derived from participants who reported ever using disposable devices (n = 885). Modifications related to nicotine and/or cannabis liquids were derived from the whole sample (N = 1018). Asterisks indicate P ≤ .05.

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In the adjusted multivariable logistic regression models (Table 2), learning about ENDS modifications from friends was associated with refilling rechargeable pods/cartridges (adjusted odds ratio [aOR] 1.74, 95% confidence interval [CI] 1.20–2.53), recharging disposable pod devices (aOR 2.16, 95% CI 1.48–3.14), modifying nicotine e-liquids (aOR 1.65, 95% CI 1.13–2.41), and combining nicotine and cannabis liquids (aOR 1.57, 95% CI 1.03–2.37). Information from social media was associated with recharging disposable pod devices (aOR 1.47, 95% CI 1.06–2.04) and combining nicotine and cannabis liquids (aOR 1.46, 95% CI 1.01–2.11). Information from nonsocial media Web sites and vape shops was associated with rewicking pods/cartridges (Web sites: aOR 2.05, 95% CI 1.31–3.20; vape shops: aOR 2.45, 95% CI 1.31–3.20), recharging disposable devices (Web sites: aOR 1.58, 95% CI 1.06–2.04; vape shops: aOR 2.04, 95% CI 1.2–3.35), and modifying nicotine e-liquids (Web sites aOR 1.94, 95% CI 1.29–2.92; vape shops: aOR 2.25, 95% CI 1.42–3.56). Information from nonsocial media Web sites also was associated with refilling rechargeable pods/cartridges (aOR 1.89, 95% CI 1.26–2.85) and disposable pod devices (aOR 1.71, 95% CI 1.11–2.63). Information from vape shops was associated with combining nicotine and cannabis liquids (aOR 2.42, 95% CI 1.48–3.95). Additionally, low-harm perceptions and perceptions of “coolness” were associated with most modifications (Table 2). Additionally, vaping more frequently and past-month cannabis use were associated with most modifications (Table 2).

