Use of a total traffic count metric to investigate the impact of roadways on asthma severity: a case-control study

The impact of outdoor pollution and extreme temperatures on asthma-related outcomes: A systematic review for the EAACI guidelines on environmental science for allergic diseases and asthma

Air pollution is one of the biggest environmental threats for asthma. Its impact is augmented by climate change. To inform the recommendations of the EAACI Guidelines on the environmental science for allergic diseases and asthma, a systematic review (SR) evaluated the impact on asthma-related outcomes of short-term exposure to outdoor air pollutants (PM2.5, PM10, NO2, SO2, O3, and CO), heavy traffic, outdoor pesticides, and extreme temperatures. Additionally, the SR evaluated the impact of the efficacy of interventions reducing outdoor pollutants. The risk of bias was assessed using ROBINS-E tools and the certainty of the evidence by using GRADE. Short-term exposure to PM2.5, PM10, and NO2 probably increases the risk of asthma-related hospital admissions (HA) and emergency department (ED) visits (moderate certainty evidence). Exposure to heavy traffic may increase HA and deteriorate asthma control (low certainty evidence). Interventions reducing outdoor pollutants may reduce asthma exacerbations (low to very low certainty evidence). Exposure to fumigants may increase the risk of new-onset asthma in agricultural workers, while exposure to 1,3-dichloropropene may increase the risk of asthma-related ED visits (low certainty evidence). Heatwaves and cold spells may increase the risk of asthma-related ED visits and HA and asthma mortality (low certainty evidence).

Associação da distância da habitação em relação a sítios de reciclagem sobre habilidades cognitivas em escolares

Objetivos: Verificar a associação da distância da habitação em relação a sítios de reciclagem sobre habilidades cognitivas em escolares.Métodos: Estudo transversal, no qual aplicou-se a escala Wechsler Abreviada de Inteligência em 100 escolares de 6 a 14 anos. As crianças foram divididas em um grupo de estudo (expostos), cujas residências estavam situadas a menos de 100 metros de sítios de reciclagem, em um bairro da cidade de Caxias do Sul. Houve um grupo controle, cujas residências estavam a mais de 150 metros de algum sítio de reciclagem, no mesmo bairro ou adjacências.Resultados: A habitação próxima a sítios de reciclagem aumentou a chance de apresentar quociente de inteligência baixo nos escolares na análise univariada (OR 2,19; IC95% 1,21–3,95). No quociente de inteligência total, o escore obtido foi de 84 no grupo exposto e 95 no grupo controle (p≤0,01). Quando ajustadas para outras variáveis potencialmente prejudiciais, a escolaridade materna elevada mostrou-se um fator atenuador do impacto da distância (OR 0,28; IC95% 0,11–0,72). A diferença encontrada entre os escores de quociente de inteligência verbal foi de 14 pontos (p<0,01); no quociente de inteligência de execução a diferença foi de 4 pontos (p=0,04).Conclusões: A distância entre a habitação e os sítios de reciclagem de resíduos pode reduzir habilidades cognitivas em escolares, mas esse efeito parece ser atenuado pela escolaridade materna. Essa associação reforça as preocupações sobre o impacto do manejo inadequado de resíduos urbanos, podendo vir a subsidiar a criação de políticas públicas que visem diminuir exposições ambientais potencialmente danosas.

Effect of Ambient Air Pollution on Hospital Readmissions among the Pediatric Asthma Patient Population in South Texas: A Case-Crossover Study

