The Japanese Association of Mineralogists, Petrologists and Economic Geologists, The Mineralogical Society of Japan and Ehime University held the open symposium on asbestos problem at Ehime University in September, 2005. Asbestos is a fibrous mineral that is chemically inert with heat resistant properties and has been used in over 3000 products for fire proofing, thermal, electrical and sound insulation, plasters, roof and flooring materials, gasket and friction products. However, the inhalation of asbestos fibers causes various serious illnesses of the lungs. Most uses of asbestos are prohibited in many countries. We would like to widely introduce the asbestos and its related problem and contribute the answer of this problem in some way.
The term asbestos is a generic designation given to six types of naturally occurring mineral fibers that are or have been used in commercial products. These fibers belong to two mineral groups: serpentines and amphiboles. The serpentine group contains a single asbestiform variety: chrysotile. The amphibole group contains five asbestiform amphibole varieties: anthophyllite, grunerite (amosite), riebeckite (crocidolite), tremolite and actinolite. These fibrous minerals share several properties which qualify them as asbestiform fibers. They are bundles of fibers which can be easily cleaved into thinner fibers. Several properties that make asbestos so versatile and cost effective are high tensile strength, chemical and thermal stability, high flexibility, and low electrical conductivity. Asbestos fibers have been used in a broad variety of industrial application; some 3000 applications such as roofing products, gaskets, and friction products. 80% of imported asbestos is used for cement products such as asbestos boards and slates which are used for building materials, 7% for friction materials, and less than 3% for asbestos textile. Nearly all of the asbestos produced worldwide is chrysotile. Historically, chrysotile has accounted for more than 90% of the world’s asbestos production, and it presently accounts for over 99% of the world production. Two types of amphiboles, commonly designated as amosite and crocidolite are no longer mined. With the onset of the health issues concerning asbestos in the late 1960s and early 1970s, world production and consumption began to decline during the 1980s. Japan used approximately 6.7 million tons between 1974 and 2004. About 67% of this amount was used since 1930. The relationship between workplace exposure to airborne asbestos fibers and respiratory diseases is one of the most widely studied subjects of modern epidemiology. The research efforts resulted in significant consensus that asbestos fibers can be associated with diseases of asbestosis, lung cancer and mesothelioma. Its carcinogenic nature, an overall lack of knowledge of minimum safe exposure levels, and the long latency for the development of lung cancer and mesothelioma are the main contributing factors to these controversies.
Asbestos consists of fibrous aggregates of serpentines and/or amphiboles including chrysotile, anthophyllite-gedrite, cummingtonite-grunerite, tremolite-actinolite and riebeckite. The dispersion staining method, X-ray diffractometry, electron-probe microanalysis and Raman spectroscopy are briefly reviewed to assess their potential use for asbestos identification. Optical, crystal chemical and spectrographic characteristics of asbestos are summarized along with their powder X-ray diffraction patterns, energy dispersive spectra and Raman spectra data.
Characterization of man-made rock-wool fibers were investigated by using optical and electron microscopic techniques and discussed how to affect on human health. The rock-wool fibers were collected from spraying on the roof. Mineralogical analyses were carried out by X-ray powder diffraction. Most fibers can exist as straight or curved fine threads with sharp points μm-nm in diameter under electron microscopy observations. The rock-wool is complex agglomerates of fibers and fumes with cement of calcite. The shape and size are significantly important factors for hazardous assessment of man-made fibers. The fibers are easily adhering to protein-rich spherical materials in 1% BSA (bovine serum albumin) and in ringer’s solution for few days aging. Spherical protein-like materials are similar to “asbestos body” with dumbbells shape. Man-made fibers have been manufactured for over 20 years, but there have been few concerns raised regarding the safety of rock-wool, were considered to be non-hazardous, because of the different durability in the lung. Present study consistently suggests that man-made fibers with fine and sharp points have similar risk as carcinogen of asbestos. The results of both patch test and adhesion materials with dumbbells shape provide clues regarding the mechanisms of tolerance in the lungs of exposed animals, and may be relevant for humans.
An increase in the number of patients with asbestos-related diseases was manifested by analysis of autopsy cases registered in the Annual of the Pathological Autopsy Cases in Japan (by the Japanese Society of Pathology), and the increase incidence implies that health hazard due to asbestos exposure has extended to asbestos workers and some residents in Japan. Asbestos body counts in the lungs of autopsies performed at random of 235 patients revealed that the positive rate was 97.4%. Pollution by asbestos has widely affected the residents in Japan. In addition, from the counts of asbestos bodies in asbestos-related diseases, approximately a half of malignant mesothelioma and 10% of lung cancer patients has been received an occupational asbestos exposure. In our selected asbestos-related diseases, mainly amosite and crocidolite were found in the lungs. The long fibers with a high aspect ratio were frequently found to be amosite fibers. Among crocidolite fibers, thin fibers with a high aspect ratio were also found frequently. It is thought that such size in both fibers has biologically strong effects. Asbestos bodies were frequently formed in long fibers with a high aspect ratio, and it means that their counts evaluate harmful fibers. Therefore, the evaluation of asbestos body counts is a good indicator for asbestos exposure. It almost relies on the import for the use of asbestos in Japan, and an amount of the import was about 300000 tons until 1990. The latent period of the asbestos-related diseases is 20-40 year. Therefore, an increase of the patients with asbestos-related diseases will be worried in the future.