The Effect of Human Occupancy on Indoor Air Quality through Real-Time Measurements of Key Pollutants.

The primarily emitted compounds by human presence, e.g., skin and volatile organic compounds (VOCs) in breath, can react with typical indoor air oxidants, ozone (O3), and hydroxyl radicals (OH), leading to secondary organic compounds. Nevertheless, our understanding about the formation processes of the compounds through reactions of indoor air oxidants with primary emitted pollutants is still incomplete. In this study we performed real-time measurements of nitrous acid (HONO), nitrogen oxides (NOx = NO + NO2), O3, and VOCs to investigate the contribution of human presence and human activity, e.g., mopping the floor, to secondary organic compounds. During human occupancy a significant increase was observed of 1-butene, isoprene, and d-limonene exhaled by the four adults in the room and an increase of methyl vinyl ketone/methacrolein, methylglyoxal, and 3-methylfuran, formed as secondary compounds through reactions of OH radicals with isoprene. Intriguingly, the level of some compounds (e.g., m/z 126, 6-methyl-5-hepten-2-one, m/z 152, dihydrocarvone, and m/z 194, geranyl acetone) formed through reactions of O3 with the primary compounds was higher in the presence of four adults than during the period of mopping the floor with commercial detergent. These results indicate that human presence can additionally degrade the indoor air quality.

Exhaled breath analysis using on-line preconcentration mass spectrometry for gastric cancer diagnosis.

Breath volatile biomarkers are capable of distinguishing patients with various cancers. However, high throughput analytical technology is a prerequisite to a large-cohort study intended to discover reliable breath biomarkers for cancer diagnosis. Single-photon ionization (SPI) is a universal ionization technology, and SPI-mass spectrometry (SPI-MS) shows a remarkable advantage in the comprehensive detection of volatile organic compounds (VOCs), in particular, nonpolar compounds. In this study, we have introduced SPI-MS coupled with on-line thermal desorption (TD-SPI-MS) to demonstrate nontarget analysis of breath VOCs for gastric cancer patients. The breath fingerprints of the gastric cancer patients were significantly distinct from that of the control group. Acetone, isoprene, 1,3-dioxolan-2-one, phenol, meta-xylene, 1,2,3-trimethylbenzene, and phenyl acetate showed higher relative peak intensities in the breath profiles of gastric cancer patients. A diagnostic prediction model was further developed by using a training set (121 samples) and validated with a test set (53 samples). The predication accuracy of the developed model was 96.2%, and the area under the curve (AUC) of the receiver operator characteristic curve (ROC) was 0.997, indicating a satisfactory prediction ability of the developed model. Thus, by taking gastric cancer as an example, we have shown that TD-SPI-MS will be a promising tool for high throughput analysis of breath samples to discover characteristic VOCs in patients with various cancers.