Few studies have evaluated the association between ambient air pollution and hospital readmissions among children with asthma, especially in low-income communities. This study examined the short-term effects of ambient air pollutants on hospital readmissions for pediatric asthma in South Texas. A time-stratified case-crossover study was conducted using the hospitalization data from a children’s hospital and the air pollution data, including particulate matter 2.5 (PM_2.5) and ozone concentrations, from the Centers for Disease Control and Prevention between 2010 and 2014. A conditional logistic regression analysis was performed to investigate the association between ambient air pollution and hospital readmissions, controlling for outdoor temperature. We identified 111 pediatric asthma patients readmitted to the hospital between 2010 and 2014. The single-pollutant models showed that PM_2.5 concentration had a significant positive effect on risk for hospital readmissions (OR = 1.082, 95% CI = 1.008–1.162, p = 0.030). In the two-pollutant models, the increased risk of pediatric readmissions for asthma was significantly associated with both elevated ozone (OR = 1.023, 95% CI = 1.001–1.045, p = 0.042) and PM_2.5 concentrations (OR = 1.080, 95% CI = 1.005–1.161, p = 0.036). The effects of ambient air pollutants on hospital readmissions varied by age and season. Our findings suggest that short-term (4 days) exposure to air pollutants might increase the risk of preventable hospital readmissions for pediatric asthma patients.

Association between exposure to urban waste and emotional and behavioral difficulties in schoolchildren

OBJECTIVE

To evaluate the association between living near waste recycling sites and emotional or behavioral difficulties in schoolchildren.

METHODOLOGY

A cross-sectional study with schoolchildren aged 6-13 years old from disadvantaged communities in a Brazilian city, divided between those who live less than 100m away from the central point of the recycling site and those that live more than 150m away from the site, as a control group and classified through georeferencing. The emotional and behavioral difficulties were investigated using the Strengths and Difficulties Questionnaire tool. Other variables were analyzed through logistic regression to determine their contribution to the outcomes.

RESULTS

Children living near waste recycling sites had a higher prevalence of emotional and behavioral problems than children living farther away. In the logistic regression model, no other covariates had a significant impact on the results, except for attending preschool. As expected, the families of the exposed group had lower income and lower levels of schooling, thus being characterized as a highly vulnerable population.

CONCLUSION

The association between living near waste recycling sites and lower test performance raises concerns about the impact of inappropriate waste management in urban centers on children's health.

Self-reported traffic-related air pollution and respiratory symptoms among adults in an area with modest levels of traffic

Health effects of traffic-related air pollution (TRAP) concentrations in densely populated areas are previously described. However, there is still a lack of knowledge of the health effects of moderate TRAP levels. The aim of the current study, a population-based survey including 16 099 adults (response rate 33%), was to assess the relationship between TRAP estimates and respiratory symptoms in an area with modest levels of traffic; Telemark County, Norway. Respondents reported respiratory symptoms the past 12 months and two TRAP exposure estimates: amount of traffic outside their bedroom window and time spent by foot daily along a moderate to heavy traffic road. Females reported on average more symptoms than males. Significant relationships between traffic outside their bedroom window and number of symptoms were only found among females, with the strongest associations among female occasional smokers (incidence rate ratio [IRR], 1.75, 95% confidence interval (CI) [1.16–2.62] for moderate or heavy traffic compared to no traffic). Significant relationship between time spent daily by foot along a moderate to heavy traffic road and number of symptoms was found among male daily smokers (IRR 1.09, 95% CI [1.04–1.15] per hour increase). Associations between traffic outside bedroom window and each respiratory symptom were found. Significant associations were primarily detected among females, both among smokers and non-smokers. Significant associations between time spent by foot daily along a moderate to heavy traffic road (per hour) and nocturnal dyspnoea (odds ratio (OR) 1.20, 95% CI [1.05–1.38]), nocturnal chest tightness (OR 1.13 [1.00–1.28]) and wheezing (OR 1.14 [1.02–1.29]) were found among daily smokers, primarily men. Overall, we found significant associations between self-reported TRAP exposures and respiratory symptoms. Differences between genders and smoking status were identified. The findings indicate an association between TRAP and respiratory symptoms even in populations exposed to modest levels of TRAP.

