IL6 and chronic obstructive pulmonary disease: In our study, IL-6 was correlated significantly with cigarette smoking history expressed in pack-years (r = −0.253, p = 0.024), and IL-8 was associated with biomass fuel exposure duration (r = 0.251, p = 0.045), underlining the contribution of both tobacco and environmental pollutants to the systemic inflammatory burden in COPD.