Fibrogenic effect of wollastonite compared with asbestos dust and dusts containing quartz.

Abstract

The distribution of length and diameter and the aspect ratio of crocidolite asbestos, a mineral substitute for asbestos (wollastonite), a manmade mineral fibre (lass wool), and synthetic fibres (pobpopylene and polyacrylonitrite) were determined by light microscopy with phase contrast and, for crocidolite, also with trasission electron microscopy. The synthetic organic fibres and manmade mineral fibre used were of a size exceeding that considered respirable. Respirable materials were given to rats by the itratracheal method and after exposure for a standard time interval the main indices of fibrogenic effects-the total hydroxyproline content, the wet weight of the lung, and the total lipid content in the lung-were estimated. We decided, therefore, to determine its fibrogenicity in vivo. Materials and methods MORPHOMETRIC ANALYSISThis study examined the morphometric variables of asbestos (crocidolite), of a manmade mineral fibre (glass wool), of synthetic organic fibres (polypropylene, polyacrylonitrile), and of two sources of wollastonite, a recent mineral substitute for asbestos. ' The length, diameter, and aspect ratio of fibres were determined by light microscopy with phase contrast as previously described'2; crocidolite was also examined by transmission electron microscopy.Microphotographic recordings of the individual variables of fibre size and distribution were analysed. For all variables, the average, geometric mean, and SD were calculated. ANIMALS AND CONDITIONS OF EXPOSUREThe samples of fibres that could be given to the experimental animals (specific pathogen free male Wistar rats, about 300 g body weight) were obtained by mechanical treatment (crushing, sedimentation, etc).In the fibrogenicity test'3 the samples of fibrous dusts were given intratracheally during mild ether anaesthesia. For comparison highly fibrogenic standard quartz and low fibrogenic mineral dust of magnesite of mine origin were given. Particles of these two samples were of respirable size (diameter < 5pm).In our experiment wollastonite fibres were given and their effects were compared with the action of crocidolite, quartz, mineral mine dust, and controls.As the synthetic organic fibres were not respirable they were not expected to be fibrogenic.

Properties of talc/wollastonite/polyamide 6 hybrid composites

“…Recently, acicular grades of wollastonite with an aspect ratio range of 15:1–20:1 (called as needle‐like or fiber‐like) have been used as a reinforcing agent in replacements of chopped glass fiber. Other key characteristics of wollastonite are chemical purity, thermal stability, low water absorptivity, white color, and relatively small health hazard in comparison to other fibrous inorganic fillers such as asbestos . Some disadvantages of wollastonite are its relatively high price and high hardness in comparison to other particulate fillers that may damage the processing equipment.…”

A Review of the Toxicology and Epidemiology of Wollastonite

“…Two exceptions are the intrapleural study of colleagues (1972, 1981), which resulted in an excess of pleural sarcomas compared to controls, and a short-term intratracheal instillation study of Cambelová and Juck (1994), which produced adverse effects (e.g., increase in lung wet weight, lipid content, and hydroxyproline levels) indicative of possible fibrosis. Both of these studies have limitations.…”

“…The Stanton study did not adequately characterize the source of the wollastonite-which may have been contaminated with asbestiform minerals-and, moreover, the wollastonite was dispersed in hardened gelatin, which may have altered the otherwise low biopersistence of the test material. The study of Cambelová and Juck (1994) has also been criticized and deemed (McConnell, 1995) not to be relevant for determining the potential health effects of wollastonite in humans.…”

“…In contrast, exposure to chrysotile produced significant fibrosis, hyperplasia, and bronchoalveolar carcinomas. Cambelová and Juck (1994) performed an intratracheal instillation study of male Wistar rats exposed to various materials, including wollastonite (samples from China and NYCO Minerals), quartz, crocidolite (geometric mean length 3.9 µm), glass fiber (geometric mean length 45.1 µm), and two synthetic organic fibers (polyacrylonitrile with geometric mean length of 227.4 µm and polypropylene with geometric mean length of 253.8 µm). The same gravimetric dose (25 mg in 1 ml saline) was used for each instillation.…”

Microstructural characteristics of glass bead‐ and wollastonite‐filled isotactic‐polypropylene composites modified with thermoplastic elastomers

“…Other key characteristics of wollastonite used in polymers are chemical purity, thermal stability, low water absorbtivity, white color, and relatively small health hazard in comparison with other fibrous inorganic fillers such as asbestos. Detailed information on wollastonite has been given elsewhere [3–5].…”