In regards to the environmental main effects, the high risk of NO2 on airway inflammatory biomarkers was also found in a study on 242 elderly COPD patients (mean age of 67.8 years) in which ESCAPE-derived exposures to PM2.5 and NO2 were examined on C-reactive protein, TNF-α, interleukin (IL)-6, IL-8, and hepatocyte growth factor. Here, CXCL8 is linked to chronic obstructive pulmonary disease.