The variability of volatile organic compounds in clinical environments

The development of clinical breath-analysis is confounded by the variability of background volatile organic compounds (VOC). Interpretation of clinical breath-data at individual, and cohort levels requires characterisation of clinical-VOC levels and exposures. Active-sampling with thermal-desorption/gas chromatography-mass spectrometry recorded and evaluated VOC concentrations in 245 samples of indoor air from three sites in a large NHS provider trust in the UK over 27 months. 7344 clinical VOC were isolated and 328 VOC and 68 were observed in more than 5% and 30% of samples respectively; associated with exogenous and endogenous sources. 17 VOC were seasonal differentiators. Metabolites from the anaesthetic sevoflurane, and putative-disease biomarkers in room air indicated that exhaled VOC were a source of background-pollution in clinical breath-tests. Apart from solvents, and PPE-waxes, exhaled VOC concentrations above 3 µgm-3 are unlikely to arise from room air contamination. This level could be applied as a threshold for inclusion in studies.