Use of symptom diary in primary students: association of nitrogen dioxide with prevalence of symptoms.

Air pollution is a global public health concern, and numerous studies have attempted to identify the health effects of air pollutants, including nitrogen dioxide (NO). In China, there are few studies investigating the relationship between NO exposure and symptoms among children at an individual level. The aim of the study was to evaluate the acute effects of NO on prevalence of symptoms of primary students. An environmental and health questionnaire survey was administered to 4240 primary students in seven districts of Shanghai. Daily symptoms, as well as the daily air pollution and meteorological data from each community, were recorded during the corresponding period. A multivariable logistic regression model was utilized to analyze the relationship between the prevalence of symptoms and NO exposure in school-age children. A model with interaction items was adopted to estimate the interactive effects of NO and confounding factors on symptoms. The average NO level in central urban, industrial and rural areas were 62.07 ± 21.66, 54.86 ± 18.32 and 36.62 ± 21.23 μg m, respectively. Our findings demonstrate that the occurrence of symptoms was significantly affected by NO exposure in the short-term. The largest associations were observed for a 10 μg m increase in 5-day moving average (lag04) NO concentration with prevalence of general symptoms (odds ratio [OR] = 1.15, 95% confidence interval [95% CI]: 1.07-1.22), throat symptoms (OR = 1.23, 95% CI: 1.13-1.35) and nasal symptoms (OR = 1.142, 95% CI: 1.02-1.27). Subgroup analysis showed that non-rural areas, boys, nearby environmental pollution source and history of present illness were all susceptible factors to the effects of NO exposure. Furthermore, there were interactive effects between NO exposure and area types on reported symptoms. NO can increase the risk of symptoms in primary students in the short-term, which could be significantly enhanced in central urban and industrial areas.