This study aims to compare serum cotinine levels in e-cigarette and combustible cigarette
smokers, in an attempt to quantify the potential chronic nicotine addiction risk that e-
cigarettes pose. We analyzed 428 participants in 2015–2016 NHANES: 379 (87.03%)
smoked combustible cigarettes alone and 49 (12.97%) smoked e-cigarettes. Serum cotinine
levels were measured by isotope-dilution high-performance liquid chromatography/
atmospheric pressure chemical ionization tandem mass spectrometric method with a …