INCREASED AMOUNTS OF HYDROGEN PEROXIDE IN THE EXHALED BREATH OF OZONE-EXPOSED HUMAN SUBJECTS

Abstract

The analysis of exhaled breath components for indicators of inflammation and oxidative stress rarely has been applied to studies involving exposure to an environmental pollutant. The examination of exhaled substances as biomarkers of exposure and/or effect is extremely useful for human studies due to the noninvasive nature of the sample collection. We utilized exhaled breath analysis to demonstrate oxidative stress in humans exposed to the air pollutant ozone (O3). O3 has been hypothesized to exert oxidative stress by react- ing with lung biomolecules to form secondary reaction products such as hydrogen perox ide (H2O2) and carbonyl substances, and by inducing an influx of polymorphonuclear phagocytes (PMNs), which can release reactive oxygen species into the lung. We collected the exhaled breath of healthy human volunteer subjects (age 18-35 yr) immediately before and after exposure to air or 0.4 ppm O3 for 2 h with or without exercise. For assay of H2O2, breath condensate was collected in Tygon tubing submerged in an ice-water bath, and H2O2 was quantitated by a fluorescence assay. In a subset of subjects, exhaled carbonyls were examined by collection of exhaled breath into Tedlar bags. Breath carbonyls were subsequently derivatized and concentrated on column packing containing 2,4-dinitrophenylhydrazine, derivatives eluted, and analyzed by high-performance liquid chromatography with ultraviolet detection. The data showed an increase in exhaled breath H2O2 in O3-exposed, exercising subjects but not in subjects exposed to O3 without exer- cise. An increase in an aldehydic derivative that eluted with a similar retention time as derivatized acetaldehyde was found in the breath of O3-exposed subjects. These data sug gest that O3 exposure of humans in vivo can induce an oxidative stress as evidenced by increased formation of H2O2 and carbonyls. The analysis of exhaled breath was able to show the increased lung oxidative stress in an easy, noninvasive manner and has applicability to examining similar responses of humans exposed to other environmental pollutants either in controlled settings or in field studies.