The modification of the SHS effect by GSTM1 is consistent with previous studies on the association between SHS, GST polymorphisms, and lung cancer in never smokers (Wenzlaff et al. 2005) and may reflect the additional impact of GSTM1 on liver metabolism of tobacco-derived electrophils (Hayes and Strange 2000; Landi 2000; Rowe et al. 1997). Here, GSTM1 is linked to lung carcinoma.