Dust on Earth existed even long before appearance of the person. There is no way to get rid finally of it as dust is formed constantly, and this process lasts for millions of years. According to opinion of scientists, only 30% of its general weight are formed directly thanks to activity of people, and other 70% appear as a result of various natural phenomena.
Dust which contains in air and gradually accumulates on a furniture surface, causing irritation of housewives, consists of a huge number of various particles. It is non-uniform: by the smallest consideration it is possible to find in it tiny parts of human skin and hair and also fabrics, a tree, houseanimals wool, flower pollen and even the space bodies which were once crashing into Earth. There is also a special category to which the star dust getting on the planet directly from Space belongs.
The huge amount of dust is formed as a result of various natural phenomena. From the soil the smallest particles which weight is so small that they can travel by air on long distances separate. During eruption of volcanoes these particles are released into the atmosphere and move, overcoming hundreds of kilometers. One of the most "dusty" volcanoes is located in Japan. Every year it releases about 14 million tons of dust into the atmosphere, and it, moving, gradually settles on the earth. A lot of dust "is born" also in deserts, traveling then to various corners of the world. So pinkish dust of the Sahara quite often reaches even America and Great Britain.
Opinion as if where there is water, there cannot be a dust, mistakenly. It is known that sea air sometimes seems saltish on taste. It actually too is connected with dust: drying on coast, rocks and even just evaporating, water marks out a huge number of the smallest particles of seaweed, microorganisms, salts and so forth. Even in purely cleaned closed room dust will be emitted. It appears from fabrics, furniture, human skin, wall and floor materials, decorative elements. It will get from the street through the smallest cracks, to extend in air and to settle gradually. In this ability of small particles to get everywhere and to be formed of different materials the answer to a question why in a week after clear-out in the room where nobody lives, it becomes so dusty is.