Chemiluminescent measurements of nitric oxide pulmonary diffusing capacity and alveolar production in humans

Measurements of nitric oxide (NO) pulmonary diffusing capacity (DL(NO)) multiplied by alveolar NO partial pressure (PA(NO)) provide values for alveolar NO production (VA(NO)). We evaluated applying a rapidly responding chemiluminescent NO analyzer to measure DL(NO) during a single, constant exhalation (Dex(NO)) or by rebreathing (Drb(NO)). With the use of an initial inspiration of 5-10 parts/million of NO with a correction for the measured NO back pressure, Dex(NO) in nine healthy subjects equaled 125 +/- 29 (SD) ml x min(-1) x mmHg(-1) and Drb(NO) equaled 122 +/- 26 ml x min(-1) x mmHg(-1). These values were 4.7 +/- 0.6 and 4.6 +/- 0.6 times greater, respectively, than the subject's single-breath carbon monoxide diffusing capacity (Dsb(CO)). Coefficients of variation were similar to previously reported breath-holding, single-breath measurements of Dsb(CO). PA(NO) measured in seven of the subjects equaled 1.8 +/- 0.7 mmHg x 10(-6) and resulted in VA(NO) of 0.21 +/- 0.06 microl/min using Dex(NO) and 0.20 +/- 0.6 microl/min with Drb(NO). Dex(NO) remained constant at end-expiratory oxygen tensions varied from 42 to 682 Torr. Decreases in lung volume resulted in falls of Dex(NO) and Drb(NO) similar to the reported effect of volume changes on Dsb(CO). These data show that rapidly responding chemiluminescent NO analyzers provide reproducible measurements of DL(NO) using single exhalations or rebreathing suitable for measuring VA(NO).

Human breathing and eye blink rate responses to airborne chemicals

Increased levels of air pollution have been linked with morbidity and mortality, but mechanisms linking physiologic responses to quality of life and productivity issues remain largely unknown. Individuals often report irritation of the nose and/or eyes upon exposures to environmental contaminants. Evaluation of these self-reports would be greatly aided by the development of valid physiological markers. Chamber studies (unencumbered exposures) of nonsmoker responses to environmental tobacco smoke offer two candidate end points: (a) Tidal volume increases and breathing frequency declines with stimuli that elicit only moderate irritation. (b) Eye blink rate increases only with a concentration sufficiently high to cause progressive worsening of eye irritation with prolonged exposure. Experiments with very brief nasal-only presentations also suggest the value of breathing changes as sensitive markers of irritation: (a) Tidal volume is inversely related to perceived nasal irritation (NI) intensity in both normal and anosmic (lacking olfactory input) individuals, although normals exhibit greater NI sensitivity. (b) Inhalation duration, in both groups, declines only with trigeminal activation sufficient to cause readily perceptible NI in anosmics. Changes in eye blink rate and breathing may be useful in the investigation of irritation and other effects of air pollution, and could be quite useful in investigations of mixtures of volatile organic compounds.

Ozone exposure and the production of reactive oxygen species by bronchoalveolar cells in humans

Exposure to ozone injures respiratory epithelium, and the mechanisms may involve the generation of reactive oxygen species (ROS). This study tested the hypothesis that ozone exposure increases the airway burden of ROS to a greater degree in smokers than nonsmokers, and that this effect is independent of ozone-induced changes in spirometry. Healthy subjects were selected as either responders (decrement in FEV1 > 15%) or nonresponders (decrement in FEV1 < 5%) to ozone; each underwent 2 exposures to ozone and 1 to air, with bronchoalveolar lavage (BAL) performed 30 min (early) and 18 h (late) after exposure. Release of superoxide anion (O2(-)) was used as a measure of ROS release by all BAL cells, and flow cytometry was used to detect ROS production in alveolar macrophages (AM) only. Recovery of AM was approximately threefold greater in smokers than nonsmokers. Unstimulated, but not stimulated, cells obtained by BAL from smokers released approximately twofold greater amounts of O2(-) than cells from nonsmokers, both early and late after ozone exposure (p =.012 and p =.046, respectively). Stimulated, but not unstimulated, ROS generation by AM from smokers increased following ozone exposure, but the ozone effect was not significant. ROS production by AM decreased in nonsmokers (air vs. ozone late, p =.014). Total protein, albumin, and immunoglobulin M (IgM) increased in BAL fluid, consistent with an increase in epithelial permeability. In addition, the concentration of alpha2-macroglobulin increased approximately threefold 18 h after exposure in nonsmokers (p <.001). No relationship was found between measures of ROS production and lung function responsiveness to ozone. These studies suggest the airways of smokers experience a greater burden of ROS than those of nonsmokers following ozone exposure.

Neutrophils in lung inflammation: Which reactive oxygen species are being measured?

The oxidative burst in circulating polymorphonuclear leukocytes (PMN) plays a fundamental role in pulmonary defense and injury. Flow cytometric techniques have been developed for quantitation of oxidative burst activity at the single cell level using 2',7'-dichlorofluorescin (DCFH). However, the specific reactive oxidant species being measured using this method are not clearly defined. Isolated human PMN were loaded with DCFH diacetate, stimulated with phorbol myristate acetate (PMA) in the presence or absence of specific reagents, and analyzed using flow cytometry. Addition of PMA resulted in a 90-fold increase in the fluorescence intensity of DCFH-loaded neutrophils (p <.01). Inhibition of NADPH oxidase activity using a calmodulin antagonist (W-13) decreased PMA-induced DCFH oxidation by 70% (p <.05). Inhibition of nitric oxide synthase using N(G)-monomethyl-L-arginine (NMMA) did not significantly reduce DCFH oxidation, and did not alter the action of W-13. Addition of superoxide dismutase (SOD) had no effect, but catalase, with or without SOD, suppressed DCFH oxidation by 90% (p <.01). These data suggest that hydrogen peroxide, and not NO, is primarily responsible for the PMA-induced oxidation of DCFH in human PMN under these conditions.

Acute health effects of ambient air pollution: the ultrafine particle hypothesis

A strong and consistent association has been observed between adjusted mortality rates and ambient particle concentration. The strongest associations are seen for respiratory and cardiac deaths, particularly among the elderly. Particulate air pollution is also associated with asthma exacerbations, increased respiratory symptoms, decreased lung function, increased medication use, and increased hospital admissions. The U.S. Environmental Protection Agency (EPA) has recently promulgated a new national ambient air quality standard for fine particles, and yet the mechanisms for health effects at such low particle mass concentrations remain unclear. Hypotheses to identify the responsible particles have focused on particle acidity, particle content of transition metals, bioaerosols, and ultrafine particles. Because ultrafine particles are efficiently deposited in the respiratory tract and may be important in initiating airway inflammation, we have initiated clinical studies with ultrafine carbon particles in healthy subjects. These studies examine the role of ultrafines in: (1) the induction of airway inflammation; (2) expression of leukocyte and endothelial adhesion molecules in blood; (3) the alteration of blood coagulability; and (4) alteration in cardiac electrical activity. These events could lead to exacerbation of underlying cardiorespiratory disease. For example, airway inflammation may activate endothelium and circulating leukocytes, and induce a systemic acute phase response with transient hypercoagulability; this could explain the epidemiologic linkages between pollutant exposures and cardiovascular events. These approaches should be useful in identifying mechanisms for pollutant-induced respiratory and systemic effects, and in providing data for determining appropriate air quality standards.

