Approaching the RSV season with a nursing plan of action

As the statistics show with year-in, year-out regularity, during November through March in the United States, approximately 90,000 infants and young children will be hospitalized with a severe lower respiratory infection attributable to the respiratory syncytial virus (RSV). This virus, discovered only as recently as 1956, appears to be ubiquitous, infecting virtually 100% of children by age 4. For most of them the resulting illness will be mild and easily vanquished by an intact immune system. For some, however, RSV infection confers considerable morbidity, and these infants and children are the concern of the symposium held in conjunction with Pediatric Nursing's 11th annual conference. The symposium addressed several aspects of RSV infection: Who is at risk and should be hospitalized? How can nurses contribute to the care of hospitalized patients? Are there environmental risks to health-care personnel from ribavirin aerosol, the antiviral treatment approved for RSV infection? Are there special considerations for mechanically ventilated patients? Speakers generally concluded that symptomatic treatment and antiviral therapy with ribavirin aerosol can reduce severe morbidity in severely infected patients with minimal occupation risk to health-care personnel.

Exposures of health-care workers to ribavirin aerosol: a pharmacokinetic study

We assessed health risks to nurses and therapists exposed occupationally to ribavirin aerosol, a known rodent teratogen, by measuring uptake as a function of exposure concentration. During a 4-d period, healthy, nonsmoking, young adult volunteers (N = 14) were exposed 4 h/d respirable ribavirin aerosol at concentrations that exceeded occupational levels. Intermittent exercise occurred during exposure, and all activities occurred in a simulated hospital room. Ribavirin was assayed in plasma, red cells, and urine; lung function and symptoms were also measured. In 7 volunteers who were exposed to 30 mg/m3 (i.e., received approximately 10% of therapeutic dose), postexposure ribavirin concentrations in plasma and urine were similar on all 4 d, averaging (0.89 mumol/l and 131 mumol/l, respectively. These concentrations decreased after exposure, with half-times of 37-39 h. Red-cell concentrations averaged 31 mumol/l on d 4, accounting for < 5% of inhaled ribavirin mass, and they remained stable for 4 d afterward. In 7 volunteers exposed to 3 mg/m3 (i.e., approximately 1% of therapeutic dose), plasma averaged 0.075 mumol/l and red cells averaged 3 mumol/l on d 4 (i.e., near detection limits). Small variations occurred in lung function, reported symptoms, and hematologic values for exposures to both 3 and 30 microgram/m3; therefore, these effects were most likely not caused by ribavirin. Typical occupational exposures to ribavirin, without recommended protective measures, should result in undetectable or barely detectable body burdens, i.e., approximately 0.1%-1% of levels reported to be toxic to laboratory animals.

Comparative short-term health responses to sulfur dioxide exposure and other common stresses in a panel of asthmatics

We studied 14 unmedicated sulfur dioxide (SO2)-sensitive asthmatics to test the hypothesis that SO2 exacerbates asthma more than other everyday respiratory stressors. In Phase I, subjects underwent controlled exposures to 0.0, 0.5, and 1.0 ppm SO2 with light, medium, and heavy exercise (average ventilation 30, 36, and 43 l/min, respectively). Lung function, symptoms of asthma, and psychophysical (stamina) changes were measured. Function, symptom, and stamina responses correlated modestly. Increasing SO2 had stronger unfavorable effects than increasing exercise. In Phase II, subjects performed eight different physical tasks in SO2-free ambient air while symptoms and stamina were measured. Fast stair-climbing evoked symptoms similar to the effects of 0.5 ppm SO2/light exercise, while stamina reduction was comparable to 0.5 ppm SO2/heavy exercise. In Phase III, subjects recorded time-activity patterns, symptoms, and stamina during randomly selected intervals on a typical weekday and weekend day. Most reported activities were sedentary. Infrequent, strenuous Phase III exercise increased symptoms more than did 0.5 ppm SO2/light exercise, but with less effect on stamina. We conclude that for typical mild asthmatics, ten-minute SO2 exposures at concentrations > 0.5 ppm and ventilation > 30 l/min can cause short-term asthma manifestations more intense than those usually experienced from everyday stresses without SO2 exposure.

