Identification of exposure markers in smokers' breath.

Volatile organic compounds present in the exhaled breath of 26 smokers and 43 non-smokers were evaluated in an effort to identify possible biochemical markers resulting from the exposure to cigarette smoke. The total ion current profiles obtained from gas chromatography-mass spectrometry (GC-MS), which contained about 230 GC-MS peaks, were first analyzed by using standard statistical procedures to select a subset of 22 peaks. The importance of the peaks was ranked using factor analysis, which further reduced the dimensionality of the data, and discriminant analysis served to develop classification functions. One peak, 2,5-dimethyl furan, had sufficient discriminatory power in the GC-MS profiles to allow almost complete differentiation (96% correct classification) between the smokers and non-smokers groups. In addition, several other compounds were able to separate the groups with a high level of accuracy.