In the present paper, we have reviewed experimental animal studies on the effects of the two most important oxidant airborne pollutants, nitrogen dioxide and ozone, on the respiratory system.The toxic effects depend on concentration and length of exposure, and are generally similar for both oxidants, with ozone operative at lower concentrations. High doses of both oxidants cause death due to lung oedema Exposure to sublethal levels causes functional alterations such as airflow limitation and airway hyperresponsiveness to bronchoconstrictor stimuli. These effects, which are generally reversible, are associated with epithelial injury, oedema and airway and parenchymal infiltration by inflammatory cells. Loss of cilia of airway epithelium and necrosis of type I alveolar epithelial cells are the most prominent consequences at the epithelial level. Inmation is characterized by early neutrophilic infiltration, followed by an increased number of mononuclear cells, predominantly alveolar macrophages.After long-term exposure, whilst nitrogen dioxide causes predominantly emphysema, ozone produces mainly pulmonary fibrosis. Biochemical effects include lipid peroxidation, increased antioxidant metabolism, and alteration of enzyme activity. Nitrogen dioxide and ozone may also alter the immunological response and reduce the defence against infections, increasing the susceptibility of exposed animals to infections.
To assess the nature and the time-course of the cellular component of airway inflammation induced by isocyanates, we examined nine subjects with occupational asthma induced by toluene- or methylene diphenyl-diisocyanate (TDI, MDI) and four control subjects never exposed to isocyanates. Sputum was induced by inhalation of ultrasonically nebulized hypertonic saline (3-4% NaCl) before and 8, 24, 48 h after inhalation challenge with TDI or MDI. Expectorated samples were incubated with dithiothreitol, washed and cytocentrifuged. Differential cell counts were obtained on slides stained with May-Grünwald-Giemsa. Metachromatic cells (mast cells and basophils) were counted on slides stained with toluidine blue at pH 0.1. One occupational asthmatic exhibited a dual reaction to TDI, two exhibited a single early asthmatic reaction to MDI, six exhibited a late asthmatic reaction to TDI (n = 5) or MDI (n = 1), whereas no reactions were observed in control subjects after TDI challenge. In sensitized subjects eosinophils increased from a median value (interquartile range) of 5 (15)% before challenge to 29 (29)% (P = 0.014) and to 30 (31)% (P = 0.031) 8 and 24 h after TDI/MDI challenges, respectively. Sputum eosinophilia was observed both in early and late reactors and declined to near to baseline values 48 hr after challenge. Percentages of eosinophils in control subjects did not exceed 7% during the study.(ABSTRACT TRUNCATED AT 250 WORDS)
Physiological and clinical studies have shown that the standard method of measuring respiratory impedance by forced oscillation leads to less efficient control of the upper airway shunt effect than the head generator method. To test the effects of these two techniques in epidemiological studies, we compared, in a sample of 73 French agricultural workers, the values obtained with each method for five forced oscillation parameters: resistance, frequency dependence of resistance, inertance, compliance and resonant frequency. For these comparisons, subjects were classified according to four respiratory status factors: smoking status, cough, expectoration and airway obstruction assessed from the maximum expiratory flow volume curve. Logistic regression models using the set of four forced oscillation parameters (excluding resonant frequency, which is derived from compliance and inertance) were then used to analyse the ability of each method to classify the subjects in each group. Significant differences between the two methods were observed for the mean values obtained for all five parameters. However, when each parameter was considered separately, the correlations between the values for each method were significant. Each method possessed the necessary ability to separate subjects into our group classification, but the significant relationships were not always found for the same parameters. Finally, logistic regression models showed that the two methods led to almost the same classification of the subjects. According to our results, the standard method of applying forced oscillation at the mouth seems an acceptable device for measuring respiratory impedance for epidemiological purposes.
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