A retrospective review of the carcinogenicity of refractory ceramic fiber in two chronic fischer 344 rat inhalation studies: an assessment of the MTD and implications for risk assessment

The purpose of this article is to review previous chronic inhalation studies in rats with refractory ceramic fiber (RCF), the mathematical modeling efforts to describe the deposition, clearance, and retention of RCF fiber in the rat and human, and the concept of "overload," and to assess the possibility that the maximum tolerated dose (MTD) was exceeded. Lastly, based on recent biopersistence and pulmonary clearance studies of several investigators with a particulate-free RCF, we examine the potential impact on the chronic RCF rat bioassay of coexposure to both RCF particulate and RCF fibers. The review concludes, inter alia, that RCF particulate coexposure probably had a major impact on the observed chronic adverse effects, that the MTD was probably exceeded at the highest exposure concentration of 30 mg/m(3) in the rat bioassay, and that inclusion of the highest dose in the risk assessment process may overstate human health risk if a linear rather than nonlinear model is used.

Toxicologic methods: controlled human exposures

The assessment of risk from exposure to environmental air pollutants is complex, and involves the disciplines of epidemiology, animal toxicology, and human inhalation studies. Controlled, quantitative studies of exposed humans help determine health-related effects that result from breathing the atmosphere. The major unique feature of the clinical study is the ability to select, control, and quantify pollutant exposures of subjects of known clinical status, and determine their effects under ideal experimental conditions. The choice of outcomes to be assessed in human clinical studies can be guided by both scientific and practical considerations, but the diversity of human responses and responsiveness must be considered. Subjects considered to be among the most susceptible include those with asthma, chronic obstructive lung disease, and cardiovascular disease. New experimental approaches include exposures to concentrated ambient air particles, diesel engine exhaust, combustion products from smoking machines, and experimental model particles. Future investigations of the health effects of air pollution will benefit from collaborative efforts among the disciplines of epidemiology, animal toxicology, and human clinical studies.

Refractory ceramic fiber: toxicology, epidemiology, and risk analyses--a review

Refractory ceramic fiber (RCF) is an energy-efficient, high-temperature insulation, used principally in industrial furnaces, heaters, and reactors. Prior to the 1980s, there were few publications dealing with the potential health effects of this material. However, with the advent of higher energy costs and the need for thermally efficient high-temperature insulating materials, production of RCF grew rapidly, as did interest in its potential health effects. This article provides a comprehensive and integrated review of the toxicology (in vitro and in vivo), epidemiology, and risk analysis literature of RCF. Based on the available literature, we conclude that an occupational exposure of 0.5 fibers per cubic centimeter (cm(3)) [8-h time-weighted average (8-h TWA)] results in an occupational health risk no greater than 9.1 x 10(-5).

Environmental tobacco smoke exposure and asthma in adults

Environmental tobacco smoke (ETS) contaminates indoor air in homes and workplaces. Although the adverse effects of active cigarette smoking on the respiratory tract have been extensively characterized, the effects of ETS exposure on adult asthma have not yet been investigated extensively and the available data are limited. This article examines the evidence for ETS exposure as a cause of asthma and asthma exacerbation in adults, and for ETS exposure in the workplace specifically as contributing to these health effects. It addresses methodological barriers that limit the available data and evaluates the adequacy of the data for risk assessment.

Aldehydes (nonanal and hexanal) in rat and human bronchoalveolar lavage fluid after ozone exposure

We hypothesized that exposure of healthy humans to ozone at concentrations found in ambient air causes both ozonation and peroxidation of lipids in lung epithelial lining fluid. Smokers (12) and nonsmokers (15) were exposed once to air and twice to 0.22 ppm ozone for four hours with exercise in an environmental chamber; each exposure was separated by at least three weeks. Bronchoalveolar lavage (BAL) was performed immediately after one ozone exposure and 18 hours after the other ozone exposure. Lavage fluid was analyzed for two aldehyde products of ozonation and lipid peroxidation, nonanal and hexanal, as well as for total protein, albumin, and immunoglobulin M (IgM) as markers of changes in epithelial permeability. Ozone exposure resulted in a significant early increase in nonanal (p < 0.0001), with no statistically significant relationship between increases in nonanal and lung function changes, airway inflammation, or changes in epithelial permeability. Increases in hexanal levels were not statistically significant (p = 0.16). Both nonanal and hexanal levels returned to baseline by 18 hours after exposure. These studies confirm that exposure to ozone with exercise at concentrations relevant to urban outdoor air results in ozonation of lipids in the airway epithelial lining fluid of humans.

Simultaneous measurement of nitric oxide production by conducting and alveolar airways of humans

Human airways produce nitric oxide (NO), and exhaled NO increases as expiratory flow rates fall. We show that mixing during exhalation between the NO produced by the lower, alveolar airways (VL(NO)) and the upper conducting airways (VU(NO)) explains this phenomenon and permits measurement of VL(NO), VU(NO), and the NO diffusing capacity of the conducting airways (DU(NO)). After breath holding for 10-15 s the partial pressure of alveolar NO (PA) becomes constant, and during a subsequent exhalation at a constant expiratory flow rate the alveoli will deliver a stable amount of NO to the conducting airways. The conducting airways secrete NO into the lumen (VU(NO)), which mixes with PA during exhalation, resulting in the observed expiratory concentration of NO (PE). At fast exhalations, PA makes a large contribution to PE, and, at slow exhalations, NO from the conducting airways predominates. Simple equations describing this mixing, combined with measurements of PE at several different expiratory flow rates, permit calculation of PA, VU(NO), and DU(NO). VL(NO) is the product of PA and the alveolar airway diffusion capacity for NO. In seven normal subjects, PA = 1.6 +/- 0.7 x 10(-6) (SD) Torr, VL(NO) = 0.19 +/- 0.07 microl/min, VU(NO) = 0.08 +/- 0.05 microl/min, and DU(NO) = 0.4 +/- 0.4 ml. min(-1). Torr(-1). These quantitative measurements of VL(NO) and VU(NO) are suitable for exploring alterations in NO production at these sites by diseases and physiological stresses.

