Brief exposures to NO2 augment the allergic inflammation in asthmatics

Spatiotemporal analysis of airborne pollutants and health risks in Mashhad metropolis: enhanced insights through sensitivity analysis and machine learning

The study delved into an extensive assessment of outdoor air pollutant levels, focusing specifically on PM2.5, SO2, NO2, and CO, across the Mashhad metropolis from 2017 to 2021. In tandem, it explored their intricate correlations with meteorological conditions and the consequent health risks posed. Employing EPA health risk assessment methods, the research delved into the implications of pollutant exposure on human health. Results unveiled average annual concentrations of PM2.5, SO2, NO2, and CO, standing at 27.22 µg/m3, 72.48 µg/m3, 26.8 µg/m3, and 2.06 mg/m3, respectively. Intriguingly, PM2.5 displayed positive correlations with temperature and wind speed, while exhibiting negative associations with relative humidity and precipitation. Conversely, both SO2 and NO2 concentrations showcased negative correlations with temperature, relative humidity, wind speed, and precipitation. Furthermore, CO demonstrated negative relationships with both wind speed and precipitation. The analysis of mean hazard quotients (HQ) for PM2.5 and NO2 indicated values exceeding 1 under 8- and 12-h exposure scenarios, pointing towards concerning health risks. Spatial distribution revealed elevated CO levels in the northwest, north, and east areas, while NO2 concentrations were predominant in the north and south regions. Through Sobol sensitivity analysis, PM2.5, EF, and NO2 emerged as pivotal influencers, offering valuable insights for refining environmental models and formulating effective pollution mitigation strategies. Air pollution index (AQI) forecasting was modeled using advanced machine learning comprising Random Forest (RF), Decision Tree (DT), K-Nearest Neighbors (KKN), and Naive Bayesian (NB). Results showed that the RF model with the highest accuracy (R2 = 0.99) was the best prediction model.

Spatiotemporal variability and health risk assessment of PM2.5 and NO2 over the Indo-Gangetic Plain: A three years long study (2019-21)

Studying the spatiotemporal variability of pollutants is necessary to identify the pollution hotspots with high health risk and enable the agencies to implement pollution abatement strategies in a targeted manner. Present study reports the spatio-temporal variability and health risk assessment (HRA) of PM2.5 (Particulate matter with aerodynamic diameter <2.5μm) and NO2 over IGP from 2019-2021. The HRA is expressed as passively smoked cigarettes (PSC) for four different health outcomes i.e., low birth weight (LBW), percentage decreased lung function (DLF) in school aged children, lung cancer (LC), and cardiovascular mortality (CM). The findings confirm very high PM2.5 and NO2 mass concentrations and high health risk over middle IGP and Delhi as compared to upper and lower IGP. Within Delhi, north Delhi region is the most polluted and at highest risk as compared to central and south Delhi. The health risk associated with PM2.5 over IGP is highest for DLF, equivalent to 21.63 PSCs daily, followed by CM (11.69), LBW (8.27) and LC (6.94). For NO2, the health risk is highest for DLF (3.09 PSCs) and CM (2.95), followed by LC (1.47) and LBW (1.04). PM2.5 and NO2 concentrations, along with the associated health risks, are highest during the post-monsoon and winter seasons and lowest during the monsoon season.

Lung Effects of Household Air Pollution

Biomass fuel smoke, secondhand smoke, and oxides of nitrogen are common causes of household air pollution (HAP). Almost 2.4 billion people worldwide use solid fuels for cooking and heating, mostly in low- and middle-income countries. Wood combustion for household heating is also common in many areas of high-income countries, and minorities are particularly vulnerable. HAP in low- and middle-income countries is associated with asthma, acute respiratory tract infections in adults and children, chronic obstructive pulmonary disease, lung cancer, tuberculosis, and respiratory mortality. Although wood smoke exposure levels in high-income countries are typically lower than in lower-income countries, it is similarly associated with accelerated lung function decline, higher prevalence of airflow obstruction and chronic bronchitis, and higher all-cause and respiratory cause-specific mortality. Household air cleaners with high-efficiency particle filters have mixed effects on asthma and chronic obstructive pulmonary disease outcomes. Biomass fuel interventions in low-income countries include adding chimneys to cookstoves, improving biomass fuel combustion stoves, and switching fuel to liquid petroleum gas. Still, the impact on health outcomes is inconsistent. In high-income countries, strategies for reducing biomass fuel-related HAP are centered on community-level woodstove changeout programs, although the results are again inconsistent. In addition, initiatives to encourage home smoking bans have mixed success in households with children. Environmental solutions to reduce HAP have varying success in reducing pollutants and health problems. Improved understanding of indoor air quality factors and actions that prevent degradation or improve polluted indoor air may lead to enhanced environmental health policies, but health outcomes must be rigorously examined.

Synergistic or Antagonistic Health Effects of Long- and Short-Term Exposure to Ambient NO2 and PM2.5: A Review

Studies on adverse health effects associated with air pollution mostly focus on individual pollutants. However, the air is a complex medium, and thus epidemiological studies face many challenges and limitations in the multipollutant approach. NO2 and PM2.5 have been selected as both originating from combustion processes and are considered to be the main pollutants associated with traffic; moreover, both elicit oxidative stress responses. An answer to the question of whether synergistic or antagonistic health effects of combined pollutants are demonstrated by pollutants monitored in ambient air is not explicit. Among the analyzed studies, only a few revealed statistical significance. Exposure to a single pollutant (PM2.5 or NO2) was mostly associated with a small increase in non-accidental mortality (HR:1.01-1.03). PM2.5 increase of <10 µg/m3 adjusted for NO2 as well as NO2 adjusted for PM2.5 resulted in a slightly lower health risk than a single pollutant. In the case of cardiovascular heart disease, mortality evoked by exposure to PM2.5 or NO2 adjusted for NO2 and PM2.5, respectively, revealed an antagonistic effect on health risk compared to the single pollutant. Both short- and long-term exposure to PM2.5 or NO2 adjusted for NO2 and PM2.5, respectively, revealed a synergistic effect appearing as higher mortality from respiratory diseases.

Detailed Investigation of the Contribution of Gas-Phase Air Contaminants to Exposure Risk during Indoor Activities

Analytical capabilities in atmospheric chemistry provide new opportunities to investigate indoor air. HOMEChem was a chemically comprehensive indoor field campaign designed to investigate how common activities, such as cooking and cleaning, impacted indoor air in a test home. We combined gas-phase chemical data of all compounds, excluding those with concentrations <1 ppt, with established databases of health effect thresholds to evaluate potential risks associated with gas-phase air contaminants and indoor activities. The chemical composition of indoor air is distinct from outdoor air, with gaseous compounds present at higher levels and greater diversity─and thus greater predicted hazard quotients─indoors than outdoors. Common household activities like cooking and cleaning induce rapid changes in indoor air composition, raising levels of multiple compounds with high risk quotients. The HOMEChem data highlight how strongly human activities influence the air we breathe in the built environment, increasing the health risk associated with exposure to air contaminants.

