A team of scientists from Denmark and Sweden discovered that indoor air polluted with tiny particles that are breathed in and get into the bloodstream affected the performance of blood vessels, and potentially increased the risk of cardiovascular disease, in elderly people. When the air quality was improved using filters, their blood vessels worked much better.
The study is published in the American Journal of Respiratory and Critical Care Medicine and was the work of Dr Steffen Loft of the Institute of Public Health, Department of Environmental Health, Copenhagen, in Denmark, and colleagues.
Scientists already knew that exposure to air pollutants such as the microscopic particles emitted in various types of vehicle, industrial and power plant exhaust fumes increased risk factors for cardiovascular disease. This is probably because the endothelial cells that line the walls of all blood vessels become damaged by the tiny particles once they get into the bloodstream. This study extends that knowledge to indoor air quality.
Loft and colleagues investigated the effect of air particles on three markers of blood vessel health: microvascular function (MVF), oxidative stress, and inflammation.
They recruited a total of 21 non smoking elderly couples, aged between 60 and 75, to take part in a randomized, double blind, crossover study of two exposure episodes lasting 48 hours each, both in their homes.
This meant the couples were randomly selected to be exposed either to filtered air first and then to non-filtered air, or the other way around. Double blind meant that neither the couples nor the scientists who assigned them to their groups knew which exposure came first: filtered or non-filtered air. All the couples were in good health and lived near busy roads. The exposure was controlled by putting air purifiers in their homes, with and without an air filter fitted inside.
When the air filter was fitted, it created an exposure in the range of 2,533 to 4,058 particles per cm3. Without the filter the exposure ranged from 7,718 to 12,988 particles/cm3. The concentration, diameter range and mass range, as well as the chemical properties of the particles in the air were also monitored at all times.
The researchers measured MVF by assessing the artery tone of a finger after applying a blood pressure cuff on the arm (arm ischemia). They also took blood samples to measure a range of blood materials to assess oxidative stress and inflammation, including hemoglobin, red blood cells, platelets, coagulants, C-reactive protein, and many others.
The results showed that:
- Filtered air significantly improved MVF by 8.1 per cent.
- The diameter of the air particles (smaller than 2.5 micrometers) and their mass, had a greater effect than their total number concentration.
- MVF was also significantly linked to being exposed to particles containing iron, potassium, copper, zinc, arsenic, and lead.
- After applying a test of statistical significance, none of the other biomarkers (oxidative stress and inflammation) varied significantly with particle exposure.
The researchers concluded that:
“Reduction of particle exposure by filtration of recirculated indoor air for only 48 hours improved MVF in healthy elderly citizens, suggesting that this may be a feasible way of reducing the risk of cardiovascular disease.”
Endothelial cells line the walls of all blood vessels throughout the body from the smallest capillary to the largest artery . They are involved in lots of important jobs from controlling blood flow, reducing clotting, keeping arteries clear, reducing swelling and forming new blood vessels. They also control the movement of blood materials like white blood cells into and out of the bloodstream, and in some organs like the kidneys and the brain, they act as a blood filter.
Endothelial dysfunction therefore affects all these aspects of the cardiovascular system, and often results in atherosclerosis, where arteries get clogged up with plaques and then swell (and sometimes burst) with the resulting inflammation. This also narrows the arteries and stops the blood getting to the organ concerned, for instance as in a heart attack.
“Indoor Particles Affect Vascular Function in the Aged: An Air Filtration-based Intervention Study.”
Elvira Vaclavik Bräuner, Lykke Forchhammer, Peter Møller, Lars Barregard, Lars Gunnarsen, Alireza Afshari, Peter Wåhlin, Marianne Glasius, Lars Ove Dragsted, Samar Basu, Ole Raaschou-Nielsen, and Steffen Loft.
American Journal of Respiratory and Critical Care Medicine Vol 177. pp. 419-425, (2008).
First published online October 11 2007 as doi:10.1164/rccm.200704-632OC
Source: journal article.
Written by: Catharine Paddock, PhD