Dust consists of mites

Dust - this solid particles ranging in size from 10 to 0, 01 micron. Dust size less than 10 microns is constantly floating in the air, the particles from 10 microns to 50 gradually settle, while larger - precipitated almost immediately. House dust may contain wool, animal dander, fragments feathers, insect parts, hair and human skin, mold spores, nylon, fiberglass, sand, particles of textiles and paper, minute fragments of the materials making up the walls, furniture and household articles. But the bulk - 80% - and most harmful part of house dust mites constitute a microscopic dust. They settled in a person's home for a long time, put them down with a pen and birds and some species - from agricultural products. House dust mites do not bite, and itself is not dangerous to humans, the problem presented by the waste of its natural life activity, which often causes severe allergies. Each mite daily devotes about 20 particles of excrement. Dust can absorb on their surface any substance, including harmful, so the house dust can be found in almost half of the periodic table and more than 100 organic compounds. Also harmful impurities in the dust particles is full of bacteria (they do not move freely in the air and travel on dust particles). One thimble house dust contains five million germs. After the death of microorganisms released bacterial endotoxins (bacteria are normal products of metabolism, and for people, and other large animals, they are poisonous), which can also cause allergies. During the day, a resident of the capital of "passes" through their light six billion particles of dust, which would fit in two tablespoons.

via factroom.ru