Outdoor NO2 Research Articles

Indoor air quality in London schools. Part 2: long-term integrated assessment

The overall aim of the study is to provide empirical evidence on indoor pollution levels to assist the formation of indoor air quality (IAQ) benchmarking of school buildings under operational conditions. This article is the second part of the study and aims to quantify seasonal variation of chemical and microbial levels in London schools. Passive diffusive sampling was employed for radon, NO2, and O3 measurements. Fungal and bacterial groups and allergens were sampled with suction-based methods in settled dust and endotoxin levels were sampled in dust collected with natural deposition. Biological contaminants were analysed with molecular, cultivation-independent methods. The strong temporal and spatial variability of outdoor NO2 levels affected indoor levels and is therefore an important consideration when selecting sites for new school buildings. There is a need to further clarify on the effect of finishing, such as wall-to-wall carpeting, which may act as a significant reservoir of irritants and allergens and impact school IAQ.

National patterns in environmental injustice and inequality: outdoor NO2 air pollution in the United States.

We describe spatial patterns in environmental injustice and inequality for residential outdoor nitrogen dioxide (NO2) concentrations in the contiguous United States. Our approach employs Census demographic data and a recently published high-resolution dataset of outdoor NO2 concentrations. Nationally, population-weighted mean NO2 concentrations are 4.6 ppb (38%, p<0.01) higher for nonwhites than for whites. The environmental health implications of that concentration disparity are compelling. For example, we estimate that reducing nonwhites’ NO2 concentrations to levels experienced by whites would reduce Ischemic Heart Disease (IHD) mortality by ∼7,000 deaths per year, which is equivalent to 16 million people increasing their physical activity level from inactive (0 hours/week of physical activity) to sufficiently active (>2.5 hours/week of physical activity). Inequality for NO2 concentration is greater than inequality for income (Atkinson Index: 0.11 versus 0.08). Low-income nonwhite young children and elderly people are disproportionately exposed to residential outdoor NO2. Our findings establish a national context for previous work that has documented air pollution environmental injustice and inequality within individual US metropolitan areas and regions. Results given here can aid policy-makers in identifying locations with high environmental injustice and inequality. For example, states with both high injustice and high inequality (top quintile) for outdoor residential NO2 include New York, Michigan, and Wisconsin.

Outdoor Formaldehyde and NO 2 Exposures and Markers of Genotoxicity in Children Living Near Chipboard Industries

Background: Industrial air pollution is a public health hazard. Previous evidence documented increased respiratory symptoms and hospitalizations in children who live near the factories in the largest chipboard manufacturing district in Italy (Viadana).Objectives: We evaluated the association of outdoor exposure to formaldehyde and nitrogen dioxide (NO2) with markers of early genotoxic damage in oral mucosa cells of randomly selected children (6–12 years of age) living in Viadana.Methods: In 2010–2011, DNA strand breaks and nuclear abnormalities were evaluated in exfoliated buccal cells by the comet and micronucleus assays, respectively, and formaldehyde and NO2 were monitored by passive sampling. Annual exposure estimates to pollutants were assigned to children’s houses by spatial interpolation.Results: Of 656 children, 413 (63%) participated. Children living near (< 2 km) the chipboard industries had the highest average exposure to formaldehyde and NO2 (p < 0.001). A 1-SD increase in formaldehyde (0.20 μg/m3) was associated with a 0.13% (95% CI: 0.03, 0.22%) higher comet tail intensity, a 0.007 (95% CI: 0.001, 0.012) higher tail moment, and a 12% relative increase [relative risk (RR) = 1.12; 95% CI: 1.02, 1.23] in nuclear buds. A 1-SD NO2 increase (2.13 μg/m3) was associated with a 0.13% (95% CI: 0.07, 0.19%) increase in binucleated cells and a 16% relative increase (RR = 1.16; 95% CI: 1.06, 1.26) in nuclear buds.Conclusions: Exposure to pollutants was associated with markers of genotoxicity in exfoliated buccal cells of children living in a region with chipboard industries. These findings, combined with previously reported associations between chipboard industrial activities and respiratory outcomes in children, add to concerns about potential adverse effects of industry-related exposures in the Viadana district.Citation: Marcon A, Fracasso ME, Marchetti P, Doria D, Girardi P, Guarda L, Pesce G, Pironi V, Ricci P, de Marco R. 2014. Outdoor formaldehyde and NO2 exposures and markers of genotoxicity in children living near chipboard industries. Environ Health Perspect 122:639–645; http://dx.doi.org/10.1289/ehp.1307259