Influence of Selected Air Pollutants on Mortality and Pneumonia Burden in Three Polish Cities over the Years 2011-2018

Poland has one of the worst air qualities in the European Union, particularly regarding concentrations of particulate matter (PM). This study aimed to evaluate the short-term effects of air pollution and weather conditions on all-cause mortality and pneumonia-related hospitalizations in three Polish agglomerations. We investigated data from 2011 to 2018 on a number of health outcomes, concentrations of PM2.5, PM10, nitrogen dioxide (NO2), ozone (O3), and selected meteorological parameters. To examine the impact of air pollutants and weather conditions on mortality and pneumonia burden, we identified optimal general regression models for each agglomeration. The final models explained <24% of the variability in all-cause mortality. In the models with interactions, O3 concentration in Warsaw, NO2, O3, and PM2.5 concentrations in Cracow and PM10 and O3 concentrations in the Tricity explained >10% of the variability in the number of deaths. Up to 46% of daily variability in the number of pneumonia-related hospitalizations was explained by the combination of both factors, i.e., air quality and meteorological parameters. The impact of NO2 levels on pneumonia burden was pronounced in all agglomerations. We showed that the air pollution profile and its interactions with weather conditions exert a short-term effect on all-cause mortality and pneumonia-related hospitalizations. Our findings may be relevant for prioritizing strategies to improve air quality.

Personal NO2 sensor demonstrates feasibility of in-home exposure measurements for pediatric asthma research and management

BACKGROUND

One of the most common pollutants in residences due to gas appliances, NO₂ has been shown to increase the risk of asthma attacks after small increases in short term exposure. However, standard environmental sampling methods taken at the regional level overlook chronic intermittent exposure due to lack of temporal and spatial granularity. Further, the EPA and WHO do not currently provide exposure recommendations to at-risk populations.

AIMS

A pilot study with pediatric asthma patients was conducted to investigate potential deployment challenges as well as benefits of home-based NO₂ sensors and, when combined with a subject's hospital records and self-reported symptoms, the richness of data available for larger-scale epidemiological studies.

METHODS

We developed a compact personal NO₂ sensor with one minute temporal resolution and sensitivity down to 15 ppb to monitor exposure levels in the home. Patient hospital records were collected along with self-reported symptom diaries, and two example hypotheses were created to further demonstrate how data of this detail may enable study of the impact of NO₂ in this sensitive population.

RESULTS

17 patients (55%) had at least 1 h each day with average NO₂ exposure >21 ppb. Frequency of acute NO₂ exposure >21 ppb was higher in the group with gas stoves (U = 27, p ≤ 0.001), and showed a positive correlation (r_s = 0.662, p = 0.037, 95% CI 0.36-0.84) with hospital admissions.

SIGNIFICANCE

Similar studies are needed to evaluate the true impact of NO₂ in the home environment on at-risk populations, and to provide further data to regulatory bodies when developing updated recommendations.

Variation and correlation between ultraviolet index and tropospheric ozone during COVID-19 lockdown over megacities of India

Worldwide spread out of COVID-19 in a short-time has brought a significant decline of road traffic, tourist flow and industrial ventures. During this emergency period, the restricted human dealings with nature have appeared as blessing for health of the total environment. The variation of atmospheric O₃ may modulate the range of UV index (UVI) at any region of the earth. The objective of the study is to examine the variation of UV index over the megacities of India with respect to tropospheric O₃ level modification during COVID-19 lockdown. The meteorological or environmental data (temperature in °C, gust in km/h, wind speed km/h, relative humidity in %, air pressure in mb and cloud cover in okta) of four selective megacities of India (Kolkata, Chennai, Delhi, Mumbai) during and pre lockdown period have been obtained to comprehend about the variation of UV index and tropospheric O₃. The descriptive statistical applications i.e. standard deviation, standard errors and K-means clustering have been done through standard statistical software. In the present study, t-test has been used to understand level of significance of surface O₃ and UVI during pre-lockdown (2019) and lockdown (2020) phase. The result shows that the four major megacities in India namely New Delhi, Mumbai, Kolkata and Chennai have experienced the vibrant diminution in terms of the concentration of UV index with slightly increasing the tropospheric O₃ level during the lockdown phase. The higher accumulation of O₃ during the lockdown in the lower atmosphere of four megacities does not exceed the permissible limit. The excess amount of O₃ has remarkably contributed to trap the harmful UV radiation which has lowered the UVI in these worst polluted megacities of India. In the meantime, the prominent reduction of NO_x during the lockdown period decreases the titration impact to O₃ and this mechanism helps to revitalize the ozone concentration level. The uniqueness of the current study is highlighted the ground reality regarding reduction of UV index and amplification of tropospheric O₃ concentration during lockdown phase. This study definitely assists to make new environmental policy, act and law for recover the health of the total environment.

Impact of air pollution on symptom severity during the birch, grass and ragweed pollen period in Vienna, Austria: Importance of O3 in 2010-2018

Air pollution is a threat to the general population, especially to pollen allergy sufferers in urban environments. Different air quality parameters have hitherto been examined which add to the burden of pollen allergy sufferers. Parameters such as NO₂, SO₂, PM₁₀, PM_2.5, and O₃ are supposed to have additional impact, not only on health in general (increase in asthma, allergy sensitization frequency), but also on pollen grains (increase of allergenicity). However, it remains unknown if those air quality parameters increase symptom severity during the pollen season. We selected the birch, grass, and ragweed pollen seasons as different time periods throughout the year and analyzed the relationship of symptom data to pollen, air quality, and meteorological data (temperature, relative humidity) for the metropolis of Vienna (Austria). A linear regression model was computed based on different symptom data, and both pollen and air quality data were tested simultaneously. Ozone was positively and significantly associated with symptom scores in all three seasons, whereas this was only rarely the case with other pollutants. Therefore, only ozone was selected for further analysis in a model including meteorological parameters. In this model, effect estimates of ozone were attenuated but remained significant for the grass pollen season. The lack of significance in the other seasons may be attributed to the less numerous symptom data entries and the shorter duration of the pollen seasons for birch and ragweed. All other air quality parameters usually showed lower concentrations during the pollen seasons and displayed little variation. This might explain the lack of a clear signal. Our results suggest that today's allergic population is already affected by air quality (rising O₃ levels). Air quality should be considered as well in pollen information and pollen allergy studies in general because of its increasing importance in the light of global warming.