Controlled exposures of young asthmatics to mixed oxidant gases and acid aerosol

To help assess short-term respiratory responses to summertime air pollution, we exposed 24 asthmatic volunteers aged 11-18 in a chamber to respirable acid aerosol (mass median aerodynamic diameter 0.66 micron) plus 0.3 ppm nitrogen dioxide (NO2) plus 0.2 ppm ozone (O3). The aerosol contained available hydrogen ions (H-) at an average concentration of 2.6 mumol/m-, equivalent to 127 micrograms/m3 sulfuric acid (H2SO4); some H+ probably was in NH4HSO4 rather than H2SO4. The volunteers were exposed separately to O3/NO2 without acid and to clean air. Exposures lasted 90 min, including three 15-min exercise sessions with ventilation averaging 32 L/min, at 21 degrees C and 50% relative humidity. Asthma medications were withheld before and during exposures. Subjects gargled lemonade to minimize acid neutralization by oral ammonia (NH3). Exercise-induced bronchospasm was evident in all exposures. Differences in group mean lung function response among H2SO4/O3/NO2, O3/NO2, and clean-air exposures were not statistically significant. Individuals' measured oral NH3 concentrations or estimated inhaled doses of H2SO4 did not significantly predict their lung function changes. A few subjects showed unfavorable function changes during pollutant exposures, which might be chance occurrences or might indicate the existence of an acid-pollution-susceptible subgroup among young asthmatic subjects.

Effects of prolonged, repeated exposure to ozone, sulfuric acid, and their combination in healthy and asthmatic volunteers

To evaluate effects of "acid summer haze" on individuals who exercise extensively outdoors, we exposed 45 adult volunteers (15 normal or atopic, 30 asthmatic) in a chamber to a mixture of 0.12 ppm ozone (O3) and approximately 100 micrograms/m3 of respirable sulfuric acid aerosol (H2SO4). On separate occasions we exposed the same subjects to O3 alone, to H2SO4 alone, and to clean air. In exposures involving H2SO4, excess acid was generated to consume ammonia released by the subjects, and the aerosol therefore contained ammonium salts in addition to H2SO4. Subjects were exposed to each atmosphere on two successive days, for 6.5 h/d, with six 50-min exercise periods at ventilation rates averaging 29 L/min. Exposures were conducted during four successive weeks, in random order. Lung function and symptoms were measured before exposure and hourly during exposure. Bronchial reactivity to inhaled methacholine was measured just after the end of each exposure. Exposure to H2SO4 alone caused no significant changes in lung function, symptoms, or bronchial reactivity relative to clean air. Exposure to O3 alone or O3 + H2SO4 caused a progressive, statistically significant (p < 0.05) decline in forced expiratory function, smaller on the second day than the first, as previously found by others for O3 exposure. Bronchial reactivity increased significantly after exposure to O3 with or without H2SO4. Changes in mean lung function and bronchial reactivity with O3 + H2SO4 exposure were modestly larger than changes with O3 exposure, but the differences were nonsignificant or marginally significant. A minority of individual asthmatic and nonasthmatic subjects showed substantially greater declines in function with exposure to O3 + H2SO4 relative to O3 alone. Repeat exposure studies of these subjects again showed an excess response to O3 + H2SO4 on the average, but there was no significant correlation between the excess responses of individual subjects in the original and repeat studies. We conclude that for typical healthy or asthmatic adults heavily exposed to acid summer haze, O3 is more important than H2SO4 as a cause of short-term respiratory irritant effects.

Pre-exposure to ozone does not enhance or produce exercise-induced asthma

We evaluated whether acute exposure to ozone (O3) enhances or produces exercise-induced asthma (EIA) in asthmatic subjects who have or do not have EIA, according to standardized exercise challenge. Twenty-one otherwise healthy asthmatic subjects, 19 to 40 yr of age, with forced expiratory volume in one second (FEV1) greater than 70% of predicted and methacholine hyperresponsiveness, underwent three 1-h exposures on separate days to 0.10 ppm ozone in filtered air (FA), 0.25 ppm ozone in FA, and FA alone (randomized order, single-blinded, crossover design). Of these subjects, 12 underwent an additional exposure to 0.40 ppm ozone in FA. The subjects performed intermittent light exercise (with mean ventilation of 27 L/min) while in an environmentally controlled chamber (21 degrees C and 40% relative humidity). After each exposure, the subjects rested 1 h in clean air and performed serial postexposure spirometry. The subjects then underwent a standardized exercise challenge in clean air, followed by serial spirometry for 60 min. No significant changes in FEV1 or forced vital capacity (FVC) were found following 1-h exposures to 0, 0.10, and 0.25 ppm ozone (regardless of EIA status). The 12 subjects who underwent all four exposures showed a significant excess reduction in FEV1 (-0.35 +/- 0.37 L or -9.6%) after 1-h exposure to 0.40 ppm O3 (p = 0.017), regardless of EIA status. Postexposure FEV1 returned to baseline levels within 1 h. Postexposure changes in FVC showed similar magnitude and time course but were not statistically significant across exposure conditions or EIA status.(ABSTRACT TRUNCATED AT 250 WORDS)