TABLE 2

Adjusted Multivariable Logistic Regression Analyses

VariablesaOR (95% CI)
Refill Rechargeable Pods/Cartridges (n = 827)Refill Disposable Pods (n = 885)Rewick Disposable Pods/Cartridges (n = 885)Recharge Disposables (n = 885)Modify Nicotine E-Liquid (n = 1018)Combine Nicotine and Cannabis Liquid (n = 1018)Put Cannabis in Nicotine Device (n = 1018)
Source of information 
 Friends 10.74 (1.20–2.53) 1.42 (0.95–2.11) 1.33 (0.87–2.04) 2.16 (1.48–3.14) 10.65 (1.13–2.41) 1.57 (1.03–2.37) 1.21 (0.81–1.79) 
 Social media 1.14 (0.82–1.57) 1.36 (0.95–1.930 1.22 (0.93–1.78) 1.47 (1.06–2.04) 1.19 (0.85–1.65) 1.46 (1.01–2.11) 1.05 (0.74–1.50) 
 Nonsocial media Web sites 1.89 (1.26–2.85) 1.71 (1.11–2.63) 2.05 (1.31–3.20) 1.58 (1.06–2.04) 1.94 (1.29–2.92) 1.37 (0.87–2.17) 1.32 (0.85–2.04) 
 Vape shop 1.55 (0.95–2.54) 1.48 (0.89–2.45) 2.45 (1.47–4.09) 2.04 (1.24–3.35) 2.25 (1.42–3.56) 2.42 (1.48–3.95) 0.98 (0.59–1.61) 
  Other 1.09 (0.46–2.63) 1.81 (0.69–4.71) 2.36 (0.91–6.12) 1.62 (0.63–4.15) 1.76 (0.74–4.20) 2.51 (0.99–6.30) 1.27 (0.50–3.24) 
Perceptions 
 Harmful 0.69 (0.57–0.83) 0.69 (0.57–0.85) 0.86 (0.69–1.06) 0.69 (0.57–0.84) 0.76 (0.63–0.91) 0.74 (0.61–0.91) 0.83 (0.68–1.00) 
 Cool 1.19 (1.04–1.38) 1.56 (1.35–1.82) 1.45 (1.24–1.69) 1.27 (1.09–1.46) 1.34 (1.16–1.54) 1.53 (1.31–1.78) 1.49 (1.28–1.72) 
Covariates 
 Age 0.97 (0.93–1.00) 0.97 (0.93–1.01) 1.00 (0.96–1.05) 0.90 (0.87–0.94) 1.04 (1.00–1.09) 1.10 (1.06–1.15) 1.12 (1.08–1.17) 
 Sex (ref. = female) 0.91 (0.65–1.28) 0.94 (0.65–1.28) 1.24 (0.84–1.84) 0.87 (0.62–1.23) 1.38 (0.99–1.95) 1.18 (0.80–1.72) 1.28 (0.89–1.83) 
 Hispanic (ref. = no) 0.79 (0.51–1.23) 0.98 (0.62–1.55) 0.99 (0.60–1.64) 0.69 (0.45–1.07) 1.13 (0.73–1.74) 0.78 (0.48–1.27) 1.04 (0.66–1.63) 
 White (ref. = no) 0.45 (0.17–1.23) 0.63 (0.25–1.61) 0.54 (0.18–1.58) 0.73 (0.33–1.62) 0.70 (0.28–1.73) 0.41 (0.13–1.32) 1.02 (0.42–2.51) 
 Black (ref. = no) 0.40 (0.15–1.09) 0.52 (0.20–1.34) 0.40 (0.13–1.18) 0.84 (0.38–1.87) 0.73 (0.29–1.81) 0.42 (0.13–1.35) 1.32 (0.54–3.23) 
 Asian American (ref. = no) 0.28 (0.09–0.89) 0.78 (0.27–2.29) 0.90 (0.27–2.97) 1.09 (0.42–2.83) 0.76 (0.27–2.15) 0.59 (0.16–2.14) 0.63 (0.21–1.88) 
 Other race (ref. = no) 0.89 (0.32–2.44) 0.99 (0.38–2.58) 0.74 (0.25–2.26) 0.92 (0.41–2.09) 0.57 (0.22–1.45) 0.50 (0.15–1.65) 1.10 (0.44–2.76) 
 Finance security 1.02 (0.84–1.24) 1.14 (0.92–1.41) 1.02 (0.81–1.28) 1.00 (0.91–1.34) 0.99 (0.82–1.21) 0.93 (0.74–1.16) 0.87 (0.70–1.08) 
 Vaping frequency 1.04 (1.02–1.06) 1.03 (1.01–1.04) 1.03 (1.35–3.21) 1.03 (1.02–1.05) 1.03 (1.02–1.05) 1.02 (1.00–1.04) 1.00 (0.99–1.02) 
 Past-mo cannabis use (ref. = no) 1.42 (1.02–1.06) 1.59 (1.09–2.32) 2.08 (1.35–3.21) 1.54 (1.09–2.17) 1.25 (0.88–1.77) 2.66 (1.73–4.07) 2.52 (1.68–3.76) 
VariablesaOR (95% CI)
Refill Rechargeable Pods/Cartridges (n = 827)Refill Disposable Pods (n = 885)Rewick Disposable Pods/Cartridges (n = 885)Recharge Disposables (n = 885)Modify Nicotine E-Liquid (n = 1018)Combine Nicotine and Cannabis Liquid (n = 1018)Put Cannabis in Nicotine Device (n = 1018)
Source of information 
 Friends 10.74 (1.20–2.53) 1.42 (0.95–2.11) 1.33 (0.87–2.04) 2.16 (1.48–3.14) 10.65 (1.13–2.41) 1.57 (1.03–2.37) 1.21 (0.81–1.79) 
 Social media 1.14 (0.82–1.57) 1.36 (0.95–1.930 1.22 (0.93–1.78) 1.47 (1.06–2.04) 1.19 (0.85–1.65) 1.46 (1.01–2.11) 1.05 (0.74–1.50) 
 Nonsocial media Web sites 1.89 (1.26–2.85) 1.71 (1.11–2.63) 2.05 (1.31–3.20) 1.58 (1.06–2.04) 1.94 (1.29–2.92) 1.37 (0.87–2.17) 1.32 (0.85–2.04) 
 Vape shop 1.55 (0.95–2.54) 1.48 (0.89–2.45) 2.45 (1.47–4.09) 2.04 (1.24–3.35) 2.25 (1.42–3.56) 2.42 (1.48–3.95) 0.98 (0.59–1.61) 
  Other 1.09 (0.46–2.63) 1.81 (0.69–4.71) 2.36 (0.91–6.12) 1.62 (0.63–4.15) 1.76 (0.74–4.20) 2.51 (0.99–6.30) 1.27 (0.50–3.24) 
Perceptions 
 Harmful 0.69 (0.57–0.83) 0.69 (0.57–0.85) 0.86 (0.69–1.06) 0.69 (0.57–0.84) 0.76 (0.63–0.91) 0.74 (0.61–0.91) 0.83 (0.68–1.00) 
 Cool 1.19 (1.04–1.38) 1.56 (1.35–1.82) 1.45 (1.24–1.69) 1.27 (1.09–1.46) 1.34 (1.16–1.54) 1.53 (1.31–1.78) 1.49 (1.28–1.72) 
Covariates 
 Age 0.97 (0.93–1.00) 0.97 (0.93–1.01) 1.00 (0.96–1.05) 0.90 (0.87–0.94) 1.04 (1.00–1.09) 1.10 (1.06–1.15) 1.12 (1.08–1.17) 
 Sex (ref. = female) 0.91 (0.65–1.28) 0.94 (0.65–1.28) 1.24 (0.84–1.84) 0.87 (0.62–1.23) 1.38 (0.99–1.95) 1.18 (0.80–1.72) 1.28 (0.89–1.83) 
 Hispanic (ref. = no) 0.79 (0.51–1.23) 0.98 (0.62–1.55) 0.99 (0.60–1.64) 0.69 (0.45–1.07) 1.13 (0.73–1.74) 0.78 (0.48–1.27) 1.04 (0.66–1.63) 
 White (ref. = no) 0.45 (0.17–1.23) 0.63 (0.25–1.61) 0.54 (0.18–1.58) 0.73 (0.33–1.62) 0.70 (0.28–1.73) 0.41 (0.13–1.32) 1.02 (0.42–2.51) 
 Black (ref. = no) 0.40 (0.15–1.09) 0.52 (0.20–1.34) 0.40 (0.13–1.18) 0.84 (0.38–1.87) 0.73 (0.29–1.81) 0.42 (0.13–1.35) 1.32 (0.54–3.23) 
 Asian American (ref. = no) 0.28 (0.09–0.89) 0.78 (0.27–2.29) 0.90 (0.27–2.97) 1.09 (0.42–2.83) 0.76 (0.27–2.15) 0.59 (0.16–2.14) 0.63 (0.21–1.88) 
 Other race (ref. = no) 0.89 (0.32–2.44) 0.99 (0.38–2.58) 0.74 (0.25–2.26) 0.92 (0.41–2.09) 0.57 (0.22–1.45) 0.50 (0.15–1.65) 1.10 (0.44–2.76) 
 Finance security 1.02 (0.84–1.24) 1.14 (0.92–1.41) 1.02 (0.81–1.28) 1.00 (0.91–1.34) 0.99 (0.82–1.21) 0.93 (0.74–1.16) 0.87 (0.70–1.08) 
 Vaping frequency 1.04 (1.02–1.06) 1.03 (1.01–1.04) 1.03 (1.35–3.21) 1.03 (1.02–1.05) 1.03 (1.02–1.05) 1.02 (1.00–1.04) 1.00 (0.99–1.02) 
 Past-mo cannabis use (ref. = no) 1.42 (1.02–1.06) 1.59 (1.09–2.32) 2.08 (1.35–3.21) 1.54 (1.09–2.17) 1.25 (0.88–1.77) 2.66 (1.73–4.07) 2.52 (1.68–3.76) 