Residential Links to Air Pollution and School Children with Asthma in Vilnius (Population Study)

Background and objectives: Many studies have been carried out on the negative health effects of exposure to PM₁₀, PM _2.5, NO₂, CO, SO₂ and B[a]P for small populations. The main purpose of this study was to explore the association of air pollution to diagnosis of asthma for the whole huge population of school children between 7–17 years in Vilnius (Lithuania) using geographical information system analysis tools. Material and Methods: In the research, a child population of 51,235 individuals was involved. From this large database, we identified children who had asthma diagnosis J45 (ICD-10 AM). Residential pollution concentrations and proximity to roads and green spaces were obtained using the ArcGIS spatial analysis tool from simulated air pollution maps. Multiple stepwise logistic regression was used to explore the relation between air pollution concentration and proximity between the roads and green spaces where children with asthma were living. Further, we explored the interaction between variables. Results: From 51,235 school children aged 7–17 years, 3065 children had asthma in 2017. We investigated significant associations, such as the likelihood of getting sick with age (odds ratio (OR) = 0.949, p < 0.001), gender (OR = 1.357, p = 0.003), NO₂ (OR = 1.013, p = 0.019), distance from the green spaces (OR = 1.327, p = 0.013) and interactions of age × gender (OR = 1.024, p = 0.051). The influence of gender on disease is partly explained by different age dependency slopes for boys and girls. Conclusions: According to our results, younger children are more likely to get sick, more cases appended on the lowest age group from 7 to 10 years (almost half cases (49.2%)) and asthma was respectively nearly twice more common in boys (64.1%) than in girls (35.9%). The risk of asthma is related to a higher concentration of NO₂ and residence proximity to green spaces.

Short-term effects of air pollution on respiratory mortality in Ahvaz, Iran

Background: Urban air pollutants may affect respiratory mortality. This study was conducted to investigate this effect in Ahvaz, one of the most polluted cities in the world. Methods: The impact of 7 major air pollutants including O3, PM10, NO2, CO, and SO2 were evaluated on respiratory mortality in different gender and age groups using a quasi-Poisson, second degree polynomial constrained, distributed lag model, with single and cumulative lag structures adjusted by trend, seasonality, temperature, relative humidity, weekdays, and holiday. Data were analyzed using the dlnm package in R x64 3.2.5 software. Significance level was set at less than 0.05. Results: In adjusted models, for each IQR increase of O3 in the total population, the risk ratio (RR) for respiratory deaths in 0 to 14- day lags was, respectively, 1.009 (95% CI:1.001-1.016) and 1.009 (95% CI:1.002-1.017), and it was 1.021 (95% CI: 1.002-1.040) in cumulative 0 to 14- day lags. For PM10, in the total population and in adjusted models after 0 to 14- day lags and in cumulative lags of 0 to 14 for an IQR increase in the mean concentration of PM10, the RR for respiratory deaths increased significantly and was, respectively, 1.027 (95% CI:1.002-1.051), 1.029 (95% CI:1.006-1.052), and 1.065 (95% CI:1.005-1.128). NO2 showed a significant association with respiratory deaths only in the 18 to 60 year- old age group and in 9- day lags (RR= 1.318, 95% CI:1.002-1.733). Finally, the results showed that for an IQR increase in the mean concentration of CO and SO2, the adjusted RR for respiratory deaths in 9- day lags in the total population was, respectively, RR= 1.058 (95% CI:1.008-1.111) and 1.126 (95% CI:1.034-1.220). Conclusion: Air pollution in Ahvaz is probably causing increased respiratory mortality.

NO2 inhalation enhances asthma susceptibility in a rat model

Nitrogen dioxide (NO₂) is a major air pollutant. Epidemiologic studies have found that NO₂ exposure is associated with an increased risk of asthma. Nevertheless, the potential molecular mechanisms remain unclear. In this study, we investigated the effect of NO₂ inhalation on the occurrence of allergic airway inflammation and its underlying mechanisms. Firstly, male Wistar rats were exposed to 2 and 5 mg/m³ NO₂ (28 days, 5 h/day). The results showed that NO₂ exposure could induce pulmonary inflammatory response, mucus formation, and Th1/Th2 imbalance in the lung of normal rats, resulting in allergic asthma-like features. Secondly, male Wistar rats were exposed to 5 mg/m³ NO₂ (42 days, 5 h/day), sensitized with ovalbumin (OVA), challenged with aerosolized OVA, and characterized in asthma models. Results showed that NO₂ exposure aggravated lung inflammation in the OVA-sensitized rats, accompanied by the increase in inflammatory cell infiltration, mucus hypersecretion, and collagen deposition. Furthermore, NO₂ exposure promoted the increase in the expression of mucin gene (MUC5AC) and pro-inflammatory factors [interleukin (IL)-1β, intercellular adhesion molecule-1 (ICAM-1), and IL-6] as well as serum OVA-specific immunoglobulin E (IgE) production. Taken together, we established that NO₂ exposure promotes allergic airway inflammation and increases the asthma susceptibility. The underlying mechanisms involve the promotion of activation of interleukin-4/signal transducer and activator of transcription-6 (IL-4/STAT6) pathway [IL-4 receptor (IL-4R) α, janus kinase (JAK) 1, JAK 3, and STAT6] and related transcription factor [T cell-specific protein-tyrosine kinase (Lck), extracellular-regulated kinase (ERK)1/2, and nuclear factor-κB (NF-κB)]. In particular, the imbalance of Th1/Th2 cell differentiation [IL-4, interferon (IFN)-γ, GATA-binding protein-3 (GATA-3), and T-box expressed in T cells (T-bet)] plays a pivotal role in NO₂-induced inflammatory responses. These findings may provide a better understanding of mechanism of NO₂-associated respiratory diseases.

Rainfall-Associated Bronchospasm Epidemics: The Epidemiological Effects of Air Pollutants and Weather Variables

BACKGROUND

This study compares different risk factors in patients visiting a hospital during five rainfall-associated bronchospasm epidemics in Ahvaz and those visiting on other occasions.

METHODS

This case-control study was conducted on 5307 patients with bronchospasm admitted to the Emergency Department of Imam Khomeini Hospital in Ahvaz (Iran) from late October to December (as the epidemic) and 916 patients admitted from late January to March (as the nonepidemic) in 2011 to 2015.

