Epidemiological and toxicological studies indicate that the adverse outcomes of PM2.5 exposure associated closely with the chemical composition in PM2.5. Metals in PM2.5 are highly concerned for their induced disruption of iron homeostasis in the lung and following oxidative stress, which is one of the key mechanisms underlying the cardiovascular autonomic dysfunction of PM2.5 exposure. However, there is no clear evidence on whether COPD patients are more susceptible to cardiovascular autonomic dysfunction associated with exposure to metals in ambient PM2.5 than individuals without COPD. Based on a panel study, the researchers directly compared metal-associated cardiovascular autonomic dysfunction between COPD patients and healthy controls.