Bold font indicates statistical significance at P < .05. The percentages of refilling rechargeable pod/cartridges were derived from participants who reported ever using those devices (n = 827). The percentages of refilling, rewicking, and recharging disposable pods were derived from participants who reported ever using disposable devices (n = 885). Modifications related to nicotine and/or cannabis liquids were derived from the whole sample (N = 1018). Refill rechargeable pods/cartridges: Refilling a vape pod/cartridge that is not designed to be refilled (eg, hacking a JUUL pod). Refill disposable pods: Refilling a disposable vape like a Puffbar by taking it apart and adding more nicotine or nicotine-free e-liquid (not cannabis). Rewick pods/cartridges: Rewicking a pod/cartridge that is designed for 1-time use. For example, taking the cotton wick out of a JUUL pod and replacing it with a new cotton wick that you made. Recharge disposable pods: Recharging the battery in a disposable vape that is not designed to be recharged. For example, taking the vape apart and attaching its wires to a different power source like a stripped-down universal serial bus cord to charge it. Modify nicotine e-liquid: Mixing, creating, or changing nicotine e-liquids (for example, changing propylene glycol/vegetable glycerin flavors, nicotine level). Combine nicotine and cannabis liquids: Mixing, creating, or changing e-liquids to combine nicotine and cannabis. Put cannabis in nicotine device: Putting cannabis/tetrahydrocannabinol liquid into a vape that originally was designed to vape nicotine, not cannabis. Ref, reference.

