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

The analysis of exhaled breath components for indicators of inflammati on and oxidative stress rarely has been applied to studies involving e xposure to an environmental pollutant. The examination of exhaled subs tances 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 i n humans exposed to the air pollutant ozone (O-3). O-3 has been hypoth esized to exert oxidative stress by reacting with lung biomolecules to form secondary reaction produces such as hydrogen peroxide (H2O2) and carbonyl substances, and by inducing an influx of polymorphonuclear p hagocytes (PMNs) which can release reactive oxygen species into the lu ng. We collected the exhaled breath of healthy human volunteer subject s (age 18-35 yr) immediately before and after exposure to air or 0.4 p pm O-3 for 2 h with or without exercise. For assay of H2O2, breath con densate was collected in Tygon tubing submerged in an ice-water bath, and H2O2 was quantitated by a fluorescence assay. in a subset of subje cts, exhaled carbonyls were examined by collection of exhaled breath i nto Tedlar bags. Breath carbonyls were subsequently derivatized and co ncentrated on column packing containing 2,4-dinitrophenylhydrazine, de rivatives eluted, and analyzed by high-performance liquid chromatograp hy with ultraviolet detection. The data showed an increase in exhaled breath H2O2 in O-3-exposed, exercising subjects but not in subjects ex posed to O-3 without exercise. An increase in an aldehydic derivative that eluted with a similar retention time as derivatized acetaldehyde was found in the breath of O-3-exposed subjects. These data suggest th at O-3 exposure of humans in vivo can induce an oxidative stress as ev idenced 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 simila r responses of humans exposed to other environmental pollutants either in controlled settings or in field studies.