Jill D. Whynot

Effects of 0.2 ppm nitrogen dioxide on pulmonary function and response to bronchoprovocation in asthmatics

To study the respiratory effects of nitrogen dioxide (NO2) at ambient concentrations, we exposed 31 asthmatic volunteers to purified air (control) and to 0.2 ppm NO2 for 2-h periods with light intermittent exercise. Bronchial reactivity (loss of forced expiratory performance in response to graded doses of methacholine chloride aerosol) was determined postexposure, using a newly developed apparatus that allowed accurate quantitation of methacholine dose. Forced expiratory performance, total respiratory resistance, and symptoms were also recorded immediately pre- and postexposure (prior to methacholine challenges). No significant direct effect of NO2 exposure on forced expiratory function or total respiratory resistance was observed. Symptoms showed a small significant (p less than 0.05) excess in purified air relative to NO2 exposures. Individual responses to methacholine varied greatly. About two-thirds of the subjects showed greater response after NO2 than after purified air, but the mean excess response was small. Mean changes attained significance in some but not all applicable statistical tests. Thus we cannot conclude unequivocally that NO2 exposure increased bronchial reactivity in this group, although there was some tendency in that direction.

Respiratory dose-response study of normal and asthmatic volunteers exposed to sulfuric acid aerosol in the sub-micrometer size range.

Twenty-one healthy and 21 asthmatic volunteers were exposed to respirable sulfuric acid aerosol (mass median particle diameter approximately 0.9 pm, geometric standard deviation 2.5) in a chamber at 21° and 50% relative humidity. Measured sulfuric acid concentrations averaged 0, 380, 1060, and 1520 μg/m3 (in the occupational range, higher than concentrations observed in ambient air pollution). Exposures to different concentrations occurred in randomized order 1 week apart. They lasted 1 hr and included three 10-min periods of heavy exercise. Healthy volunteers showed no statistically significant changes in pulmonary function. airway reactivity to inhaled methacholine, or overall reporting of irritant symptoms which could be attributed to acid exposure. They did show a slight statistically significant (P <. 01) increase in cough with increasing acid concentration. At the two highest acid concentrations, asthmatics showed significant increases in irritant symptoms and decrements in pulmonary function, without significant changes in airway reactivity. Their function decrements appeared to increase with time during exposure. Previous studies in fog (10°, median particle diameter approximately 10 urn) with similar concentrations of sulfuric acid showed more symptoms but less pulmonary function change, perhaps reflecting different sites of particle deposition in airways and/or different degrees of neutralization by airway ammonia. This and earlier evidence predicts little, if any, acute irritant response in short-term (1 hr or less) exposures to sulfuric acid at concentrations found in ambient air pollution.

Short-term respiratory effects of sulfuric acid in fog: a laboratory study of healthy and asthmatic volunteers.

To explore short-term respiratory health risks from acid-polluted fog, 22 normal and 22 asthmatic adult volunteers were exposed in an environmental control chamber to light fogs (∼0.1 g/m3 liquid water content, 10 μm median droplet diameter, 10°C) containing nominally 0, 500, 1000, and 2000 μg/m3 of sulfuric acid. Fog was produced by atomizing dilute acid solution Into purified air humidified to near 100 percent by steam injection. Exposures were administered in random order at 1-week intervals, lasted 1 h, and Included three 10-min periods of moderately heavy exercise. Responses were measured in terms of forced expiratory function, airway resistance, Irritant symptoms, and bronchial reactivity to methacholine aerosol. Sulfuric acid per se showed no more than a slight effect on pulmonary function, even at the highest concentration. Asthmatics experienced bronchoconstrlction, attributable to exercise, under all exposure conditions. Despite the lack of substantial function changes, modest statistically sign...

Experimental exposures of young asthmatic volunteers to 0. 3 ppm nitrogen dioxide and to ambient air pollution

Asthmatic volunteers aged 8 to 16 (N = 34) were exposed on separate occasions to clean air (control), to 0.30 ppm nitrogen dioxide (NO2) in otherwise clean air, and to polluted Los Angeles area ambient air on summer mornings when NO2 pollution was expected. Exposures lasted 3 hr, with alternating 10-min periods of exercise and rest. In ambient pollution exposures, 3-hr average NO2 concentrations ranged from 0.01 to 0.26 ppm, with a mean of 0.09 ppm. Ambient exposures did not significantly affect lung function, symptoms, or bronchial reactivity to cold air, relative to the control condition. Responses to 0.3 ppm NO2 exposures were equivocal. Asthma symptoms were more severe during 1-week periods before 0.3 ppm exposures, and lung function was decreased immediately before 0.3 ppm exposures, compared to other conditions. Lung function declined slightly during the first hour at 0.3 ppm, but improved over the remaining 2 hr. Compared to other conditions, symptoms were not increased during 0.3 ppm exposures, but were increased during 1-week periods afterward. These observations may reflect untoward effects of 0.3 ppm NO2, or may reflect chance increases in asthma severity prior to 0.3 ppm exposures.

