Q&A - Could pollution affect blood cells?
By Nick Morgan, health journalist | Tuesday, July 3, 2007 1.17pm
Q: I'm a regular commuter in London and have been for over a year. I do 50-to-60 miles a week, plus the occasional longer ride at weekends. My commute is mostly along busy roads.
I recently had a medial check-up as part of my employer's new health insurance policy. During the live blood analysis, the doctor pointed out that some of my red blood cells were spiky. Apparently this can be caused by exposure to high levels of atmospheric pollution, stress or illness.
As I hadn't been ill before the test, the doctor suggested that my commute was the most likely cause. I'd tend to agree, as my work hadn't been particularly stressful prior to the test.
There have been plenty of articles in the paper recently about the amount of pollution that cyclists are exposed to: basically, the levels are pretty high!
I'm very aware that there are a lot of buses and taxis on the road belching out diesel fumes, but what I'm not clear on is whether there's anything that I can do to protect myself from them. I know that face masks are available, but do they really help? In particular, I'm sceptical that they would help with diesel fumes, as these are composed of very fine particles. Have any studies been done which prove the relative effectiveness of the different types of masks available or are they all basically gimmicks?
Simon Robinson, email
A:There has been some recent research in this area, although the results are slightly inconclusive. First of although, you're right to be concerned; a recent study by a team at Imperial College London found that, contradictory to popular belief, air breathed by cyclists contains double the level of particulate matter (80,000 particles per cubic centimetre) of motorists (40,000pt/cm3), and significantly more than pedestrians (50,000/cm3).
So, do the masks work? Well, Respro, one of the leading mask manufacturers, claims to have conducted thorough research. This shows that good quality masks are 99 per cent effective against particles over 0.3 microns in size (that's the same as a third of one thousandth of a millimetre!)
The trouble, as you rightly point out, is that some of the nastiest particles, like those in diesel fumes, are smaller than 0.3 microns, and these are the ones that could pass through the mask filter, and also the mucous membranes in your throat and possibly on into the
Although there is much scholarly debate over exactly how much damage they do, it's reasonable to assume that they're not doing a whole lot of good. In 2002 the US Environmental Protection Agency concluded that Diesel exhaust is a "likely human carcinogen", and a "chronic respiratory hazard to humans, carrying possible carcinogenic chemicals into your blood stream."
Respro admits that the filtration of these really small particles, such as diesel, reduces at a linear rate (so, the smaller they are, the less the masks stop them). Saying that, it and other mask manufacturers have more expensive models with secondary charcoal filters. These are claimed to go some way to mopping up these residual nano-particles. If you're commuting in the city every day, it may well be worth spending the extra cash and investing in one of these.
The impartial experts remain unconvinced however: "I would very much doubt that masks would be very effective against particles like diesel," said Dr Zoran Ristovski of the International Laboratory for Air Quality and Health in Queensland, Australia. "They are just too small."
So, I guess the answer is that a mask certainly won't do you any harm and is likely to filter out some of the larger particle-sized rubbish that's out there. But it's not going to stop all of it, so it might be time to rethink your route to work - or get a new job of course!
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