Time-activity patterns and diurnal variation of respiratory status in a panel of asthmatics: implications for short-term air pollution effects

To understand the short-term health risks to people from air pollution exposure, we investigated time-activity patterns and temporal variation of the respiratory status in 49 asthmatic Los Angeles area residents 18-50 years old. During the summer (May-September) and winter (November-March), subjects measured their lung function two to four times daily at home for one week periods, and every hour recorded their symptoms, medication, and activity hourly in diaries. Almost all subjects recorded heart rates (HR), which were converted to ventilation rate (VR) estimates using individual laboratory exercise data. Most subjects' lung function and symptoms varied diurnally, and were worst in early morning. For subjects with clinically mild asthma, diurnal forced expired volume in 1 sec (FEV1) changes averaged 7%, versus 12% in those with moderate symptoms, and 18% in severely asthmatic subjects. Lung function was similar in summer and winter, but symptoms and medication use decreased in winter. In the aggregate, subjects reported spending 75% of waking hours indoors at self-rated slow activity and 11% in vehicles. HR records usually corroborated reports of medium or fast activity. Mean estimated VR at slow, medium, and fast activity was 19, 37, and 61 L/min for men, and 16, 24, and 32 L/min for women. Outdoor fast activity, representing the greatest vulnerability to outdoor pollution, occupied approximately 0.2% of waking hours (2 min/day on average); outdoor medium activity occupied about 2% of waking hours (19 min/day on average). Estimated cumulative ventilation was higher than that of previous healthy panels because of asthmatics' higher VR at slow activity. If these activity patterns are typical, asthmatics may be especially vulnerable to pollutants with effects dependent on cumulative inhaled dose. Effects dependent on high inhaled dose rates over a short period, e.g., sulfur dioxide effects, would be unlikely, except perhaps for uncommonly active individuals in uncommonly polluted areas.

Active and passive ozone samplers based on a reaction with a binary reagent

Ozone is one of the most toxic common air pollutants (judging from short-term animal and human exposure studies at realistic concentrations) and one of the most difficult and expensive pollutants to control. Because of ozone's high chemical reactivity, its concentrations may vary greatly over short distances, and fixed-site air quality monitors may not accurately estimate exposures of human populations. Epidemiologic research on ozone's long-term health effects has been inconclusive, partly because of the lack of reliable personal exposure information. The objective of this project was to develop a practical personal ozone exposure monitoring technique, and to document its precision and accuracy in actual use by representatives of freely ranging, ozone-exposed populations. The project site, Los Angeles, is the nation's metropolitan area with the highest level of ozone pollution and, thus, probably the most important locale for personal exposure assessment. Our overall strategy was (1) to select the most promising laboratory technique for ozone detection from published literature and private communications; (2) to design and test personal monitors using this technique; and (3) when feasible, to evaluate concurrently alternative methodologies developed by others. As indicated below, parts 1 and 2 of our strategy yielded a limited success with respect to short-term active sampling, i.e., measuring personal ozone exposure levels during one to two hours with a monitor incorporating a battery-powered air pump of the type used in industrial hygiene investigations. The same approach was not successful in passive sampling, i.e., measuring exposure levels during multihour or multiday periods with a light-weight, diffusion-controlled "badge" sampler having no moving parts. Passive badge samplers could be calibrated reasonably well in laboratory exposures to ozone in otherwise pure air, but they greatly overestimated ozone levels in outdoor ambient air. Part 3 of our strategy yielded more promising information on an alternative passive badge design. After testing and rejecting two other possibilities, we chose a binary organic reagents, 3-methyl-2-benzothiazolinone acetone azine with 2-phenylphenol, as the most promising chemical detector of ozone. Filter papers impregnated with the binary reagent develop a characteristic intense pink color when exposed to ozone. The inventors, J.E. Lambert and associates of Kansas State University, had intended only to develop a rough qualitative ozone monitor (Lambert et al. 1989). However, our initial laboratory testing (in exposure chambers containing ozone in otherwise very clean air, away from humans), revealed fairly accurate quantitative response.(ABSTRACT TRUNCATED AT 400 WORDS)