RESULTS

A total of the 41.7% of the cases and 48.8% of the controls had episodes of bronchospasm, suggesting a significant difference between the two groups (P < 0.001). The mean concentrations of PM10, NO, NO2, and NO x pollutants (except O3) were significantly higher in the nonepidemic periods (P < 0.05). The adjusted analysis showed a direct significant relationship between emergency respiratory admissions and each unit of increase in NO and SO2 concentration during the epidemic periods and NO2 concentration during the nonepidemic periods. During the epidemic periods, a direct and significant relationship was also observed between respiratory admissions and each unit of increase in relative humidity and evaporation.

CONCLUSION

The results suggest that certain pollutants and weather variables are associated with the risk of emergency respiratory admissions during epidemic periods.

Do individuals with asthma experience airway hyper-responsiveness after exposure to nitrogen dioxide?

The current 100 ppb short-term National Ambient Air Quality Standard for NO₂, and EPA's determination of a causal association for respiratory effects, are based in part on controlled human exposure studies evaluating airway hyper-responsiveness (AHR). A meta-analysis by Goodman et al. (2009) found increased AHR at 100 ppb NO₂ but no clear concentration-response relationship up to 600 ppb, and an overall lack of an AHR effect for studies involving exercise or exposure to allergens. Several factors have been suggested to explain why effects on AHR are observed while people are at rest, but not during exercise or after exposure to allergens. These include an exercise-induced refractory period; partial reversal of bronchospasm from use of forced expiration maneuvers; and greater airway responsiveness of participants exposed to NO₂ at rest. We reviewed the scientific evidence to determine whether there is biological support for these factors and found that none sufficiently explained the lack of an effect during exercise or after exposure to allergens. In the absence of either a consistent concentration-response or a plausible explanation for the paradoxical AHR findings, the biological significance of these findings is uncertain and provides equivocal support for NO₂ as a causal factor of AHR at these exposure levels.

Meteorological parameters and pollutants on asthma exacerbation in Bangalore, India - an ecological retrospective time-series study

BACKGROUND

Literature has shown a significant association between asthma exacerbations and pollutant levels during that time. There is very limited evidence in India, especially Bangalore, for impacts of meteorological changes and pollution on asthma hospital admissions in adults. The objective was to study the impact of air pollution and meteorological parameters on asthma exacerbation in Bangalore.

METHODS

This study quantitatively analyzed the relation between acute exacerbations of asthma and related admissions to the hospital with the air pollution and the meteorological conditions during that time. Data regarding the daily hospital admissions in about 13 tertiary care centers in Bangalore, Karnataka and air pollutant levels and the meteorological conditions prevailing during each day over a year were collected from the Karnataka State pollution control board and meteorology departments, respectively.

RESULTS

An average daily asthma admission of 4.84±2.91, with clear seasonal variation and autocorrelations between meteorological parameters and pollutants was observed. Multiple linear regression analysis revealed that average temperature (p=0.005) and nitrogen dioxide (NO2) (p=0.034) were the two factors that were affecting the number of admissions. Quasi-poisson regression analysis using multi-pollutants and meteorological variables showed that particulate matter and NO2 had significant lag effect for up to 5 days (p<0.05) and rainfall for 1 day (p<0.001).

CONCLUSIONS

In Bangalore city, levels of NO2 and particulate matter, temperature, rainfall, and season increase asthma exacerbations.

Relación de los mecanismos inmunológicos del asma y la contaminación ambiental

Introducción. Se calcula que más de 300 millones de personas alrededor del mundo padecen asma y se estima que para el año 2025 esta cifra se incremente a 400 millones debido a los contaminantes criterio. Sin embargo, dadas sus limitaciones, los estudios epidemiológicos son controversiales sobre la contaminación y el desarrollo de asma.Objetivos. Describir las diferencias y similitudes de la respuesta inmunológica de pacientes asmáticos y los modelos animales de asma alérgica después de la exposición a contaminantes criterio y elementos biológicos, para así identificar los factores inmunológicos relacionados con el desarrollo de asma.Materiales y método. Se realizó una búsqueda sistemática en las bases de datos sobre asma y los diferentes contaminantes criterio.Resultados. La respuesta Th2 es activada por la inhalación de ozono, dióxido de nitrógeno, azufre y la exposición aguda a material particulado, mientras que el contacto con ciertos tipos de pólenes y glucanos y la exposición crónica de partículas incrementa la respuesta Th1, la cual inhibe a la respuesta Th2 produciendo un “efecto protector”.Conclusiones. La respuesta Th1 podría causar baja o nula asociación entre la exposición a contaminación y el desarrollo de asma en las diferentes ciudades, adicionando de esta manera otra limitación a los estudios epidemiológicos.

Biological effects of inhaled nitrogen dioxide in healthy human subjects

PURPOSE

Several epidemiological studies indicate that inhaled nitrogen dioxide (NO2) at low concentrations have been statistically associated with adverse health effects. However, these results are not reflected by exposure studies in humans. The aim of the study was to assess the acute functional and cellular responses to different NO2 concentrations in healthy human subjects with various techniques.

METHODS

Twenty-five subjects were exposed for 3 h to NO2 concentrations 0, 0.1, 0.5, and 1.5 ppm in a randomized crossover study design during 4 consecutive weeks. In each subject, lung function, diffusion capacity and exhaled nitric oxide were measured and inflammation markers were assessed in blood, nasal secretions, induced sputum and exhaled breath condensate.

RESULTS

From all lung function indices under consideration, only intrathoracic gas volume was borderline significantly increased after 0.5 ppm (p = 0.048) compared to 0.1 ppm NO2. Regarding the cellular effect parameters, the macrophage concentration in induced sputum decreased with increasing NO2 concentration, although these changes were only borderline significant (p = 0.05).

CONCLUSION

These results do not suggest a considerable acute adverse response in human subjects after 3 h of exposure to NO2 in the NO2 concentration range investigated in this study.

Link between environmental air pollution and allergic asthma: East meets West

With the levels of outdoor air pollution from industrial and motor vehicle emissions rising rapidly in the fastly-industrializing countries of South East Asia, the prevalence of asthma and allergic diseases has also been increasing to match those in the West. Epidemiological and experimental exposure studies indicate a harmful impact of outdoor air pollution from vehicles and factories both on the development of allergic diseases and asthma and the increase in asthma symptoms and exacerbations. The level of outdoor pollution in Asia is much higher and more diverse than those encountered in Western countries. This may increase the impact of outdoor pollution on health, particularly lung health in Asia. This review discusses the constituents of air pollution in Asia with a special focus on studies in mainland China and Taiwan where the levels of pollution have reached high levels and where such high levels particularly in winter can cause a thick haze that reduces visibility. The onus remains on regulatory and public health authorities to curb the sources of pollution so that the health effects on the population particularly those with lung and cardiovascular diseases and with increased susceptibility can be mitigated.

