Respiratory effects of exposure to diesel traffic in persons with asthma

Effects of ambient air pollution on hemostasis and inflammation

BACKGROUND

Air pollution has consistently been associated with increased morbidity and mortality due to respiratory and cardiovascular disease. Underlying biological mechanisms are not entirely clear, and hemostasis and inflammation are suggested to be involved.

OBJECTIVES

Our aim was to study the association of the variation in local concentrations of airborne particulate matter (PM) with aerodynamic diameter < 10 mum, carbon monoxide, nitrogen monoxide, nitrogen dioxide, and ozone with platelet aggregation, thrombin generation, fibrinogen, and C-reactive protein (CRP) levels in healthy individuals.

METHODS

From 40 healthy volunteers, we collected 13 consecutive blood samples within a 1-year period and measured light-transmittance platelet aggregometry, thrombin generation, fibrinogen, and CRP. We performed regression analysis using generalized additive models to study the association between the hemostatic and inflammatory variables, and local environmental concentrations of air pollutants for time lags within 24 hr before blood sampling or 24-96 hr before blood sampling.

RESULTS

In general, air pollutants were associated with platelet aggregation [average, +8% per interquartile range (IQR), p < 0.01] and thrombin generation (average, +1% per IQR, p < 0.05). Platelet aggregation was not affected by in vitro incubation of plasma with PM. We observed no relationship between any of the air pollutants and fibrinogen or CRP levels.

CONCLUSIONS

Air pollution increased platelet aggregation as well as coagulation activity but had no clear effect on systemic inflammation. These prothrombotic effects may partly explain the relationship between air pollution and the risk of ischemic cardiovascular disease.

Childhood asthma and environmental exposures at swimming pools: state of the science and research recommendations

OBJECTIVES

Recent studies have explored the potential for swimming pool disinfection by-products (DBPs), which are respiratory irritants, to cause asthma in young children. Here we describe the state of the science on methods for understanding children's exposure to DBPs and biologics at swimming pools and associations with new-onset childhood asthma and recommend a research agenda to improve our understanding of this issue.

DATA SOURCES

A workshop was held in Leuven, Belgium, 21-23 August 2007, to evaluate the literature and to develop a research agenda to better understand children's exposures in the swimming pool environment and their potential associations with new-onset asthma. Participants, including clinicians, epidemiologists, exposure scientists, pool operations experts, and chemists, reviewed the literature, prepared background summaries, and held extensive discussions on the relevant published studies, knowledge of asthma characterization and exposures at swimming pools, and epidemiologic study designs.

SYNTHESIS

Childhood swimming and new-onset childhood asthma have clear implications for public health. If attendance at indoor pools increases risk of childhood asthma, then concerns are warranted and action is necessary. If there is no such relationship, these concerns could unnecessarily deter children from indoor swimming and/or compromise water disinfection.

CONCLUSIONS

Current evidence of an association between childhood swimming and new-onset asthma is suggestive but not conclusive. Important data gaps need to be filled, particularly in exposure assessment and characterization of asthma in the very young. Participants recommended that additional evaluations using a multidisciplinary approach are needed to determine whether a clear association exists.

Respiratory morbidity attributed to auto-exhaust pollution in traffic policemen of Jaipur, India

AIMS

This study was conducted to evaluate pulmonary effects of traffic pollution on traffic police.

METHODS

The traffic police working in Jaipur city were given a predetermined respiratory health questionnaire, and their clinical profile and lung functions were measured.

RESULTS

This study showed that there were prominent respiratory symptoms and reduced forced expiratory volume in 1 second (FEV(1)) in subjects exposed to traffic pollution. When smokers were excluded, it showed a significant difference in FEV(1) data of non-smoking subjects exposed to traffic generated pollution and those not exposed. The difference observed was 95.3 +/- 13.6 versus 87.8 +/- 0.95%, respectively, and 95%CI = 4.420-10.517, p = 0.001.

CONCLUSIONS

Respiratory morbidity with respect to lung function tests is observed more in groups working in heavy traffic than the control group.