Exposures of older adults with chronic respiratory illness to nitrogen dioxide. A combined laboratory and field study

We combined field and laboratory experimentation to evaluate the effects of nitrogen dioxide in a panel of Los Angeles area residents with chronic respiratory illness, 15 men and 11 women aged 47 to 69. All had heavy smoking history, chronic symptoms, and low FEV1; some also had low FVC. During the fall-winter high-NO2 season, they monitored themselves for 2-wk periods using spirometers in the home, passive NO2 sampling badges, and diaries to record time and activity patterns and clinical status. In the middle of each self-monitoring week they were exposed in a chamber, once to clean air and once to 0.3 ppm NO2. Chamber exposures were double blind, lasted 4 h, and included four 7-min exercise sessions with average ventilation rates near 25 L/min. Symptom reports and hourly forced expiratory function tests showed no statistically significant differences between clean air and NO2 chamber exposures, although peak flow showed a approximately 3% loss with NO2 relative to clean air during the first 2 h of exposure only (p = 0.056). No significant overall differences were found between field self-measurements and measurements of lung function in the chamber or between field measurements in clean air and NO2 exposure weeks. Field data showed that group average lung function and symptom levels were worse in the morning than later in the day (p < 0.005) but otherwise were stable over 2 wk. Even though most subjects smoked and stayed indoors 80 to 90% of the time, personal NO2 exposures correlated significantly with outdoor NO2 concentrations as reported by local monitoring stations.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity patterns in elementary and high school students exposed to oxidant pollution

We investigated activity patterns of 17 elementary school students aged 10-12, and 19 high school students aged 13-17, in suburban Los Angeles during the oxidant pollution season. Individuals' relationships between ventilation rate (VR) and heart rate (HR) were "calibrated" in supervised outdoor walking/jogging. Log VR was consistently proportional to HR; although "calibrations" were limited by a restricted range of exercise, and possibly by artifact due to mouthpiece breathing, which may cause overestimation of VR at rest. Each subject then recorded activities in diaries, and recorded HR once per minute by wearing Heart Watches, over 3 days (Saturday-Monday). For each activity the subject estimated a breathing rate--slow (like slow walking), medium (like fast walking), or fast (like running). VR ranges for each breathing rate and activity type were estimated from HR recordings. High-school students' diaries showed their aggregate distribution of waking hours as 68% slow inside, 8% slow outside, 10% medium inside, 9% medium outside, 1.5% fast inside, 1.5% fast outside. Elementary students' distribution was 47% slow inside, 15% slow outside, 20% medium inside, 12% medium outside, 2.5% fast inside, 3.5% fast outside. Sleep occupied 38% of high-school students' and 40% of elementary students' time; HR were generally lower in sleep than in slow waking activity. High school students' mean VR estimates were 13 L/min for slow breathing, 18 for medium, and 23 for fast; elementary students' were 14 slow, 18 medium, and 19 fast. VR distributions were approximately lognormal. Maximum estimated VR were approximately 70 L/min in elementary and approximately 100 L/min in high school students. Compared to adults studied similarly, students reported more medium or fast breathing, and had equal or higher VR estimates during slow and medium breathing despite their smaller size. These results suggest that, relative to body size, young people inhale larger doses of outdoor air pollutants than adults.