The relationship between air pollution and asthma in Malaysian schoolchildren

Rapid increases in traffic volumes in countries such as Malaysia may lead to exposure to poor air quality both outdoors and indoors. This study investigated asthma symptoms among Malaysian schoolchildren in relation to indoor and outdoor air pollution in urban and semi-rural settings in a school-based cross-sectional study of 1,952 schoolchildren living in urban and semi-rural areas. Parents completed a questionnaire including questions on asthma symptoms and environmental risk factors. Air pollutant concentrations were measured at 16 schools. Analysis used multiple logistic regression controlling for sociodemographic and indoor air pollution factors. A total of 11.4, 7.6, 9.5 and 7.0 % schoolchildren had asthma, current wheeze, dry cough at night and wheezing after exercise, respectively. Asthma and dry cough were significantly higher among urban schoolchildren. A 10-μg/m3 increase in outdoor NO2 level was associated with a twofold increase in the reporting of current wheeze (odds ratio (OR) 1.90; 95 % confidence interval (CI) 1.02–3.52); a 10-μg/m3 increase in indoor PM2.5 was similarly associated with a twofold increase in the reporting of wheeze during exercise (OR 2.08; 95 % CI 1.02–4.26). Secondhand smoke (SHS), mold and the presence of new furniture at home were also linked to asthma symptoms. NO2 concentrations in urban Malaysia frequently exceed those of the international standards. Exposure to traffic-related air pollution may be linked to asthma symptoms among children in Malaysia.

Outdoor air pollution, subtypes and severity of ischemic stroke--a small-area level ecological study.

BackgroundEvidence linking outdoor air pollution and incidence of ischemic stroke subtypes and severity is limited. We examined associations between outdoor PM10 and NO2 concentrations modeled at a fine spatial resolution and etiological and clinical ischemic stroke subtypes and severity of ischemic stroke.MethodsWe used a small-area level ecological study design and a stroke register set up to capture all incident cases of first ever stroke (1995–2007) occurring in a defined geographical area in South London (948 census output areas; population of 267839). Modeled PM10 and NO2 concentrations were available at a very fine spatial scale (20 meter by 20 meter grid point resolution) and were aggregated to output area level using postcode population weighted averages. Ischemic stroke was classified using the Oxford clinical classification, the Trial of Org 10172 in Acute Stroke Treatment (TOAST) etiological classification, National Institutes of Health Stroke Scale (NIHSS) score and a pragmatic clinical severity classification based on Glasgow coma score, ability to swallow, urinary continence and death <2 days of stroke onset.ResultsMean (SD) concentrations were 25.1 (1.2) ug/m3 (range 23.3-36.4) for PM10 and 41.4 (3.0) ug/m3 (range 35.4-68.0) for NO2. There were 2492 incident cases of ischemic stroke. We found no evidence of association between these pollutants and the incidence of ischemic stroke subtypes classified using the Oxford and TOAST classifications. We found no significant association with stroke severity using NIHSS severity categories. However, we found that outdoor concentrations of both PM10 and NO2 appeared to be associated with increased incidence of mild but not severe ischemic stroke, classified using the pragmatic clinical severity classification. For mild ischemic stroke, the rate ratio in the highest PM10 category by tertile was 1.20 (1.05-1.38) relative to the lowest category. The rate ratio in the highest NO2 category was 1.22 (1.06-1.40) relative to the lowest category.ConclusionsWe found no evidence of association between outdoor PM10 and NO2 concentrations and ischemic stroke subtypes but there was a suggestion that living in areas with elevated outdoor PM10 and NO2 concentrations might be associated with increased incidence of mild, but not severe, ischemic stroke.