Increased levels of outdoor air pollutants are associated with reduced bronchodilation in children with asthma

BACKGROUND

Increased outdoor air pollution levels are associated with more frequent use of rescue inhalers in subjects with asthma. However, it is unknown whether this phenomenon is explained by an air pollution-mediated increase in respiratory symptom severity or whether air pollutants decrease the efficacy of short-acting beta-agonists (SABAs).

METHODS

We examined the relationship between the percentage change in FEV(1) after SABA use with outdoor air pollution exposure in 85 children with asthma who were 7 to 12 years of age. Outdoor air pollution exposure was determined by measuring nitrogen dioxide (NO(2)), ozone (O(3)), and fine particulate matter (ie, particulate matter with an aerodynamic diameter < 2.5 microm [PM(2.5)]) levels. These measurements were obtained from the Mexico City Automated Monitoring Network from network sites located within a 5-km radius of each child's home and school.

RESULTS

We found that a same-day interquartile increase of 10 parts per billion (ppb) in NO(2) concentration was associated with a reduced response of FEV(1) to SABA therapy (-15%; 95% CI, -29 to -0.5). This association was also significant when considering NO(2) levels in each of the preceding 3 days. An interquartile O(3) increase (16 ppb) in the preceding fifth day was associated with a reduced response to SABA (-11%; 95% CI, -23 to -1); an interquartile PM(2.5) increase (14 microg/m(3)) was not associated with any significant reductions in the response to SABA therapy. These associations were not observed in children receiving therapy with inhaled corticosteroids.

CONCLUSIONS

Our results suggest that recent exposure to NO(2) and possibly O(3) may reduce the response to SABAs in producing bronchodilation in children with asthma. The association between NO(2) and FEV(1) response to SABA administration may have important implications in understanding how outdoor air pollution levels relate to asthma control.

Role of oxidative stress in ultrafine particle-induced exacerbation of allergic lung inflammation

RATIONALE

The effects of ultrafine particle inhalation on allergic airway inflammation are of growing interest. The mechanisms underlying these effects are currently under investigation.

OBJECTIVES

To investigate the role of oxidative stress on the adjuvant activity of inhaled elemental carbon ultrafine particles (EC-UFPs) on allergic airway inflammation.

METHODS

Ovalbumin-sensitized mice were exposed to EC-UFPs (504 microg/m(3) for 24 h) or filtered air immediately before allergen challenge and systemically treated with N-acetylcysteine or vehicle before and during EC-UFP inhalation. Allergic inflammation was measured up to 1 week after allergen challenge by means of bronchoalveolar lavage, cytokine/total protein assays, lung function, and histology. Isoprostane levels in lung tissue served to measure oxidative stress. Transmission electron microscopy served to localize EC-UFPs in lung tissue and both electrophoretic mobility shift assay and immunohistochemistry to quantify/localize nuclear factor-kappaB (NF-kappaB) activation.

MEASUREMENTS AND MAIN RESULTS

In sensitized and challenged mice EC-UFP inhalation increased allergen-induced lung lipid peroxidation and NF-kappaB activation in addition to inflammatory infiltrate, cytokine release, and airway hyperresponsiveness. Prominent NF-kappaB activation was observed in the same cell types in which EC-UFPs were detected. N-acetylcysteine treatment significantly reduced the adjuvant activity of EC-UFPs. In nonsensitized or sensitized but not challenged mice EC-UFP exposure induced a moderate increase in isoprostanes but no significant effect on other parameters of lung inflammation.

CONCLUSIONS

Our findings demonstrate a critical role for oxidative stress in EC-UFP-induced augmentation of allergen-induced lung inflammation, where EC-UFP exposure has potentiating effects in lung allergic inflammation. Our data support the concept that allergic individuals are more susceptible to the adverse health effects of EC-UFPs.

