Increase of Exhaled Nitric Oxide in Children Exposed to Low Levels of Ambient Ozone

Abstract

Ozone (O₃) is known to induce lung function impairment and airways inflammation during episodes of photochemical smog. The aim of the present study was to assess the inflammatory effect of ambient O₃ in healthy children using nitric oxide in exhaled air (eNO) as a noninvasive test. The study was performed on 6 groups of children (n = 11–15), aged 6.5 to 15 yr, who attended summer camps in rural areas of the south of Belgium in 2002. Ambient O₃ concentrations continuously monitored in the camps ranged from 48 to 221 μg/m³ (1-h maximal concentration). Children remained outdoors during the experimental days, doing various recreational activities but no sports. Lung function tests (forced expiratory volume in 1s [FEV₁] and forced vital capacity [FVC]) and eNO were measured twice in each child in the morning and in the evening. While lung function tests did not show any consistent pattern of decrease at these O₃ levels, a highly significant increase in eNO was found in all subjects from an ambient 1-h O₃ level of 167 μg/m³. A multivariate analysis did not reveal any influence of age, gender, height, weight, and body mass index (BMI) of the children. The threshold for this O₃-induced increase in eNO estimated benchmark dose analysis was 135 μg/m³ for 1-h exposure and 110 μg/m³ for 8-h exposure. These observations suggest that ambient ozone produces early inflammatory changes in the airways of children at levels slightly below current air quality standards.