GSTM1 and asthma: Islam et al.[34] examined asthma incidence among school children in southern California and reported increased risk among carriers of the GSTM1-null allele (Hazard Ratio (HR): 1.61, 95% CI: 1.2, 2.2) and decreased asthma risk among carriers of the Valine105 allele for GSTT1 (HR: 0.60, 95% CI: 0.4, 0.8).