Association between asthma symptoms and NO2 exposure

Background/Aim: Exposure to air pollution is often estimated by one or two monitoring stations per city, which may lead to measurement error and potentially to underestimation of air pollution risks. A recently developed air quality sensor network in the city of Eindhoven, the Netherlands, measures air pollution at a fine spatio-temporal resolution. We set up a panel study in Eindhoven with the aim to evaluate associations between short-term variation of nitrogen dioxide (NO2) and fine particles concentrations, and short-term variation of asthma-related symptoms and lung function in children.

Methods: Children with asthma-related symptoms, aged between 7-11 years, reported daily symptoms and use of on-demand asthma medication over a period of four months in an electronic diary. Lung function was measured daily at home by the children. Associations with air pollution of the past days from the nearest air quality sensor were obtained using a mixed effects model, correcting for potential confounders and baseline differences between participants.

Results: Only five children could be recruited. Some symptoms in the upper airways were positively related to NO2 concentrations on the same day. Odds ratios per 10 µg/m3 (95% C.I.) were 1.06 (0.85, 1.33) for cough and 1.13 (0.87, 1.45) for nose complaints. For short breath related to NO2 on the previous day, the odds ratio was 1.33 (1.01, 1.75). Odds ratios were 1.82 (1.29, 2.55) for short of breath after exercise, and 1.66 (1.10, 2.51) for on-demand asthma medication use, both related to the mean NO2 concentration of the last three days. No associations were found between NO2 and lung function and PM10 with any symptom and lung function.

Conclusions: Despite the small sample, we found associations between short-term variation of NO2 concentrations and short-term variation of asthma-related symptoms, possibly due to the use of fine resolution air quality sensor data.