Re: The effect of air pollution on lung function in children.

Using data from two large, prospective German birth cohorts (GINIplus and LISAplus), we reported that early-life and current long-term air pollution exposures were not associated with lung function at the age of 15 years in the general study population (Fuertes et al. 2015). In response to our manuscript, Kawada et al. (2016) raised two points: 1) that our primary null findings are in contrast to some previous studies that reporte significant associations and 2) that air pollution cannot be excluded as a risk factor for respiratory symptoms. To these two points, we respond, that we completely agree. However, despite the numerous studies that have evaluated the potential adverse role of air pollution on respiratory health, the evidence for an association remains inconsistent for most outcomes. For example, although the meta-analysis conducted by Gehring et al. 2013, that was highlighted by Kawada et al. (2016), reported associations between levels of nitrogen dioxide, total nitrogen oxides, mass concentrations of particulate matter with diameters < 2.5  (PM2.5) and PM2.5 absorbance at the current address only and small decreases in lung function overall, the cohort-specific associations appeared consistent in certain areas (the Dutch PIAMA cohort) and null in others (the German GINIplus and LISAplus cohorts, in line with the results of Fuertes et al. (2015)). Such heterogeneity is evident throughout the literature and emphasizes the need for continued high quality research efforts in this field, including the publication of “negative results” to avoid publication bias.  We agree that the study presented in Fuertes et al. (2015) is only one piece of this complex problem. Nonetheless, it contributes to the development of a comprehensive understanding of the potential effects of air pollution on respiratory health