The subtype of nitric oxide synthase-2 may be affected by oxidative stress and cytokines produced after inhalation of air pollutants34, and the acute effect of PM2.5 exposure on FeNO in c-SLE patients suggests that these patients have a higher degree of epithelial-mediated airway inflammation after exposure to fine particles35,36. Here, NOS2 is linked to systemic lupus erythematosus.