Activity patterns in a panel of outdoor workers exposed to oxidant pollution

We investigated summer activity patterns in a panel of volunteers drawn from a population segment with potentially high exposure to ambient oxidant pollution. The subjects were 15 men and 5 women aged 19-50, all of whom worked outdoors in the Los Angeles area at least 10 hr per week. The general approach was to (i) calibrate the relationship between ventilation rate (VR) and heart rate (HR) for each subject in controlled exercise; (ii) have subjects monitor their own normal activities with diaries and electronic HR recorders; (iii) estimate VR from HR recordings; and (iv) relate VR with diary descriptions of activities. Calibration data were fit to the equation log (VR) = (intercept) + (slope x HR), intercept and slope being determined separately for each individual to provide a specific equation to predict her/his VR from measured HR. Individuals' correlation coefficients relating log (VR) with HR ranged from 0.83 to 0.95. Subjects monitored themselves for three 24-hr periods during one week, including their most active work day and their most active non-work day. They wore Heart Watch(R) athletic training instruments which recorded HR once per minute; and recorded each change in their activity, location, or breathing rate in diaries. Breathing rates were classified as sleep, slow (like slow or normal walking), medium (like fast walking), or fast (like running). Diaries showed that sleep occupied about 33% of subject's time, slow activity 59%, medium 7%, and fast 1%. Fast activity was reported only at leisure, never at work. For the group, arithmetic means and standard deviations of predicted VR were 7 +/- 3 L/min for sleep, 12 +/- 7 for slow activity, 14 +/- 8 for medium, and 44 +/- 36 for fast. For the group and for most individuals, distributions of predicted VR within a given activity level (breathing rate) were approximately lognormal, with many values in a narrow range below the arithmetic mean and fewer values in a broader range above it. In the most active individuals, predicted VR exceeded 100 L/min for a total of 5 to 30 min during the three days. These data should prove useful in estimating outdoor workers' inhaled doses of ambient pollutants at existing or projected levels of air quality. Activity diary records are of significant value in pollutant dose estimation, but concurrent heart rate recording improves the estimates substantially.

Respiratory responses of young asthmatic volunteers in controlled exposures to sulfuric acid aerosol

Thirty-two asthmatic volunteers 8 to 16 yr of age, recruited through local schools and private physicians, were exposed in a chamber to clean air (control condition) and to sulfuric acid aerosol at a "low" concentration (46 +/- 11 micrograms/m3; mean +/- SD) and at a "high" concentration (127 +/- 21 micrograms/m3). Acid aerosols had mass median aerodynamic diameters near 0.5 microns with geometric standard deviations near 1.9. Temperature was 21 degrees C, and relative humidity was near 50%. Subjects were exposed with unencumbered oronasal breathing for 30 min at rest plus 10 min at moderate exercise (ventilation rate approximately 20 L/min/m2 of body surface). A subgroup (21 subjects) were exposed similarly to clean air and to "high" acid (134 +/- 20 micrograms/m3) with 100% oral breathing. Increased symptoms and bronchoconstriction were found after exercise under all exposure conditions. For the group, symptom and lung function responses were not statistically different during control and during acid exposures with unencumbered breathing or with oral breathing. By contrast, other investigators have reported statistically significant lung function disturbances in groups of young asthmatics exposed similarly with oral breathing. A minority of our subjects showed possibly meaningful excess bronchoconstriction with "high" acid exposure relative to control with both routes of breathing. This could be the result of chance, or it could suggest the existence of an acid-sensitive subpopulation of young asthmatics.

Responses to sulfur dioxide and exercise by medication-dependent asthmatics: effect of varying medication levels

Twenty-one volunteers with moderate to severe asthma were exposed to sulfur dioxide (SO2) at concentrations of 0 (control), 0.3, and 0.6 ppm in each of three medication states: (1) low (much of their usual asthma medication withheld), (2) normal (each subject on his own usual medication schedule), and (3) high (usual medication supplemented by inhaled metaproterenol before exposure). Theophylline, the medication usually taken by subjects, was often supplemented by beta-adrenergics. Exposures were for 10 min and were accompanied by continuous heavy exercise (ventilation approximately 50 l/min). Lung function and symptoms were measured before and after exposure. With normal medication, symptomatic bronchoconstriction occurred with exercise and was exacerbated by 0.6 ppm SO2, as reported for mildly unmedicated asthmatics studied previously. Both baseline and post-exposure lung function were noticeably worse in the low-medication state. High medication improved baseline lung function and prevented most bronchoconstrictive effects of SO2/exercise. High medication also increased heart rate and apparently induced tremor or nervousness in some individuals.

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.

Effect of droplet size on respiratory responses to inhaled sulfuric acid in normal and asthmatic volunteers