Cardiovascular diseases and air pollution in Novi Sad, Serbia

A large body of evidence has documented that air pollutants have adverse effect on human health as well as on the environment. The aim of this study was to determine whether there was an association between outdoor concentrations of sulfur dioxide (SO2) and nitrogen dioxide (NO2) and a daily number of hospital admissions due to cardiovascular diseases (CVD) in Novi Sad, Serbia among patients aged above 18. The investigation was carried out during over a 3-year period (from January 1, 2007 to December 31, 2009) in the area of Novi Sad. The number (N = 10 469) of daily CVD (ICD-10: I00-I99) hospital admissions was collected according to patients' addresses. Daily mean levels of NO2 and SO2, measured in the ambient air of Novi Sad via a network of fixed samplers, have been used to put forward outdoor air pollution. Associations between air pollutants and hospital admissions were firstly analyzed by the use of the linear regression in a single polluted model, and then trough a single and multi-polluted adjusted generalized linear Poisson model. The single polluted model (without confounding factors) indicated that there was a linear increase in the number of hospital admissions due to CVD in relation to the linear increase in concentrations of SO2 (p = 0.015; 95% confidence interval (95% CI): 0.144-1.329, R(2) = 0.005) and NO2 (p = 0.007; 95% CI: 0.214-1.361, R(2) = 0.007). However, the single and multi-polluted adjusted models revealed that only NO2 was associated with the CVD (p = 0.016, relative risk (RR) = 1.049, 95% CI: 1.009-1.091 and p = 0.022, RR = 1.047, 95% CI: 1.007-1.089, respectively). This study shows a significant positive association between hospital admissions due to CVD and outdoor NO2 concentrations in the area of Novi Sad, Serbia.

Land use regression models for estimating individual NOx and NO2 exposures in a metropolis with a high density of traffic roads and population

This study is conducted to characterize the intra-urban distribution of NOx and NO2; develop land use regression (LUR) models to assess outdoor NOx and NO2 concentrations, using the ESCAPE modeling approach with locally specific land use data; and compare NOx and NO2 exposures for children in the Taipei Metropolis by the LUR models, the nearest monitoring station, and kriging methods based on data collected at the measurement sites. NOx and NO2 were measured for 2weeks during 3 seasons at 40 sampling sites by Ogawa passive badges to represent their concentrations at urban backgrounds and streets from October 2009 to September 2010. Land use data and traffic-related information in different buffer zones were combined with measured concentrations to derive LUR models using supervised forward stepwise multiple regressions. The annual average concentrations of NOx and NO2 in Taipei were 72.4±22.5 and 48.9±12.2μg/m3, respectively, which were at the high end of all 36 European areas in the ESCAPE project. Spatial contrasts in Taipei were lower than those of the European areas in the ESCAPE project. The NOx LUR model included 6 land use variables, which were lengths of major roads within 25m, 25–50m, and 50–500m, urban green areas within 300m and 300–5000m, and semi-natural and forested areas within 500m, with R2=0.81. The NO2 LUR model included 4 land use variables, which were lengths of major roads within 25m, urban green areas within 100m, semi-natural and forested areas within 500m, and low-density residential area within 500m, with R2=0.74. The LUR models gave a wider variation in estimating NOx and NO2 exposures than either the ordinary kriging method or the nearest measurement site did for the children of Taiwan Birth Cohort Study (TBCS) in Taipei.

Impact of maternal exposure to nitrogen dioxide (NO2) during pregnancy on birth weight: a preliminary study in São Paulo, Brazil.

Air pollution exposure during pregnancy might have trimester-specific effects on birth weight. To evaluate the impact of maternal exposure to indoor, outdoor and individual NO2 concentrations durin...

Monthly national satellite-based land-use regression of NO2 in the United States for 2000 - 2010

Background: Land use regression (LUR) is widely used for estimating within-urban variability in air pollution, typically at the urban level and for long-term averages. LUR techniques have recently been extended to national and continental scales. Aims: Our aim is a LUR for NO2 in the continental US that provides the excellent spatial resolution found in most LURs (~100-m scale), incorporates satellite estimates, covers 100% of US Census Blocks, and provides monthly average concentrations for one decade. Methods: Our work extends a previously-published national LUR for year-2006 in the US. We employ eleven years (2000-2010) of hourly NO2 measurements from US EPA monitors to calculate monthly scaling factors, which account for deviations relative to the reference year. We then create a spatially-varying (inverse-distance weighted) “scaling surface” for each month, to estimate monthly concentration deviations at non-measurement locations.Results: The resulting model captures, on average, 86% of the spatial variability and 72% of the temporal variability with low average bias (26%). Model performance is best at locations near monitors (e.g., spatial R2 = 0.90, mean bias 8% for the tertile with the lowest mean distance to the three nearest monitors). Urban and suburban locations perform moderately better than rural locations at predicting spatial (R2: 0.80 , 0.84, and 0.77, respectively) and temporal (R2: 0.78, 0.76, 0.63) variability and significantly better at predicting absolute concentrations (mean bias: 18%, 10%, 59%). Conclusions: Our approach reliably estimates monthly outdoor NO2 concentration at a spatial resolution capable of capturing within-urban and near-roadway variability in concentrations. We apply this technique to the ~8 million US Census blocks in the contiguous United States to provide a decade (2000 - 2010) of high-resolution monthly NO2 concentration estimates; these data are publicly available.