Less air pollution leads to rapid reduction of airway inflammation and improved airway function in asthmatic children

OBJECTIVE

Air pollution can promote airway inflammation, posing significant health risks for children with chronic respiratory problems. However, it is unknown whether this process is reversible, so that limiting pollution will benefit these children. We measured the short-term response of allergic asthmatic children exposed to a real-life reduction in outdoor air pollution by using noninvasive biomarkers of airway inflammation and function.

PATIENTS AND METHODS

Thirty-seven untreated allergic children with mild persistent asthma were recruited from a highly polluted urban environment and relocated to a less polluted rural environment. Air pollution, pollen counts, and meteorological conditions were carefully monitored at both sites. Nasal eosinophils, fractional exhaled nitric oxide, peak expiratory flow, and urinary leukotriene E(4) were measured first in the urban environment and then again 7 days after relocation to the rural environment.

RESULTS

One week after relocation to the rural environment, we measured, on average, a fourfold decrease in nasal eosinophils and significant decrease in fractional exhaled nitric oxide. We also noted an improvement in lower airway function, reflected by highly significant increase in peak expiratory flow. In contrast, mean urinary leukotriene E(4) concentration remained unchanged after 1 week of exposure to the rural environment.

CONCLUSIONS

Better air quality is associated with a rapid reduction of airway inflammation in allergic asthmatic children. Nasal eosinophils and fractional exhaled nitric oxide are sensitive indicators of this effect, and their rapid decline is paralleled by improved airway function measured by peak expiratory flow. Leukotriene synthesis has a more variable response to environmental modifications.

Exposure to traffic: lung function and health status in adults with asthma

BACKGROUND

Exposure to traffic has been associated with asthma outcomes in children, but its effect on asthma in adults has not been well studied.

OBJECTIVE

To test the hypothesis that lung function and health status are associated with traffic exposures.

METHODS

We measured FEV(1) % predicted, general health status using the Physical Component Scale of the 12-item Short Form (SF-12 PCS), and quality of life (QoL) using the Marks Asthma Quality of Life questionnaire in a cohort of adults with asthma or rhinitis (n = 176; 145 with asthma). We assessed exposures to traffic by geocoding subjects' residential addresses and assigning distance to roadways. Associations between distance to nearest roadway and distance to nearest major roadway and FEV(1) % predicted or SF-12 PCS were studied by using linear regression.

RESULTS

FEV(1) % predicted was positively associated with distance from both nearest roadway (P = .01) and nearest major roadway (P = .02). SF-12 PCS and QoL were not significantly associated with either traffic variable. Adjustment for income, smoking, and obesity did not substantively change the associations of the traffic variables with FEV(1) % predicted (P = .04 for nearest roadway and P = .02 for nearest major roadway) and did not cause associations with either SF-12 PCS or QoL to become significant.

CONCLUSIONS

Traffic exposure was associated with decreased lung function in adults with asthma.

Proapoptotic Noxa is required for particulate matter-induced cell death and lung inflammation

Elevated ambient levels of particulate matter air pollution are associated with excess daily mortality, largely attributable to increased rates of cardiovascular events. We have previously reported that particulate matter induces p53-dependent apoptosis in primary human alveolar epithelial cells. Activation of the intrinsic apoptotic pathway by p53 often requires the transcription of the proapoptotic Bcl-2 proteins Noxa, Puma, or both. In this study, we exposed alveolar epithelial cells in culture and mice to fine particulate matter <2.5 microm in diameter (PM(2.5)) collected from the ambient air in Washington, D. C. Exposure to PM(2.5) induced apoptosis in primary alveolar epithelial cells from wild-type but not Noxa(-/-) mice. Twenty-four hours after the intratracheal instillation of PM(2.5), wild-type mice showed increased apoptosis in the lung and increased levels of mRNA encoding Noxa but not Puma. These changes were associated with increased permeability of the alveolar-capillary membrane and inflammation. All of these findings were absent or attenuated in Noxa(-/-) animals. We conclude that PM(2.5)-induced cell death requires Noxa both in vitro and in vivo and that Noxa-dependent cell death might contribute to PM-induced alveolar epithelial dysfunction and the resulting inflammatory response.