We exposed groups of healthy and asthmatic volunteers to sulfuric acid aerosols with volume median droplet diameters of approximately 20, 10, and 1 microns, at nominal concentrations of 2,000 micrograms/m3, and exposed them similarly to aerosols of purified water as a control. Exposures lasted 1 h each, and included three 10-min periods of exercise (ventilation rate typically 40 to 45 L/min). Exposures occurred in randomized order 7 days apart. Temperature was 10 degrees C, relative humidity was approximately 100% in 20- and 10-microns (fog) exposures, and approximately 75 to 80% in 1-micron aerosol exposures. Healthy subjects showed no statistically significant changes in lung function or in bronchial reactivity to methacholine attributable to acid exposures. They showed significant increases in lower and upper respiratory irritant symptoms when exposed to 20- or 10-microns acid fog, but not when exposed to 1-micron acid aerosol. Asthmatics showed significant excess decreases in forced expiratory performance, increases in airway resistance, and increases in irritant symptoms during acid exposures, relative to control conditions. Lung function changes in asthmatics tended to increase with time during exposure; they did not vary significantly with acid droplet size. Symptoms in asthmatics were slightly worse with 10- or 20-microns fog as compared with 1-micron aerosol. In a few instances, symptoms and lung function decrements necessitated stopping exercise or terminating the exposure early. Thus, asthma is a risk factor for unfavorable physiologic response to sulfuric acid at occupational exposure concentrations. Large droplet size (i.e., fog) tends to exacerbate short-term symptomatic response, but we have not been able to demonstrate a consistent effect of droplet size on physiologic response.

Acid fog: effects on respiratory function and symptoms in healthy and asthmatic volunteers

Acidic air pollutants generally are dissolved in water droplets. Mean droplet diameter may range from more than 10 microns in dense fog to less than 1 micron at low relative humidity. Droplet size influences the deposition of inhaled acid within the respiratory tract and thus may influence toxicity. To help assess health risks from acid pollution, we performed controlled exposures of normal and asthmatic volunteers to sulfuric acid aerosols at nominal concentrations of 0 (control), 500, 1000, and 2000 micrograms/m3. Exposures lasted 1 hr with intermittent heavy exercise. Response was assessed by lung function tests and symptom questionnaires. Under foggy conditions (mean droplet size 10 microns, temperature 50 degrees F), no marked effects on lung function were found. However, both normal and asthmatic subjects showed statistically significant dose-related increases in respiratory symptoms. In a separate study, normal subjects exposed at 70 degrees F with mean droplet size 0.9 microns showed no marked effect on function or symptoms. Asthmatics showed dose-related decrements in forced expiratory performance and increases in symptoms, most obvious at 1000 and 2000 micrograms/m3. The different results of the two studies probably reflect an influence of droplet size, but further investigation is needed to confirm this. The aggregate results suggest that only mild, if any, short-term respiratory irritant effects are likely at acid concentrations attained in ambient pollution.

Repeated laboratory ozone exposures of volunteer Los Angeles residents: an apparent seasonal variation in response

This study was intended to help explain individual differences in susceptibility to irritant effects of ozone (O3), by determining whether prior ambient O3 exposures and/or recent acute respiratory illness modified response to laboratory O3 exposures. Response was measured in terms of lung function changes and irritant symptoms. Initially, 59 adult volunteer Los Angeles area residents underwent screening exposures in spring, before the season of frequent high ambient O3 levels. Unusually responsive and nonresponsive individuals (N = 12 and 13 respectively) underwent followup exposures in autumn (late in the high-O3 season) and in winter (low-O3 season). All exposures were to 0.18 ppm O3 for 2 hr with intermittent heavy exercise at 31 degrees C and 35% relative humidity. Nonresponders tended to remain nonresponsive throughout. In fall, responders had lost much of their reactivity, as if they had "adapted" to summer ambient O3 exposures. They did not regain reactivity by winter. Clinical laboratory findings suggestive of acute respiratory illness did not appear to correlate with O3 response. Eight responders and 9 nonresponders underwent another followup exposure in spring, about 1 yr after screening. By that time most responders had regained their reactivity; individual function changes were significantly correlated with changes 1 yr earlier. These results suggest that response to O3 is a persistent individual characteristic, but can be modified by repeated ambient exposures.

Effect of metaproterenol sulfate on mild asthmatics' response to sulfur dioxide exposure and exercise