Scaling Relationship for NO2Pollution and Urban Population Size: A Satellite Perspective

Concern is growing about the effects of urbanization on air pollution and health. Nitrogen dioxide (NO2) released primarily from combustion processes, such as traffic, is a short-lived atmospheric pollutant that serves as an air-quality indicator and is itself a health concern. We derive a global distribution of ground-level NO2 concentrations from tropospheric NO2 columns retrieved from the Ozone Monitoring Instrument (OMI). Local scaling factors from a three-dimensional chemistry-transport model (GEOS-Chem) are used to relate the OMI NO2 columns to ground-level concentrations. The OMI-derived surface NO2 data are significantly correlated (r = 0.69) with in situ surface measurements. We examine how the OMI-derived ground-level NO2 concentrations, OMI NO2 columns, and bottom-up NOx emission inventories relate to urban population. Emission hot spots, such as power plants, are excluded to focus on urban relationships. The correlation of surface NO2 with population is significant for the three countries and one continent examined here: United States (r = 0.71), Europe (r = 0.67), China (r = 0.69), and India (r = 0.59). Urban NO2 pollution, like other urban properties, is a power law scaling function of the population size: NO2 concentration increases proportional to population raised to an exponent. The value of the exponent varies by region from 0.36 for India to 0.66 for China, reflecting regional differences in industrial development and per capita emissions. It has been generally established that energy efficiency increases and, therefore, per capita NOx emissions decrease with urban population; here, we show how outdoor ambient NO2 concentrations depend upon urban population in different global regions.

A new exposure metric for traffic-related air pollution? An analysis of determinants of hopanes in settled indoor house dust

BackgroundExposure to traffic-related air pollution (TRAP) can adversely impact health but epidemiologic studies are limited in their abilities to assess long-term exposures and incorporate variability in indoor pollutant infiltration.MethodsIn order to examine settled house dust levels of hopanes, engine lubricating oil byproducts found in vehicle exhaust, as a novel TRAP exposure measure, dust samples were collected from 171 homes in five Canadian cities and analyzed by gas chromatography–mass spectrometry. To evaluate source contributions, the relative abundance of the highest concentration hopane monomer in house dust was compared to that in outdoor air. Geographic variables related to TRAP emissions and outdoor NO2 concentrations from city-specific TRAP land use regression (LUR) models were calculated at each georeferenced residence location and assessed as predictors of variability in dust hopanes.ResultsHopanes relative abundance in house dust and ambient air were significantly correlated (Pearson’s r=0.48, p<0.05), suggesting that dust hopanes likely result from traffic emissions. The proportion of variance in dust hopanes concentrations explained by LUR NO2 was less than 10% in Vancouver, Winnipeg and Toronto while the correlations in Edmonton and Windsor explained 20 to 40% of the variance. Modeling with household factors such as air conditioning and shoe removal along with geographic predictors related to TRAP generally increased the proportion of explained variability (10-80%) in measured indoor hopanes dust levels.ConclusionsHopanes can consistently be detected in house dust and may be a useful tracer of TRAP exposure if determinants of their spatiotemporal variability are well-characterized, and when home-specific factors are considered.

Role of highway traffic on spatial and temporal distributions of air pollutants in a Swiss Alpine valley