Exhaled nitric oxide and breath condensate ph in asthmatic reactions induced by isocyanates

BACKGROUND

We investigated the usefulness of measurements of fractional exhaled nitric oxide (FeNO) and pH of exhaled breath condensate (EBC) for monitoring airway response after specific inhalation challenges with isocyanates in sensitized subjects.

METHODS

Lung function (FEV(1)), FeNO, and pH in argon-deaerated EBC were measured before and at intervals up to 30 days after a specific inhalation challenge in 15 subjects with isocyanate asthma, in 24 not sensitized control subjects exposed to isocyanates, and in 3 nonasthmatic subjects with rhinitis induced by isocyanate. Induced sputum was collected before and 24 h after isocyanate exposure.

RESULTS

Isocyanate-induced asthmatic reactions were associated with a rise in sputum eosinophil levels at 24 h (p < 0.01), and an increase in FeNO at 24 h (p < 0.05) and 48 h (p < 0.005), whereas FeNO level did not vary with isocyanate exposure in subjects with rhinitis and in control subjects. FeNO changes at 24 h positively correlated with corresponding sputum eosinophil changes (rho = 0.66, p < 0.001). A rise in pH was observed in the afternoon samples of EBC, irrespective of the occurrence of isocyanate-induced asthmatic reactions.

CONCLUSIONS

We demonstrated that isocyanate-induced asthmatic reactions are associated with a consistent delayed increase in FeNO but not with the acidification of EBC.

Airborne monitoring to distinguish engineered nanomaterials from incidental particles for environmental health and safety

Two methods were used to distinguish airborne engineered nanomaterials from other airborne particles in a facility that produces nano-structured lithium titanate metal oxide powder. The first method involved off-line analysis of filter samples collected with conventional respirable samplers at each of seven locations (six near production processes and one outdoors). Throughout most of the facility and outdoors, respirable mass concentrations were low (<0.050 mg/m(3)) and were attributed to particles other than the nanomaterial (<10% by mass titanium determined with inductively coupled plasma atomic emission spectrometry). In contrast, in a single area with extensive material handling, mass concentrations were greatest (0.118 mg m(-3)) and contained up to 39% +/- 11% lithium titanium, indicating the presence of airborne nanomaterial. Analysis of the filter samples collected in this area by transmission electron microscope and scanning electron microscope revealed that the airborne nanomaterial was associated only with spherical aggregates (clusters of fused 10-80 nm nanoparticles) that were larger than 200 nm. This analysis also showed that nanoparticles in this area were the smallest particles of a larger distribution of submicrometer chain agglomerates likely from welding in an adjacent area of the facility. The second method used two, hand-held, direct-reading, battery-operated instruments to obtain a time series of very fine particle number (<300 nm), respirable mass, and total mass concentration, which were then related to activities within the area of extensive material handling. This activity-based monitoring showed that very fine particle number concentrations (<300 nm) had no apparent correlation to worker activities, but that sharp peaks in the respirable and total mass concentration coincided with loading a hopper and replacing nanomaterial collection bags. These findings were consistent with those from the filter-based method in that they demonstrate that airborne nanoparticles in this facility are dominated by "incidental" sources (e.g., welding or grinding), and that the airborne "engineered" product is predominately composed of particles larger than several hundred nanometers. The methods presented here are applicable to any occupational or environmental setting in which one needs to distinguish incidental sources from engineered product.

Total serum IgE levels are associated with ambient ozone concentration in asthmatic adults

BACKGROUND

Effects of air pollution exposure on IgE-mediated response in asthmatics are poorly investigated. The aim was to examine the relationship between air pollution concentrations and total IgE levels in adult asthmatics.

