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. 2024 Jul 1;7(7):e2421246.
doi: 10.1001/jamanetworkopen.2024.21246.

Secondhand Nicotine Absorption From E-Cigarette Vapor vs Tobacco Smoke in Children

Harry Tattan-Birch  1   2 , Jamie Brown  1   2 , Sarah E Jackson  1   2 , Martin J Jarvis  1   2 , Lion Shahab  1   2
Affiliations

Secondhand Nicotine Absorption From E-Cigarette Vapor vs Tobacco Smoke in Children

Harry Tattan-Birch et al. JAMA Netw Open. .

Abstract

Importance: With the prevalence of e-cigarette use (vaping) increasing worldwide, there are concerns about children's exposure to secondhand vapor.

Objective: To compare nicotine absorption among children who are (1) exposed to secondhand tobacco smoke only or (2) exposed to secondhand vapor only with (3) those exposed to neither.

Design, setting, and participants: The US Continuous National Health and Nutrition Examination Survey (NHANES) is a repeat cross-sectional survey. Participants are interviewed in their homes and, several days after, visit a mobile examination center to provide biological specimens. This study uses data from a nationally representative sample of US households from 2017 to 2020. Participants were children aged 3 to 11 years with serum cotinine levels incompatible with current firsthand nicotine use (ie, <15 μg/L). The final analysis was conducted on January 9, 2024.

Exposures: Reported exposure to secondhand smoke or vapor indoors in the past 7 days (only secondhand smoke, only secondhand vapor, or neither). Covariates included age, sex, ethnicity, family income, body weight, and height.

Main outcomes and measures: The primary outcome was serum cotinine concentration, an objective biomarker of nicotine absorption. Geometric mean cotinine levels and 95% CIs were calculated using log-normal tobit regression, accounting for the complex survey design and weights.

Results: The mean (SD) age of the 1777 children surveyed was 7.4 (2.6) years, 882 (49.6%) were female, and 531 (29.9%) had family incomes below the poverty level. Nicotine absorption, as indexed by serum cotinine level, was highest among children only exposed to secondhand smoke (0.494 μg/L μg/L; 95% CI, 0.386-0.633 μg/L), followed by those exposed only to secondhand vapor (0.081 μg/L; 95% CI, 0.048-0.137 μg/L), equating to 83.6% (95% CI, 71.5%-90.5%; P < .001) lower nicotine absorption. Among children with no reported secondhand exposure, the geometric mean cotinine level was 0.016 μg/L (95% CI, 0.013-0.021 μg/L), or 96.7% (95% CI, 95.6%-97.6%; P < .001) lower than for those with exposure to secondhand smoke. Results were similar after covariate adjustment.

Conclusions and relevance: In this cross-sectional study of US children, nicotine absorption was much lower in children who were exposed to secondhand vapor vs secondhand smoke, but higher than in those exposed to neither. These findings suggest that switching from smoking to vaping indoors may substantially reduce, but not eliminate, children's secondhand exposure to nicotine and other noxious substances.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Brown reported receiving grants from Cancer Research UK, Pfizer, and Johnson & Johnson, which manufactures smoking cessation medications, outside the submitted work. Dr Shahab reported receiving grants from Pfizer and personal fees from Johnson & Johnson outside the submitted work; being a Higher Education Funding Council for England–funded member of staff at University College London; acting as a paid reviewer for grant-awarding bodies and as a paid consultant for health care companies; and receiving other research funding from the government, a community-interested company (National Centre for Smoking Cessation), and charitable sources. Dr Shahab has never received personal fees or research funding of any kind from alcohol, electronic cigarette, or tobacco companies. No other disclosures were reported.

Figures

Figure.
Figure.. Nicotine Absorption by Reported Secondhand Exposure to Tobacco Smoke and E-Cigarette Vapor in Children Aged 3 to 11 Years
Serum cotinine concentration is used as a biomarker of recent nicotine absorption. To convert cotinine to nanomoles per liter, multiply by 5.675. Estimates come from unadjusted log-normal tobit regression accounting for complex design of the National Health and Nutrition Examination Survey. Error bars represent 95% CIs. Data and analysis code are openly available online.
See this image and copyright information in PMC

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