Oxidized dietary oils enhance immediate- and/or delayed-type allergic reactions in BALB/c mice

BACKGROUND

The consumption of cooking oils may exacerbate some allergic diseases. In the present study, the effects of naturally oxidized olive oil on immediate- and/or delayed-type allergic reactions were investigated in BALB/c mice.

METHODS

Mouse models of 3 types of allergic reactions: contact hypersensitivity (CHS), active cutaneous anaphylaxis (ACA), and DNFB-induced hypersensitivity, were orally administered naturally oxidized olive oil that was obtained by keeping the oil at room temperature for more than 3 years. The effects of ultraviolet ray (UV)-irradiated olive oil and other dietary oils as well as their possible oxidation products on CHS were also investigated.

RESULTS

Naturally oxidized olive oil had a high peroxide value (POV) and exacerbated CHS, ACA, and DNFB-induced hypersensitivity in a POV-dependent manner. UV-irradiated olive oil, corn oil, sesame oil and triolein had high POVs, but almost the same acid value (AV) and thiobarbituric acid-reactive substance (TBARS) level as fresh oils. Fresh olive oil and the representative oxidation product with a high AV or TBARS level had no effect on CHS, whereas all UV-irradiated oils and naturally oxidized olive oil exacerbated it.

CONCLUSIONS

Oxidized dietary oils that have high POVs exacerbated immediate- and/or delayed-type allergic reactions regardless of the different oil constituents or oxidation processes.

Repeated nitrogen dioxide exposures and eosinophilic airway inflammation in asthmatics: a randomized crossover study

BACKGROUND

Nitrogen dioxide (NO2), a ubiquitous atmospheric pollutant, may enhance the asthmatic response to allergens through eosinophilic activation in the airways. However, the effect of NO2 on inflammation without allergen exposure is poorly studied.

OBJECTIVES

We investigated whether repeated peaks of NO2, at various realistic concentrations, induce changes in airway inflammation in asthmatics.

METHODS

Nineteen nonsmokers with asthma were exposed at rest in a double-blind, crossover study, in randomized order, to 200 ppb NO2, 600 ppb NO2, or clean air once for 30 min on day 1 and twice for 30 min on day 2. The three series of exposures were separated by 2 weeks. The inflammatory response in sputum was measured 6 hr (day 1), 32 hr (day 2), and 48 hr (day 3) after the first exposure, and compared with baseline values measured twice 10-30 days before the first exposure.

RESULTS

Compared with baseline measurements, the percentage of eosinophils in sputum increased by 57% after exposure to 600 ppb NO2 (p = 0.003) but did not change significantly after exposure to 200 ppb. The slope of the association between the percentage of eosinophils and NO2 exposure level was significant (p = 0.04). Eosinophil cationic protein in sputum was highly correlated with eosinophil count and increased significantly after exposure to 600 ppb NO2 (p = 0.001). Lung function, which was assessed daily, was not affected by NO2 exposure.

CONCLUSIONS

We observed that repeated peak exposures of NO2 performed without allergen exposure were associated with airway eosinophilic inflammation in asthmatics in a dose-related manner.

Urban air pollution & its assessment in Lucknow City--the second largest city of North India

Investigations were carried out during the summer season (March-June 2012) to observe the quality of indoor air by monitoring the levels of some selected air pollutants at 15 different houses covering the urban areas of Lucknow City. Concentrations of CO2, CO, PM10, PM2.5, SO2 and NO2 were monitored indoors and outdoors simultaneously and I/O ratios were calculated. Regression analysis for I/O relationship was performed to assess the contribution of outdoor sources to indoor air quality. Air Quality Index (AQI) for indoor air was also calculated to have an idea about the quality of indoor air and their health effects. In collaboration with the medical college doctors of the city, we surveyed 197 persons to find out different diseases/symptoms being faced due to indoor air pollution. Results of the study revealed that the average levels of PM10 and PM2.5 were above the permissible limits laid by WHO at densely populated and roadside sites with 189 μg/m(3) (PM2.5 76 μg/m(3)) and 226 μg/m(3) (PM2.5 91 μg/m(3)) respectively. Correlation analysis showed positive results. At sites like Alambagh and Chowk, the indoor AQI range was alarming with the values of 302 and 209. Survey results also showed that 46% of urban people suffered from acute respiratory infections like bronchial asthma, headache, depression and dizziness and these people were mostly from Roadside colonies.

Physicochemical Characterization of Simulated Welding Fume from a Spark Discharge System

This study introduces spark discharge system (SDS) as a way to simulate welding fumes. The SDS was developed using welding rods as electrodes with an optional coagulation chamber. The size, morphology, composition, and concentration of the fume produced and the concentration of ozone (O3) and nitrogen oxides (NOX) were characterized. The number median diameter (NMD) and total number concentration (TNC) of fresh fume particles were ranged 10-23 nm and 3.1×107-6×107 particles/cm3, respectively. For fresh fume particles, the total mass concentration (TMC) measured gravimetrically ranged 85-760 μg/m3. The size distribution was stable over a period of 12 h. The NMD and TNC of aged fume particles were ranged 81-154 nm and 1.5×106-2.7×106 particles/cm3, respectively. The composition of the aged fume particles was dominated by Fe and O with an estimated stoichiometry between that of Fe2O3 and Fe3O4. Concentrations of O3 and NOX were ranged 0.07-2.2 ppm and 1-20 ppm, respectively. These results indicate that the SDS is capable of producing stable fumes over a long-period that are similar to actual welding fumes. This system may be useful in toxicological studies and evaluation of instrumentation.

A review on human health perspective of air pollution with respect to allergies and asthma

The increase in cases of asthma and allergies has become an important health issue throughout the globe. Although these ailments were not common diseases a few short decades ago, they are now affecting a large part of the population in many regions. Exposure to environmental (both outdoor and indoor) pollutants may partially account for the prevalence of such diseases. In this review, we provide a multidisciplinary review based on the most up-to-date survey of literature regarding various types of airborne pollutants and their associations with asthma-allergies. The major pollutants in this respect include both chemical (nitrogen dioxide, ozone, sulfur dioxide, particulate matter, and volatile organic compounds) and biophysical parameters (dust mites, pet allergens, and mold). The analysis was extended further to describe the development of these afflictions in the human body and the subsequent impact on health. This publication is organized to offer an overview on the current state of research regarding the significance of air pollution and its linkage with allergy and asthma.

