Asbestos fibers-as contrasted to other particulate matter in the air-are longer than they are wide. The IOM committee found that an asbestos mineral’s property, such as its particle size, shape, dissolution, and precipitation, can affect its potential relationship to pathogenesis, especially when it is breathed in.
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October 2006In general, the smaller the particle, the farther it can travel in the human body before it is deposited-a function of gravity. Smaller particles are usually deposited in the lower airways, whereas larger particles are deposited higher in the respiratory tract, the committee found.
In contrast with studies of asbestos fiber deposits in the lower respiratory tract, there are few data on fiber deposition and clearance in the upper respiratory tract. Although data show that a fraction of inhaled fibers would be deposited in the larynx, those that are can be damaging, especially in smokers.
For example, available studies show that tobacco-smoking and other causes of chronic laryngeal irritation might interfere with the clearance of asbestos fibers from laryngeal mucosal surfaces.
Regarding the dose of inhaled asbestos fibers known to be harmful, the data are scant. The IOM committee reached the conclusion that the most relevant dose measure for cancer is probably the cumulative number of fibers that reach and persist in the target organ. The biologically effective dose is related to fibers that interact with target cells.
©2006 The Triological Society
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