Awareness of and engagement in ENDS modifications were common among AYAs who reported past-month ENDS use. The most common modifications were refilling rechargeable pod/cartridge devices and recharging disposable pod devices, with underage youth (<21 years old) more likely than young adults (≥21 years old) to modify rechargeable pods/cartridges and disposable pods. Young adults (≥21 years old) were more likely than underage youth (<21 years old) to manipulate nicotine and cannabis liquids. Adjusted models showed that lower perceptions of harm and greater perceptions of coolness were associated with an increased likelihood of ENDS modifications.

Consistent with the existing literature indicating the crucial role of peers in promoting tobacco use among AYAs,25 we observed that the most frequent sources of information regarding ENDS modification were friends and social media. Learning about ENDS on social media is particularly concerning because of the substantial presence of pro–e-cigarette content on these platforms, because these platforms lack sufficient regulation to curb e-cigarette promotion.26,27 However, exposure to ENDS modifications on social media was not associated with engaging in many of the modifications in the adjusted models. It may be that exposure to these behaviors on social media is creating and reinforcing a sense of positive social norms surrounding ENDS use among AYAs,28 including modifications of ENDS, but other factors such as nicotine may be contributing to continued use. Indeed, we observed that perceptions of ENDS modifications as being cool or trendy were associated with engaging in these modifications. Social media may be contributing to positive perceptions and knowledge of ENDS modifications, but AYAs may be turning to other sources like vape shops and other nonsocial media Web sites to learn about how to engage in modifications (as our adjusted models show).

Previous studies have documented that vape shop employees communicate with consumers by sharing personal anecdotes, health information, and general information about ENDS.29–31 Vape shops are considered a hub for the vaping community that supports ENDS use by providing advice to novice users about how to use ENDS and ongoing support to experienced ENDS users.30,31 Our findings suggest that vape shops may be communicating about harmful vaping behaviors such as rewicking, recharging, and refilling devices that are not intended to be modified. Also of note, although only 11.3% of participants reported hearing about ENDS modifications from vape shops, adjusted models showed that vape shops were significantly associated with engaging in ENDS modifications even after controlling for age. This finding suggests that some youth under the US legal age of 21 years for purchasing tobacco products, including ENDS, are learning about ENDS modifications in vape shops. This highlights the need for greater enforcement of age restrictions for purchasing ENDS.

Learning about ENDS modifications from nonsocial media Web sites was associated with a wide range of ENDS modifications. There are many Web sites that have ENDS content, including information sites, online vendors, blogs, product ratings, storefront sites, and manufacturer sites.32 However, we did not assess which nonsocial media Web sites were used to obtain information about ENDS modifications. Future studies should examine which Web sites AYAs use to obtain information about ENDS and what information about modifications exists to inform regulations and prevention efforts.

Our study findings underscore the significant intersection between nicotine and cannabis vaping. Sixty-six percent of our sample reported cannabis use in the past month, with approximately half aware of combining nicotine and cannabis liquids, and 20% engaging in this behavior. These findings are concerning because the devices used for nicotine and cannabis vaping are very similar and there is substantial overlap in their use.33 Regulating these products poses significant challenges because of shared characteristics.

The US Food and Drug Administration (FDA) Center for Tobacco Products has regulatory authority over ENDS products,34 but they do not have regulatory authority over cannabis, leaving cannabis in regulatory limbo. Without appropriate regulations, individuals may be mixing or creating their own cannabis liquids with or without nicotine to be used in ENDS, which may be harmful. For instance, cannabis concentrates that are mixed with nicotine or created at home have unknown health risks and may contain contaminants. This concern is highlighted by the 2019 outbreak of E-cigarette or Vaping Product Use-Associated Lung Disease (EVALI), which was linked to 2807 hospitalizations and 68 deaths in the United States. EVALI is largely believed to be caused by vitamin E acetate, which is an additive used in some cannabis concentrates.35 The cannabis products thought to cause EVALI are unregulated, and patients with EVALI reported obtaining these products from informal sources (eg, dealers, friends). These findings underscore the critical need to regulate cannabis vaping.

