Review: Coalinga Chrysotile: Dissolution, Concentration, Regulation and General Relevance

Abstract

Coalinga chrysotile's lack of biological activity in animals and humans is due to its amphibole-free nature, short fiber length, and enhanced width, all of which contribute to a greatly reduced bio-persistence. Compared to most other chrysotile types, it has greater solubility and enhanced dissolution, especially the very small percentage of long, thin respirable fibers that reach the alveolar portions of the lung. In consequence, the mineral poses no health threat. The ultra-structural features underlying the susceptibility to dissolution include spiral structures, permanent ledges, an absence of inter- and intra-fibrillar matrix, extremely narrow fibrillar width giving very high surface areas and surface reactivity potentials, and a relatively high number of fibrillar `ends'. Any fibers released from products made from Coalinga type material; including friction products, ceiling tiles, acoustic tiles, shingles, piping and other cement products as well as fireproofing materials, through manipulation will, on aerosolization, show re-aggregation and other properties of the parent fiber. Fiber analysis of any chrysotile containing material has always been problematic because of the fundamental structure of the fibers. Research has shown the need for indirect preparation methods of Coalinga type chrysotiles for risk assessment purposes. Direct preparation methods do not give correct answers and therefore cannot reflect biological potential. Fiber counts made by phase contrast microscopy, for example, will include large numbers of long pseudo-fibers and give results that are very misleading. The true biological nature of short and long Coalinga type chrysotiles can only be predicted using the results of indirect analysis.

Review: The Fiber Length of Coalinga Chrysotile: Enhanced Clearance due to Its Short Nature in Aqueous Solution with a Brief Critique on ``Short Fiber Toxicity''

“…The true biological potency of Coalinga type fibers is therefore only apparent on indirect examination. Future regulatory counting methods must use both direct and indirect analyses to assess accurately biological activity [18]. Such methods must require separate indirect analyses of the respirable and nonrespirable fractions found on direct examination.…”

Review: The Fiber Width of Coalinga Chrysotile: Reduced Respirability due to its Thick Nature in an Aerosol and its ``Ultra-Thin'' Nature in Aqueous Solution (In Vivo)

“…The types of isomorphic substitution that appear to be peculiar to Coalinga chrysotile have been mentioned by Ilgren [28] and may also contribute to its narrowness. Similarly, the ledge and fringe anomalies cited above and by Ilgren [37] might also provide a form of strain relief. Other factors such as temperature, pH, and pressure may also be determining [35,53].…”

“…Short fiber chrysotile is the most common type of asbestos irrespective of source. Most types of short fiber chrysotile exist in an aerosol as clusters containing single fibers either bound to each other and/or to other material (also see paper following [37]). Such ''clustered'' material is often nonrespirable and thus of very little biological consequence.…”

“…High surface areas would be expected with the lack of inter-and intra-fibrillar matrix (see ''Clean surfaces'' in the following paper [37], illustrated in Figure 2) and extremely narrow width (above) (also see [27]). Previous work on the nature of chrysotile asbestos has also indicated that ''surface area is a measure of the degree of cementation of the chrysotile fibre bundles: Samples having low surface areas are more completely cemented than those having high surface areas'' [27].…”

“…The equation relating these variables is: Specific surface area ¼ ð4=pÞ:d where p is fiber diameter and d ¼ 2:5 g Á cc À1 : Many workers have demonstrated that the surface areas for Coalinga and Stragiari chrysotile fiber (both formed geologically in a similar manner [28]) are ''higher than those reported for any natural chrysotile'' [13,27]. High surface areas would be expected with the lack of inter-and intra-fibrillar matrix (see ''Clean surfaces'' in the following paper [37], illustrated in Figure 2) and extremely narrow width (above) (also see [27]). Previous work on the nature of chrysotile asbestos has also indicated that ''surface area is a measure of the degree of cementation of the chrysotile fibre bundles: Samples having low surface areas are more completely cemented than those having high surface areas'' [27].…”