Traffic-related air pollutants show high spatial variability near roads, posing a challenge to adequately assess exposures. Recent modeling approaches (e.g. dispersion models, land-use regression (LUR) models) have addressed this but mostly in urban areas where traffic is abundant. In contrast, our study area was located in a rural Swiss Alpine valley crossed by the main North–south transit highway of Switzerland.We conducted an extensive measurement campaign collecting continuous nitrogen dioxide (NO2), particulate number concentrations (PN), daily respirable particulate matter (PM10), elemental carbon (EC) and organic carbon (OC) at one background, one highway and seven mobile stations from November 2007 to June 2009. Using these measurements, we built a hybrid model to predict daily outdoor NO2 concentrations at residences of children participating in an asthma panel study.With the exception of OC, daily variations of the pollutants followed the temporal trends of heavy-duty traffic counts on the highway. In contrast, variations of weekly/seasonal means were strongly determined by meteorological conditions, e.g., winter inversion episodes. For pollutants related to primary exhaust emissions (i.e. NO2, EC and PN) local spatial variation strongly depended on proximity to the highway. Pollutant concentrations decayed to background levels within 150 to 200m from the highway.Two separate daily NO2 prediction models were built using LUR approaches with (a) short-term traffic and weather data (model 1) and (b) subsequent addition of daily background NO2 to previous model (model 2). Models 1 and 2 explained 70% and 91% of the variability in outdoor NO2 concentrations, respectively. The biweekly averaged predictions from the final model 2 agreed very well with the independent biweekly integrated passive measurements taken at thirteen homes and nine community sites (validation R2=0.74). The excellent spatio-temporal performance of our model provides a very promising basis for the health effect assessment of the panel study.

Contribution of Indoor and Outdoor Nitrogen Dioxide to Indoor Air Quality of Wayside Shops

Indoor nitrogen dioxide (NO₂) concentration is an important factor for personal exposure despite the wide distribution of its sources. Exposure to NO₂ may produce adverse health effects. The aims of this study were to characterize the indoor air quality of wayside shops using multiple NO₂ measurements, and to estimate the contribution of outdoor NO₂ sources such as vehicle emission to indoor air quality. Daily indoor and outdoor NO₂ concentrations were measured for 21 consecutive days in wayside shops (5 convenience stores, 5 coffee shops, and 5 restaurants). Contributions of outdoor NO₂ sources to indoor air quality were calculated with penetration factors and source strength factors by indoor mass balance model in winter and summer, respectively. Most wayside shops had significant differences in indoor and outdoor NO₂ concentrations both in winter and in summer. Indoor NO₂ concentrations in restaurants were twice more than those in convenience stores and coffee shops in winter. While outdoor NO₂ contributions in indoor convenience stores and coffee shops were dominant, indoor NO₂ contributions were dominant in restaurants. These could be explained that indoor NO₂ sources such as gas range and smoking mainly affect indoor concentrations comparing to outdoor sources such as vehicle emission. The indoor mass balance model by multiple measurements suggests that quantitative contribution of outdoor air on indoor air quality might be estimated without measurements of ventilation, indoor generation and decay rate.

Urban Air Pollutants Are Significant Risk Factors for Asthma and Pneumonia in Children: The Influence of Location on the Measurement of Pollutants

BackgroundAir pollution is associated with a substantial burden on human health; however, the most important pollutants may vary with location. Proper monitoring is necessary to determine the effect of these pollutants on respiratory health. ObjectivesThis study was designed to evaluate the role of outdoor, indoor and personal exposure to combustion-related pollutants NO2 and O3 on respiratory health of children in a non-affluent urban area of São Paulo, Brazil. MethodsLevels of NO2 and O3 were continuously measured in outdoor and indoor air, as well as personal exposure, for 30 days using passive measurement monitors. Respiratory health was assessed with a Brazilian version of the ISAAC questionnaire. ResultsComplete data were available from 64 children, aged 6–10 years. Respiratory morbidity was high, with 43 (67.2%) reporting having had wheezing at any time, 27 (42.2%) wheezing in the last month, 17 (26.6%) asthma at any time and 21 (32.8%) pneumonia at any time. Correlations between levels of NO2 and O3 measured in the three locations evaluated were poor. Levels of NO2 in indoor air and personal exposure to O3 were independently associated with asthma (both cases P=.02), pneumonia (O3, P=.02) and wheezing at any time (both cases P<.01). No associations were seen between outdoor NO2 and O3 and respiratory health. ConclusionsExposure to higher levels of NO2 and O3 was associated with increased risk for asthma and pneumonia in children. Nonetheless, the place where the pollutants are measured influences the results. The measurements taken in indoor and personal exposure were the most accurate.