Hazard assessment and risk analysis of two new synthetic vitreous fibers

Isofrax and Insulfrax are two new synthetic vitreous fibers (SVFs) developed for high-temperature insulation (1800-2300 degrees F) applications. In an attempt to significantly reduce or eliminate the potential of adverse health effects, these two fibers were specifically designed to have high solubility and, thus, low in vivo biodurability. In this paper, we review the effects of chemical composition on biodurability, in vitro fiber dissolution rates (K(dis)), and the relevance and relationship of K(dis) to pulmonary fibrosis and lung tumors in chronic rat inhalation studies. We also examine the correlations between K(dis) and weighted in vivo half-life (t(0.5)) of long fibers (>20 microm) and their relation to pulmonary effects in chronic rat inhalation bioassays. Predictions for outcomes of inhalation bioassays and development of nonsignificant risk levels of exposure are provided. Additionally, justification for the use of inhalation versus noninhalation animal data is provided as is a brief review of human health effects of SVFs. We conclude, inter alia, that Isofrax and Insulfrax have low biodurability, would not be expected to produce either pulmonary fibrosis or lung tumors in a well-designed animal inhalation bioassay, have weighted half-lives beneath the threshold established by the European Union for classification as a carcinogen, and based on epidemiological data for SVFs would not be expected to result in incremental cancer in human cohorts. Finally, it is estimated that approximately 90% of workplace exposure concentrations of these materials would be beneath 1 f/cc. At a concentration of 1 f/cc, neither fiber would be expected to result in an incremental working lifetime cancer risk greater than 10(-5).

Ozone exposure increases aldehydes in epithelial lining fluid in human lung

We hypothesized that exposure of healthy humans to ozone causes both ozonation and peroxidation of lipids in lung epithelial lining fluid. Twelve smokers and 15 nonsmokers (eight lung function "responders" and seven "nonresponders") were exposed once to air and twice to 0. 22 ppm ozone for 4 h with exercise in an environmental chamber, with each exposure separated by at least 3 wk. Bronchoalveolar lavage (BAL) was performed immediately after one ozone exposure and 18 h after the other ozone exposure. BAL fluid was analyzed for the aldehyde products of ozonation and lipid peroxidation, nonanal (C9) and hexanal (C6), as well as total protein, albumin, and immunoglobulin M as markers of changes in epithelial permeability. Ozone exposure resulted in a significant early increase in C9 (p = 0. 0001), with no statistically significant relationship between increases in C9 and lung function changes, airway inflammation, or changes in epithelial permeability. Increases in C6 levels were not statistically significant (p = 0.16). Both C9 and C6 levels returned to baseline by 18 h after exposure. These studies confirm that exposure to ozone with exercise, at concentrations relevant to urban outdoor air, results in ozonation of lipids in the airway epithelial lining fluid of humans.

Rate of nitric oxide production by lower alveolar airways of human lungs

This report describes methods for measuring nitric oxide production by the lungs' lower alveolar airways (VNO), defined as those alveoli and bronchioles well perfused by the pulmonary circulation. Breath holding or vigorous rebreathing for 15-20 s minimizes removal of NO from the lower airways and results in a constant partial pressure of NO in the lower airways (PL). Then the amount of NO diffusing into the perfusing blood will be the pulmonary diffusing capacity for NO (DNO) multiplied by PL and by mass balance equals VNO, or VNO = DNO(PL). To measure PL, 10 normal subjects breath held for 20 s followed by exhalation at a constant flow rate of 0.83 +/- 0.14 (SD) l/s or rebreathed at 59 +/- 15 l/min for 20 s while NO was continuously measured at the mouth. DNO was estimated to equal five times the single-breath carbon monoxide diffusing capacity. By using breath holding, PL equaled 2.9 +/- 0.8 mmHg x 10(-6) and VNO equaled 0.39 +/- 0.12 microl/min. During rebreathing PL equaled 2.3 +/- 0.6 mmHg x 10(-6) and VNO equaled 0.29 +/- 0.11 microl/min. Measurements of NO at the mouth during rapid, constant exhalation after breath holding for 20 s or during rebreathing provide reproducible methods for measuring VNO in humans.

Measurement of cytochrome P450 2A6 and 2E1 gene expression in primary human bronchial epithelial cells

Bronchogenic carcinomas arise from bronchial epithelial cells (BECs). Inhalation exposure of BECs to nitrosamines in cigarette smoke is an important exogenous risk factor for malignant transformation of BECs. Thus, an important endogenous risk factor is likely to be the capacity of BECs to metabolize nitrosamines. Among the cytochrome P450 enzymes capable of metabolizing nitrosamines, CYP2A6, CYP2E1 and CYP2B6 are expressed in BECs. In this study, we used quantitative RT-PCR to evaluate expression of CYP2A6 and CYP2E1 in primary human BECs from 12 non-smokers and eight smokers. CYP2A6 was expressed in 20/20 cases and quantifiable in 18/20 cases, with a mean level of 580 mRNA/10(6) beta-actin mRNA. CYP2E1 expression was observed in 9/20 cases, but in all cases it was expressed at levels below our limit of quantification (10 mRNA/10(6) beta-actin mRNA). There was significant (P < 0.05) 20-fold inter-individual variation in expression of CYP2A6. Further, the mean level of CYP2A6 among smokers (260 mRNA/10(6) beta-actin mRNA) was significantly lower than among non-smokers (740 mRNA/10(6) beta-actin mRNA). It is hypothesized that: (i) inter-individual variation in CYP2A6 gene expression may contribute to inter-individual variation in risk for bronchogenic carcinoma; (ii) smoking may reduce the level of expression of CYP2A6 in the BECs of some individuals; and (iii) CYP2A6 is more important than CYP2E1 for metabolic activation of nitrosamines in bronchial epithelial cells.

Quantitative exposure of humans to an octamethylcyclotetrasiloxane (D4) vapor

There is potential for human exposure to cyclic siloxanes by the respiratory route. To determine the pharmacokinetics of octamethylcyclotetrasiloxane (D4), a material commonly found in personal care products, the respiratory intake and uptake of D4 were measured in 12 healthy volunteers (25-49 years) on two occasions. Subjects inhaled 10 ppm D4 (122 micrograms/liter) or air (control) during a 1-h exposure via a mouthpiece in a double-blind, randomized fashion. Inspiratory and expiratory D4 concentrations were continuously measured. Exhaled air and plasma D4 levels were measured before, during, and after exposures. Individual D4 uptakes were measured under steady-state conditions during three rest periods (10, 20, and 10 min, respectively) alternating with two 10-min exercise periods. Mean D4 intake was 137 +/- 25 mg (SD) and the mean deposition efficiency was equivalent to 0.74/(1 + 0.45 VE), where VE is the minute ventilation. No changes in lung function were induced by the D4 vapor. Plasma measurements of D4 gave a mean peak value of 79 +/- 5 ng/g (SEM) and indicated a rapid nonlinear blood clearance. Using lung volume and respiratory surface area estimates based on functional residual capacity measurements, we developed a model and determined that the effective mass transfer coefficient for D4 was 5.7 x 10(-5) cm/s from lung air to blood. In an additional eight subjects, we compared D4 deposition with mouthpiece and nasal breathing at resting ventilations. For these individuals, mean deposition was similar for the two exposure protocols, averaging 12% after correction for exposure system losses. These are the first data describing the intake and absorption of D4 and they should contribute to a meaningful safety assessment of the compound.

