Following a single session of hydrogen inhalation, a notable reduction in monocyte chemotactic protein 1 levels was observed in both the COPD group (564.70–451.51 pg/mL, p = 0.019) and the asthma group (386.39–332.76 pg/mL, p = 0.033). Here, CCL2 is linked to chronic obstructive pulmonary disease.