The aim of this study was to evaluate the impact of urban air pollution, assessed through reliable indicators of exposure, on asthma and allergies in schoolchildren.A validated dispersion model combining data on traffic conditions, topography, meteorology and background pollution was used to relate 3-yrs averaged concentrations of major urban pollutants at the sites of schools to skin prick tests, exercise-induced asthma and reported asthma and allergies in 6,683 children (9-11 yrs) attending 108 schools randomly selected in six French communities.For the 4,907 children who had resided at their current address for the past 3 yrs, asthma (exercise induced, past year and lifetime) was significantly positively associated with benzene, SO 2 , particles with a 50% cut-off aerodynamic diameter of 10 mm (PM10), nitrogen oxides (NO x ) and CO. In the same children, eczema (lifetime and past year) was significantly positively associated with benzene, PM10, NO 2 , NO x and CO, lifetime allergic rhinitis with PM10 and sensitisation to pollens with benzene and PM10. Among the 2,213 children residing at their current address since birth, the associations persisted for lifetime asthma with benzene (adjusted OR per interquartile range (95% CI) 1.3 (1.0-1.9)) and PM10 (1.4 (1.0-2.0)), and for sensitisation to pollens with volatile organic compounds (1.3 (1.0-1.9)) and PM10 (1.2 (1.0-1.9)).Accurately modelled urban air pollution was associated with some measures of childhood asthma and allergies.

A moderate increase in long-term exposure to background ambient air pollution was associated with an increased prevalence of respiratory and atopic indicators in children.

The relationships between FA and asthma and AR could be totally explained neither by the existence of respiratory manifestations of FA nor by sensitization to aeroallergens. The FA might intervene differently in asthma and AR.

Educational aims To provide a thorough presentation of sources, dispersion and transformation of major air pollutants.  To describe the health effects of these air pollutants.  To explain the differences between emissions, immissions, exposure and absorbed dose.  To help readers to understand what is at stake in the topical scientific and political debate on air pollution. SummaryAir pollution, particularly in urban areas, constitutes a public health concern, as it has a harmful effect on the health, survival and activities of humans and other living organisms. Here, the main types of air pollution commonly found in urban environments are presented, along with their sources, levels of emissions, mechanisms of dispersion, transformation, concentrations in ambient air (=immissions), and effects on the environment and health. In particular, the concepts of exposure, absorbed dose and individual susceptibility are explained. The recent evolution in air pollutant emissions and immissions due to the growing weight of road traffic is also described. Finally, European air quality criteria are highlighted.C. Pénard-Morand I. Annesi-Maesano

Among early-life environmental factors, parental smoking (ETS) has been associated with adverse respiratory outcomes in children. The aim of the study was to evaluate whether parental smoking might lead to asthma and allergies taking into account family history of asthma, personal atopy, breast feeding as confounders and owing pets and day-care during the first 6 months of life as modifiers. About 9000 children of fourth and fifth grade were selected in six cities of France. About 7798 answered an epidemiological questionnaire, underwent a medical examination including skin prick test positivity to common allergens, skin examination for eczema, and run test to assess exercise-induced asthma (EIA). Prevalence of allergies was, respectively, 25.2% for eczema, 12.9% for rhinitis, 9.9% for asthma and 25% for atopy. About 8.3% had an EIA. About 21.6% of children were exposed to maternal tobacco smoking during pregnancy. Maternal smoking, in utero and later, was significantly related to lifetime wheezing (odds ratio (OR): 1.24[1.10-1.56]) and asthma (OR: 1.22[1.04-1.66]). There was no association between atopy, rhinitis, eczema and parental smoking, respectively. ETS remains a risk factor of wheezing in childhood. Counselling parents of children to quit smoking still remains a public health policy.

Air pollution is associated with a wide range of adverse respiratory events. In order to study the mechanism associated with these effects, the relationships between fractional exhaled nitric oxide (FeNO), a potential marker of airway inflammation, and exposure to air pollution were examined in schoolchildren. FeNO was measured in 104 children (34 asthmatics and 70 non-asthmatics) drawn from the general population simultaneously with air pollution assessments (fine particles with an aerodiameter under 2.5 microm, nitrogen dioxide, acetaldehyde, and formaldehyde, with pumps and passive samplers) in schoolyards and classrooms. Asthmatics exhaled more FeNO than non-asthmatics. FeNO levels were significantly elevated in both asthmatic and non-asthmatic children exposed to high concentrations of formaldehyde, acetaldehyde, and PM(2.5). Differences between high versus low exposure in non-asthmatics resulted in an FeNO increase ranging from 45% for indoor acetaldehyde to 62% for indoor PM(2.5). Stronger associations were found in non-asthmatic children who were atopic, suggesting that atopic children may be more sensitive to air pollution than non-atopic children. Exposure to air pollution may lead to airway inflammation, as measured by FeNO, in schoolchildren. These associations occur even in children with no history of airway damage and seem to be enhanced in atopic subjects.

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