From Henry Sanford, Cromwell Hospital
Following the article on PM10s (21 September, Inside Science) and Max Wallis’s timely warning on fine particles (19 October, p 28), let me offer some hope based on our own experience.
I have recently recorded, in ordinary office environments in London, a horrifying range of between 250,000 and 410,000 particles per cubic foot of air (equivalent to between 9 million and 15 million particles per cubic metre of air) at 0.5 micrometres in size. This is a size that can enter the bloodstream through the alveoli of the lungs.
These tiny menaces have various origins: not just vehicle fumes but also the skin cells that we all shed, printer toner, delaminating carpets, and even fragments of cellulose from paper.
The hope comes from the fact that I have recorded reductions in these particles of more than 90 per cent by using a combination of negative ionisation and HEPA (High Efficiency Particulate Air) filtration. This results in a significant reduction in upper respiratory problems, especially where a lot of time is spent in any indoor environment.
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The negative ionisation has the added benefit of removing the positive charge of the particles, so they sink to the floor.
London, UK