It is important to note that combined regulatory efforts of both nicotine and cannabis are complicated by the fact that cannabis is legalized at the state level rather than at the federal level in the United States, prohibiting a federal entity such as the FDA from regulating most cannabis vaping products. However, the FDA is still positioned to regulate ENDS devices created to vape nicotine that are used to vape cannabis. Additionally, states that have legalized cannabis can develop additional policies regarding where and how each of these products can be sold in the state to minimize unintended crossover between substances (eg, vape shops endorsing modification and use of ENDS with cannabis products).

We acknowledge several limitations to this study. First, there may be other types of ENDS modifications not assessed in this study. Second, we did not examine the extent to which individuals engage in these modified uses. Third, we did not examine perceptions related to each modification behavior. Fourth, subjective financial security, used as a proxy for SES,23 was not significantly associated with any ENDS modifications. This finding contrasts with other studies that identified saving cost as a factor for ENDS modifications.13,17 Fifth, our study sample consisted of AYAs endorsing current ENDS use, who were market research panelists, potentially limiting generalizability. Finally, the items related to adding/using cannabis with nicotine and nicotine-based devices were similar, so the responses may overlap. Future research should explore the frequency and motivations for ENDS modifications using more refined items among a representative sample.

Future studies should continue to track and evaluate the health consequences of ENDS modifications. Specifically, as the ENDS marketplace and regulations continue to evolve, surveillance studies should examine whether consumers are modifying new ENDS products and using them for purposes unintended by manufacturers and assess how these products are portrayed in various sources including social media, nonsocial media Web sites, and retailers such as vape shops. Qualitative studies and social media/Web site content analyses may be used to answer other nuanced and detailed questions, such as what components are modified and the reasons for modification. Laboratory and health studies should identify the potential health impact of modified use of ENDS. Studies to date have mostly studied chemicals in e-liquids that could potentially be harmful (eg, formaldehyde, acetaldehyde, carcinogens, nicotine) from commercially available e-liquids,36 but examination of the unique health risks from self-created and mixed e-liquids is warranted. These studies should also examine potential bodily injuries (eg, burns, nicotine poisoning) associated with ENDS modifications.

Findings show that AYAs are aware of and engage in modifying ENDS, and typically learn about these behaviors from friends, digital media, and retailers. Future research should examine whether vaping-modified ENDS confers respiratory harm and nicotine toxicity. Prevention and educational efforts should include the risks of modifications such as explosions and burns, as well as address cannabis vaping, given its high prevalence among AYAs who vape nicotine. Regulatory decisions need to account for how ENDS are modified or hacked for unintended purposes. In conclusion, addressing ENDS modification is crucial in research, prevention, and regulatory efforts to mitigate potential harm among AYAs.

Dr Kong conceptualized and designed the study, developed the data collection instruments, drafted the initial manuscript, conducted data analysis, interpreted the results, and revised the manuscript; Drs Lee and Ouellette conceptualized and designed the study, developed the data collection instruments, interpreted the results, and critically reviewed drafts of the manuscript; Dr Morean conceptualized and designed the study, developed the data collection instruments, built the data collection instrument, interpreted the results, and critically reviewed drafts of the manuscript; and all authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

FUNDING: Funded by the National Institute of Drug Abuse and the US Food and Drug Administration’s Center for Tobacco Products grant R01DA049878. Support for authors is also provided by grant U54DA036151 and National Institute of Drug Abuse grant T32 DA019426-18. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or the US Food and Drug Administration.

CONFLICT OF INTEREST DISCLOSURES: The authors have indicated they have no conflicts of interest relevant to this article to disclose.

aOR

adjusted odds ratio

AYA

adolescent and young adult

CI

confidence interval

ENDS

electronic nicotine delivery systems

EVALI

E-cigarette or Vaping Product Use-Associated Lung Disease

FDA

US Food and Drug Administration

SES

socioeconomic status

THC

tetrahydrocannabinol

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