Dirt is any matter considered unclean, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to becomedirty.Common types of dirt include:
The worddirt first appears inMiddle English and was probably borrowed from theOld Norsedrit, meaning'excrement'.[2]
A season of artworks and exhibits on the theme of dirt was sponsored by theWellcome Trust in 2011. The centrepiece was an exhibition at theWellcome Collection showing pictures and histories of notable dirt such as the great dust heaps atEuston andKing's Cross in the 19th century and theFresh Kills landfill which was once the world's largest landfill.[3]
When things are dirty, they are usually cleaned with solutions likehard surface cleaner and other chemical solutions; much domestic activity is for this purpose—washing, sweeping, and so forth.[4]
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 requires major renovation to remove. Deliberate dirt is that which results from design decisions such as decor in dirty orange or grunge styling.[5]
As cities developed, arrangements were made for the disposal of trash through the use of waste management services. In the United Kingdom, thePublic Health Act 1875 required households to place their refuse into a container that could be moved so that it could be carted away. This was the first legal creation of thedustbin.[6]
Modern society is now thought to be more hygienic. Lack of contact withmicroorganisms in dirt when growing up is hypothesised to be the cause of the epidemic ofallergies such asasthma.[7] The humanimmune system requires activation and exercise in order to function properly and exposure to dirt may achieve this.[8] For example, the presence ofstaphylococcus bacteria on the surface of the skin regulates theinflammation which results from injury.[9]
Even when no visible dirt is present, contamination by microorganisms, especiallypathogens, 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 moremicrobes than alavatory seat.[10]
People and animals mayeat dirt. This is thought to be caused bymineral deficiency[citation needed] and so the condition is commonly seen inpregnant women.[11]
People may become obsessed by dirt and engage in fantasies andcompulsive behaviour about it, such as making and consuming mud pies and pastries.[12] The source of such thinking may be genetic, as the emotion ofdisgust is common and the location for this activity in the brain has been proposed.[13]
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