Diesel exhaust nanoparticulate impairs vascular function in humans
MedWire News: Combustion-derived nanoparticulate mediates the adverse vascular effects of diesel exhaust inhalation, show study findings, suggesting the need for environmental health interventions targeting particulate emissions.
Lead study author Mark Miller (Edinburgh University, UK) said: "While many people tend to think of the effects of air pollution in terms of damage to the lungs, there is strong evidence that is has an impact on the heart and blood vessels as well.
"Our research shows that while both gases and particles can affect our blood pressure, it is actually the miniscule chemical particles that are emitted by car exhausts that are really harmful."
For the study, 16 healthy participants were exposed for 2 hours to dilute diesel exhaust, pure carbon nanoparticulate, filtered diesel exhaust, or filtered air on four separate occasions at least 2 weeks apart. Exposure was standardized to ensure a particle concentration of 300 µg/m3 - a concentration found on a regular basis in polluted cities.
Forearm blood flow was measured during intrabrachial bradykinin, acetylcholine, sodium nitroprusside, and verapamil infusions 6-8 hours after each challenge.
Compared with inhalation of filtered air, inhalation of diesel exhaust significantly increased systolic blood pressure (145 vs 133 mmHg). While there was a dose-dependent increase in blood flow with each vasodilator, this response was significantly attenuated during bradykinin, acetylcholine, and sodium nitroprusside infusions following exposure to diesel exhaust compared with filtered air.
Exposure to pure carbon nanoparticulate or filtered exhaust had no effect on endothelium-dependent or independent vasodilatation, suggesting that the nature of the particles is a critical factor.
When the researchers exposed isolated rat aortic rings to diesel exhaust particulate and pure carbon nanoparticulate, they found that compared with controls, diesel exhaust, but not pure carbon, nanoparticulate significantly attenuated both acetylcholine and sodium nitroprusside-induced vasorelaxation.
Furthermore, the observed vascular dysfunction appeared to be attributable to both soluble and insoluble fractions present on the surface of the particulate.
"We are now investigating which of the chemicals carried by these particles cause harmful actions, so that in the future we can try and remove these chemicals and prevent the health effects of vehicle emissions," said Miller.
The findings are published in the European Heart Journal.
By Ingrid Grasmo