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Biomedical subjects

J D Hackney

Publications and source records attributed to J D Hackney.

At least 37 records · Page 2Linked to original sources
PubMed1987

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.

Administration, Inhalation↗
PubMed1986

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 volunteers, free of asthma or clinical respiratory allergies, were exposed to purified air containing ozone (O3) 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 degree 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 (approximately 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, during, 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 O3. 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 O3. The comparative lack of response may relate to the favorable clinical status of the subjects, the pattern of exercise during exposure, or some other factor not yet identified.

Adult↗
PubMed1985

Controlled exposures of volunteers with chronic obstructive pulmonary disease to sulfur dioxide.

Twenty-four volunteers with chronic obstructive pulmonary disease (COPD) were exposed to sulfur dioxide (SO2) at 0, 0.4, and 0.8 ppm in an environmental control chamber. Exposures lasted 1 hr and included two 15-min exercise periods (mean exercise ventilation rate 18 liter/min). Pulmonary mechanical function was evaluated before exposure, after initial exercise, and at the end of exposure. Blood oxygenation was measured by ear oximetry before exposure and during the second exercise period. Symptoms were recorded throughout exposure periods and for 1 week afterward. No statistically significant changes in physiology or symptoms could be attributed to SO2 exposure. Older adults with COPD seem less reactive to a given concentration of SO2 than heavily exercising young adult asthmatics. This may be due to lower ventilation rates (i.e., lower SO2 dose rates) and/or to lower airway reactivity in the COPD group.

Aged↗
PubMed1985

Effects of heat and humidity on the responses of exercising asthmatics to sulfur dioxide exposure.

Twenty-two asthmatic young adult volunteers, predetermined to be reactive to sulfur dioxide (SO2) with exercise at normal room temperature, were studied to document short-term effects of SO2 exposure under hot conditions, both humid and dry. For comparison, similar exposures were conducted at mild temperatures. All subjects were exposed in an environmental control chamber to all possible combinations of 2 atmospheric conditions (purified air and 0.6 ppm SO2), 2 temperatures (near 21 and 38 degrees C), and 2 levels of relative humidity (near 20 and 80%). Exposures involved 5 min of heavy exercise (target ventilation rate, 50 L/min) plus brief warm-up and cool-down periods. Body plethysmographic measurements and symptom questionnaire interviews were administered before and at the end of each exposure. Response was expressed in terms of change in airway size or change in intensity of symptoms during exposure. Atmospheric condition showed the most marked and significant overall effect on physiologic responses; temperature and humidity effects were also significant. High temperature and high humidity tended to mitigate the bronchoconstriction produced by 0.6 ppm SO2 exposure: group mean specific airway resistance approximately tripled at 21 degrees C and low humidity, but increased by less than 40% at 38 degrees C and high humidity. Temperature and humidity affected symptoms less consistently than physiologic responses, but in general, symptom responses paralleled physiologic responses.

Adult↗
PubMed1985

Respiratory effects of photochemical oxidant air pollution in exercising adolescents.

Healthy volunteers 12 to 15 yr of age (46 boys, 13 girls) were exposed to purified air and to smoggy Los Angeles ambient air on different occasions. The studies were performed in random order approximately 2 wk apart. They included 1 h of continuous bicycle exercise (mean ventilation, 32 L/min) plus brief warm-up and cool-down periods. Symptoms and forced expiratory performance were recorded preexposure in purified air, immediately postexposure, and after 1 h recovery in purified air. Mean exposure temperature was 32 degrees C, and mean relative humidity was 45%. In ambient exposure, pollutant concentrations averaged 0.144 ppm for ozone and 153 micrograms/m3 for total suspended particulates. Group mean FEV1 decreased during ambient exposure (p less than 0.01) and only partially recovered during the following 1 h. Unlike adults studied previously, this subject group reported no significant increase in respiratory symptoms accompanying changes in FEV1. Adolescents may be less aware of early respiratory irritation by oxidants and thus more at risk from ambient exposures than are adults.

Adolescent↗
PubMed1985

Potential risks to human respiratory health from "acid fog": evidence from experimental studies of volunteers.

Observations of high acidity (pH as low as 1.7) in fogwater collected in polluted areas have provoked concern for public health. Effects of exposure to acidic pollutants have not been studied under foggy conditions; thus there is no directly relevant information from which to estimate the health risk. Indirectly relevant information is available from numerous studies of volunteers exposed to "acid fog precursors" under controlled conditions at less than 100% relative humidity. The effect of fog in modifying responses to inhaled acidic pollutants is difficult to predict: depending on circumstances, fog droplets might either increase or decrease the effective dose of pollutants to the lower respiratory tract. Fog inhalation per se may have unfavorable effects in some individuals. Sulfur dioxide is known to exacerbate airway constriction in exercising asthmatics, at exposure concentrations attainable in ambient air. Nitrogen dioxide has shown little untoward respiratory effect at ambient concentrations in most studies, although it has been suggested to increase bronchial reactivity. Sulfuric acid aerosol has shown no clear effects at concentrations within the ambient range. At somewhat higher levels, increased bronchial reactivity and change in mucociliary clearance have been suggested. Almost no information is available concerning nitric acid.

Acids↗
PubMed1984

Respiratory responses of humans exposed to an aerosol-gas pollutant mixture: multivariate contrast of a complex atmosphere to clean air and sodium chloride aerosol controls.