METHODS

The present study relates to the 369 asthmatic adults from the French Epidemiological study on Genetics and Environment of Asthma (EGEA), with availability of data on both total serum IgE measurements and air pollution concentrations. Geo-statistical models were performed on 4 x 4 km grids to assess individual outdoor air pollution exposure. Annual outdoor concentrations of ozone (O(3)), nitrogen dioxide (NO(2)), sulphur dioxide (SO(2)), and particulate matter smaller than 10 microm size (PM(10)), and concentrations of summer ozone were assigned to subject's home address.

RESULTS

The geometric mean of total IgE was 161 IU/ml and the average of O(3) exposure was 44.9 +/- 9.5 microg/m(3). Ozone concentrations were positively related to total IgE levels and an increase of 10 microg/m(3) of O(3) resulted in an increase of 20.4% (95% CI = 3.0-40.7) in total IgE levels. Adjustment for age, gender, smoking habits and previous life in the countryside did not change the results, and an increase of 19.1% (2.4-38.6) in total IgE was observed with O(3). Negative associations observed between NO(2) and total IgE levels disappeared after including O(3) in the models. Neither SO(2) nor PM(10) were correlated with total IgE levels.

CONCLUSIONS

Results suggest that O(3) or related ambient pollutants may up-regulate total IgE levels among asthmatic adults.

Asthma in Latin America: a public heath challenge and research opportunity

Asthma has emerged as an important public health problem in many Latin American countries over the past decade. In Brazil and Costa Rica, the prevalence of asthma and associated morbidity is as great or greater as reported in traditional high prevalence countries such as the US, but remains neglected as a public health priority. Asthma in Latin America is associated particularly with underprivileged populations living in cities but remains relatively rare in many rural populations. The causes of asthma in Latin America are likely to be associated with urbanization, migration, and the adoption of a modern 'Westernized' lifestyle and environmental changes that follow these processes that include changes in diet, physical activity, hygiene, and exposures to allergens, irritants, and outdoor and indoor pollutants. Because of the enormous social, genetic, and environmental contrasts within and between Latin American countries, and the large differences in prevalence associated with these differences, the investigation of asthma in Latin America provides important research opportunities to identify the social and biological mechanisms that underlie asthma development. Asthma in Latin America poses enormous challenges for health policy makers, health services, and researchers to respond to and alleviate the growing burden of asthma disability, particularly among marginalized urban populations.

Environment and health in the twenty-first century

There are major challenges facing the countries in the Pacific Basin. These include issues of hazardous waste management and the consequent adverse effects of hazardous wastes on human health, the potential disruption of our whole way of life as a consequence of global climate change, and the increasing problem on human health of air pollution and the effects of breathing polluted air. These issues and others were the focus of the 12th meeting of the Pacific Basin Consortium for Environment and Health Sciences, held in Beijing in late 2007. This volume is a collection of papers presented at that meeting, and this introductory chapter provides some perspective on three of the major issues that are of concern in all of the countries in this region. This meeting provided an opportunity for Chinese scientists and those from other countries in the Pacific Basin to share perspectives and possible solutions with others from the international community, and these various approaches are reflected in these proceedings.

Mitochondrial complex III-generated oxidants activate ASK1 and JNK to induce alveolar epithelial cell death following exposure to particulate matter air pollution

We have previously reported that airborne particulate matter air pollution (PM) activates the intrinsic apoptotic pathway in alveolar epithelial cells through a pathway that requires the mitochondrial generation of reactive oxygen species (ROS) and the activation of p53. We sought to examine the source of mitochondrial oxidant production and the molecular links between ROS generation and the activation of p53 in response to PM exposure. Using a mitochondrially targeted ratiometric sensor (Ro-GFP) in cells lacking mitochondrial DNA (rho0 cells) and cells stably expressing a small hairpin RNA directed against the Rieske iron-sulfur protein, we show that site III of the mitochondrial electron transport chain is primarily responsible for fine PM (PM2.5)-induced oxidant production. In alveolar epithelial cells, the overexpression of SOD1 prevented the PM2.5-induced ROS generation from the mitochondria and prevented cell death. Infection of mice with an adenovirus encoding SOD1 prevented the PM2.5-induced death of alveolar epithelial cells and the associated increase in alveolar-capillary permeability. Treatment with PM2.5 resulted in the ROS-mediated activation of the oxidant-sensitive kinase ASK1 and its downstream kinase JNK. Murine embryonic fibroblasts from ASK1 knock-out mice, alveolar epithelial cells transfected with dominant negative constructs against ASK1, and pharmacologic inhibition of JNK with SP600125 (25 microM) prevented the PM2.5-induced phosphorylation of p53 and cell death. We conclude that particulate matter air pollution induces the generation of ROS primarily from site III of the mitochondrial electron transport chain and that these ROS activate the intrinsic apoptotic pathway through ASK1, JNK, and p53.

