Dust in the indoor and outdoor environment and human exposure to particulate matter pollution in dust causes a significant public health problem. There is no getting away from dust – it is present in the desert, the countryside, the city and even in outer space.
In her fascinating book 'The Secret Life of Dust', Hannah Holmes gives a useful working description of dust as Particulate Matter of size 63 microns or less. She gives a few examples of dust and other substances, just for comparison:
Another important dust definition is the classification of Particulate Matter into PM10, PM2.5 and ultrafine particles (UFPs). The first refers to particles of size 10 microns or less and 2.5 microns or less, while UFPs have a size of 0.1 microns (100 nanometres) or less. These are often used in environmental monitoring reports. These working definitions take no account of what the dust is made of but, as scientific sampling and analysis indicate, the composition of dust is highly variable.
Smaller particles of dust remain airborne for a very long time and can travel through great distances. Ragweed pollen grains, for instance, have actually been found nearly 400 miles out at sea. Cat allergen borne on tiny flakes of cat skin or fur is another dust that travels far and can persist in the air for months after the animal has left a location. Heavier particles form settled dust. Carpet is the main reservoir for dust in a house. Research shows that houses with hard wood floors and rugs harbour one-tenth of the dust that is found in houses that have carpets. Horizontal surfaces collect far more dust than vertical surfaces but do be aware that dust will gather on the latter and will certainly be present on soft furnishings like curtains and also on window blinds.
Dust is composed of a mixture of substances of biological and chemical origin. Biological dust components include:
Chemical dust come mainly from industrial activities and traffic. Some significant chemical dust include:
For people with allergies, including asthma and hay fever, house dust mite droppings, pollen grains and fungal spores, may act as potent triggers. Asbestos, heavy metal and cigarette smoke can cause various forms of cancer and lung disease. The ‘Six Cities’ study suggested that exposure to particulate matter pollution regardless of the composition is associated with excess mortality. The health effects of exposure to indoor dust have been far less studied but it is likely that it does not matter whether the pollution originates indoors or outdoors, it is still a health hazard.
Damp dusting, or using an electrostatic dusting cloth, will do a far better job of capturing dust from a surface than a dry or feather duster will. Dry dusting just stirs up the dust into the air. Regular vacuuming is a must if you have carpet, but vacuum cleaners do vary in their performance. Hannah Holmes quotes some interesting research from the Carpet and Rug Institute which shows that many vacuum cleaners subjected to testing actually leaked significant amounts of dust into the air. So rather than capturing dust into the dust bag, they were merely transferring it from the carpet to the air. A vacuum cleaner fitted with a High-Efficiency Particulate Air (HEPA) filter is more likely to trap dust particles, but some do not suck much dust up from the carpet, according to further study from the Carpet and Rug Institute researchers. A HEPA air filter, so long as it is a reputable brand and well maintained, will do an excellent job of removing dust from the air. For instance, the IQAir HealthPro 250 contains HEPA technology that is capable of removing 99.5 per cent of particles down to 0.003 microns in size.