Acute respiratory exposure of human volunteers to octamethylcyclotetrasiloxane (D4): absence of immunological effects

Humans are exposed to silicones in a number of commercial and consumer products. Some of these silicones, including octamethylcyclotetrasiloxane (D4), are volatile. Therefore, there is a potential for respiratory exposure. A pharmacokinetic analysis of respiratory exposure to D4 is presented in the accompanying paper (M. J. Utell et al., 1998, Toxicol. Sci. 44, 206-213). Possible immune effects of respiratory exposure to D4 are investigated in this paper. Normal volunteers were exposed to 10 ppm D4 or air for 1 h via a mouthpiece using a double-blind, crossover study design. Assays were chosen to screen for immunotoxicity or a systemic inflammatory response. Assessment of immunotoxicity included enumeration of peripheral lymphocyte subsets and functional assays using peripheral blood mononuclear cells. Because in humans there is no direct test for adjuvant effect of respiratory exposure, we analyzed proinflammatory cytokines and acute-phase reactants in peripheral blood, markers for a systemic inflammatory response, as surrogate markers for adjuvancy. These tests were repeated when the volunteers were reexposed to D4 approximately 3 months after this initial exposure. Blood was obtained prior to exposure, immediately postexposure, and 6 and 24 h postexposure. In these short-term, controlled human exposures, no immunotoxic or proinflammatory effects of respiratory exposure to D4 were found.

Metabolism of 1,1-dichloro-1-fluoroethane (HCFC-141b) in human volunteers

Human subjects were exposed by inhalation to 250, 500, and 1000 ppm 1,1-dichloro-1-fluoroethane (HCFC-141b) for 4 hr, and urine samples were collected from 0-4, 4-12, and 12-24 hr for metabolite analysis. 19F nuclear magnetic resonance spectroscopic analysis of urine samples from exposed subjects showed that 2,2-dichloro-2-fluoroethyl glucuronide and dichlorofluoroacetic acid were the major and minor metabolites, respectively, of HCFC-141b. Urinary 2, 2-dichloro-2-fluoroethyl glucuronide was hydrolyzed to 2, 2-dichloro-2-fluoroethanol by incubation with beta-glucuronidase, and the released 2,2-dichloro-2-fluoroethanol was quantified by gas chromatography/mass spectrometry. Concentrations of 2, 2-dichloro-2-fluoroethanol were highest in the urine samples collected 4-12 hr after exposure, but 2,2-dichloro-2-fluoroethanol was also detected in the samples collected 0-4 and 12-24 hr after exposure. Exposure concentration-dependent excretion of 2, 2-dichloro-2-fluoroethanol, obtained by hydrolysis of 2, 2-dichloro-2-fluoroethyl glucuronide, was observed in seven of the eight subjects studied. In conclusion, HCFC-141b is metabolized in human subjects to 2,2-dichloro-2-fluoroethanol, which is conjugated with glucuronic acid and excreted as its glucuronide in urine in a time- and exposure concentration-dependent manner.

Mutational spectra of a 100-base pair mitochondrial DNA target sequence in bronchial epithelial cells: a comparison of smoking and nonsmoking twins

Seventeen separate mitochondrial hot spot mutations in a 100-bp target sequence (mitochondrial bp 10,030-10,130) were detected and measured in bronchial epithelial cell samples isolated from smokers and nonsmokers. Among the individuals sampled were three pairs of monozygotic twins in which one twin had never smoked and had a nonsmoking spouse, and the other had a smoking history of >10 pack-years. Individual point mutations present at frequencies as low as 10(-6) were detected. Partially denaturing electrophoresis was used to separate mutant from nonmutant sequences on the basis of their melting temperatures, and the target sequence was subsequently amplified via high-fidelity PCR with Pfu DNA polymerase. Tests were performed to determine whether mismatch intermediates or DNA adducts present in the cellular DNA were converted to mutants during PCR. Hot spot mutations were clearly observed in bronchial epithelial cells, and the same hot spots were observed consistently in different samples. Significant numerical variability in the mutant fractions for individual mutants was observed among samples and are ascribed to unequal mitochondrial segregation in stem and transition cells. The mutational spectra in smokers' samples did not differ significantly from the mutational spectra in nonsmokers' samples for this 100 bp of mitochondrial DNA. No smoking-specific hot spots were detected. The overall mutant fractions in smokers' samples were not elevated compared to those of nonsmokers. As much variability was observed between two samples from the same individual's lung as between a sample from a smoker and a sample from a nonsmoker. These findings demonstrate that inhaled tobacco smoke does not induce prominent point mutations in this 100-bp target mitochondrial sequence in smokers' bronchial epithelial cells. Endogenous factors (e.g., DNA replication errors or DNA damage by endogenous reactive chemicals) are suggested to be more likely to represent the most important contributors to mitochondrial mutagenesis.

Airway inflammation in smokers and nonsmokers with varying responsiveness to ozone

Exposure to ozone causes symptoms, changes in lung function, and airway inflammation. We studied whether individuals who differ in lung-function responsiveness to ozone, or in smoking status, also differ in susceptibility to airway inflammation. Healthy subjects were selected on the basis of responsiveness to a classifying exposure to 0.22 ppm ozone for 4 h with exercise (responders, with a decrease in FEV1 > 15%; and non-responders, with a decrease in FEV1 < 5%). Three groups were studied: nonsmoker-nonresponders (n = 12), nonsmoker-responders (n = 13), and smokers (n = 13, 11 nonresponders and two responders). Each subject underwent two exposures to ozone and one to air, separated by at least 3 wk; bronchoalveolar and nasal lavages were performed on three occasions: immediately (early) and 18 h (late) after ozone exposure, and either early or late after air exposure. Recovery of polymorphonuclear leukocytes (PMN) increased progressively in all groups, and by up to 6-fold late after ozone exposure. Interleukin-6 (IL-6) and IL-8 increased early (by up to 10-fold and up to 2-fold, respectively), and correlated with the late increase in PMN. Lymphocytes, mast cells, and eosinophils also increased late after exposure. We conclude that ozone-induced airway inflammation is independent of smoking status or airway responsiveness to ozone.