On exposure and response relationships for health effects associated with exposure to vehicular traffic

This work examines various metrics and models that have been used to estimate long-term health effects of exposure to vehicular traffic. Such health impacts may include effects of air pollution due to emissions of combustion products and from vehicle or roadway wear, of noise, stress, or from socioeconomic effects associated with preferred residential locations. Both categorical and continuous exposure metrics are considered, typically for distances between residences and roadways, or for traffic density or intensity. It appears that continuous measures of exposure tend to yield lower risk estimates that are also more precise than categorical measures based on arbitrary criteria. The selection of appropriate exposure increments to characterize relative risks is also important in comparing pollutants and other agents. Confounding and surrogate variables are also important issues, since studies of traffic proximity or density cannot identify the specific agents related to traffic exposures that might be responsible for the various health endpoints that have been implicated. Studies based on ambient air quality measurements are necessarily restricted to species for which data are available, some of which may be serving as markers for the actual agents of harm. Studies based on modeled air quality are limited by the accuracy of mobile source emission inventories, which may not include poorly maintained (high emitting) vehicles. Additional exposure modeling errors may result from precision limitations of geocoding methods. Studies of the health effects of traffic are progressing from establishing the existence of relationships to describing them in more detail, but effective remedies or control strategies have generally not yet been proposed in the context of these epidemiological studies. Resolution of these dose-response uncertainties is important for the development of effective public health strategies for the future.

Traffic, outdoor air pollution, and asthma

The epidemiology of asthma and outdoor air pollution has shown that respiratory health effects can vary in relation to different emission sources, types of pollutants, underlying nutritional status, medication use, and genetic polymorphisms. Using sophisticated exposure assessment methods in conjunction with clinical tests and biomarkers that provide mechanistic information, the study of outdoor epidemiology and asthma has evolved into a complex multidisciplinary field. This article presents an overview of the mechanisms by which outdoor air pollution and traffic-related emissions lead to changes in respiratory health and lung function in subjects with asthma.

Association between traffic-related black carbon exposure and lung function among urban women

BACKGROUND

Although a number of studies have documented the relationship between lung function and traffic-related pollution among children, few have focused on adult lung function or examined community-based populations.

OBJECTIVE

We examined the relationship between black carbon (BC), a surrogate of traffic-related particles, and lung function among women in the Maternal-Infant Smoking Study of East Boston, an urban cohort in Boston, Massachusetts.

METHODS

We estimated local BC levels using a validated spatiotemporal land-use regression model, derived using ambient and indoor monitor data. We examined associations between percent predicted pulmonary function and predicted BC using linear regression, adjusting for sociodemographics (individual and neighborhood levels), smoking status, occupational exposure, type of cooking fuel, and a diagnosis of asthma or chronic bronchitis.

RESULTS

The sample of 272 women 18-42 years of age included 57% who self-identified as Hispanic versus 43% white, and 18% who were current smokers. Mean +/- SD predicted annual BC exposure level was 0.62 +/- 0.2 microg/m3. In adjusted analysis, BC (per interquartile range increase) was associated with a 1.1% decrease [95% confidence interval (CI), -2.5% to 0.3%] in forced expiratory volume in 1 sec, a 0.6% decrease (95% CI, -1.9% to 0.6%) in forced vital capacity, and a 3.0% decrease (95% CI, -5.8% to -0.2%) in forced mid-expiratory flow rate. We noted differential effects by smoking status in that former smokers were most affected by BC exposure, whereas current smokers were not affected.

