Research Program Area: Health & Exposure
Topic Areas: Health Effects of Air Pollution
This research consisted of eight separate projects designed collectively to investigate: (1) the efficacy of the ozone (03) effective dose concept (expressed as the product of 03 concentration, minute ventilation (VE) and exposure duration), in predicting the acute 03 toxicity response in young adult males; (2) the relative 03 toxicity response of young adult females, clinically normal middle-aged males, and highly trained endurance athletes, compared to young adult males at the same effective dose; and (3) the possible interactive effects of 03 inhalation in the presence of ambient heat and nitrogen dioxide (N02). A summary statement of the purpose, major observations and their significance for each of the eight studies follows:
1. Refinement of the 03 Effective Dose Concept. Pulmonary function impairment has been shown to be highly correlated with a second-order polynomial function of 03effective dose (expressed as the simple product of Cl3 concentration, VE and exposure time) in both intermittent exercise (IE) and continuous exercise (CE) exposures. However, calculated multiple regression equations, which yielded a greater weighting to 03 concentration than to either VE or exposure time: have been shown to provide a closer fit. To study further the physiological effects of exposure to divergent 0 a concentrations at several similar effective doses, we exposed 10 young adult mates to 12 protocols varying in i3 3 concentration (0 to 0.40 ppm), exercise VE (30 and 70 ah-min-l), and duration (30 to 100 min). The slopes of pulmonary function impairment for exposures to 0.20, 0.30 and 0.40 ppm 03 were found to differ significantly, and to be related as an exponential function of 0 concentration. These observations underline the need to further investigate the factors involved in 03 toxicity response.
2. Effects of Exercise Continuity on Acute 03Toxicity. The use of continuous exercise (CE) during 03 exposures, as opposed to intermittent exercise (IE) employed in other laboratories, is among several factors that can confound comparison of acute physiological responses. In this study, six aerobically trained adult male subjects were exposed by mouthpiece inhalation to 0.40 pprn 03 during bouts of exercise that were either 1 h CE, or 2 h IE, but matched for total ventilation and effective dose, Statistical analysis revealed no significant differences in pu1monar.y function impairment between the 1. H CE and the 2 h 1E protocols. However- alterations in exercise ventifatory pattern and subjective symptoms were more pronounced during the 1 h CE protocols at both levels of total ventilation. It was concluded that the enhanced responses with CE could not be definitively attributed to differences between the two exercise modes without assessment of filtered air (FA) control exposure responses.
3. Effects of Inspiratory Route on Physiologic Responses to 03. Inspiratory route is among several factors that potentially confound comparison of physiologic responses to acute 03 exposure in our obligatory oral inhalation method to that of ad-lib breathing permitted in chamber exposures. In this study: six young adult males were exposed on five occasions to 0.40 ppm 03 while exercising continuously at one of two work loads .e+min-1). (V f of -30 and 75 'The VE exposure time product was similar for a 1 protocols. Four exposures were randomly delivered with a Hans-Rudolph respiratory valve attached to a silicone facemask: with inspiratory route effected with and without noseclip. No statistically significant differences across conditions in pulmonary function or subjective symptoms were observed. The fifth Exposure, de1ivered via the same respiratory valve, but without facemask, revealed significantly greater forced expiratory volume in 1 second (FEV7.0) impairment than that observed for the respiratory valve, facemask with nose clip exposure (-20.4 and -1.5.9X, respective? y). The latter suggests partial 03 reactivity to the facemask and clean shaven facial surface of the subjects, but-fails to negate our conclusion that inspiratory route, during rnoderate and heavy continuous exercise, does not affect acute physiologic responses to 03.
4. Comparison of Aerobically Trained and non-trained Young Adult Females Physiologic Responses to 03. While there are considerable data available on the response of young adult males to 03 inhalation during exercise, there is a paucity of such data for females. In this investigation, the effects of 1 h continuous exercise at VE of 23, 34, 2nd 46 l.min-1, while exposed to FA, C.2, 0.3, and 0.4 ppm 03, were studied in a group of ten aerobically trained and 30 normally active, non-trained females. Both groups demonstrated significant pulmonary function impairment and a greater number of reported subjective symptoms in .the 03 exposures compared to FA. 'There were no statistically significant differences in the responses to 03 inhalation observed between the trained group and their non-trained counterparts. However, the equivalent VE -imposed on both groups was elicited at absolute work loads approximately 10% less for the trained group. Thus, were the non-trained subjects to jog or ride a bicycle at the same sub-maximal speed as their trained counterparts in a given photochemical smog condition, they would incur a greater VE and hence, a greater 03 effective close and acute toxicity response. 80th groups of females incurred greater pulmonary function impairment at the 03 effec tive dose imposed (-600 ppm l; than that observed for young adult males. This difference appears to be primarily associated with ,the mean lung size difference between the sexes, which is approximately 1% times larger for males (i.e. a smaller lung volume to amount of 0.,3 inhaled for .the females).
5. Comparison of Aerobically Trained and Non-trained Middle Aged Males; Physiologic Responses to 03. While the present South Coast Air Quality Management District (SCAQMD) advisory chart states that the elderly should stay indoors and reduce physical activity upon occurrence of a first stage alert (i.e., 0.20 ppm 03 ), .there are no laboratory studies of alder human's response to 03. In this investigation, we studied the effects of 1 h continuous exercise at VE of both 34 and 46 l-min-1, while exposed to FA or 03, in a group of six aerobically trained middle-aged males and 20 non-trained middle-aged males. Both groups demonstrated a trend toward pulmonary function impairment and altered exercise ventilatory pattern when exposed to 03, but only a few differences were significantly different from FA control.. Further, their pulmonary function impairment was slightly less than that incurred by young adult males at similar 03 effective doses, There were no significant differences between the responses to 03 inhalation of the trained and non-trained groups. It was observer, however, that the non-trained group would elicit a VE (and thus, 03 inhaled) approximately 30 percent greater than the trained group if they walked, jogged or bicycled at the same speed.
6. Endurance Performance and 03 Toxicity Responses of Competitive Athletes during Low Ambient Level Exposures. Ten highly trained endurance athletes were studied to determine the effects of exposure to low 03 concentrations on pulmonary function and simulated competitive endurance performance. Each subject was randomly exposed to FA and to 0.12, 0.18 and 0.24 PPM 03.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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