Quantitative RT-PCR measurement of cytochromes p450 1A1, 1B1, and 2B7, microsomal epoxide hydrolase, and NADPH oxidoreductase expression in lung cells of smokers and nonsmokers

Bronchial epithelial cells (BEC) are the progenitors of bronchogenic carcinomas and are exposed to polycyclic aromatic hydrocarbon (PAH) procarcinogens through inhalation of combustion products. PAH are converted to carcinogenic molecules through a combination of monoxygenation by cytochrome p450 (CYP) enzymes in the presence of NADPH oxidoreductase (OR) and hydrolysis by microsomal epoxide hydrolase (mEH). In artificial systems, the relative expression of these genes determines whether carcinogenic or noncarcinogenic species are generated during metabolism. This relationship was explored in humans by using quantitative competitive reverse transcriptase polymerase chain reaction amplification to determine the range of expression of CYP1A1, CYP1B1, mEH, and NADPH OR in BEC recovered from 10 nonsmokers and 9 smokers. CYP2B7 expression was evaluated because, although little is known of its substrate specificity, it is expressed at high levels in human lung tissue. CYP1A1 and CYP1B1 were expressed in BEC at significantly different levels (P < 0.05) in the 9 smokers at 1.4 +/- 2.3 x 10(4) and 2.4 +/- 3.2 x 10(3) molecules/10(6) beta-actin molecules (mean +/- STD), respectively, but each was measurable in only one of the 10 nonsmokers. There was significant inter-individual variation (P < 0.05) in both CYP1A1 and CYP1B1 expression among the subjects for whom sufficient data were obtained. The inducibility of human BEC CYP1A1 gene by PAH exposure was confirmed in vitro by incubating cultured immortalized human BEC with beta-naphthoflavone and observing a > 6-fold induction of CYP1A1 after 24 h. In contrast to BEC, alveolar macrophages expressed CYP1A1 at low (30-70 molecules/10(6) beta-actin molecules) to unmeasurable levels in both smokers and nonsmokers. There was no significant difference in expression of mEH, CYP2B7, or NADPH OR in smokers compared with nonsmokers. The inter-individual variation in absolute and relative expression of PAH metabolism enzymes in BEC reported here supports the hypothesis that inter-individual variation in ability to activate/inactivate inhaled PAH carcinogens accounts for at least some of the inter-individual variation in risk for bronchogenic carcinoma.

Effects of ozone on normal and potentially sensitive human subjects. Part II: Airway inflammation and responsiveness to ozone in nonsmokers and smokers

Exposure to ozone at levels near the National Ambient Air Quality Standard causes respiratory symptoms, changes in lung function, and airway inflammation. Although ozone-induced changes in lung function have been well characterized in healthy individuals, the relationship between airway inflammation and changes in pulmonary function have not been prospectively examined. The purpose of this study was to determine whether individuals who differ in, lung function responsiveness to ozone also differ in susceptibility to airway inflammation and injury. A secondary goal was to determine whether ozone exposure induces airway inflammation in smokers, a population known to have airway inflammation and an increased burden of toxic oxygen species. Healthy nonsmokers (n = 56) and smokers (n = 34) were exposed to 0.22 parts per million (ppm)* ozone for 4 hours, with intermittent exercise, for the purpose of selecting ozone "responders" (decrement in forced expiratory volume in 1 second [FEV1] > 15%) and "nonresponders" (decrement in FEV1 < 5%). Selected subjects then were exposed twice to ozone (0.22 ppm for 4 hours with exercise) and once to air (with the same exposure protocol), each pair of exposures separated by at least 3 weeks, in a randomized, double-blind fashion. Nasal lavage (NL) and bronchoalveolar lavage (BAL) were performed immediately after one ozone exposure and 18 hours after the other, and either immediately or 18 hours after the air exposure. Indicators of airway effects in lavage fluid included changes in inflammatory cells, proinflammatory cytokines, protein markers of epithelial injury and repair, and generation of toxic oxygen species. In the classification exposure, fewer smokers than nonsmokers were responsive to ozone (11.8% vs. 28.6%, respectively); an insufficient number of smoker-responders were identified to study as a separate group. In the BAL study, all groups developed a similar degree of airway inflammation, consisting of increases in interleukins 6 and 8 (maximal immediately after exposure), and increases in polymorphonuclear leukocytes (PMNs), lymphocytes, and mast cells (maximal 18 hours after exposure). The increase in PMNs was inversely correlated with age (p = 0.013), but gender, nonspecific airway responsiveness, and allergy history were not predictive of inflammation. Alveolar macrophage production of toxic oxygen species decreased after ozone exposure in nonsmokers; however, not in smokers. Findings from nasal lavage did not mirror lower airway inflammatory responses in these studies. We conclude that, in response to ozone exposure, smokers experienced smaller decrements in lung function and fewer symptoms than nonsmokers; however, the intensity of the airway inflammatory response was independent of smoking status or airway responsiveness to ozone. Furthermore, the burden of toxic oxygen species following ozone exposure was greater for smokers than for nonsmokers. Subjects were young, healthy, and able to sustain exercise; the results may not be representative of nonsmokers or smokers in general. Nevertheless, the findings indicate that measuring symptoms and spirometric changes is not sufficient to assess the potential risks associated with ozone exposure.

Effects of ozone on normal and potentially sensitive human subjects. Part III: Mediators of inflammation in bronchoalveolar lavage fluid from nonsmokers, smokers, and asthmatic subjects exposed to ozone: a collaborative study

To provide bases of comparison between the studies described in Parts I and II of this Research Report, concentrations of interleukin 6 (IL-6)*, interleukin 8 (IL-8), and alpha 2-macroglobulin (a2M) were measured in airway lavage fluids obtained in the Balmes study (Part I) and compared with the same measurements in the Frampton study (Part II). For healthy subjects in the Balmes study, IL-6 and a2M, but not IL-8, increased in association with ozone exposure. Statistical analyses suggested that effects of ozone on IL-8 levels observed in the first exposure and bronchoscopy may have carried over to the second exposure and bronchoscopy, which may have obscured an effect of ozone on IL-8 after the second exposure. For asthmatic subjects in the Balmes study, IL-6 and IL-8 increased in both bronchial and alveolar lavage fluid, but not in proximal airway lavage fluid. The mean interval between exposures was longer for asthmatic subjects than for healthy subjects, and no carryover effects were seen. When the Balmes and Frampton data were analyzed together, subject groups in the two studies (nonsmokers, smokers, and subjects without and with asthma) did not differ significantly in the response of cytokines to ozone exposure. The finding of possible carryover effects in one group suggests that subtle effects of ozone exposure, or bronchoscopy including proximal airway lavage and biopsy, or both, may persist for three weeks in some subjects.

Determination of production of nitric oxide by lower airways of humans--theory

Exercise and inflammatory lung disorders such as asthma and acute lung injury increase exhaled nitric oxide (NO). This finding is interpreted as a rise in production of NO by the lungs (VNO) but fails to take into account the diffusing capacity for NO (DNO) that carries NO into the pulmonary capillary blood. We have derived equations to measure VNO from the following rates, which determine NO tension in the lungs (PL) at any moment from 1) production (VNO); 2) diffusion, where DNO(PL) = rate of removal by lung capillary blood; and 3) ventilation, where V A(PL)/(PB - 47) = the rate of NO removal by alveolar ventilation (V A) and PB is barometric pressure. During open-circuit breathing when PL is not in equilibrium, d/dt PL[V(L)/ (PB - 47)] (where V(L) is volume of NO in the lower airways) = VNO - DNO(PL) - V A(PL)/(PB - 47). When PL reaches a steady state so that d/dt = 0 and V A is eliminated by rebreathing or breath holding, then PL = VNO/DNO. PL can be interpreted as NO production per unit of DNO. This equation predicts that diseases that diminish DNO but do not alter VNO will increase expired NO levels. These equations permit precise measurements of VNO that can be applied to determining factors controlling NO production by the lungs.