Meta-analysis of nitrogen dioxide exposure and airway hyper-responsiveness in asthmatics

The effects of 0.1 to 0.6 ppm nitrogen dioxide (NO2) on airway hyper-responsiveness (AHR) to airway challenges in asthmatics have been evaluated in several controlled exposure studies. The authors conducted meta-analyses and meta-regressions of these studies using several effect measures for AHR: a change (in NO2 versus air) in (1) the provocative dose of a challenge agent necessary to cause a specified change in lung function (PD), (2) the change in FEV1 after an airway challenge, and (3) the fraction of subjects with increased AHR. Although several effect estimates from the meta-analyses are statistically significant, they are all so small that they are not likely to be clinically relevant. More importantly, there are no exposure-response associations for any effect estimates based on linear meta-regressions or analyses of effect estimates for exposure groups (0.1 to <0.2 ppm, 0.2 to <0.3 ppm, etc.). This is also generally the case for analyses stratified by airway challenge (specific/nonspecific), exposure method (mouthpiece/whole chamber), and activity during exposure (rest/exercise). The results of these analyses indicate that, to the extent the effects observed are associated with NO2 exposure, they are sufficiently small such that they do not provide evidence that NO2 has a significant adverse effect on AHR at concentrations up to 0.6 ppm.

Critical review of the human data on short-term nitrogen dioxide (NO2) exposures: evidence for NO2 no-effect levels

Nitrogen dioxide (NO2) is a ubiquitous atmospheric pollutant due to the widespread prevalence of both natural and anthropogenic sources, and it can be a respiratory irritant when inhaled at elevated concentrations. Evidence for health effects of ambient NO2 derives from three types of studies: observational epidemiology, human clinical exposures, and animal toxicology. Our review focuses on the human clinical studies of adverse health effects of short-term NO2 exposures, given the substantial uncertainties and limitations in interpretation of the other lines of evidence. We examined more than 50 experimental studies of humans inhaling NO2, finding notably that the reporting of statistically significant changes in lung function and bronchial sensitivity did not show a consistent trend with increasing NO2 concentrations. Functional changes were generally mild and transient, the reported effects were not uniformly adverse, and they were not usually accompanied by NO2-dependent increases in symptoms. The available human clinical results do not establish a mechanistic pathway leading to adverse health impacts for short-term NO2 exposures at levels typical of maximum 1-h concentrations in the present-day ambient environment (i.e., below 0.2 ppm). Our review of these data indicates that a health-protective, short-term NO2 guideline level for susceptible (and healthy) populations would reflect a policy choice between 0.2 and 0.6 ppm. EXTENDED ABSTRACT: Nitrogen dioxide (NO2) is a ubiquitous atmospheric pollutant due to the widespread prevalence of both natural and anthropogenic sources, and it can be a respiratory irritant when inhaled at elevated concentrations. Natural NO2 sources include volcanic action, forest fires, lightning, and the stratosphere; man-made NO2 emissions derive from fossil fuel combustion and incineration. The current National Ambient Air Quality Standard (NAAQS) for NO2, initially established in 1971, is 0.053 ppm (annual average). Ambient concentrations monitored in urban areas in the United States are approximately 0.015 ppm, as an annual mean, i.e., below the current NAAQS. Short-term (1-h peak) NO2 concentrations outdoors are not likely to exceed 0.2 ppm, and even 1-h periods exceeding 0.1 ppm are infrequent. Inside homes, 1-h NO2 peaks, typically arising from gas cooking, can range between 0.4 and 1.5 ppm. The health effects evidence of relevance to ambient NO2 derives from three lines of investigation: epidemiology studies, human clinical studies, and animal toxicology studies. The NO2 epidemiology remains inconsistent and uncertain due to the potential for exposure misclassification, residual confounding, and co-pollutant effects, whereas animal toxicology findings using high levels of NO2 exposure require extrapolation to humans exposed at low ambient NO2 levels. Given the limitations and uncertainties in the other lines of health effects evidence, our review thus focused on clinical studies where human volunteers (including asthmatics, children, and elderly) inhaled NO2 at levels from 0.1 to 3.5 ppm during short-term ((1/2)-6-h) exposures, often combined with exercise, and occasionally combined with co-pollutants. We examined the reported biological effects and classified them into (a) lung immune responses and inflammation, (b) lung function changes and airway hyperresponsiveness (AHR), and (c) health effects outside the lungs (extrapulmonary). We examined more than 50 experimental studies of humans inhaling NO2, finding that such clinical data on short-term exposure allowed discrimination of NO2 no-effect levels versus lowest-adverse-effects levels. Our conclusions are summarized by these six points: For lung immune responses and inflammation: (1) healthy subjects exposed to NO2 below 1 ppm do not show pulmonary inflammation; (2) at 2 ppm for 4 h, neutrophils and cytokines in lung-lavage fluid can increase, but these changes do not necessarily correlate with significant or sustained changes in lung function; (3) there is no consistent evidence that NO2 concentrations below 2 ppm increase susceptibility to viral infection; (4) for asthmatics and individuals having chronic obstructive pulmonary disease (COPD), NO2-induced lung inflammation is not expected below 0.6 ppm, although one research group reported enhancement of proinflammatory processes at 0.26 ppm. With regard to NO2-induced AHR: (5) studies of responses to specific or nonspecific airway challenges (e.g., ragweed, methacholine) suggest that asthmatic individuals were not affected by NO2 up to about 0.6 ppm, although some sensitive subsets may respond to levels as low as 0.2 ppm. And finally, for extra-pulmonary effects: (6) such effects (e.g., changes in blood chemistry) generally required NO2 concentrations above 1-2 ppm. Overall, our review of data from experiments with humans indicates that a health-protective, short-term-average NO2 guideline level for susceptible populations (and healthy populations) would reflect a policy choice between 0.2 and 0.6 ppm. The available human clinical results do not establish a mechanistic pathway leading to adverse health impacts for short-term NO2 exposures at levels typical of maximum 1-h concentrations in the present-day ambient environment (i.e., below 0.2 ppm).

Climate change and allergic disease

Climate change is potentially the largest global threat to human health ever encountered. The earth is warming, the warming is accelerating, and human actions are largely responsible. If current emissions and land use trends continue unchecked, the next generations will face more injury, disease, and death related to natural disasters and heat waves, higher rates of climate-related infections, and wide-spread malnutrition, as well as more allergic and air pollution-related morbidity and mortality. This review highlights links between global climate change and anticipated increases in prevalence and severity of asthma and related allergic disease mediated through worsening ambient air pollution and altered local and regional pollen production. The pattern of change will vary regionally depending on latitude, altitude, rainfall and storms, land-use patterns, urbanization, transportation, and energy production. The magnitude of climate change and related increases in allergic disease will be affected by how aggressively greenhouse gas mitigation strategies are pursued, but at best an average warming of 1 to 2 degrees C is certain this century. Thus, anticipation of a higher allergic disease burden will affect clinical practice as well as public health planning. A number of practical primary and secondary prevention strategies are suggested at the end of the review to assist in meeting this unprecedented public health challenge.

