Since Mmp12 production is induced by CS (Churg et al., 2003) and is involved in atypical ECM proteolysis in several lung diseases (Lagente et al., 2005, 2009; Greenlee et al., 2007), it is plausible that in utero SHS exposures, similarly to what is observed in adult CS exposures (Hautamaki et al., 1997; Churg et al., 2003), up-regulate Mmp12 expression, leading to exacerbated dysregulation of ECM remodeling after exposure to a second environmental risk factor. Here, MMP12 is linked to lung disorder.