Retention modeling of refractory ceramic fibers (RCF) in humans

A mathematical retention model has been developed to predict the lung burden and size distribution of kaolin refractory ceramic fibers (RCF) in the pulmonary region of the human lung during exposure. Fiber dissolution, breakage, and differential clearance are considered in this model; rates for these processes are obtained by extrapolation from available data on laboratory rats. The lung burden predicted by this model is in general agreement with fiber counts from three factory workers. An important prediction from this study is that clearance of RCF is not significantly impaired at a fiber concentration beneath 10 f/cm3 during occupational exposure.

Ozone responsiveness in smokers and nonsmokers

Short-term exposure to ozone causes decrements in lung function, but predictors of responsiveness remain largely unknown. Ninety healthy volunteers (56 never-smokers, age [mean +/- SD] 25 +/- 4 yr; 34 current smokers, 13 +/- 9 pack-yr, age 28 +/- 1 yr) were exposed to 0.22 ppm ozone for 4 h, with exercise, in an environmental chamber. We measured spirometry and specific airway conductance before, during, and immediately after exposure, and assessed symptoms by questionnaire. Smokers experienced a smaller increase in respiratory symptoms following exposure to ozone than did nonsmokers. Decrements in FEV1 were significantly less than for smokers than for nonsmokers (p = 0.0013). Ozone responsiveness (> 15% fall in FEV1) occurred in 16 of 56 never-smokers (28.6%) and 4 of 34 smokers (11.8%). Multiple logistic regression analysis found pack-yr of smoking to be associated with decreased ozone responsiveness (odds ratio [OR] 0.87, p = 0.017). Age, gender, and methacholine responsiveness were not predictive of responder status. Fourteen smokers and 25 nonsmokers were subsequently exposed once to air and twice to ozone; smokers as well as nonsmokers were consistent in their subsequent responsiveness (or lack of responsiveness) to ozone. Healthy smokers have smaller decrements in lung function and fewer symptoms in response to ozone exposure than do nonsmokers.

Human performance during exposure to toluene

PURPOSE

The purpose of this research was to examine the effects of inhalation of toluene on respiratory function and neuropsychological performance of humans.

METHODS

We exposed six healthy adults to 100 ppm toluene or air (control) for 6 h, in a double-blind, randomized fashion, with exposures separated by at least 14 d and including 30 min of exercise at a level that quadrupled minute ventilation. Blood and exhaled air toluene levels were measured before, during, immediately, and 1 and 2 h post-exposure. Lung function was measured before and immediately after exposure. Three repetitions of two computerized neuropsychological tests were performed, including a brief standard neuropsychological battery (ANAM) and a 1-h complex performance test (SYNWORK). Statistical analysis of the psychological data was conducted as a repeated measures ANOVA.

FINDINGS

Following exercise, the mean blood and exhaled air toluene levels averaged 1.5 micrograms and 28 ppm, respectively. Lung function was unchanged post-exposure. On the SYNWORK test, the Composite score obtained over time during toluene exposure was lower than that during room air (F = 29.20, p = 0.005), with the score from the final hour reduced by 10%. On standard neuropsychological tests, latency but not accuracy proved the sensitive measure for five of the seven subtests presented.

CONCLUSIONS

Performance of complex tests and response time to simple brief tests can be disrupted by toluene inhalation at 100 ppm. Differences in performance between air and toluene conditions were greatest after exercise, indicating that physical activity may enhance the response to volatile organic solvents.

Xenobiotic metabolism enzyme gene expression in human bronchial epithelial and alveolar macrophage cells

Human bronchial epithelial cells (BEC), a primary defense against inhaled materials, are the progenitor cells for bronchogenic carcinomas and have important metabolic capabilities. We used reverse transcriptase-polymerase chain reaction (RT-PCR) to identify xenobiotic metabolism enzymes expressed in primary BEC and alveolar macrophages (AM) of non-smoking volunteers. Cytochromes P450 (CYP) 1A1, 1B1, 2B7, 2E1, and 4B1 and microsomal epoxide hydrolase (mEH) were expressed in BEC but not AM. CYP2F1 was expressed in BEC, but it was expressed at barely detectable levels or not at all in AM. NADPH oxidoreductase (NADPH OR), microsomal glutathione transferase (GST 12), glutathione transferase mu, phenol sulfotransferase (PST), thermolabile phenol sulfotransferase (TL PST), and the clara cell-specific gene, CC10 were expressed in both BEC and AM. CYP3A4 and glucuronosyl transferases-1 and 2 were not expressed in either BEC or AM. In contrast to primary BEC, of the genes evaluated, the immortalized human bronchial epithelial cell line BEP2D constitutively expressed only CYP1A1, CYP2E1, NADPH OR, glucuronosyl transferase 1, GST 12, GST mu, PST, TL PST, and CC10. The loss of xenobiotic metabolism enzyme gene expression in the BEP2D cell line may result from either reduced exposure to inducing agents, or loss of differentiative characteristics in culture. It is clear from the data comparing BEC and AM that there are important intertissue differences in expression of xenobiotic metabolism enzymes.

Environmentally induced asthma

Asthma is characterized by inflammation, reversible airway obstruction, and increased airway responsiveness to various stimuli. Despite advances in understanding of the pathophysiology and in developing new treatments, asthma prevalence and mortality have been rising over the last decade, after a steady decline in the 1970s. Risk factors for environmentally induced asthma include air pollutants, tobacco smoke, wood smoke, and excessive allergen exposure. In controlled human chamber studies, asthmatics demonstrate increased susceptibility to outdoor pollutants such as sulfur dioxide, nitrogen dioxide, and acidic particles with acute reductions in lung function during and following exposures; responses are enhanced by increased ventilation, for example during exercise, or breathing cold air and/or dry air. The evidence is even stronger that inhaled indoor allergens have a causal relationship to asthma. It is possible that changes in housing conditions have led to increased levels of dust mite and other proteins in homes with consequent increases in the prevalence of sensitization. Avoidance of specific allergens such as house dust mite over months results in a reduction in clinical symptoms and bronchial hyperresponsiveness. The interaction between aeroallergens and air pollutants in triggering environmentally induced asthma is an area of active research.

