Nicotine Exposure From Smoking Tobacco and Vaping Among Adolescents

Abstract

Importance: It remains unknown whether nicotine intake among youths who vape is lower, comparable, or higher than among youths who smoke.

Objective: To examine potential differences in biomarkers of exposure to nicotine (1) between adolescents who smoke tobacco, vape, both vape and smoke (dual use), or do not use; (2) between adolescents in 3 countries; and (3) by nicotine content and form in the vaping product last used among adolescents who exclusively vaped.

Design, setting, and participants: This population-based, observational cross-sectional study invited adolescents aged 16 to 19 years in Canada, England, and the US who had previously completed national surveys to participate in a biomarker study based on their vaping and smoking status. Participants completed questionnaires and self-collected urine samples between September 2019 and January 2022. Analyses were conducted in February 2023 and between January and June 2024.

Exposures: Vaping, tobacco smoking, dual use, or no use in the past 7 days.

Main outcomes and measures: Urine concentration of cotinine, trans-3'-hydroxycotinine (3OH-cotinine), and total nicotine equivalents (TNE-2; molar sum of cotinine and 3OH-cotinine), normalized for creatinine concentration.

Results: Among the 364 participants (mean [SD] age, 17.6 [1.1] years; 203 females [55.8%]) who provided usable urine samples and completed questionnaires, no differences in TNE-2 concentration were observed between adolescents who exclusively vaped (n = 73; geometric mean [SD], 3.10 [16.69] nmol/mg creatinine), exclusively smoked (n = 68; geometric mean [SD], 3.78 [18.00] nmol/mg creatinine), or both vaped and smoked (n = 77; geometric mean [SD], 6.07 [19.08] nmol/mg creatinine) in the past week, adjusting for creatinine concentration, age, sex, country, and cannabis use. All vaping and/or smoking groups had higher concentrations of TNE-2 than no use (n = 146; geometric mean [SD], 0.19 [1.14] nmol/mg creatinine; P < .001 for all contrasts). Among adolescents who exclusively vaped (n = 73), TNE-2 concentrations were not significantly different between those who reported using products containing more than 20 mg/mL nicotine (n = 33; geometric mean [SD], 4.35 [18.25] nmol/mg creatinine) and containing 20 mg/mL nicotine or less (n = 28; geometric mean [SD], 5.13 [15.64] nmol/mg creatinine). Reported use of vaping products containing nicotine salts (n = 23) was associated with higher concentration of TNE-2 (geometric mean [SD], 10.78 [18.03] nmol/mg creatinine) than reported use of products without nicotine salts (n = 29; geometric mean [SD], 2.72 [15.42] nmol/ng creatinine; P = .03) or reporting "don't know" (n = 14; geometric mean [SD], 1.55 [15.01] nmol/ng creatinine; P = .009). Similar patterns of exposure were observed for cotinine and 3OH-cotinine.

Conclusions and relevance: This cross-sectional study found that vaping was associated with similar nicotine exposure as smoking among adolescents. Reported use of a nicotine salt product was associated with higher nicotine exposure among those who exclusively vaped, consistent with findings from laboratory and population studies indicating greater dependence for nicotine salt e-cigarettes.

Figure 1.. Nicotine Metabolites by Past-Week Vaping and Tobacco Smoking Status

Boxplots represent median (IQR) values, whiskers represent minimum and maximum nonoutlier values for creatinine level–adjusted biomarker values within groups, and dots represent outliers. Some outliers were excluded for clarity of presentation. 3OH-cotinine indicates trans-3′-hydroxycotinine; TNE-2, total nicotine equivalents. Separate linear regression models for concentration of each biomarker (log-transformed) included testing all pairwise comparisons between past-week vaping and/or smoking status groups, adjusting for creatinine, country, age, sex, and past-week cannabis use. Significant differences between groups are noted; all other comparisons were not significantly different (see eTable 3 in Supplement 1 for model estimates and P values for all pairwise comparisons). ^aSignificant difference between the no use group and the vaping group (P < .001 for each of cotinine, 3OH-cotinine, and TNE-2, respectively). ^bSignificant difference between the no use group and the smoking group (P < .001 for each of cotinine, 3OH-cotinine, and TNE-2, respectively). ^cSignificant difference between the no use group and the dual use group (P < .001 for each of cotinine, 3OH-cotinine, and TNE-2, respectively).

Figure 2.. Nicotine Biomarkers by Nicotine Characteristics of Last Vaping Product Used Among Adolescents Who Reported Vaping Exclusively in the Past Week

Boxplots represent median (IQR) values, whiskers represent minimum and maximum nonoutlier values for creatinine level–adjusted biomarker values within user groups, and dots represent outliers. 3OH-cotinine indicates trans-3′-hydroxycotinine; TNE-2, total nicotine equivalents. Separate linear regression models for concentration of each biomarker (log transformed) included testing all pairwise comparisons between groups, adjusting for creatinine, country, age, sex, and past-week cannabis use. Significant differences between groups are noted; all other comparisons were not significantly different (see eTable 5 and eTable 6 in Supplement 1 for model estimates and P values for all pairwise comparisons). ^aSignificant difference between the no nicotine group and the up to 20 mg/mL nicotine group (P = .001 for cotinine, P = .004 for 3OH-cotinine, and P = .002 for TNE-2, respectively). ^bSignificant difference between the no nicotine group and the more than 20 mg/mL nicotine group (P = .04 for cotinine). ^cSignificant difference between the up to 20 mg/mL nicotine group and the “don’t know” group (P = .01 for cotinine, 3OH-cotinine, and TNE-2, respectively). ^dExcluding those reporting no nicotine in the last vaping product used. ^eSignificant difference between the nicotine salt group and the “don’t know” group (P = .004 for cotinine, P = .02 for 3OH-cotinine, and P = .009 for TNE-2, respectively). ^fSignificant difference between the not salt group and the nicotine salt group (P = .02 for 3OH-cotinine and P = .03 for TNE-2, respectively).