The air we breathe

22 Nov 2010

Do we really know what we are inhaling? This crucial question was answered at the SCI London Regional Group's recent lecture, 'The Air We Breathe'. Held at UCL, it featured a multi-media presentation by the Group's current chairman, Dr Fred Parrett.

We are all aware of dust caused by industrial processes, but are perhaps less aware of the considerable amount of airborne dust created by nature. The eruption of the Eyjafjallajökull volcano in Iceland in April 2010 left us in no doubt of the impact such sources of airborne dust can cause, and it is not the last time that we can expect this type of event.

There's not much we can do about nature, but even man-made dust can be created on such a scale that its control is challenging. Building demolition, for example, is a major dust creator, and when the largest ever demolition occurred at the hands of terrorists - the tragic collapse of the Twin Towers - there was so much toxic dust in the air that for many months after, area residents suffered heath-related problems.

Car tyres are well known for issues surrounding their disposal, but we ignore the fact that about 15% of each tyre is worn away in use and ends up as very tiny particles of airborne dust. In a big city such as Los Angeles, that's five tonnes of dust per day. Since modern tyres use high amounts of latexes, vulcanised with sulphur and zinc accelerators, this airborne tyre dust contains toxic metals and allergy-inducing latex.

Given how widespread dust is, it is remarkable that its monitoring is a relatively new concern. In 1988, COSHH (Control of Substances Hazardous to Health) regulations created a greater awareness of the health implications, and monitoring of dust levels using simple sampling pumps is now routine. A wide range of control methods is currently available based on enclosure, extraction and suppression methods - all of which were outlined in the lecture.

It is not just simple or dead dust that cause problems - dust can also be alive. Air naturally contains a number of airborne viruses, bacteria and moulds, though the study of these living particles (bioaerosols) is a field that perhaps doesn't get enough attention from either microbiologists or university teaching programmes. In fact, quantitative monitoring of airborne bacteria can now be routinely carried out using simple impact samplers and is becoming more widely used in medical, pharmaceutical and food industries. Bioaerosol monitoring is now essential because of the increase in composting operations to handle waste in many organisations and industries.

Dr Parrett presented graphic illustrations of actual levels of bioaerosols in critical areas - including hospitals - as well as explaining how they can be controlled. At present, expected levels of these airborne particles in domestic and industrial areas are recognised, but the recommended maximum levels expressed as colony-forming units per m3 cannot easily be legislated. However, monitoring the situation is half way to dealing with it.

Dr Fred Parrett, London Regional Group

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