Composition of human airway mucins and effects after inhalation of acid aerosol

Characterization of normal airway mucus is required to elucidate mechanisms protecting the airways and to understand changes associated with disease and environmental insult. Toward this goal, we collected bronchial washes (10 ml saline) from healthy human subjects to 1) evaluate the yield of high-density material (delta > or = 1.35 g/ml), and 2) characterize glycoconjugates associated with collected secretions. Samples were lipid extracted followed by CsCl density gradient centrifugation. The yield of high-density material from individual subjects was variable but sufficient to demonstrate that mucin glycoproteins are a major constituent of mucus from healthy airways and that proteoglycans are absent. Next, we investigated whether inhalation of H2SO4 aerosol (1,000 microgram/m3), an environmental insult associated with alterations in mucociliary clearance, changes the composition of high-density glycoproteins in airway secretions. In a paired, double-blinded study, high-density fractions of bronchial secretions from 12 subjects were collected 18 h after exposures of 2 h to aerosolized NaCl and H2SO4. In all cases the high-density material displayed characteristics of mucin glycoproteins. In addition, a unique 150-kDa glycoprotein was detected in most but not all samples and may represent a small mucin glycoprotein differentially expressed in humans. No differences were noted between the two exposure conditions in the profiles of the glycoproteins or proteins after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Statistically, large changes with acid exposure in the composition of carbohydrates and amino acids were absent. Thus no substantial systematic changes in airway mucin glycoproteins or closely associated proteins and glycoproteins were correlated with H2SO4 exposure. Alternatively, statistical analysis of the differences between exposures in glycoprotein constituents among subjects denoted greater variability in carbohydrates compared with amino acids with repeated sampling, suggesting normal daily variations in the mucin composition of individual airway mucus.

The acute respiratory distress syndrome: current trends in pathogenesis and management

Management of patients in ARD remains a complex diagnostic and difficult therapeutic problem. Although the authors have focused on several new and exciting management strategies, it is important to recognize that the vast majority of patients with ARDS simply require meticulous general medical care. In this era of invasive monitoring and other care. In this era of invasive monitoring and other complex technologies, there is sometimes a tendency to neglect the basic issues such as judicious use of antibiotics to avoid superinfection with resistant organisms or antibiotic-associated diarrhea; removal of unnecessary intravenous lines to minimize line related infections; and maintenance of adequate nutrition to promote good skin and mucosal integrity as well as preserving important muscle mass all too often receive a low priority. It is anticipated that with meticulous general medical care, as well as selective implementation of the above treatment strategies, improvement in the outcome of patients is an achievable goal.

Sulfuric acid aerosol followed by ozone exposure in healthy and asthmatic subjects

These studies evaluated symptom and pulmonary function responses of humans sequentially exposed to sulfuric acid aerosol and ozone. Thirty healthy subjects and 30 allergic asthmatic subjects underwent 3-hr exposures in an environmental chamber to 100 micrograms/m3 sulfuric acid and sodium chloride (control) aerosols (in random order), followed 24 hr later by 3-hr exposures to ozone (0.08, 0.12, or 0.18 ppm). Each subject was studied four times, receiving each aerosol preexposure followed by two of the three ozone concentrations. For the healthy group, no convincing symptomatic or physiologic effects of exposure to either the aerosol or ozone on lung function were found. For the asthmatic group, preexposure to sulfuric acid altered the pattern of response to ozone in comparison with sodium chloride preexposure and appeared to enhance the small mean decrements in FVC that occurred in response to 0.18 ppm ozone (means +/- SE: -3.6 +/- 1.5% with sodium chloride preexposure, -6.8 +/- 1.7% with sulfuric acid preexposure). Individual responses among asthmatic subjects were quite variable, some demonstrating reductions in FEV1 of more than 35% following ozone exposure. Analysis of variance of changes in FVC revealed evidence for interactions between aerosol and ozone exposure both immediately after (P = 0.005) and 4 hr after (P = 0.030) exposure. Similar effects were seen for FEV1. When normal and asthmatic subjects were combined, four-way analysis of variance revealed an interaction between ozone and aerosol for the entire group (P = 0.0022) and a difference between normal and asthmatic subjects (P = 0.0048). There was no significant effect of exposures on symptoms for either normal or asthmatic subjects. Asthmatic subjects differ from healthy volunteers in their functional responses following sequential exposures to aerosols and ozone and appear to represent a susceptible population.

Oxidant and acid aerosol exposure in healthy subjects and subjects with asthma. Part II: Effects of sequential sulfuric acid and ozone exposures on the pulmonary function of healthy subjects and subjects with asthma

These studies were undertaken to evaluate pulmonary responses of humans sequentially exposed to acidic aerosols and ozone at levels that could reasonably be encountered in actual environmental exposures. Subjects first were exposed to sulfuric acid (H2SO4) aerosol to sensitize the airways to ozone. The exposure protocols were designed to provide more quantitative information about the threshold levels of ozone that produce adverse biological effects and to provide exposure-response data on ozone. Two groups of 30 nonsmoking volunteers of both sexes, between the ages of 18 and 45 years, were recruited. The healthy study population comprised 16 men and 14 women with an average age of 28 years and no airway hyperreactivity. The second group comprised 10 men and 20 women comparable in age to the control group, but with allergic asthma and positive skin tests. The study examined an exposure-response relationship using three levels of ozone ranging from below the current standard to one and one-half times the ambient air quality standard (0.08, 0.12, and 0.18 ppm* [parts per million]) with preexposure 24 hours earlier to H2SO4 (100 micrograms/m3) or sodium chloride (NaCl) (control) aerosol in a 45-m3 environmental chamber. The study used an incomplete block design in which each subject was exposed to four of the six paired experimental atmospheres. Both the selection of paired exposures and the order in which they were presented were randomized. The exposure protocol required nine days: Day 1, training and baseline preexposure measurements; Day 2, the first of the three-hour particle (H2SO4 or NaCl) exposures; Day 3 (24 hours after Day 2), ozone exposure at 0.08, 0.12, or 0.18 ppm for three hours; Day 4 (two to four weeks later), exposure to the same ozone concentration as on Day 4. After at least another two weeks, Days 6, 7, 8, and 9 repeated Days 2, 3, 4, and 5 using a second ozone concentration. All three-hour exposures included several predetermined periods of exercise and pulmonary function measurements. To examine for delayed effects, pulmonary function tests were measured two and four hours after exposure on the ozone days. Data were analyzed over the time course of exposure and by exposure level of ozone at each time point to reveal dose-response relationships more closely. The main findings of the study are as follows. No significant symptomatic or physiologic effects of exposure to either aerosol or ozone on lung function were found for the healthy group.(ABSTRACT TRUNCATED AT 400 WORDS)

Clearance of refractory ceramic fibers (RCF) from the rat lung: development of a model

Chronic exposure and postexposure experiments have been recently performed in rats to evaluate the biological responses of inhaled refractory ceramic fibers (RCF) at different concentration levels. The lung burden data in the accessory lobe of the rat lung were collected during and after different exposure and postexposure periods. The size distribution of retained fibers in the lung at different time points was also measured. We used these data to develop a mathematical model of fiber clearance from the rat lung. It was found that the clearance rate did not depend significantly upon fiber size but there was a clear dependence on lung burden. As lung burden increased, the clearance rate was found to decrease. An empirical equation was derived for the clearance rate as a function of lung burden. At low burdens, rats had a retention half-time of about 126 days for RCF compared to a typical half-time of about 60 days for insoluble nonfibrous particles.

