Children exposed to secondhand e-cigarette vapor had substantially lower nicotine absorption compared to those exposed to secondhand tobacco smoke, but higher absorption than children with no exposure, according to a cross-sectional study published in JAMA Network Open.

Study Details

The study analyzed data from 1,777 children aged 3–11 years (mean age = 7.4 years; standard deviation = 2.6) who participated in the National Health and Nutrition Examination Survey from 2017–2020. Serum cotinine levels were used as a biomarker of nicotine absorption.

Of the total population:

• 14.8% of children were exposed to secondhand tobacco smoke only.
• 2.5% were exposed to secondhand e-cigarette vapor only.
• 80.1% had no reported exposure.
• 1.8% were exposed to both secondhand smoke and vapor, and were thus excluded from the analysis.

About 50% of the demographic was female; 29.9% of participants had family incomes below the poverty line; and 26.8% of participants were Hispanic, 26.1% were non-Hispanic Black, 29.2% were non-Hispanic White, and 17.9% were multiracial or other races/ethnicities.

Proxy respondents (usually parents) provided information on children's secondhand exposure. Blood samples were assayed using high-performance liquid chromatography/atmospheric-pressure ionization tandem mass spectrometry. The lower limit of detection for cotinine assay was 0.01 μg/L; log-normal tobit regression models were used to account for children with undetectable cotinine levels.

Key Findings

Children exposed only to secondhand vapor had 83.6% lower nicotine absorption than those exposed only to secondhand smoke (geometric mean cotinine 0.081 μg/L vs 0.494 μg/L, P < .001).

Children with no reported exposure had 96.7% lower nicotine absorption than those exposed to secondhand smoke (0.016 μg/L vs 0.494 μg/L, P < .001).

Exposure to secondhand vapor resulted in 402% higher cotinine levels compared to no exposure (0.081 μg/L vs 0.016 μg/L, P < .001).

Results remained similar after adjusting for age, sex, ethnicity, family income, body weight, and height.

The study authors concluded that switching from smoking to vaping indoors may substantially reduce, but not eliminate, children's secondhand exposure to nicotine and other potentially harmful substances. However, they emphasized that vaping around children should still be avoided.

Limitations of the study included potential social desirability bias in reporting exposure, changes in the vaping market since data collection, and insufficient sample size to examine associations stratified by race/ethnicity or household income.

Conflict of interest disclosures can be found in the study.