Abstract
Nitrogen dioxide is known as a deep lung irritant. The aim of this study was to find out whether the relatively low ambient air NO2 concentrations in the northern city of Helsinki had an impact on the respiratory health of children. The association between personal exposure to ambient air NO2 and respiratory health was investigated in a 13-week follow-up study among 163 preschool children aged 3-6 yrs. Personal weekly average exposure to NO2 was measured by passive diffusion samplers attached to the outer garments. Symptoms were recorded daily in a diary by the parents. Among 53 children, peak expiratory flow (PEF) was measured at home in the mornings and evenings. The association between NO2 exposure and respiratory symptoms was examined with Poisson regression. The median personal NO2 exposure was 21.1 microg x m(-3) (range 4-99 microg x m(-3)). An increased risk of cough was associated with increasing NO2 exposure (risk ratio = 1.52; 95% confidence interval 1.00-2.31). There was no such association between personal weekly NO2 exposure and nasal symptoms, but a nonsignificant negative association was found between the exposure and the weekly average deviation in PEF. In conclusion, even low ambient air NO2 concentrations can increase the risk of respiratory symptoms among preschool children.
Highlights
The median personal NO2 exposure was 21.1 mg.m-3
The adjusted risk ratio in the highest NO2 category was slightly reduced, if SO2 or ozone was added into the model (risk ratio (RR)=1.50, 95% confidence interval (CI) 1.00±2.26 and RR=1.47, 95% CI 0.96±2.25, respectively) and slightly increased when TSP was added into the model (RR=1.55, 95% CI 1.01±2.40)
A significantly increased risk of cough was found among preschool children, who were exposed to low ambient air NO2 concentrations in Helsinki
Summary
An increased risk of cough was associated with increasing NO2 exposure (risk ratio=1.52; 95% confidence interval 1.00±2.31). Nitrogen dioxide is a major air pollutant both indoors and outdoors It is formed in combustion processes, either directly or through secondary oxidation of nitric oxide. The most susceptible population groups to the adverse effects seem to be small children and asthmatic subjects [1±4]. In these studies, the associations between the estimated NO2 exposure and the prevalence of childhood respiratory symptoms and illnesses, illness duration or lung function have not been consistent [3, 5±9]
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