Theodore G. Venet

Comparative respiratory effects of ozone and ambient oxidant pollution exposure during heavy exercise.

Fifty volunteer bicyclists were exposed to purified air containing ozone (O/sub 3/) at controlled concentrations of 0, 0.08, 0.16, 0.24, and 0.32 ppm, and to oxidant polluted ambient air (mean O/sub 3/ concentration 0.15 ppm, mean total particulate concentration 295 ..mu..g/m/sup 3/) in suburban Los Angeles. Exposures (in random order, 14 days apart) involved one hour of heavy continuous exercise (mean minute volume 57 L) plus brief warm up and cool down periods. Significant forced expiratory function decrements and symptom increases occurred in ambient air exposures. In controlled O/sub 3/ exposures, responses were significant at 0.16 ppm and higher; their severity increased with increasing O/sub 3/ concentration. Effects were only partially reversed after one hours rest in purified air. Ambient exposures produced about the same response as O/sub 3/ alone at the same concentration. Thus coexisting pollutants do not appear to enhance the irritancy of O/sub 3/ in typical moderate ambient oxidant pollution episodes. However, O/sub 3/ itself can produce respiratory irritation at concentrations slightly above the health based federal ambient air quality standard of 0.12 ppm O/sub 3/, at high ventilation rates required during heavy exercise.

Effects of Exposure to 4 PPM Nitrogen Dioxide in Healthy and Asthmatic Volunteers

Healthy and asthmatic volunteer subjects (N = 25 and N = 23, respectively) were exposed twice each to purified air (control) and to 4 ppm nitrogen dioxide (NO2) in a controlled-environment chamber. Exposures lasted 75 min, and included 15 min each of light exercise (ventilation rate near 25 L/min) and heavy exercise (near 50 L/min). Compared to control, NO2 exposure produced no statistically significant untoward effects on airway resistance, symptoms, heart rate, skin conductance, or self-reported emotional state in normal or asthmatic subjects. Exercise was associated with significantly (P less than .001) increased airway resistance in both subject groups, although the increase in normals was small. In both groups, systolic blood pressure showed small but significant (P less than .01) decreases with NO2 exposure, compared to control. This effect, if real, may relate to formation of a vasodilating nitrite or nitrate from inhaled NO2. The lack of respiratory response contrasts with previous findings elsewhere; at present, this inconsistency is unexplained.

Respiratory effects of 0.75 ppm sulfur dioxide in exercising asthmatics: Influence of upper-respiratory defenses

To determine the influence of mouthpiece breathing on respiratory responses to sulfur dioxide (SO2), 23 young adult asthmatic volunteers were exposed in a chamber to 0.75 ppm SO2 during heavy exercise, once with breathing unencumbered and once while they wore noseclips and mouthpieces. These conditions (more severe than in typical ambient exposures) were deliberately chosen to produce significant physiological and clinical responses. Similar exposures to clean air served as controls. Exposure studies were separated by 1-week intervals and order was randomized. The protocol consisted of 10 min on a bicycle ergometer (mean load 650 kg-m/min, mean ventilation 40 liter/min), preceded and followed by response testing (body plethysmography, symptom questionnaires, and forced expiratory function tests; the last were performed only postexposure). During clean-air exposures, specific airway resistance (SRaw) and symptoms increased significantly, but no meaningful differences between mouthpiece breathing and unencumbered breathing were observed. Exposures to SO2 under these relatively severe conditions produced greater increases in SRaw than clean-air exposures regardless of the mode of breathing, but the excess increase was significantly greater with mouthpiece than with unencumbered breathing. Symptom changes and postexposure forced expiratory function showed qualitatively the same pattern of decrements with SO2 ad did SRaw, but the excess responses attributable to mouthpiece breathing did not attain statistical significance. Mouthpiece breathing can compromise upper-respiratory defenses against SO2 to the extent that responses are greater than with more natural breathing. The mode of breathing should be taken in account when applying laboratory human exposure data to air-quality risk assessment.

A Dose-Response Study of Healthy, Heavily Exercising Men Exposed To Ozone At Concentrations Near the Ambient Air Quality Standard

Twenty-four healthy, well-conditioned young adult male volun teers, free of asthma or clinical respiratory allergies, were exposed to purified air containing ozone (03) at 0.16, 0.14, 0.12, 0.10, 0.08, and 0.00 part per million (ppm). Exposures were separated by 2- week intervals, occurred in random order, and lasted 2 hours each. Temperature was 32 ± 1° C and relative humidity was 38 ± 3%, simulating Los Angeles area smog conditions. Subjects exercised 15 minutes of each half hour, attaining ventilation rates averaging 68 L/min (∼35 L/min per m2 body surface area). Lung function was measured pre-exposure and after 1 hr and 2 hr of exposure. Airway responsiveness to a cold-air challenge was measured immediately following the 2-hr exposure. Symptoms were recorded before, dur ing, and for one-week periods following exposures. For the group as a whole, no meaningful untoward effects were found except for a mild typical respiratory irritant response after 2 hr exposure to 0.16 ppm 03. Two individual subjects showed possible responses at 0.14 ppm, and one of them also at 0.12 ppm. In comparison to some previous investigations, this study showed generally less response to 03. The comparative lack of response may relate to the favorable clinical status of the subjects, the pattern of exercise dur ing exposure, or some other factor not yet identified.

