Whether or not atopic mechanisms can explain the increased risk of asthma symptoms and adverse lung function effects remains unclear. It is of interest to note that, in the current study, the effect on asthma symptoms was found in the high dry dust exposure group, whereas the effect on atopy was observed in the high green dust exposure group, and effects on baseline lung function were found in both the high green dust and high dry dust exposure categories. This suggests that, in the present population, the underlying mechanisms and/or causal exposures might be different for atopy, asthma symptoms and lung function.