EBC IL-6 [46], MDA [101], S-nitrosothiols [102], and nitrite [102] are elevated in patients with COPD, and there is further elevation of IL-6 [103], IL-1-beta [101], TNF-alpha [81], and H2O2 [104] during exacerbations compared with normal smokers. Here, TNF is linked to chronic obstructive pulmonary disease.