Measurement of gene expression by multiplex competitive polymerase chain reaction

We have developed a polymerase chain reaction (PCR)-based method to measure glutathione peroxidase (GSH-Px) mRNA levels. Expression was measured by multiplex competitive PCR amplification of (a) cDNA from GSH-Px and the "housekeeping" gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and (b) two internal standards consisting of single-base mutants of GSH-Px and GAPDH cDNA that cause either a loss (GSH-Px) or a gain (GAPDH) of an EcoRI restriction endonuclease recognition site. RNA extracted from a human papillomavirus-immortalized human bronchial epithelial cell line (BEP2D) was reverse transcribed. Serial dilutions of cDNA were PCR amplified in the presence of GSH-Px and GAPDH primers and quantified amounts of mutated internal standards. The amplified DNA was restriction digested with EcoRI and electrophoresed on an agarose gel stained with ethidium bromide, separating native from mutated products. Densitometry was performed to quantitate the bands. Our studies demonstrate that this technique measures the relative expression of GSH-Px to GAPDH precisely and reproducibly for studies done with the same master mixture and dilution of internal standards. Ratios of relative gene expression varied less than 25% from the mean. This technique will be useful to measure changes in gene expression, particularly when the amount of study sample is limited or the level of gene expression is low.

Air pollution health risks: do class and race matter?

Air pollution is not spread evenly across demographic groups. Exposures and associated health risks appear to fall disproportionately on populations that are poor and nonwhite. Although scientific evidence documenting disparities in air pollution exposures, doses, and health effects is scant, the available data strongly support the contention that disadvantaged groups, many of whom are ethnic and racial minorities, routinely encounter levels of air pollution that are higher than average. The extent to which exposure differentials contribute to observed differences in health status by class and race is unknown, but worthy of further investigation. We recommend several steps, all of them feasible and most of them relatively inexpensive, to improve our understanding and ability to address environmental health disparities.

Sulfuric acid aerosol exposure in humans assessed by bronchoalveolar lavage

Epidemiologic and experimental evidence suggests that exposure to acidic aerosols may affect human health. Brief exposures to acidic aerosols alter mucociliary clearance and increase airway responsiveness, but effects on host defense mechanisms at the alveolar level have not been studied in humans. Twelve healthy, nonsmoking volunteers between 20 and 39 yr of age were exposed for 2 h to aerosols of approximately 1,000 micrograms/m3 sulfuric acid (H2SO4) or sodium chloride (NaCl [control]), with intermittent exercise, in a randomized, double-blind fashion. Each subject received both exposures, separated by at least 2 wk. Bronchoalveolar lavage (BAL) was performed 18 h after exposure in order to detect evidence of an inflammatory response, changes in alveolar cell subpopulations, or changes in alveolar macrophage (AM) function, which is important in host defense. When compared with NaCl, exposure to H2SO4 did not increase polymorphonuclear leukocytes in BAL fluid. The percentage of T lymphocytes decreased in association with H2SO4 exposure, but the difference was not statistically significant (14.9% after NaCl, 11.5% after H2SO4; p = 0.14). Antibody-mediated cytotoxicity of AM increased in association with H2SO4 exposure (percent lysis 19.1 after NaCl, 23.6 after H2SO4; p = 0.16). No significant change was seen in release of superoxide anion or inactivation of influenza virus in vitro. Brief exposures to H2SO4 aerosol at 1,000 micrograms/m3 do not cause an influx of inflammatory cells into the alveolar space, and no evidence was found for alteration in antimicrobial defense 18 h after exposure.

Effect of pattern of aerosol inhalation on clearance of technetium-99m-labeled diethylenetriamine pentaacetic acid from the lungs of normal humans

The clearance rate of inhaled aerosols of technetium-99m-labeled diethylenetriamine pentaacetic acid (99mTc-DTPA) from the lungs provides a rapid, clinically useful, noninvasive index of pulmonary epithelial permeability. In order to identify a method that minimizes intrasubject and intersubject variability and thereby provides a reliable means to identify patients with abnormal values, we administered a submicronic aerosol of 99mTc-DTPA to 10 healthy, nonsmoking male subjects with either tidal breathing (Vtidal) or multiple vital capacity maneuvers (VVC). Subjects then spontaneously breathed room air while counting continued for 30 min. Monoexponential clearance rates over 7, 15, and 30 min were compared with a two-compartment, biexponential analysis over 30 min. Intrasubject reproducibility was evaluated by repeating clearance 2 to 156 days later. Monoexponential clearance following VVC at 30 min equaled 1.36 +/- 0.55%/min compared with 0.83 +/- 0.25%/min for Vtidal (p less than 0.025). VVC inhalations resulted in a larger fast compartment of 16 +/- 12% compared with 3 +/- 2% with tidal breathing (p less than 0.01). The least intrasubject variability with coefficient of variation (CV) of +/- 18% was obtained with monoexponential analyses after Vtidal during 15 min of scanning and with either breathing maneuver over 30 min. Monoexponential clearance for 30 min with Vtidal gave the least scatter between subjects, with CV of +/- 30%. These data show that simple tidal inhalations of 99mTc-DTPA followed by a monoexponential analysis of the 30-min time-activity curve from both lungs minimize the degree of variability between and among subjects and provide a predicted normal value of clearance of 0.83 +/- 0.25%/min. The development of a more rapid curvilinear clearance followed by delivery VVC suggests that several deep breaths transiently increase epithelial permeability or reduce the volume of liquid in the alveolar subphase in some regions. Resting for 20 min prior to inhaling the aerosol of 99mTc-DTPA is recommended to avoid alterations in clearance rates from deep breathing.

Pulmonary performance of elderly normal subjects and subjects with chronic obstructive pulmonary disease exposed to 0.3 ppm nitrogen dioxide

Symptoms and changes in pulmonary function of subjects with chronic obstructive pulmonary disease (COPD) and elderly normal subjects, induced by a 4-h exposure to 0.3 ppm NO2, were investigated using a double-blind, crossover design with purified air. The 5-day experimental protocol required approximately 2 wk with at least a 5-day separation between randomized 4-h exposures to either NO2 or air which included several periods of exercise. Over a 2-yr period, COPD subjects, all with a history of smoking, consisting of 13 men and 7 women (mean age of 60.0 yr) and 20 elderly normal subjects of comparable age and sex were evaluated. During intermittent light exercise, COPD subjects demonstrated progressive decrements in FVC and FEV1 compared with baseline with 0.3 ppm NO2, but not with air. Differences in percent changes from baseline data (air-NO2) showed an equivocal reduction in FVC by repeated measures of analysis of variance and cross-over t tests (p less than 0.10). Subgroup analyses suggested that responsiveness to NO2 decreased with severity of COPD; in elderly normal subjects, NO2-induced reduction in FEV1 was greater among smokers than never-smokers. A comparison of COPD and elderly normal subjects also revealed distinctions in NO2-induced responsiveness.