Hybrid Resiliency-Stressor Conceptual Framework for Informing Decision Support Tools and Addressing Environmental Injustice and Health Inequities

While structural factors may drive health inequities, certain health-promoting attributes of one's "place" known as salutogens may further moderate the cumulative impacts of exposures to socio-environmental stressors that behave as pathogens. Understanding the synergistic relationship between socio-environmental stressors and resilience factors is a critical component in reducing health inequities; however, the catalyst for this concept relies on community-engaged research approaches to ultimately strengthen resiliency and promote health. Furthermore, this concept has not been fully integrated into environmental justice and cumulative risk assessment screening tools designed to identify geospatial variability in environmental factors that may be associated with health inequities. As a result, we propose a hybrid resiliency-stressor conceptual framework to inform the development of environmental justice and cumulative risk assessment screening tools that can detect environmental inequities and opportunities for resilience in vulnerable populations. We explore the relationship between actual exposures to socio-environmental stressors, perceptions of stressors, and one's physiological and psychological stress response to environmental stimuli, which collectively may perpetuate health inequities by increasing allostatic load and initiating disease onset. This comprehensive framework expands the scope of existing screening tools to inform action-based solutions that rely on community-engaged research efforts to increase resiliency and promote positive health outcomes.

The Use of Geographic Data to Improve Asthma Care Delivery and Population Health

The authors examine uses of geographic data to improve asthma care delivery and population health and describe potential practice changes and areas for future research.

Child Poverty, Toxic Stress, and Social Determinants of Health: Screening and Care Coordination

Social determinants of health (SDOH) refer to the social, economic, and physical conditions in which people live that may affect their health. Poverty, which affects nearly 15 million children in the United States, has far-reaching effects on children's physical and mental health. Although it is difficult to change a family's economic circumstances, nurses can play a critical role to address SDOH through screening and effective coordination of care. As nurses, our role is to minimize the effects of SDOH, including poverty, on child health and well-being through our practice, research, and professional education. We present three exemplars of child poverty to demonstrate the impact on child health and well-being and propose a model of care for nurses to assess and address SDOH in the pediatric clinical setting.

Ambient air pollution and emergency department visits for asthma in Erie County, New York 2007-2012

PURPOSE

8% of the US population has asthma. Air pollution is linked to exacerbation in susceptible individuals. The objective was to identify air pollutants that increased the risk of asthma emergency department visits during a time wherein a polluting factory was criminally convicted, changing local air pollutant levels.

METHODS

An ecological time-series design used a daily count of asthma emergency visits from 2007 to 2012 as the dependent variable. Independent variables air pollutants (NO₂, PM_2.5 CO, and O₃), controlling for meteorological conditions, were analyzed using time-series and Poisson GLM models.

RESULTS

76,651 emergency asthma visits were included with an average of 35 visits per day (SD = 9.2, range 11-80) in a stationary time series. Increased visit volume in fall and spring had no associations to the air pollutants. Associations between individual air pollutants occurred in otherwise low-volume months for asthma emergency visits. The strongest relationship was an 11.6% increase in the asthma emergency visit rate during the month of June. In monthly groupings that removed most of the autumn and spring months, O₃, PM_2.5, CO, and NO₂ were associated with 5, 4, 2, and 2% increases in asthma emergency visits, respectively. CO was the only pollutant with a negative association with asthma emergency visits, occurring in the month of April.

CONCLUSIONS

Pollutants NO₂, PM_2.5 CO, and O₃ were associated with increased emergency asthma visits in some, but not all months of the year. Air pollution's impact on asthma emergencies may be masked by other, more influential seasonal triggers, such as infections or allergies.

Interpretation of epidemiologic studies very often lacked adequate consideration of confounding

BACKGROUND AND OBJECTIVE

Confounding bias is a most pervasive threat to validity of observational epidemiologic research. We assessed whether authors of observational epidemiologic studies consider confounding bias when interpreting the findings.

STUDY DESIGN AND SETTING

We randomly selected 120 cohort or case-control studies published in 2011 and 2012 by the general medical, epidemiologic, and specialty journals with the highest impact factors. We used Web of Science to assess citation metrics through January 2017.

