How vehicle emissions contribute to heart disease

Researchers have found that breathing in vehicle emissions alters high-density lipoprotein (HDL), otherwise known as ‘good cholesterol’, meaning that instead of protecting the cardiovascular system, it clogs up arteries.

The group of researchers, including scientists from UCLA and other institutions, carried out the study on mice.  They exposed mice to vehicle emissions for two weeks and found that the HDL of these mice had a lower ability to protect against oxidation and inflammation caused by low-density cholesterol (LDL), or ‘bad cholesterol’.  The altered HDL not only failed to prevent LDL causing oxidation, but contributed to the oxidation process itself, working with LDL to cause more damage.

Other components of the oxidation process were also affected, with the emissions causing early cell and tissue damage leading to inflammation and therefore hardening of the arteries.  There was an increase in additional oxidation products in the blood of these mice, the amount of which correlated with the degree of HDL dysfunction.

This damage found in the blood and liver after exposure to emissions was not reversed after exposure to clean, filtered air for one week afterwards.  The researchers suggest that this may be partly due to the altered HDL.  As senior author Dr Jesus Araujo said: “This is the first study showing that air pollutants promote the development of dysfunctional, pro-oxidative HDL cholesterol and the activation of an internal oxidation pathway, which may be one of the mechanisms in how air pollution can exacerbate clogged arteries that lead to heart disease and stroke.”

This research builds on evidence that vehicle emissions can contribute to heart disease and that it would be wise to limit our exposure to them.