Respiratory responses of exercising asthmatic volunteers exposed to sulfuric acid aerosol

Young asthmatic adult volunteers (N = 27) were exposed in an environmental chamber to sulfuric acid aerosol at concentrations near 0, 122, 242, and 410 μg/m3, in purified background air at 22° C and 50 percent relative humidity. The polydisperse aerosol had a mass median aerodynamic diameter near 0.6 μm. Exposures occurred in random order at one-week intervals. Each lasted 1 h, during which subjects exercised (mean ventilation 42 L/min) and rested during alternate 10-min periods. Specific airway resistance and forced expiratory function were measured pre-exposure, after the initial exercise, and at end-exposure. Bronchial reactivity was determined by challenge with cold air immediately post-exposure. Symptoms were monitored during exposure for one week afterward. Exercise-induced bronchospasm was observed under all conditions. Physiologic and symptom changes possibly attributable to sulfuric acid exposure were small and not statistically significant. Our largely negative results contrast with positive fin...

Human respiratory responses to an aerosol containing zinc ammonium sulfate

Abstract Twenty-one normal volunteers and 19 volunteers with asthma were exposed in an environmental control chamber to a polydisperse aerosol of zinc ammonium sulfate (ZnSO 4 ·(NH 4 ) 2 SO 4 )—a model of ambient metallic sulfate aerosols derived from trace metals in fossil fuels—at a nominal concentration of 20 μg/m 3 . As a model of the background ambient particulate burden, polydisperse sodium chloride aerosol at a nominal concentration of 300 μg/m 3 was added to the chamber atmosphere during control as well as exposure studies. Exposure temperature was 20°C and relative humidity was 85%, simulating weather conditions typical of fall/winter ambient pollution episodes. Exposure and control studies were performed on separate days, separated by about 3 weeks, in random order under double-blind conditions. Exposure periods lasted 2 hr and included intermittent light exercise. Lung function and symptoms were evaluated before and at the end of the exposure or control period. Symptom reports showed no significant variation attributable to zinc ammonium sulfate exposure. Group mean lung function measures showed a few significant changes possibly attributable to the sulfate exposure, but these were small and inconsistent. It was concluded that zinc ammonium sulfate produced minimal or no short-term respiratory effects observable under the conditions of the experiment.

Human exposure to ferric sulfate aerosol: effects on pulmonary function and respiratory symptoms

Twenty normal and 18 asthmatic human volunteers were exposed to ferric sulfate aerosol at a nominal concentration of 75 microgram/m3 (equivalent to 20 microgram iron/m3). The concentration and particle size distribution (2 micron mass median aerodynamic diameter; geometric standard deviation of 3) were selected to simulate worst case ambient conditions. Ferric sulfate was chosen for study because it is toxic, it is a respiratory system irritant, and increased use of coal and high sulfur fuel oils will lead to increased concentrations of iron and sulfate in ambient air. A double-blind protocol was followed in which each subject was exposed on two days, separated by about a three week period. The subjects were exposed to clean air (sham) on one day and to ferric sulfate aerosol on the other (exposure); the order of exposure was selected randomly. Neither the subjects nor the staff performing the clinical testing were informed as to the nature of the atmosphere on any given day. Pulmonary function tests were performed immediately before (pre) and after (post) each 2 hr sham or exposure period; this protocol included intermittent exercise. Pre- and post-exposure symptom score interviews were also administered. On the average, the two groups of subjects did not exhibit significant pre- to post-changes in total respiratory system resistance, forced expiratory flow/volume performance, and single breath nitrogen washout parameters. None of the subjects reported more than slight changes in symptoms during exposure. Five individuals showed small but significant decremental trends in pulmonary function; however, nine subjects tended to improve after exposure.

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.

Controlled Exposure to a Mixture of SO2, NO2, and Particulate Air Pollutants: Effects on Human Pulmonary Function and Respiratory Symptoms

Exposure of 20 volunteers to sodium chloride (NaCl) aerosol or to a mixture containing NaCl plus irritant particles (zinc ammonium sulfate) and irritant gases (nitrogen dioxide and sulfur dioxide) produced no significant decrements in pulmonary function. There was a slight tendency for respiratory symptoms to be greater during the exposure to the mixture than during exposure to the NaCl aerosol alone; the differences were not statistically significant. The pollutant concentrations studied approximated worst-case ambient levels observed in the Los Angeles basin.