There is a lot of variability in lung structure among healthy adults. This variability in lung structure is thought to arise during growth - a concept that is referred to as “dysanapsis” (from the Greek, dys=unequal and anaptixy = growth). Dysanapsis is strongly associated with lung disease and death later in life, but the origins of dysanapsis are poorly understood. A recent genetic investigation identified several variants associated with dysanapsis, but when dysanapsis genetic risk manifests in childhood and whether it interacts with environmental or social factors to impair lung function is unknown. This study has two objectives: i) describe the relationship between dysanapsis genetic risk and lung function at various timepoints during lung growth; ii) test whether environmental exposures (environmental tobacco smoke) or social deprivation modify these relationships. No new measurements or samples are required for this study.