FAMILY merged children from three pediatric cohorts, as well as their mothers and siblings who were identified through HAD housed at ICES. The CHILD cohort, a national general population-based birth cohort, was established in 2008 to increase our understanding of the interactions between the environment and genetics in the development of asthma and allergy. A total of 5619 grades one and two (aged 5–9 years) Toronto school children were recruited in 2006.