Variación espacial de la exposición a contaminación atmosférica en la ciudad de Valencia y su relación con un índice de privación

ObjectiveTo evaluate spatial variation in exposure to nitrogen dioxide (NO2) air pollution in the city of Valencia, Spain, and its association with socioeconomic deprivation and age. MethodsCensus tract population data were obtained from the National Statistics Institute of Spain. Outdoor NO2 was monitored in 100 sites in the study area, through the use of passive samplers, in three campaigns between 2002 and April 2004. Land use regression (LUR) was used to obtain a map of NO2 levels. The LUR predictions were compared with the NO2 level obtained by: a) the nearest sampler of the monitoring network, b) the nearest passive sampler, c) the mean distance-weighted levels of the samplers in the neighborhood, and d) the NO2 level obtained by using Kriging. For each census tract, the NO2 levels were obtained. The association of NO2 air pollution exposure with population age (≥65 years) and the 5-category deprivation index was analyzed. ResultsThe LUR models showed less error than the other prediction methods. The safety levels proposed by the World Health Organization were exceeded in more than 99% of the population. An inverse relationship was found between NO2 levels and the deprivation index (β = –2.01μg/m3 in the most deprived quintile compared with lower deprivation, 95%CI: –3.07; –0.95) and a direct relationship was found with age (β = 0.12μg/m3 per unit increase in percentage of the population ≥ 65 years, 95%CI: 0.08; 0.16). ConclusionsThe method allowed pollution maps to be obtained and the association between NO2 levels and sociodemographic characteristics to be described.

Development of highly sensitive nitrogen dioxide monitoring device and its application to wide-area ubiquitous network

We have developed an NO2 sensing device with high time resolution for application to a wide-area ubiquitous network. The NO2 sensing device employs the colorimetric reaction between NO2 and diazo-coupling reagents. We estimated the formation and decomposition rate of the azo dye in the sensor elements and found that no decomposition occurred and that the formation rate was fast enough for us to measure NO2 concentration at 10 min intervals with a detection limit of 12 ppb. We have constructed sensing terminal units containing the NO2 sensing device, a GPS device, a compass, a switch, LEDs and a wireless terminal unit for a wide-area ubiquitous network. We successfully monitored the outdoor NO2 level at 10 min intervals using the developed terminal units mounted on a bicycle in certain areas of several cities. We also designed and implemented an application where bicycles collect geo-tagged air quality samples and post them on a map that other cyclists can use to determine their route.

Los contaminantes atmosféricos urbanos son factores de riesgo significativos para el asma y la neumonía en niños: influencia del lugar de medición de los contaminantes

BackgroundAir pollution is associated with a substantial burden on human health; however, the most important pollutants may vary with location. Proper monitoring is necessary to determine the effect of these pollutants on respiratory health. ObjectivesThis study was designed to evaluate the role of outdoor, indoor and personal exposure to combustion-related pollutants NO2 and O3 on respiratory health of children in a non-affluent urban area of São Paulo, Brazil. MethodsLevels of NO2 and O3 were continuously measured in outdoor and indoor air, as well as personal exposure, for 30 days using passive measurement monitors. Respiratory health was assessed with a Brazilian version of the ISAAC questionnaire. ResultsComplete data were available from 64 children, aged 6-10 years. Respiratory morbidity was high, with 43 (67.2%) reporting having had wheezing at any time, 27 (42.2%) wheezing in the last month, 17 (26.6%) asthma at any time and 21 (32.8%) pneumonia at any time. Correlations between levels of NO2 and O3 measured in the three locations evaluated were poor. Levels of NO2 in indoor air and personal exposure to O3 were independently associated with asthma (both cases P=.02), pneumonia (O3, P=.02) and wheezing at any time (both cases P<.01). No associations were seen between outdoor NO2 and O3 and respiratory health. ConclusionsExposure to higher levels of NO2 and O3 was associated with increased risk for asthma and pneumonia in children. Nonetheless, the place where the pollutants are measured influences the results. The measurements taken in indoor and personal exposure were the most accurate.

Roles of pollution in the prevalence and exacerbations of allergic diseases in Asia

The prevalence of asthma and allergic diseases has been found to be increasingly rapidly, especially in developing countries. Environmental factors have been found to be important contributors to the manifestations of allergic diseases. Air pollution has been extensively studied in different regions of the world. The levels of ambient air pollutants in many Asian countries are very high when compared with those in developed Western countries. However, the prevalence of asthma was relatively low across many Asian countries. Many studies have clearly documented that environmental air pollution is an important factor resulting in exacerbations of asthma. In particular, levels of traffic-related pollutants are increasing rapidly across many Asian countries in parallel with the level of urbanization and economic development. The loss of protective factors associated with a rural environment will further contribute to the adverse effect on patients with allergic diseases such as asthma. In this review the roles of air pollution were examined in relation to the inception and exacerbations of allergic diseases in Asia.

