Particulates are tiny particles often found floating in the air. They can be composed of biological materials such as mold spores, pollen grains, or dust-mite feces; minerals such as asbestos or fiberglass fibers; or metals such as lead or arsenic dust. House dust may consist of all these materials, as well as tiny cotton fibers, human hair and skin flakes, fibers from clothing, bits of soil, aerosols from cleaning compounds, waxes, and food particles. Wood and tobacco smoke are significant sources of particulates. Cigarette smoke can contain highly toxic heavy metals such as cadmium and radioactive polonium.
Larger particulates are often filtered out of the air by the nose and sinuses, but the smallest ones travel deeply into the lungs where they can lodge and irritate sensitive tissue. About forty pounds of particulate dust will settle in an average six-room home every year.
