Dirt is unclean matter, especially when in contact with a person's clothes, skin or possessions. In such case they are said to become dirty. Common types of dirt include:
- Soil: the mix of clay, sand, and humus which lies on top of bedrock
- Dust: a general powder of organic or mineral matter
- Filth: foul matter such as excrement
- Grime: a black, ingrained dust such as soot
Exhibitions and studies
A season of artworks and exhibits on the theme of dirt was sponsored by the Wellcome Trust in 2011. The centrepiece was an exhibition at the Wellcome Collection showing pictures and histories of notable dirt such as the great dust heaps at Euston and King's Cross in the 19th century and the Fresh Kills landfill which was once the world's largest landfill.
In a commercial setting, a dirty appearance gives a bad impression. An example of such a place is a restaurant. The dirt in such cases may be classified as temporary, permanent, and deliberate. Temporary dirt is streaks and detritus that may be removed by ordinary daily cleaning. Permanent dirt is ingrained stains or physical damage to an object, which require major renovation to remove. Deliberate dirt is that which results from design decisions such as decor in dirty orange or grunge styling.
As cities developed, arrangements were made for the disposal of trash through the use of waste management services. In the United Kingdom, the Public Health Act 1875 required households to place their refuse into a container which could be moved so that it could be carted away. This was the first legal creation of the dustbin.
Modern society is now thought to be more hygienic. Lack of contact with microorganisms in dirt when growing up is hypothesised to be the cause of the epidemic of allergies such as asthma. The human immune system requires activation and exercise in order to function properly and exposure to dirt may achieve this. For example, the presence of staphylococcus bacteria on the surface of the skin regulates the inflammation which results from injury.
Even when no visible dirt is present, contamination by microorganisms, especially pathogens, can still cause an object or location to be considered dirty. For example, computer keyboards are especially dirty as they contain on average 70 times more microbes than a lavatory seat.
People may become obsessed by dirt and engage in fantasies and compulsive behaviour about it, such as making and consuming mud pies and pastries. The source of such thinking may be genetic, as the emotion of disgust is common and the location for this activity in the brain has been proposed.
- Brian Dillon (23 March 2011), "Dirt: the Filthy Reality of Everyday Life, Welcome Collection", The Daily Telegraph
- Mindy Lewis (2009), Dirt: The Quirks, Habits, and Passions of Keeping House, ISBN 9781580052610
- John B. Hutchings (2003), Expectations and the Food Industry, ISBN 9780306477096
- V.K. Prabhakar (2000), Encyclopaedia of Environmental Pollution and Awareness in the 21st Century, p. 10, ISBN 9788126106516
- Dirt can be good for children, say scientists, BBC, 23 November 2009
- Mary Ruebush (2009), Why Dirt Is Good: 5 Ways to Make Germs Your Friends, ISBN 9781427798046
- Lai, Y; Di Nardo, A; Nakatsuji, T; Leichtle, A; Yang, Y; Cogen, AL; Wu, ZR; Hooper, LV; Schmidt, RR (22 November 2009), "Commensal bacteria regulate Toll-like receptor 3–dependent inflammation after skin injury", Nature Medicine, Nature Medicine, 15 (12): 1377–82, doi:10.1038/nm.2062, PMC 2880863, PMID 19966777
- The joy of dirt, The Economist, 17 December 2009
- Lawrence S. Kubie, "The Fantasy of Dirt", The Psychoanalytical Quarterly, 6: 388–425
- Valerie Curtis, Adam Biran (2001), "Dirt, Disgust, and Disease: Is Hygiene in Our Genes?", Perspectives in Biology and Medicine, 44 (1): 17–31, CiteSeerX 10.1.1.324.760, doi:10.1353/pbm.2001.0001, PMID 11253302
- Terence McLaughlin (1971), Dirt: a social history as seen through the uses and abuses of dirt, Stein and Day, ISBN 9780812814125
- Suellen Hoy (1996), Chasing Dirt: The American Pursuit of Cleanliness, Oxford University Press, ISBN 9780195111286
- Pamela Janet Wood (2005), Dirt: filth and decay in a new world arcadia, Auckland University Press, ISBN 9781869403485
- Ben Campkin, Rosie Cox (2007), Dirt: new geographies of cleanliness and contamination, I.B. Tauris, ISBN 9781845116729
- Virginia Smith; et al. (2011), Dirt: The Filthy Reality of Everyday Life, Profile Books Limited, ISBN 9781846684791
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