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Most studies of long-term air pollution exposure and children's respiratory health have been performed in urban locations with moderate pollution levels. We assessed the effect of outdoor nitrogen dioxide (NO 2 ), as a proxy for urban air pollution, on current asthma and lung function in Australia, a low-pollution setting. We undertook a national population-based cross-sectional study of children aged 7-11 years living in 12 Australian cities. We collected information on asthma symptoms from parents via questionnaire and measured children's lung function (forced expiratory volume in 1 s [FEV 1 ], forced vital capacity [FVC]) and fractional exhaled nitric oxide [Fe NO ]). We estimated recent NO 2 exposure (last 12 months) using monitors near each child's school, and used a satellite-based land-use regression (LUR) model to estimate NO 2 at each child's school and home. Our analysis comprised 2630 children, among whom the prevalence of current asthma was 14.9%. Mean (±SD) NO 2 exposure was 8.8 ppb (±3.2) and 8.8 ppb (±2.3) for monitor- and LUR-based estimates, respectively. Mean percent predicted post-bronchodilator FEV 1 and FVC were 101.7% (±10.5) and 98.8% (±10.5), respectively. The geometric mean Fe NO concentration was 9.4 ppb (±7.1). An IQR increase in NO 2 (4.0 ppb) was significantly associated with increased odds of having current asthma; odds ratios (ORs) were 1.24 (95% CI: 1.08, 1.43) and 1.54 (95% CI: 1.26, 1.87) for monitor- and LUR-based estimates, respectively. Increased NO 2 exposure was significantly associated with decreased percent predicted FEV 1 (-1.35 percentage points [95% CI: -2.21, -0.49]) and FVC (-1.19 percentage points [95% CI: -2.04, -0.35], and an increase in Fe NO of 71% (95% CI: 38%, 112%). Exposure to outdoor NO 2 was associated with adverse respiratory health effects in this population-based sample of Australian children. The relatively low NO 2 levels at which these effects were observed highlight the potential benefits of continuous exposure reduction., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The prevalence of allergic diseases in Australian children is high, but few studies have assessed the potential role of outdoor air pollution in allergic sensitization. We investigated the association between outdoor air pollution and the prevalence of aeroallergen sensitization in a national cross-sectional study of Australian children aged 7–11 years. Children were recruited from 55 participating schools in 12 Australian cities during 2007–2008. Parents completed a detailed (70-item) questionnaire. Outdoor nitrogen dioxide (NO 2), as a proxy for exposure to traffic-related emissions, was estimated using measurements from regulatory monitors near each school and a national land-use regression (LUR) model. Three averaging periods were assessed, using information on duration of residence at the address, including lifetime, previous (lifetime, excluding the last year), and recent (the last year only). The LUR model was used as an additional source of recent exposure estimates at school and home addresses. Skin prick tests (SPTs) were performed to measure sensitization to eight common aeroallergens. Multilevel logistic regression estimated the association between NO 2 and sensitization (by individual allergens, indoor and outdoor allergens, and all allergens combined), after adjustment for individual- and area-level covariates. In total, 2226 children had a completed questionnaire and SPT. The prevalence of sensitization to any allergen was 44.4%. Sensitization to house dust mites (HDMs) was the most common (36.1%), while sensitization to Aspergillus was the least common (3.4%). Measured mean (±s.d.) NO 2 exposure was between 9 (±2.9) ppb and 9.5 (±3.2) ppb, depending on the averaging period. An IQR (4 ppb) increase in measured previous NO 2 exposure was associated with greater odds of sensitization to HDMs (OR: 1.21, 95% CI: 1.01–1.43, P = 0.035). We found evidence of an association between relatively low outdoor NO 2 concentrations and sensitization to HDMs, but not other aeroallergens, in Australian children aged 7–11 years. Image 1 • Air pollution may affect aeroallergen sensitization, but evidence is inconsistent. • We performed a national cross-sectional study of Australian children. • We found that outdoor NO 2 was associated with sensitization to house dust mites. • We did not find associations between NO 2 and other aeroallergens. We have added new results to the relatively scarce evidence base on the effects of low-level urban air pollution and aeroallergen sensitization in children. [ABSTRACT FROM AUTHOR]