Traffic-Related Air Pollution and its Effect on Heart Disease

Various studies have proved that traffic-generated air pollution can induce coronary heart disease. So far, very few studies have tried to find the exact component of the polluted air that is responsible for this effect. In the present study, researchers examined the effect of carbon nanoparticles produced from the combustion of diesel on blood vessels. This study involved tests on humans as well as laboratory experiments on the aorta of rats. Combustion-derived pure carbon nanoparticulate was found to have adverse effects on the blood vessel system.

It has been proved in many studies that air pollution is an important factor for the causation of coronary heart disease. It has been observed that upon acute exposure to high doses of diesel exhaust, people tend to develop angina and myocardial infarction. Researchers of the present study have shown in their prior studies that inhalation of diesel exhausts promotes clot formation in the blood vessels. Diesel exhausts contain carbon monoxide, organic chemicals, nitrogen dioxide and nanoparticulates. Knowing the role of each pollutant may help in improving the emission purification technology, so that less toxic exhausts are released into the air.

* This study involved 16 healthy volunteers aged between 18 and 32 years. On four occasions, which were two weeks apart, all the participants were exposed to “combustion-derived nanoparticulates,” pure carbon nanoparticulates, filtered diesel exhaust and filtered air for two hours. This was done in a chamber especially designed for this experiment. Later on, drugs such as bradykinin, sodium nitroprusside, acetyl choline and verapamil, which increase the diameter of blood vessels, were administered into a vein in the arm.
* Blood flow in the arteries was measured as was blood pressure. Blood samples were collected to evaluate the clotting tendency of blood by measuring the levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1).
* Laboratory tests were done on rat aortic rings, which were exposed to diesel exhaust particulate to analyze the direct effects of exposure to nanoparticulate.

* Levels of t-PA and PAI-1 did not alter upon exposure to diesel exhaust.
* Compared to filtered air, diesel exhaust was found to inhibit the effect of bradykinin, acetyl choline and sodium nitroprusside, thus constricting blood flow. Upon exposure to pure carbon nanoparticulates and filtered diesel exhaust, no effect on blood flow was observed.
* There was a significant increase in blood pressure upon exposure to diesel exhaust when compared to filtered air.
* The maximum contractile response to phyenylephrine in rat aortic rings was found to increase in the presence of diesel exhaust.

Shortcomings/Next steps
Diesel exhaust contains a large number of active constituents that may cause adverse effects. The authors suggest that “predictive in vitro assays” should be performed to evaluate the mechanism of action of individual components. They further write that the concentrations of particulates from diesel exhaust employed in this study were very high and it is less likely that such concentrations are reached in the circulatory system without accumulating over a long period.

This study has shown that nanoparticulates produced from the combustion of diesel are able to produce adverse effects on blood vessels. However, similar effects were not produced by pure carbon particles or filtered diesel exhaust. Therefore, filtering of diesel exhaust can reduce the particulate pollutants by 1,000 times. Carbon nanoparticulates present in the diesel exhaust inhibit the dilation of blood vessels and increase blood pressure, leading to cardiovascular diseases. Hence, to reduce the prevalence of coronary heart disease, there is a need to filter out nanoparticulate pollutants from diesel exhausts. Effective remedies that address the issue of traffic-derived particulates are thus necessary.

For More Information:
Combustion-Derived Nanoparticulate Induces the Adverse Vascular Effects of Diesel Exhaust Inhalation
Publication Journal: European Heart Journal, July 2011
By Nicholas L. Mills; Mark R. Miller; Edinburgh University, Edinburgh, Scotland

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