A Statistical Analysis of Radial Keratotomy in Human Cadaver Eyes

We performed radial keratotomy using the Fyodorov techniques on 14 Eye Bank eyes. Using stepwise regression and best subset statistical analysis, we examined the effects of incision length. We found that the most significant variables affecting postoperative corneal curvature were the incision depth and length. The histologic examination of serial sections of the Eye Banks eyes after this procedure revealed that the average achieved incision depth, using a standard blade depth setting, had variations of up to 30% between eyes. This inability to standardize incision depth may lead to the variable surgical results reported in radial keratotomy.

Short-Term Respiratory Effects of Photochemical Oxidant Exposure in Exercising Children

To assess the short-term respiratory effects of photochemical oxidant pollution in children, 66 volunteers—33 boys and 33 girls aged 8 to 11—were exposed in a movable laboratory to polluted Los Angeles area ambient air and to purified air as a control. Exposures lasted one hour, during which subjects exercised continuously at roughly 50 percent of maximal oxygen consumption. Forced expiratory function and symptoms were evaluated prior to and at the end of exposure. The mean ozone concentration in ambient exposures was 0.113 ppm, reflecting an unusually mild pollution season. As a group, the subjects showed no statistically significant untoward responses to ambient air in comparison to purified air, and no significant differences in response between sexes. Nevertheless, regression analyses of individual data indicated a significant (p < 0.05) trend toward forced expiratory dysfunction with increasing ambient ozone concentrations. When the regression analyses were expanded to include older children and adul...

Response to ozone in volunteers with chronic obstructive pulmonary disease.

Twenty-eight volunteers with chronic obstructive pulmonary disease were exposed to 0.0, 0.18, and 0.25 ppm ozone in purified air for 1-hr periods with light intermittent exercise, with exposure conditions presented in random order at 1-month intervals. No statistically significant changes attributable to ozone were found in forced expiratory performance or percent oxyhemoglobin (measured near the beginning and end of each exposure). No ozone-related changes in clinical status were found by interviews that included the time for 1 wk before to 1 wk after each exposure, except that a moderate increase in lower respiratory symptoms was reported by nonsmokers in 0.18 ppm exposures only. Thus, a slight decrement in hemoglobin saturation with ozone exposure (reported in two previous studies of chronic obstructive pulmonary disease subjects) may not be a common occurrence under typical ambient exposure conditions.

Controlled Exposure of Volunteers with Chronic Obstructive Pulmonary Disease to Nitrogen Dioxide

Twenty-two volunteers with chronic obstructive pulmonary disease were exposed to nitrogen dioxide at 0.0, 0.5, 1.0, and 2.0 ppm in a controlled environment chamber. Exposure lasted 1 hr and included two 15-min exercise periods, during which the mean ventilation rate was roughly 16 L/min. Pulmonary mechanical function was evaluated pre-exposure, after initial exercise, and at the end of exposure. Blood oxygenation was measured by ear oximetry pre-exposure and during the second exposure period. Symptoms were recorded during exposures and for 1-wk periods afterward. No statistically significant changes in symptom reporting could be attributed to nitrogen dioxide exposure at any concentration, compared to the 0.0 ppm control condition. Measures of pulmonary mechanics showed either no significant changes, or small and equivocal changes. Arterial oxygen saturation showed marginal improvement with exercise, regardless of nitrogen dioxide concentration.

Respiratory responses of young adult asthmatics to sulfur dioxide exposure under simulated ambient conditions

Twenty-four young adult asthmatic volunteers were exposed to 0, 0.25, and 0.50 ppm SO/sub 2/ in random order at 1-week intervals. Exposures, conducted in a controlled-environment chamber at 23/sup 0/C and 90+% relative humidity, lasted 1 hr and incorporated alternating 10-min periods of moderate exercise (mean exercise ventilation about 27 liters/min) and rest. Airway resistance was measured before exposure, after the first exercise period, and near the end of exposure. Forced expiratory performance was measured after the final airway resistance measurement. Exposure-relatable symptoms were recorded before, during, and after exposure periods. None of these measures of response showed statistically significant variation attributable to SO/sub 2/, although small significant increases in resistance attributable to exercise were found. These negative results contrast with previous positive findings in asthmatics exposed to SO/sub 2/ via mouthpiece. The differences may relate to effects of mouthpiece breathing on respiratory defenses, or to interindividual variations in bronchial reactivity to SO/sub 2/.

Asthmatics' Responses to 6-Hr Sulfur Dioxide Exposures on Two Successive Days

Asthmatic volunteers (N = 14) aged 18 to 33 yr with documented sensitivity to sulfur dioxide (SO2) were exposed in a chamber to 0.6 ppm SO2 for 6-hr periods on 2 successive days. Similar exposures to purified air, 1 wk later or earlier, served as controls. Subjects exercised heavily (target ventilation rate 50 L/min) for 5 min near the beginning of exposure (early exercise) and for an additional 5 min beginning after 5-hr of exposure (late exercise). At all other times, they rested. Body plethysmographic measurements and symptom questionnaires were administered pre-exposure, after each exercise period, and hourly during rest. Bronchoconstriction and lower respiratory symptoms were observed during or immediately following exercise--to a slight extent with clean air, and to a more marked extent with SO2. Bronchoconstriction and symptoms were modestly less severe on the second day of SO2 exposure than on the first day, but there were no meaningful differences in response between early and late exercise periods on either day.