Effects of Steady-State and Variable Ozone Concentration Profiles on Pulmonary Function

Abstract

Measurements of ambient ozone (O2) concentration during daylight hours have shown a spectrum of concentration profiles, from a relatively stable to a variable pattern usually reaching a peak level in the early afternoon. Several recent studies have suggested that in estimating exposure dose (O3 concentration [C] x exposure time [T] x ventilation [V]), O3 concentration needs to be weighted more heavily than either ventilation or duration of exposure in the estimates. In this study we tested the hypothesis that regardless of concentration pattern and exposure rate the same exposure dose of O3 will induce the same spirometric response. We exposed 23 healthy male volunteers (20 to 35 yr of age) for 8 h to air, 0.12 ppm O3 (steady-state), and a triangular exposure pattern (concentration increased steadily from zero to 0.24 ppm over the first 4 h and decreased back to zero by 8 h). During the first 30 min of each hour, subjects exercised for 30 min at minute ventilation (VE) approximately 40 L/min. The order of the exposures was randomized, and the exposures were separated by at least 7 days. The response patterns over the 8-h periods for spirometric variables in both O3 exposures were statistically different from air exposure changes and from each other. For FEV1 the p values were 0.017 between air and steady-state profile, 0.002 between air and triangular profile, and 0.037 between steady-state and triangular profiles. Although in the triangular pattern of exposure the maximal O3 concentration was reached at 4 h, the maximum FEV1 decrement (10.2%) was observed at 6 h of exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of Chamber 6.6-h Exposures to 0.04–0.08 PPM Ozone via Square-wave and Triangular Profiles on Pulmonary Responses

“…They also indicate that subjects spend more time with reduced lung function and symptoms of breathing discomfort during an environmentally realistic variable O 3 pattern averaging 0.08 ppm than when exposed to the constant, square-wave 0.08-ppm O 3 profile. It would be very interesting to determine whether later occurring inflammatory indicators are different in the longer occurring significant pulmonary effects observed in the triangular exposures than in the square-wave exposures, especially since they were not measured by Hazucha et al (1992), in our earlier study (Adams, 2003), or in the present study.…”

“…Neither square-wave O 3 exposures nor the one study (Hazucha et al, 1992) that utilized an 8-h triangular shaped varied O 3 exposure (i.e., 0 ppm increased to 0.24 ppm at 4 h, and back to 0 ppm at 8 h), adequately mimics the variable diurnal daylight O 3 concentration pattern observed in many urban areas experiencing air pollution episodes. Accordingly, in a recent study (Adams, 2003), two types of 6.6 h exposure patterns were used:…”

Establishing Relevant Ozone Standards to Protect Vegetation and Human Health: Exposure/Dose-Response Considerations

“…22 have revealed also that concentration may be more important than duration. Humans who were exposed continuously for 8 hours to 120 ppb showed significantly less impairment than those exposed to a regime providing the same overall exposure in which the 0, level rose from zero to a peak of 240 ppb and then fell back to zero.…”

Ozon [MAK Value Documentation in German language, 1995]

“…Diese Modelle sind bisher aber nicht validiert (Kriebel und Smith 1990;McDonnell und Smith 1994 Koren et al 1990). Die Zusammensetzung der Nasenspülflüssigkeit unterschied sich mit Ausnahme einiger Entzündungs-mediatoren nicht von der der Lungenspülflüssigkeit (siehe unten) (Bascom et al 1990;Graham and Koren 1990 McDonnell et al 1991Horstman et al 1990Hazucha et al 1992McDonnell et al 1991Linder et al 1988McDonnell et al 1983Horstman et al 1990Schelegle und Adams 1986Linder et al 1988McDonnell et al 1987Horstman et al 1990McDonnell et al 1991Kehrl et al 1987McDonnell et al 1991Koren et al 1989Gerrity et al 1993Foster et al 1987 (Lippmann 1992;McDonnell et al 1993;Seal et al 1993;Weymer et al 1994). Eine anfänglich etwa 20%ige Abnahme der Lungenfunktionsparameter betrug 18 Stunden nach Exposition gegenüber 0,6 mg/m 3 (70 Minuten, incl.…”