RESULTS

Sixty-eight studies (56.7%, 95% confidence interval: 47.8-65.5%) mentioned "confounding" in the Abstract or Discussion sections, another 20 (16.7%; 10.0-23.3%) alluded to it, and there was no mention or allusion at all in 32 studies (26.7%; 18.8-34.6%). Authors often acknowledged that for specific confounders, there was no adjustment (34 studies; 28.3%) or deem it possible or likely that confounding affected their main findings (29 studies; 24.2%). However, only two studies (1.7%; 0-4.0%) specifically used the words "caution" or "cautious" for the interpretation because of confounding-related reasons and eventually only four studies (3.3%; 0.1-6.5%) had limitations related to confounding or any other bias in their Conclusions. Studies mentioning that the findings were possibly or likely affected by confounding were more frequently cited than studies with a statement that findings were unlikely affected (median 6.3 vs. 4.0 citations per year, P = 0.04).

CONCLUSIONS

Many observational studies lack satisfactory discussion of confounding bias. Even when confounding bias is mentioned, authors are typically confident that it is rather irrelevant to their findings and they rarely call for cautious interpretation. More careful acknowledgment of possible impact of confounding is not associated with lower citation impact.

Neighborhood-Level Factors Related to Asthma in Children Living in Urban Areas

Asthma disproportionately affects children who are non-White and of low socioeconomic status. One innovative approach to address these health disparities is to investigate the child's neighborhood environment and factors influencing asthma symptoms. The purpose of this integrative review is to critique research investigating the relationships between neighborhood-level factors and asthma morbidity in urban children. Three literature databases were searched using the terms "asthma," "child," "neighborhood," and "urban." The articles included were organized into six themes within the larger domains of prevalence, physical, and social factors. Literature tables provide in-depth analysis of each article and demonstrate a need for strengthening analysis methods. The current research points to the necessity for a multilevel study to analyze neighborhood-level factors that are associated with increased asthma morbidity in urban children. School nurse clinicians, working within children's neighborhoods, are uniquely positioned to assess modifiable neighborhood-level determinants of health in caring for children with asthma.

Lung function reductions associated with motor vehicle density in chronic obstructive pulmonary disease: a cross-sectional study

Background

Motor vehicle-related air pollution can potentially impair lung function. The effect of pollution in people with compromised pulmonary function such as in COPD has not been previously investigated. To examine the association of lung function with motor vehicle density in people with spirometrically determined COPD in a cross-sectional study.

Methods

In 2004–06, The North West Adelaide Health Study (NWAHS), a biomedical cohort of adults assessed pre and post-bronchodilator spirometry (n = 3,103). Traffic density, obtained from the motor vehicle inventory maintained by the South Australian Environment Protection Authority, was expressed as the daily numbers of vehicles travelling within a 200 m diameter zone around participants’ geocoded residences.

Results

In subjects with COPD (FEV₁/FVC <0.7, n = 221, 7.1 %), increasing daily vehicle density was associated with statistically significant decreases in lung function parameters after adjustment for smoking and socio-economic variables. Mean (95 % CI) post-bronchodilator % predicted FEV₁ was 81 % (76–87) in the low (≤7179/day) compared with 71 % (67–75) in the high (≥15,270/day) vehicle exposure group (p < 0.05). Linear regression analysis in all subjects with COPD showed significant decrements in post-bronchodilator FEV₁/FVC ratio and % predicted FEV₁ of 0.03 and 0.05 % respectively per daily increase in 1000 vehicles. In men with COPD (n = 150), the corresponding reductions were 0.03 and 0.06 %. Smaller, non-significant decrements were seen in females. No difference was seen in those without COPD.

Conclusions

Vehicle traffic density was associated with significant reductions in lung function in people with COPD. Urban planning should consider the health impacts for those with pre-existing respiratory conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0451-3) contains supplementary material, which is available to authorized users.

REFINING OF ASTHMA PREVALENCE SPATIAL DISTRIBUTION AND VISUALIZATION OF OUTDOOR ENVIRONMENT FACTORS USING GIS AND ITS APPLICATION FOR IDENTIFICATION OF MUTUAL ASSOCIATIONS

AIM

This study presents a procedure of complex assessment of the environment impact on asthma prevalence. This approach is also applicable for any other disease which is supposed to be associated with the quality of the outdoor environment.

