Unveiling tobacco markers in exhaled breath

Breath analysis has emerged as a promising, non-invasive diagnostic tool for monitoring tobacco exposure and its associated health risks. A key aspect of this approach is the detection of inorganic and volatile or semi-volatile organic compounds (VOCs, sVOCs) in exhaled breath (EB) or exhaled breath condensate (EBC). Smokers consistently exhibit elevated levels of key volatile markers, including 2,5-dimethylfuran, benzene, toluene, styrene, o/m/p-xylene, isoprene, and acetaldehyde, typically detected in low concentrations ranging from a few parts-per-trillion (ppt_v) to tens of parts-per-billion (ppb_v). These compounds have been linked to various tobacco related medical conditions including cardiovascular conditions, chronic obstructive pulmonary disease (COPD), asthma, liver dysfunction, and various forms of cancer. State-of-the-art analytical technologies have been widely employed for the detection of tobacco breath markers. Off-line analytical methods, such as single- and two-dimensional gas chromatography-mass spectrometry (GC-MS, GC×GC-MS) and ultra-performance liquid chromatography tandem MS (UPLC-MS/MS), can provide detailed chemical profiling of EB or EBC. Conversely, on-line techniques can offer real-time monitoring of VOC and sVOC with minimal sample preparation. Examples include selected ion flow tube MS (SIFT-MS), proton transfer reaction MS (PTR-MS), ion mobility spectrometry (IMS) and electronic nose (e-nose). Despite the diagnostic potential of breath analysis, several challenges remain, including significant interindividual variability and the lack of standardized protocols for sample collection, storage, handling, and analysis. This review examines the breath markers of smokers, highlights current analytical challenges and gaps, and discusses the future directions in the field of breath analysis.