Earwax: an innovative tool for assessment of tobacco use or exposure. A pilot study in young adults

The present work represents a novel approach using earwax (cerumen) for the evaluation of the smoking status with regards to tobacco use/exposure. The method utilizes the difference in the concentration profiles of nicotine and its related compounds in earwax to discriminate among non-, passive, and active smokers. Earwax samples were collected from three study groups (non-, passive, and active smokers) and subjected to analysis by headspace gas chromatography–mass spectrometry. The nicotine levels in earwax were much lower than cotinine levels, even for active smokers; however, it was reported that the nicotine levels in scalp hair were much higher than the cotinine levels. Therefore, it is obviously correct that earwax is protected from external contamination to a larger extent than expected. The concentration profiles of nicotine and its related compounds (o-nicotine, cotinine, and anabasine) in the analyzed earwax samples were treated by data mining techniques. It was possible to discriminate the studied groups using the evolutionary tree (evtree) algorithm and support vector machine discriminant analysis as the statistical models with the best discrimination accuracies of 96.7 and 95.0%, respectively. The analytical method applied requires no sample pretreatment which makes it easy, fast, and a low-cost alternative method to those employing other biological matrices, such as blood, urine, and hair. The earwax, which is considered a neglected body secretion, is a useful tool to determine the exposure to tobacco smoke noninvasively and without the influence of external contamination.