Levels of fractional exhaled nitric oxide in children in relation to air pollution in Chinese day care centres.

Abstract

To study fractional exhaled nitric oxide (FeNO) levels among pre-school children in day care centres (DCCs) in relation to indoor and outdoor air pollution in northern China. This was a cross-sectional study among children aged 5 years from 34 classrooms at 10 randomly selected DCCs in Taiyuan, China. A total of 507 (99%) children participated. Air pollution and carbon dioxide (CO2) levels were measured in the classroom and outside the school. Linear mixed models were applied for statistical analysis. The geometric mean FeNO was 9.1 ± 1.5 parts per billion; 11.6% of children had wheeze, 6.0% had dry cough, 26.4% rhinitis symptoms, 1.6% ever physician-diagnosed asthma and 29.2% ever physician-diagnosed pneumonia. FeNO levels were associated with current wheeze (P = 0.04) and ever physician-diagnosed pneumonia (P = 0.05). The mean indoor concentrations were particulate matter with a diameter of <2.5 μm (PM2.5) 268 μg/m3, sulfur dioxide (SO2) 40.5 μg/m3, nitrogen dioxide (NO2) 43.0 μg/m3 and CO2 827 parts per million. Outdoor concentrations were PM2.5 244 μg/m3, SO2 106.6 μg/m3 and NO2 40.9 μg/m3. PM2.5 levels inside (P = 0.002) and outside DCCs (P = 0.05) were associated with FeNO levels. PM2.5 levels inside and outside DCCs in China can contribute to airway inflammation in pre-school children. Children with current wheeze and ever physician-diagnosed pneumonia may have higher FeNO levels.