Airway inflammation following exposure to diesel exhaust: a study of time kinetics using induced sputum

Abstract

The adverse health effects of particulate matter pollution are of increasing concern. In a recent bronchoscopic study in healthy volunteers, pronounced airway inflammation was detected following exposure to diesel exhaust (DE). The present study was conducted in order to evaluate the time kinetics of the inflammatory response following exposure to DE using induced sputum from healthy volunteers.Fifteen healthy nonsmoking volunteers were exposed to DE particles with a 50% cut-off aerodynamic diameter of 10 mm 300 mg . m -3 and air for 1 h on two separate occasions. Sputum induction with hypertonic saline was performed 6 and 24 h after each exposure. Analyses of sputum differential cell counts and soluble protein concentrations were performed.Six hours after exposure to DE, a significant increase was found in the percentage of sputum neutrophils (37.7 versus 26.2% p=0.002) together with increases in the concentrations of interleukin-6 (12.0 versus 6.3 pg . mL -1 , p=0.006) and methylhistamine (0.11 versus 0.12 mg . L -1 , p=0.024). Irrespective of exposure, a significant increase was found in the percentage of sputum neutrophils at 24 as compared to 6 h, indicating that the procedure of sputum induction itself may change the composition of sputum.This study demonstrates that exposure to diesel exhaust induces inflammatory response in healthy human airways, represented by an early increase in interleukin -6 and methylhistamine concentration and the percentage of neutrophils. Induced sputum provides a safe tool for the investigation of the inflammatory effects of diesel exhaust, but care must be taken when interpreting results from repeated sputum inductions. Eur Respir J 2000; 15: 1046±1051. The adverse health effects of particulate matter (PM) pollution are of increasing concern as several epidemiological studies have revealed an association between elevations in ground level PM concentrations and increased morbidity and mortality from cardiovascular and respiratory causes [1±7].Recently, attention has been directed towards the particulate air pollution emitted from diesel engines. The number of diesel-powered cars is rising and diesel engines emit up to 100 times more particles than petrol engines [8,9]. Diesel exhaust (DE) particles contain a carbonaceous core, which adsorbs various metals and organic compounds on its surface. Consequently, the biological effects of DE may be explained by not only the gases and pure particles but also by these surface components.The number of studies investigating the effects of DE has increased during recent years. In working environments, exposure to DE has been associated with various symptoms related to the eyes and airways [10±12]. In experimental chamber studies, DE has been shown to cause airway symptoms [13] and to induce an acute inflammatory response in human airways as reflected in bronchoalveolar lavage [14,15] and bronchial biopsy [16] samples. Further, local nasal challenge with DE particles has been reported to enhance immunoglobulin E production in the ...

Wood smoke exposure induces a pulmonary and systemic inflammatory response in firefighters

“…This suggests recruitment of granulocytes into the airway and is consistent with numerous previous studies in both animals [42][43][44][45][46] and humans [7,[9][10][11], which have shown increased granulocyte counts, most commonly neutrophilia, in bronchoalveolar lavage and induced sputum samples following exposure to particulate matter. An increase in the number of macrophages in induced sputum was not found in the present study, which suggests that the predominant inflammatory response in the lung with acute wood smoke exposure is neutrophilic in nature.…”

“…Numerous epidemiological studies have documented a detrimental relationship between exposure to particulate matter in urban air pollution and cardiopulmonary morbidity and mortality with both short-and long-term exposure [1][2][3][4][5]. Although the mechanism by which exposure to particles in urban air induces adverse cardiopulmonary effects remains unclear, several studies from the present authors' laboratory and others support a mechanism in which exposure to fine particles promotes inflammation in the lung [6][7][8][9][10][11] via activation of alveolar macrophages and lung epithelial cells [12][13][14][15][16]. Such exposure is also associated with a systemic inflammatory response [17][18][19][20], which in turn is associated with an increased presence of several cytokines (interleukin (IL)-6, IL-1b) in the bloodstream [21] as well as increased production and release of polymorphonuclear leukocytes (PMN) and monocytes from the bone marrow [17][18][19][20].…”

Health effects of diesel exhaust emissions

“…Studies of induced sputum have also been used to evaluate DE effects on the human airways [32]. Sixteen healthy nonsmoking subjects were exposed to air and DE at a particle concentration of 300 mg .…”

Diesel exhaust enhances airway responsiveness in asthmatic subjects

“…During the last decade, several epidemiological studies have provided convincing evidence for an association between ambient levels of particulate matter and various health outcome indices, including respiratory symptoms [1], impaired lung function [2], exacerbations of asthma [3,4], emergency room visits [1,5], and an increased risk of respiratory illness in children [6]. Importantly, several studies have suggested that individuals with pre-existing respiratory disease such as asthma are more sensitive to elevated ground levels of particulate matter (PM) pollution as compared to healthy subjects [7,8].…”