CONCLUSION

In this cohort, exposure to traffic-related BC, a component of particulate matter, independently predicted decreased lung function in urban women, when adjusting for tobacco smoke, asthma diagnosis, and socioeconomic status.

Asthma and the elite athlete: summary of the International Olympic Committee's consensus conference, Lausanne, Switzerland, January 22-24, 2008

Respiratory symptoms cannot be relied on to make a diagnosis of asthma and/or airways hyperresponsiveness (AHR) in elite athletes. For this reason, the diagnosis should be confirmed with bronchial provocation tests. Asthma management in elite athletes should follow established treatment guidelines (eg, Global Initiative for Asthma) and should include education, an individually tailored treatment plan, minimization of aggravating environmental factors, and appropriate drug therapy that must meet the requirements of the World Anti-Doping Agency. Asthma control can usually be achieved with inhaled corticosteroids and inhaled beta(2)-agonists to minimize exercise-induced bronchoconstriction and to treat intermittent symptoms. The rapid development of tachyphylaxis to beta(2)-agonists after regular daily use poses a dilemma for athletes. Long-term intense endurance training, particularly in unfavorable environmental conditions, appears to be associated with an increased risk of developing asthma and AHR in elite athletes. Globally, the prevalence of asthma, exercise-induced bronchoconstriction, and AHR in Olympic athletes reflects the known prevalence of asthma symptoms in each country. The policy of requiring Olympic athletes to demonstrate the presence of asthma, exercise-induced bronchoconstriction, or AHR to be approved to inhale beta(2)-agonists will continue.

Comment on the Nanoparticle Conclusions in Crüts et al. (2008), "Exposure to diesel exhaust induces changes in EEG in human volunteers"

A recent publication in this journal reported interesting changes in electroencephalographic (EEG) waves that occurred in 10 young, male volunteers following inhalation for one hour of elevated levels of diesel-engine exhaust fumes 1. The authors then proposed a chain of causal events that they hypothesized underlay their observed EEG changes. Their reasoning linked the observed results to nanoparticles in diesel-engine exhaust (DEE), and went on to suggest that associations between changes in ambient particulate matter (PM) levels and changes in health statistics might be due to the effects of diesel-engine exhaust (DEE) nanoparticles on EEG. We suggest that the extrapolations of the Crüts et al. EEG findings to casual mechanisms about how ambient levels of DEE particulate might affect electrical signals in the brain, and subsequently to how DEE particulate might alter disease risk, are premature.

The role of oxidative stress in ambient particulate matter-induced lung diseases and its implications in the toxicity of engineered nanoparticles

Ambient particulate matter (PM) is an environmental factor that has been associated with increased respiratory morbidity and mortality. The major effect of ambient PM on the pulmonary system is the exacerbation of inflammation, especially in susceptible people. One of the mechanisms by which ambient PM exerts its proinflammatory effects is the generation of oxidative stress by its chemical compounds and metals. Cellular responses to PM-induced oxidative stress include activation of antioxidant defense, inflammation, and toxicity. The proinflammatory effect of PM in the lung is characterized by increased cytokine/chemokine production and adhesion molecule expression. Moreover, there is evidence that ambient PM can act as an adjuvant for allergic sensitization, which raises the possibility that long-term PM exposure may lead to increased prevalence of asthma. In addition to ambient PM, rapid expansion of nanotechnology has introduced the potential that engineered nanoparticles (NP) may also become airborne and may contribute to pulmonary diseases by novel mechanisms that could include oxidant injury. Currently, little is known about the potential adverse health effects of these particles. In this communication, the mechanisms by which particulate pollutants, including ambient PM and engineered NP, exert their adverse effects through the generation of oxidative stress and the impacts of oxidant injury in the respiratory tract will be reviewed. The importance of cellular antioxidant and detoxification pathways in protecting against particle-induced lung damage will also be discussed.