Effects of nitrogen dioxide on human health: systematic review of experimental and epidemiological studies conducted between 2002 and 2006

In order to assess health effects in humans caused by environmental nitrogen dioxide (NO(2)) a systematic review of studies in humans was conducted. MEDLINE database was searched for epidemiological studies and experiments on adverse effects of NO(2) published between 2002 and 2006. The evidence with regard to NO(2) exposure limits was assessed using the Scottish Intercollegiate Guidelines Network (SIGN) grading system and the modified three star system. Of the 214 articles retrieved 112 fulfilled the inclusion criteria. There was limited evidence that short-term exposure to a 1-h mean value below 200 microg NO(2)/m(3) is associated with adverse health effects provided by only one study on mortality in patients with severe asthma (*2+). The effect remained after adjusting for other air pollutants. There was moderate evidence that short-term exposure below a 24-h mean value of 50 microg NO(2)/m(3) at monitor stations increases hospital admissions and mortality (**2+). Evidence was also moderate when the search was restricted to susceptible populations (children, adolescents, elderly, and asthmatics). There was moderate evidence that long-term exposure to an annual mean below 40 microg NO(2)/m(3) was associated with adverse health effects (respiratory symptoms/diseases, hospital admissions, mortality, and otitis media) provided by generally consistent findings in five well-conducted cohort and case-control studies with some shortcomings in the study quality (**2+). Evidence was also moderate when the search was restricted to studies in susceptible populations (children and adolescents) and for the combination with other air pollutants. The most frequent reasons for decreased study quality were potential misclassification of exposure and selection bias. None of the high-quality observational studies evaluated was informative for the key questions due to the choice of the dose parameter (e.g., 1-week mean) and exposure levels above the limit values. Inclusion of study designs unlisted in the SIGN grading system did not bring additional evidence regarding exposures below the current air quality limit values for NO(2). As several recent studies reported adverse health effects below the current exposure limits for NO(2) particularly among susceptible populations regarding long-term exposure further research is needed. Apart from high-quality epidemiological studies on causality and the interaction of NO(2) with other air pollutants there is a need for double-blinded randomized cross-over studies among susceptible populations for further evaluation of the short-term exposure limits.

Neutrophils in asthma

Asthma is a complex disease with a significant inflammatory component. Multiple cell types are involved in its pathophysiology. The presence of eosinophils, the cell usually associated with allergic diseases, does not fully explain the inflammation found in asthma. Neutrophils are present in the airway of the patient with asthma in special circumstances and may represent different asthma phenotypes. Neutrophils are activated and are able to release mediators that promote and prolong asthma symptoms. Increasing evidence suggest that neutrophils may be central players with an important role in the pulmonary inflammatory process present in asthma.

[Effects of personal exposure to nitrogen dioxide on peak expiratory flow in asthmatic patients]

OBJECTIVES

Nitrogen dioxide (NO2) has been inconsistently associated with gradual decreases in lung function. Here, we studied the effects of NO2 exposure in asthmatics by examining the association between changes in lung function and concentrations of NO2 which were personally measured.

METHODS

Peak expiratory flow (PEF) and daily personal exposures to NO2 were recorded on 28 patients with asthma (confirmed by methacholine provocation test) over 4 weeks. We used generalized estimating equations to assess the relationship between personal NO2 exposure and PEF, adjusting for potential confounders such as age, gender, outdoor particulate matter, temperature, humidity, and exposure to environmental tobacco smoke.

RESULTS

The personal NO2 exposures were higher than the corresponding ambient levels. The mean personal: ambient ratio for NO2 was 1.48. The personal NO2 exposures were not associated with the morning PEF, evening PEF, or the diurnal PEF variability. However, environmental tobacco smoke was negatively associated with both the morning and evening PEF.

CONCLUSIONS

Among the asthmatic adults who participated in this study, we found no apparent impact of personal NO2 exposures on the peak expiratory flow.

Effect of formaldehyde on asthmatic response to inhaled allergen challenge

BACKGROUND

Exposure to formaldehyde may lead to exacerbation of asthma.

OBJECTIVES

Our aim in this study was to investigate whether exposure to a low level (500 microg/m(3)) of formaldehyde enhances inhaled allergen responses.

METHODS

Twelve subjects with intermittent asthma and allergy to pollen were exposed, at rest, in a double-blind crossover study to either formaldehyde or purified air for 60 min. The order of exposure to formaldehyde and air-only was randomized, and exposures were separated by 2 weeks. We also performed an allergen inhalation challenge after each exposure. Airway responsiveness to methacholine and lower airway inflammation (induced sputum) were assessed 8 hr after allergen challenge.

RESULTS

The median dose of allergen producing a 15% decrease in forced expiratory volume in 1 sec (PD(15)FEV(1)) was 0.80 IR (index of reactivity) after formaldehyde exposure compared with 0.25 IR after air-only exposure (p = 0.06). Formaldehyde exposure did not affect allergen-induced increase in responsiveness to methacholine (p = 0.42). We found no formaldehyde-associated effect on the airway inflammatory response, in particular the eosinophilic inflammatory response, induced by the allergen challenge 8 hr before.

CONCLUSION

In this study, exposure to 500 microg/m(3) formaldehyde had no significant deleterious effect on airway allergen responsiveness of patients with intermittent asthma; we found a trend toward a protective effect.

Modifications of Phleum pratense grass pollen allergens following artificial exposure to gaseous air pollutants (O(3), NO(2), SO(2))

BACKGROUND

Air pollution is frequently proposed as a potential cause of the increased incidence of allergy in industrialised countries. Our objective was to investigate the impact of the major gaseous air pollutants on grass pollen allergens.

METHODS

Timothy grass pollen was exposed to ozone (O(3)), nitrogen dioxide (NO(2)) and sulphur dioxide (SO(2)) alone or in combination. Allergen contents were analysed by 2-dimensional immunoblot using grass pollen-sensitive patient sera.

