Bronchoalveolar lavage samples from human subjects with COPD associated with wood-smoke exposure demonstrated significantly higher MMP activity, specifically pro-MMP-2, pro-MMP-9, and MMP-9, and gene expression of MMP-2 and MMP-12, when compared with healthy controls (Montano et al. 2004). Here, MMP2 is linked to chronic obstructive pulmonary disease.