METHODS

The input data included asthma prevalence values from the National Institute of Public Health (NIPH) cross-section questionnaire survey (13,456 children) and annual reports on activities of all paediatricians in the Czech Republic (2,072 surgeries); concentrations of PM10, PM2.5, NO2, SO2, O3, benzene, benzo(a)pyrene, As, Cd, Pb and Ni; emissions of total suspended particles, SO2, NOx, CO, VOC, NH3; traffic intensity; land cover (anthropogenic area, urban greenery, arable land, grassland, other agricultural land, forests); proportion of cultivation of individual agricultural crops (17 categories); and proportion of individual woods (15 categories). Using the Geographical Information Systems (GIS) analysis the integration of all source data through one spatial unit was achieved and complete data sets were compiled to be subjected to statistical analysis (combination of factor analysis with logistic/linear regression).

RESULTS

In this study, the approach of combined use of GIS analyses and statistical evaluation of large input data sets was tested. The asthma prevalence demonstrated positive associations with the air pollution (PM10, PM2.5, benzene, benzo(a)pyren, SO2, Pb, Cd) and the rate of agricultural use of land (growing oats, rye, arable fodder crops). Conversely, there was a negative association with the occurrence of natural forests (ash, poplar, fir, beech, spruce, pine). No significant associations were observed with the distance from the road, traffic intensity and NO2 concentration.

CONCLUSIONS

These findings suggest that the outdoor quality may be one of the crucial factors for asthma prevalence.

The EUROMED CANCER network: state-of-art of cancer screening programmes in non-EU Mediterranean countries

BACKGROUND

The EUROMED CANCER Network project aims to support non-EU Mediterranean countries in the development of cancer early detection and screening policies.

METHODS

Through a structured questionnaire information from 15 countries (Albania, Algeria, Bosnia and Herzegovina (BiH), Croatia, Egypt, Jordan, UN Interim Administration Mission in Kosovo, Lebanon, Montenegro, Morocco, Palestinian National Authority, Serbia, Syria, Tunisia and Turkey) were collected on cancer epidemiology and control.

RESULTS

Large differences between countries are evident. Breast cancer (BC) is the commonest cancer among women, though the incidence rate is much lower in non-EU than in EU Mediterranean countries. Conversely, cervical cancer (CC) is much more common in the former than in the latter countries. Colorectal cancer (CRC) is more frequent in Northern than in Eastern and Southern Mediterranean shores. Population-based cancer registries are available in few countries but most of them lack information on disease staging. Opportunistic screening for CC and BC is unevenly spread across and within countries; organised screening programmes are rare and do not meet international recommendations. BC and CC early detection is extensively considered a priority, while a few countries included CRC into their agenda.

CONCLUSIONS

Collected data witnesses inadequacy of health information system and, in general, of the strategies for cancer control in the involved countries. A uniform approach for strengthening cancer control is not realistic neither feasible. Tailored preventive actions for cancer early detection have to be started concurrently with the development of a reliable health information system and, specifically, with cancer registration.

A comparison between self-reported and GIS-based proxies of residential exposure to environmental pollution in a case-control study on lung cancer

In epidemiological studies both questionnaire results and GIS modeling have been used to assess exposure to environmental risk factors. Nevertheless, few studies have used both these techniques to evaluate the degree of agreement between different exposure assessment methodologies. As part of a case-control study on lung cancer, we present a comparison between self-reported and GIS-derived proxies of residential exposure to environmental pollution. 649 subjects were asked to fill out a questionnaire and give information about residential history and perceived exposure. Using GIS, for each residence we evaluated land use patterns, proximity to major roads and exposure to industrial pollution. We then compared the GIS exposure-index values among groups created on the basis of questionnaire responses. Our results showed a relatively high agreement between the two methods. Although none of these methods is the "exposure gold standard", understanding similarities, weaknesses and strengths of each method is essential to strengthen epidemiological evidence.