Data from a group of 20 subjects with normal baseline pulmonary function, who were exposed for 2 h to a test atmosphere containing a complex mixture of pollutants, have been contrasted with data from two other groups exposed to presumably non-toxic control atmospheres. Group 1 was exposed to clean air, group 2 was exposed to clean air containing sodium chloride aerosol at 270 micrograms m-3, and group 3 was exposed to the complex atmosphere containing sodium chloride (332 micrograms m-3) and zinc ammonium sulfate (23 micrograms m-3) aerosols plus nitrogen dioxide (0.5 ppm) and sulfur dioxide (0.5 ppm). These atmospheres (ranked according to the presumed relative toxicities of the components; clean air = 0, sodium chloride = 1, complex mixture = 2) were contrasted using multiple regression and partial correlation analyses. The effects of exposure to the complex gas-aerosol mixture on forced expiratory performance were not significantly different from those observed in subjects exposed to clean air or to sodium chloride aerosol.

Adolescent↗
PubMed1984

Time course of exercise-induced bronchoconstriction in asthmatics exposed to sulfur dioxide.

Young adult asthmatic volunteers (N = 17) were exposed to 0.75 ppm sulfur dioxide (SO2) for 3-hr periods, exercising vigorously for the first 10 min and resting thereafter. Specific airway resistance (SRaw) and symptoms were recorded preexposure, immediately postexercise, and after 1, 2, and 3 hr of exposure. Symptoms and SRaw were significantly increased after exercise, relative to preexposure measurements. Group mean SRaw and symptom increases were no longer significant at 1 hr. In a few individuals, effects may have persisted for 2 hr or more. On separate occasions, comparable exposures were conducted, and forced expiratory spirometry was performed preexposure and postexercise, in addition to the other tests. Inclusion of spirometry did not significantly affect the other results. Spirometry and SRaw showed nearly equal significance in changes postexercise. Thus, in general, asthmatics' bronchoconstriction induced by exercise in SO2 seems to reverse quickly with rest, even if SO2 exposure continues. Spirometry may be useful for studying pollution-induced bronchoconstriction when SRaw measurements are impractical.

Adult↗
PubMed1984

Comparative effects of sulfur dioxide exposures at 5 degrees C and 22 degrees C in exercising asthmatics.

Either airway cooling or sulfur dioxide (SO2) can induce bronchoconstriction in many asthmatics. Whether these two stresses act synergistically is a question with important public health implications. Eight young adult asthmatic volunteers were exposed to SO2 at 0.0, 0.2, 0.4, and 0.6 ppm, during 5 min heavy exercise at 5 degrees C, both with high (approximately 85%) and with low (approximately 50%) relative humidity. Physiologic response increased with increasing SO2 concentration but did not vary significantly with humidity. Symptom response was marginally greater at low than at high humidity. Twenty-four asthmatics were exposed similarly to clean air and to 0.6 ppm SO2, at 5 degrees C and also at 22 degrees C, always at high relative humidity. For this group, physiologic and clinical responses to SO2 (in excess of responses to clean air) were highly significant, regardless of temperature. The mean excess responses at 5 degrees compared with those at 22 degrees C were not statistically significant in clean air or SO2. Thus, moderate cold stress exacerbated the untoward response to SO2 only slightly and inconsistently in these asthmatic subjects.

Adolescent↗
PubMed1983

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.

Adult↗
PubMed1983

Respiratory effects of sulfur dioxide in heavily exercising asthmatics. A dose-response study.

Twenty-three asthmatic volunteers 19 to 31 yr of age were exposed to 0 (control), 0.2, 0.4, and 0.6 ppm sulfur dioxide (SO2) in random order at 1-wk intervals. Exposures took place in a controlled-environment chamber at 23 degrees C and 85% relative humidity; they included 5 min heavy exercise (mean minute volume, 48 L) plus time for postexercise physiologic testing. Body plethysmography (preexposure and end-exposure), spirometry (end-exposure only), and symptom questionnaires (covering the exposure period and the following week) all showed highly significant trends toward increased response with increasing SO2 concentration. Pairwise statistical comparisons showed substantial, highly significant, changes at 0.6 ppm, relative to control. Fewer and smaller significant changes were found at 0.4 ppm. At 0.2 ppm, no significant physiologic changes were found, but increases in symptoms during exposure were possibly significant. Symptom reports 1 day and 1 wk postexposure showed no significant variation related to SO2 level, i.e., exposure-related symptoms apparently reversed in less than 1 day.

Adult↗
PubMed1983

Controlled clinical studies of air pollutant exposure: evaluating scientific information in relation to air quality standards.

In controlled clinical studies, volunteers are deliberately exposed to specific air pollutants under conditions simulating ambient exposures, and health-related responses are documented. Studies of the health risks of air pollution need to be scientifically rigorous and clearly relevant to "real-world" pollution exposures. Their results should be confirmed by independent replication if they are to be used as a basis for air quality regulations. Well-designed controlled clinical studies readily meet these criteria, and complement the other methods of scientific risk assessment--animal toxicology and epidemiology. Clinical studies, toxicology, and epidemiology all have provided important information about air pollution health effects. A better understanding of the interrelationships of findings from these different fields is needed.

Air Pollutants↗