Contamination of the air with mineral fibers following the explosive destruction of buildings and fire.

Mineral fibers, including asbestos, are ubiquitous contaminants of the environment. Asbestos fibers are generally present at levels below 1 fiber/L in air though 10 fibers/L may be found in cities; these levels do not appear to be high enough to present a hazard to health. These fibers come mostly from the use of fibrous materials as thermal and acoustic insulation in buildings, and their use as friction materials. Historically, occupational air levels were often very high and as a result there was a high incidence of fibrosis and also cancer in exposed workers, mostly among those in the industries concerned with the winning or processing of asbestos fiber. Levels high enough to produce disease have also occurred paraoccupationally in the families of asbestos workers. The effect of fire and explosion in a building is to disrupt its structure and vastly increase the level of airborne fiber for a considerable distance (kilometers) around it. Air levels of fiber can remain high for months, and as a result the earliest occupational experiences are likely to be repeated. The greatest danger is from exposure to blue and brown asbestos, and it is known that even a single high exposure can be responsible for the development of a tumor decades later.