Traffic-related air pollution and asthma hospital readmission in children: a longitudinal cohort study

OBJECTIVE

To examine the association between exposure to traffic-related air pollution (TRAP) and hospital readmission for asthma or bronchodilator-responsive wheezing.

STUDY DESIGN

A population-based cohort of 758 children aged 1-16 years admitted for asthma or bronchodilator-responsive wheezing was assessed for asthma readmission within 12 months. TRAP exposure was estimated with a land use regression model using the home address at index admission, with TRAP dichotomized at the sample median (0.37 μg/m3). Covariates included allergen-specific IgE, tobacco smoke exposure, and social factors obtained at enrollment. Associations between TRAP exposure and readmission were assessed using logistic regression and Cox proportional hazards models.

RESULTS

The study cohort was 58% African American and 32% white; 19% of the patients were readmitted within 12 months of the original admission. Higher TRAP exposure was associated with a higher readmission rate (21% vs. 16%; P = .05); this association was not significant after adjusting for covariates (aOR, 1.4; 95% CI, 0.9-2.2). Race modified the observed association; white children with high TRAP exposure had 3-fold higher odds of asthma readmission (OR, 3.0; 95% CI, 1.1-8.1), compared with white children with low TRAP exposure. In African American children, TRAP exposure was not associated with increased readmission (OR, 1.1; 95% CI, 0.6-1.8). In children with high TRAP exposure, TRAP exposure was associated with decreased time to readmission in white children (hazard ratio, 3.2; 95% CI, 1.5-6.7) compared with African American children (hazard ratio, 1.0; 95% CI, 0.7-1.4). African American children had a higher readmission rate overall.

CONCLUSION

TRAP exposure is associated with increased odds of hospital readmission in white children, but not in African American children.

Outdoor air pollution and asthma

Traffic and power generation are the main sources of urban air pollution. The idea that outdoor air pollution can cause exacerbations of pre-existing asthma is supported by an evidence base that has been accumulating for several decades, with several studies suggesting a contribution to new-onset asthma as well. In this Series paper, we discuss the effects of particulate matter (PM), gaseous pollutants (ozone, nitrogen dioxide, and sulphur dioxide), and mixed traffic-related air pollution. We focus on clinical studies, both epidemiological and experimental, published in the previous 5 years. From a mechanistic perspective, air pollutants probably cause oxidative injury to the airways, leading to inflammation, remodelling, and increased risk of sensitisation. Although several pollutants have been linked to new-onset asthma, the strength of the evidence is variable. We also discuss clinical implications, policy issues, and research gaps relevant to air pollution and asthma.

Annual average ambient particulate matter exposure estimates, measured home particulate matter, and hair nicotine are associated with respiratory outcomes in adults with asthma

BACKGROUND

While exposure to outdoor particulate matter (PM) has been associated with poor asthma outcomes, few studies have investigated the combined effects of outdoor and indoor PM (including secondhand tobacco smoke).

OBJECTIVE

To examine the associations between PM and asthma outcomes.

METHODS

We analyzed data from a cohort of adults with asthma and rhinitis (n=302; 82% both conditions; 13% asthma only; 5% rhinitis alone) including measures of home PM, tobacco smoke exposure (hair nicotine and self-report), ambient PM from regional monitoring, distance to roadway, and season (wet or dry). The outcomes of interest were frequent respiratory symptoms and forced expiratory volume in 1 second (FEV1) below the lower limit of normal (NHANES reference values). Multivariable regression analyses examined the associations (Odds Ratio [OR] and 95% Confidence Interval [95%CI]) between exposures and these outcomes, adjusted by sociodemographic characteristics.