DETERMINANTS OF INDOOR AND OUTDOOR LEVELS OF NO2 IN A COHORT OF 4-YEARS-OLD CHILDREN

Background and Aims: Home outdoor NO2 has been used as a marker of personal exposure to traffic-related air pollution. However, recent studies suggest that exposure to indoor NO2 may be a risk factor in itself for respiratory health and neurodevelopment. We aimed at assessing the relationship between indoor and outdoor NO2 levels and their determinants in a subset of the INMA birth cohort of Sabadell, Spain. Methods: Indoor and outdoor NO2 levels were measured with passive samplers during two measurement campaigns of one week (1st campaign in fall/winter, 2nd campaign in summer) at home addresses of 96 children. Characteristics of the home surroundings (street configuration, building density, and traffic-related variables) were obtained by the field workers and by Geographic Information Systems (GIS). Information on sources of NO2 indoor levels (gas appliances, tobacco smoke) and additional variables (e.g.use of extractor fan, air conditioning) were obtained through questionnaires in each campaign. Results: Mean levels of outdoor NO2 were 36.7 µg/m3 in fall/winter and 34 µg/m3 in summer, while mean levels of indoor NO2 were 22.8 µg/m3 in fall/winter and 26 µg/m3 in summer. The correlation between indoor and outdoor levels was lower in fall/winter (r=0.35) than in summer (r=0.51). The main determinants of outdoor NO2 were the street configuration (continuous buildings on both sides vs. other configurations) and traffic-related GIS variables. Indoor NO2 levels were influenced by tobacco smoke, time using gas cooking, time opening windows to ventilate, house age, and an interaction between outdoor NO2 levels and use of air conditioning. Conclusions: The influence of traffic-related NO2 pollution on indoor levels is higher in summer than in fall/winter, probably due to differences in ventilation patterns. Gas cooking and tobacco smoke are the main indoor sources of NO2, whereas ventilation, use of air conditioning, and house age are additional determinants.

OUTDOOR NO 2 EXPOSURE IS ASSOCIATED WITH PERSISTENT COUGH DURING THE FIRST YEAR OF LIFE

Background and Aims: Because children’s lungs and immune system are not completely developed they are more susceptible to respiratory disease as well as more vulnerable to ambient pollution. We assessed the relation between prenatal and postnatal NO2 levels and the development of Lower Respiratory Tract Infections (LRTI), wheezing and persistent cough during the first year of life. Methods: Study population were 352 children from a birth cohort in Valencia, Spain. Prenatal exposure to NO2 was measured at 93 sampling sites spread over the study area during four different sampling periods of 7 days each. It was modelled for each residential address through land use regression using the empirical measurements and geographic information systems data. Postnatal exposures were measured indoor and outdoor the residence with passive samplers during 14 days once in each home. Outcomes studied were any episode of LRTI during the child's first year of life diagnosed by a doctor (bronchitis, bronchiolitis or pneumonia), wheezing (defined as whistling sounds coming from the chest), and persistent cough (more than three consecutive weeks). Outcomes and potential confounders were obtained from structured questionnaires. Multiple logistic regression was used to explore associations. Results: Cumulative incidence (CI) was 30.40% for LRTI (23.01% bronchiolitis, 11.93% bronchitis and 1.42% pneumonia), 26.14% for wheezing and 6.25% for persistent cough. Adjusted odds ratio (95% confidence interval) per 10 µg/m3 increment in postnatal outdoor NO2 concentration was for persistent cough 1.40 (1.02-1.92). We also found evidence of an association with bronchiolitis, bronchitis and persistent cough in different prenatal periods, although it was not statistically significant. Conclusions: Our results support that exposure to outdoor NO2 during first year increase the risk of persistent cough. Support statement: ‘‘Instituto de Salud Carlos III’’ (G03/176), FIS-FEDER 03/1615, 04/1509, 04/1112, 06/1213, RCESP C03/09, the fellowship for research training FI05/01109, “Enrique Nájera 2006” prize for young researchers and Conselleria Sanitat GV 16/2009.