RESULTS

For O(3)-treated pollen, immunoblotting showed an acidification of allergens Phl p 1b, Phl p 4, Phl p 5 and Phl p 6 and an IgE recognition decrease in Phl p 1, Phl p 2, Phl p 6 and Phl p 13. NO(2) exposure induced a decrease in Phl p 2, Phl p 5b and Phl p 6 recognition, and SO(2) treatment induced a decrease in Phl p 2, Phl p 6 and Phl p 13 recognition. Moreover, samples treated with a mix of NO(2)/O(3) or NO(2)/SO(2) showed a higher decrease in allergen content, compared with samples treated with only one pollutant. The O(3) acidification was also observed with the NO(2)/O(3) mix.

CONCLUSION

Exposure of pollen to gaseous pollutants induced a decrease in allergen detection in pollen extracts. This decrease could be due to a mechanical loss of allergens from the altered pollen grains and/or post-translational modifications affecting allergen recognition by IgE.

Gas cooking, kitchen ventilation, and asthma, allergic symptoms and sensitization in young children--the PIAMA study

BACKGROUND

Several studies reported inconsistent associations between using gas for cooking and respiratory symptoms or lung function in children. Kitchen ventilation characteristics may modify the relationship between gas cooking and respiratory health. The aim of this study was to investigate the effect of kitchen ventilation (while cooking) on the relationship between gas cooking, combustion product dispersal, and respiratory and allergic outcomes in children.

METHODS

Data on respiratory and allergic symptoms and diagnoses were collected by yearly questionnaires in a population of over 3000 children participating in a birth cohort study on development of allergy and asthma. At 4 years of age, a sub-sample of 647 children provided blood samples for antibody testing. Data on gas cooking and kitchen ventilation were collected when the children were 5 years old. Based on these data a model was constructed to determine the chance of accumulation of combustion products (CACP) in the kitchen.

RESULTS

No relationship was found between gas cooking and any of the respiratory or allergy outcomes except nasal symptoms. The overall results did not change when the 'CACP' was used as exposure variable instead, while the association for nasal symptoms decreased to borderline significance.

CONCLUSION

Our results suggest that gas cooking per se is associated with nasal symptoms in young children and not with the other respiratory symptoms that were investigated. Taking kitchen ventilation characteristics into account did not lead to different conclusions in this population where, according to the classification system, the majority of households using gas for cooking have insufficient kitchen ventilation.

Traffic-related air pollutants induce the release of allergen-containing cytoplasmic granules from grass pollen

BACKGROUND/AIM

Pollen cytoplasmic granules (PCG) are loaded with allergens. They are released from grass pollen grains following contact with water and can form a respirable allergenic aerosol. On the other hand, the traffic-related air pollutants NO2 and O3 are known to be involved in the current increase in the prevalence of allergic diseases via their adjuvant effects. Our objective was to determine the effects of air pollutants on the release of PCG from Phleum pratense (timothy grass) pollen.

METHODS

P. pratense pollen was exposed to several concentrations of NO2 and O3. The induced morphological damages were observed by environmental scanning electron microscopy, and the amount of PCG released from the pollen upon contact with water was measured.

RESULTS

The percentages of damaged grain were 6.4% in air-treated controls, 15% after treatment with the highest NO2 dose (50 ppm) and 13.5% after exposure to 0.5 ppm O3. In treated samples, a fraction of the grains spontaneously released their PCG. Upon subsequent contact with water, the remaining intact grains released more PCG than pollen exposed to air only.

CONCLUSIONS

Traffic-related pollutants can trigger the release of allergen-containing granules from grass pollen, and increase the bioavailability of airborne pollen allergens. This is a new mechanism by which air pollution concurs with the current increase in the prevalence of allergic diseases.

Gas cooking, kitchen ventilation, and exposure to combustion products

We evaluated a questionnaire-based system for classifying homes into groups with distinctly different chances of accumulating combustion products from cooking appliances. The system was based on questions about type of cooking appliance, type and use of ventilation provisions, and kitchen size. Real-time measurements were made of CO, CO(2), temperature, and water vapor, and passive sampling was performed of nitrogen oxides, over a week-long period in 74 kitchens. During the measurements, inhabitants kept a diary to record appliance use time and use of ventilation provisions. The questionnaire-based and diary-based home classifications for the 'Chance of Accumulation of Combustion Products' (CACP) turned out to agree fairly well. For CO(2) as well as for CO a significant difference between the 'high' and 'low' CACP groups was found for the mean accumulation in the kitchen during cooking of the combustion generated concentrations. These facts are considered to be important experimental evidence of the CACP stratification being valid for our study population. In the homes studied, NO(2) as well as CO concentrations were found to be lower compared with previous studies in The Netherlands. Practical Implications Previous studies on indoor combustion product dispersal conducted in the early- to mid-1980s in the Netherlands showed much higher NO(2) and CO concentrations than the present study. Apparently, the removal of combustion products formed during cooking is more efficient in the (mostly newer) homes that we studied than in the homes studied in the early- to mid-1980s. More detailed knowledge of kitchen situations is needed to improve the CACP model. Future studies can achieve this by using questionnaires on the kitchen situation, diaries and real-time measurements of the combustion products under consideration.

Nitrogen dioxide enhances allergic airway inflammation and hyperresponsiveness in the mouse

In addition to being an air pollutant, NO2 is a potent inflammatory oxidant generated endogenously by myeloperoxidase and eosinophil peroxidase. In these studies, we sought to determine the effects of NO2 exposure on mice with ongoing allergic airway disease pathology. Mice were sensitized and challenged with the antigen ovalbumin (OVA) to generate airway inflammation and subsequently exposed to 5 or 25 ppm NO2 for 3 days or 5 days followed by a 20-day recovery period. Whereas 5 ppm NO2 elicited no pathological changes, inhalation of 25 ppm NO2 alone induced acute lung injury, which peaked after 3 days and was characterized by increases in protein, LDH, and neutrophils recovered by BAL, as well as lesions within terminal bronchioles. Importantly, 25 ppm NO2 was also sufficient to cause AHR in mice, a cardinal feature of asthma. The inflammatory changes were ameliorated after 5 days of inhalation and completely resolved after 20 days of recovery after the 5-day inhalation. In contrast, in mice immunized and challenged with OVA, inhalation of 25 ppm NO2 caused a marked augmentation of eosinophilic inflammation and terminal bronchiolar lesions, which extended significantly into the alveoli. Moreover, 20 days postcessation of the 5-day 25 ppm NO2 inhalation regimen, eosinophilic and neutrophilic inflammation, pulmonary lesions, and AHR were still present in mice immunized and challenged with OVA. Collectively, these observations suggest an important role for NO2 in airway pathologies associated with asthma, both in modulation of degree and duration of inflammatory response, as well as in induction of AHR.