The relationship between low level nitrogen dioxide exposure and child lung function after cold air challenge

Background Nitrogen dioxide (NO2) or home gas appliance use has been inconsistently associated with adverse respiratory outcomes in childhood. Objectives (i) To examine the contribution of home gas appliance type and personal NO2 exposure. (ii) To examine the relationship between NO2 exposure and child lung function and respiratory history. (iii) To assess whether these relationships vary by house dust mite sensitization status. Methods A cross‐sectional survey of 344 children (71% of the eligible group) with a mean age of 9.1 years from four randomly selected schools in the Australian Capital Territory from July to September 1999. Study measurements included a parental questionnaire, NO2 exposure by passive gas samplers, skin prick testing for 10 aeroallergens and lung function at rest and after cold air challenge. Results Total NO2 exposure was low with a mean concentration of 10.1 ppb. No associations were found between NO2 exposure or gas appliance use and asthma, wheeze or baseline lung function. Personal NO2 exposure was associated with a reduction in forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) after cold air challenge (adjusted difference − 0.12% (− 0.23% to − 0.01%) per 1 ppb increase). After exclusion of children who had home heating changed because of asthma, gas heater use was also significantly associated with a reduction in this measure (adjusted difference − 2.0% (− 3.7% to − 0.2%)). There was some evidence that these reductions were greater among the non‐mite‐sensitized children. Conclusions The effect of low‐level NO2 exposure on these respiratory outcomes was not marked. The possible effect of low‐level NO2 exposure on non‐specific bronchial reactivity requires confirmation. Future studies on NO2 and respiratory health should include measures of house dust mite sensitization and bronchial hyper‐responsiveness.