[Frustrated Phagocytosis Logo] Science of the Health Effects of Fibers

What This Is All about


 

Is there a scientific question?

Before we ask why different kinds of fibers yield different responses when people or laboratory animals are exposed to them, we need to show that there really is a big difference that needs a scientific explanation. There are now several studies available that show these differences clearly including these results from chronic inhalation studies.

Why do fibers differ in biological effect?

Now that we have shown that there is a difference among different fibers, we would like to know what properties of the fibers contribute to these differences in their biological response. Recent scientific research has clarified that a fiber must possess all of the following properties for disease to result:*

How is fiber durability engineered and controlled?

The rate at which a fiber dissolves in the lung is determined mainly by its composition, which is fixed essentially forever when the fiber is manufactured. Therefore, the dissolution rate of a fiber is the most important biological property for a manufacturer of synthetic vitreous fibers. An extensive series of laboratory investigations of many fiber compositions combined with the results of animal biopersistence studies of many different fiber compositions, which are summarized here, have allowed the dependence of dissolution rate on fiber composition to be determined. For a wide range of synthetic vitreous fiber compositions, it is now possible to estimate the dissolution rate directly from the oxide composition. A paper that develops this method for borosilicate glass insulation fiber compositions may be read here. A further extension of the method to rock, slag, and other fibers is available here These methods are implemented in a calculator that runs in these web pages that you may use by clicking here.

The resolution of these scientific questions allows fibers to be designed and modified so that they have dissolution rates high enough to minimize the chance that that disease would occur even in laboratory animal studies at extremely high exposures.

*Churg, Wright, Bilks, and Dai, J. "Pathogenesis of fibrosis produced by asbestos and man-made mineral fibers: What makes a fiber fibrogenic?". Inhalation Toxicology 12 (Suppl. 3), 15-26, (2000).


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