The dangers of diesel pollution are very obvious. Diesel exhaust emissions can inflame the lungs and increase airway resistance - and that’s just in healthy people. For those suffering with asthma, exposure to diesel fumes can significantly worsen their asthma symptoms.
Recently, there was a study carried out on London’s Oxford Street (high diesel emissions) and in Hyde Park (low diesel emissions) which illustrated the dangers of diesel pollution by showing the increased airway inflammation among participants with asthma after being in the former environment. Oxford Street, as Londoners know, is restricted to diesel-powered buses and taxis so this was a good place to determine the impact of diesel traffic on lung health. But people in Oxford Street are exposed to more pollutants than just diesel fumes - there are particles from brake and tyre wear and tear and from road surface abrasion.
Diesel fumes from the exhaust is itself a complex mixture of air pollution (it can be compared, in this respect, to tobacco smoke) of particles less than 0.1 micrometre in diameter and gases including carbon monoxide, nitrogen and sulphur oxides, and Volatile Organic Compounds, including potent irritants like formaldehyde.
In a new study, Ian Mudway of King’s College London and colleagues in Sweden and Southampton exposed volunteers suffering with asthma and also healthy controls to filtered air and diesel exhaust (no particles from other traffic-related sources). They found an increase in inflammation, as measured by a higher concentration of immune cells, in the healthy controls with exposure to diesel. But no such response was found among participants suffering with asthma. What does this mean? The researchers suggest that the known increased sensitivity of people suffering with asthma to traffic-related air pollution cannot be attributed to a ‘classical’ acute inflammation response (as was seen in the healthy controls) or to the usual indicators of allergic asthmatic inflammation. Something else is going on here and further research is needed to look at the dangers of diesel pollution and to nail down the details of exactly what is going on when someone suffering with asthma is exposed to diesel fumes.
Meanwhile, in another study, David Newby of the British Heart Foundation (BHF,www.bhf.org.uk) and colleagues, looked at the impact of a new diesel filter on the heart health of a group of 19 healthy volunteers. The study was funded by the BHF and by the equivalent charity in Sweden. The men breathed in filtered air (such as you would get from a HEPA air purifier), diesel exhaust and diesel exhaust treated with the new filter. They inhaled each gas for one hour during which time they alternated 15 minute bouts of moderate exercise with 15 minutes of rest.
The exhaust filter removed 98% of all particles in the diesel exhaust and 99.8% of the smallest and most damaging particles. Compared to filtered air, the diesel exhaust also impaired the ability of blood vessels to dilate after exposure, whilst breathing filtered air improved the release of a compound which dissolves blood clots. By contrast, the diesel exhaust increased the tendency of the blood to clot, which is a major factor in heart attack risk. These findings suggest that fitting vehicles with diesel exhaust traps could help improve heart health among those exposed to traffic pollution. The study also suggests that it is the particles, rather than gases, in the diesel exhaust, which have an adverse impact upon the heart.
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Sources: Behndig AF et al Proinflammatory doses of diesel exhaust in healthy subjects fail to elicit equivalent or augmented airway inflammation in subjects with asthma Thorax;66:12-19
Newby D et al Circulation Online April 11 2011