RESULTS

In adjusted analyses of each exposure, the highest tertile of home PM and season of interview were associated with increased odds for more frequent respiratory symptoms (OR=1.64 95%CI: [1.00, 2.69] and OR=1.66 95%CI: [1.09, 2.51]). The highest tertile of hair nicotine was significantly associated with FEV1 below the lower limit of normal (OR=1.80 95%CI: [1.00, 3.25]). In a model including home PM, ambient PM, hair nicotine, and season, only two associations remained strong: hair nicotine with FEV1 below the lower limit of normal and season of measurement (dry, April-October) with increased respiratory symptoms (OR=1.85 95%CI: [1.00, 3.41] and OR=1.54 95%CI: [1.0, 2.37]). When that model was stratified by sex, the highest tertiles of ambient PM and hair nicotine were associated with FEV1 below the lower limit of normal among women (OR=2.23 95%CI: [1.08, 4.61] and OR=2.90 95%CI: [1.32, 6.38]), but not men. The highest tertile of hair nicotine was also associated with increased respiratory symptoms in women but not men (OR=2.38 95%CI: [1.26, 4.49]). When stratified by age, the middle quartile of ambient PM and the highest hair nicotine tertile were associated with increased respiratory symptoms (OR=2.07 95%CI: [1.01, 4.24] and OR=2.55 95%CI: [1.21, 5.36]) in those under 55 but not in the older stratum.

CONCLUSIONS

Exposure to PM from both home and ambient sources is associated with increased symptoms and lower lung function in adults with asthma, although these associations vary by type of PM, the respiratory outcome studied, sex and age.

Nitric oxide and superoxide mediate diesel particle effects in cytokine-treated mice and murine lung epithelial cells--implications for susceptibility to traffic-related air pollution

Background

Epidemiologic studies associate childhood exposure to traffic-related air pollution with increased respiratory infections and asthmatic and allergic symptoms. The strongest associations between traffic exposure and negative health impacts are observed in individuals with respiratory inflammation. We hypothesized that interactions between nitric oxide (NO), increased during lung inflammatory responses, and reactive oxygen species (ROS), increased as a consequence of traffic exposure ─ played a key role in the increased susceptibility of these at-risk populations to traffic emissions.

Methods

Diesel exhaust particles (DEP) were used as surrogates for traffic particles. Murine lung epithelial (LA-4) cells and BALB/c mice were treated with a cytokine mixture (cytomix: TNFα, IL-1β, and IFNγ) to induce a generic inflammatory state. Cells were exposed to saline or DEP (25 μg/cm²) and examined for differential effects on redox balance and cytotoxicity. Likewise, mice undergoing nose-only inhalation exposure to air or DEP (2 mg/m³ × 4 h/d × 2 d) were assessed for differential effects on lung inflammation, injury, antioxidant levels, and phagocyte ROS production.

Results

Cytomix treatment significantly increased LA-4 cell NO production though iNOS activation. Cytomix +  DEP-exposed cells incurred the greatest intracellular ROS production, with commensurate cytotoxicity, as these cells were unable to maintain redox balance. By contrast, saline + DEP-exposed cells were able to mount effective antioxidant responses. DEP effects were mediated by: (1) increased ROS including superoxide anion (O₂˙^-), related to increased xanthine dehydrogenase expression and reduced cytosolic superoxide dismutase activity; and (2) increased peroxynitrite generation related to interaction of O₂˙^- with cytokine-induced NO. Effects were partially reduced by superoxide dismutase (SOD) supplementation or by blocking iNOS induction. In mice, cytomix +  DEP-exposure resulted in greater ROS production in lung phagocytes. Phagocyte and epithelial effects were, by and large, prevented by treatment with FeTMPyP, which accelerates peroxynitrite catalysis.

Conclusions

During inflammation, due to interactions of NO and O₂˙^-, DEP-exposure was associated with nitrosative stress in surface epithelial cells and resident lung phagocytes. As these cell types work in concert to provide protection against inhaled pathogens and allergens, dysfunction would predispose to development of respiratory infection and allergy. Results provide a mechanism by which individuals with pre-existing respiratory inflammation are at increased risk for exposure to traffic-dominated urban air pollution.