Twenty asthmatic volunteers, most with mild disease, underwent dose-response studies with sulfur dioxide (SO2) under three pretreatment conditions: (1) drug (metaproterenol sulfate in aerosolized saline solution), (2) placebo (aerosolized saline only), and (3) no pretreatment. Sulfur dioxide exposure concentrations were 0.0, 0.3, and 0.6 ppm. Experimental conditions were presented in random order at 1-wk intervals. Exposures lasted 10 min with heavy continuous exercise. Lung function was measured at baseline, after pretreatment (immediately pre-exposure), immediately post-exposure, and during a 2-hr follow-up. Subjects could elect to take bronchodilators during follow-up. Symptoms were monitored before, during, and for 1 wk after exposure. With no pretreatment, subjects exhibited typical exercise-induced bronchospasm at 0.0 ppm, slightly increased responses at 0.3 ppm, and more marked increases at 0.6 ppm. Seven subjects took bronchodilator after 0.6-ppm exposures, compared to 2 at lower concentrations. Within 30 min post-exposure, most subjects' symptoms and lung function had returned to near pre-exposure levels. A similar sequence was observed when subjects received placebo. Drug pretreatment improved lung function relative to baseline, prevented bronchoconstrictive responses at 0.0 and 0.3 ppm, and greatly mitigated responses at 0.6 ppm. Thus, typical bronchodilator usage by asthmatics is likely to reduce their response to ambient SO2 pollution.

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 micron, geometric standard deviation 2.5) in a chamber at 21 degrees and 50% relative humidity. Measured sulfuric acid concentrations averaged 0, 380, 1060, and 1520 micrograms/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 less than .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 degrees, median particle diameter approximately 10 micron) 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.

Laboratory study of asthmatic volunteers exposed to nitrogen dioxide and to ambient air pollution

Adult volunteers with moderate to severe asthma (N = 59) underwent dose-response studies to assess their reactivity to nitrogen dioxide (NO2) in otherwise clean air. Exposure concentrations were 0.0 (control), 0.3 and 0.6 ppm. A subgroup (N = 36) also underwent exposures to Los Angeles area ambient air at times when NO2 pollution was expected. Concentrations of NO2 during ambient exposures were 0.086 +/- 0.024 ppm (mean +/- s.d.). All exposures took place in a movable chamber/laboratory facility. Each study lasted 2 hr, with alternating 10 min periods of exercise (mean ventilation rate 40 L/min) and rest. Lung function was measured prior to exposure and after 10 min, 1 hr and 2 hr of exposure. Symptoms were recorded prior to exposure, during exposure and for 1 week afterward. In some subjects bronchial reactivity to cold air was measured 1 hr after the end of exposure and again 24 hr later. Different exposure conditions were presented in randomized order, 1 week apart. No pollutant exposure produced statistically significant changes in lung function, symptoms, or bronchial reactivity, relative to clean air. Ambient air exposures produced the largest (still nonsignificant) mean changes in some lung function tests. Given the physiological and atmospheric variability, negative statistical results do not rule out a small unfavorable effect of ambient pollution on lung function. If any such effect occurred, it was not likely caused by NO2. Statistical results remained negative when the analysis was restricted to the 20 subjects with most severe lung dysfunction. In conclusion at least in the Los Angeles area, sensitivity to ambient concentrations of NO2 is not common, even among adult asthmatics with moderate to severe disease.

Replicated dose-response study of sulfur dioxide effects in normal, atopic, and asthmatic volunteers

To help assess respiratory health risks from sulfur dioxide (SO2) air pollution, we studied 24 normal, 21 atopic, 16 minimal/mild asthmatic, and 24 moderate/severe, medication-dependent asthmatic subjects classified according to history, lung function, allergy skin tests, serum IgE level, and airway reactivity to methacholine. All were exposed in a chamber (21 degrees C, 50% humidity) to 0.0, 0.2, 0.4, and 0.6 ppm SO2 in random order at 1-wk intervals; then exposures were repeated to test consistency of response. The 1-h exposures included three 10-min exercise periods (ventilation approximately 40 L/min). Physiologic response was measured early (approximately 15 min) and late (approximately 55 min) in exposure. Symptoms were evaluated during exposure and for 1 wk afterward. Normal and most atopic subjects showed little response at these SO2 levels. A few atopic subjects and many asthmatics developed bronchoconstriction and respiratory symptoms, but most were able to maintain their exercise. Effects were not markedly different between early and late measurements, nor between the first and second round of studies; however, late and second-round responses appeared slightly more favorable. No statistically significant effect of SO2 on symptoms was found 1 day or 1 wk after exposure. Minimal/mild asthmatics showed, on the average, slight responses at 0.0 ppm (attributable to exercise) and increasing responses at increasing SO2 concentrations. Moderate/severe asthmatics reacted more at 0.0 ppm, but their increments in response with increasing SO2 concentration were roughly similar to those of minimal/mild asthmatics. Thus, responses to SO2 per se were not strongly dependent on clinical severity of asthma, nor on SO2 exposure history during previous weeks.