MTS exposure has been shown to cause demethylation of the promoter region for receptor of insulin-like growth factor 1 (Igf1R) in the murine lung [109] and methylation of insulin-like growth factor 2 (Igf2) in human cord blood [110], which both play an important role in lung development and can contribute to asthma later in life. Here, IGF2 is linked to asthma.