Abstract This chapter provides a comprehensive description of the physical, chemical, biological and mineralogical parameters that play a role in determining the toxicity and pathogenicity of mineral fibres. The first steps towards a general toxicity/pathogenicity model of mineral fibres are described here. Eventually the model can be generalized and may be applied to biodurable man-made mineral fibres and other natural and synthetic fibres in addition to silicates. Because of the complexity of the topic, a truly multidisciplinary approach is essential. A concept that will be stressed in the final notes of the chapter is that a full understanding of the toxicity/pathogenicity of mineral fibres aimed at finding effective solutions for the prevention and treatment of asbestos-related diseases can only be the outcome if an holistic approach is applied which takes advantage of synergistic research activity and communication between biochemists, mineralogists/crystallographers, pathologists, physicians, physicists and toxicologists, all sharing their distinct but interrelated perspectives. This is a great challenge for all such scientific individuals to work together to resolve and develop predictive models that incorporate their research findings and conclusions.

Abstract Over time, attention to health effects induced by inorganic fibres has increased, resulting not only from non-occupational exposure to asbestos ( i.e . environmental, either natural or anthropogenic), but also of exposure to non-asbestos inorganic fibres. The International Agency for Research on Cancer classified all forms of asbestos (chrysotile, crocidolite, amosite, tremolite, actinolite and anthophyllite) as carcinogenic to humans (Group 1). The most effective source of information on the health effects of environmental contaminants in humans would be humans themselves as research subjects. Obviously, for ethical and other reasons this is rarely possible. Carcinogen bioassays, such as the ones performed by the Ramazzini Institute (RI), are currently the most predictive non-human model for studying the carcinogenicity of a substance. An alternative method for exposure assessment consists of using a non-experimental animal model represented by populations of animal sentinel systems (ASS). Even if at present there are relatively few studies in this field, the presence of fibres in samples of lung tissue of these animals shows that it is possible to use ASS as indicators of environmental background exposure. However, caution must be taken in extrapolating results from ASS and considering them in terms of human health. The physical mechanisms rather than chemical reaction between inorganic fibres and cells are still unclear. Joint research conducted by a team of biologists and mineralogists in order to investigate the mechanisms of action of the fibres in biological tissues of rodents in vivo have been undertaken by the Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia in collaboration with the Cesare Maltoni Cancer Research Centre of the Ramazzini Institute CMCRC/RI. When planned for precise purposes with attention to the key, general, and specific requisites, and when conducted by standardized methods, experimental studies represent an important tool capable of providing useful information and reducing the uncertainties in terms of risk assessment.

ABSTRACT I have been fascinated by science ever since childhood, through college, during 30 years with the U.S. Geological Survey, and to this day. Younger and smaller than my urban elementary and high-school peers, I developed a great curiosity about the outdoors early in my life. Through capturing specimens and placing them in home terrariums, building plastic models, and attending school science fairs, I looked to learn all I could about the world of science. Yet, in a span of a few years, I went from gifted student to college dropout. After breaking away from school for three years as a college sophomore, I finally found the inspiration, confidence, and an environment for success in the U.S. Army. Taking chances and making changes to live my new dream of being a geologist, I worked in lunar- and Mars-like areas of the Columbia River Plateau and at a workplace staffed by scientists I had seen on television as a teen. I made opportunities or took those that came along to help me reach my goals and became a professional geoscientist, entering perhaps the least diverse of all the sciences. There were wonderful experiences that I had, through outreach programs, activities, and the personal involvement of caring and forthright people. There were other experiences or circumstances, perpetuated against me by people with uncaring, antisocial, and even antiscience motives. Having addressed my own insecurities, I took on these extra challenges and found ways of ignoring or overcoming hatred and contempt by finding and grasping the outreaching hands that wanted to make lasting changes in our profession. Through it all, I persevered and achieved goals and happiness I had previously only dreamed of. Aside from perhaps leaving a scientific or management legacy, I also strove to help as many other underrepresented, underserved, and overlooked students as I could. Content Warning: This chapter contains several instances of a racist slur. The editors have chosen to leave this language intact in order to most faithfully convey the power of the author’s experience.

Abstract Dissolution rates of mineral fibres in several environments are obtained as proxies for their biodurability in body fluids. This chapter provides a description of the experimental methods, the parameters and characteristics to be fixed during the design of dissolution experiments in closed (batch reactors) and open systems (flow-through cells), as well as details of the dissolution media. The dissolution of mineral fibres in buffered inorganic solutions is the key to understanding their behaviour during weathering processes because it contributes not only to their chemical transformation, but also to the breakdown of the fibres that may be dispersed in the environment. On the other hand, preparation of fluids representing different interstitial conditions in the lung is described, with particular attention to artificial lysosomal fluid (ALF) employed to mimic the environment that inhaled particles would encounter after phagocytosis by alveolar and interstitial macrophages. Moreover, the use of a neutral fluid such as Gamble’s solution (GS) simulates the interstitial lung fluid and airway lining fluid. Finally, the results of studies of mineral-fibre dissolution in inorganic and body fluids, found in the literature, are discussed. Methodologies for assessing the biodurability of fibres are illustrated, starting from dissolution rate data, and focus on in vitro studies. Rate constants are used to assess fibre lifetimes utilizing a fibre-shrinking model equation. Finally, literature studies show differences in biopersistence between serpentine and amphibole asbestos, due to their different crystal structures and dissolution conditions of pH and solution composition.

Abstract This chapter deals with the synthesis and thermal stability of mineral fibres. The different structural assemblages within mineral fibres and their resistance to high temperature changes from species to species. In general, the formation of such minerals takes place in hydrothermal environments. The thermal decomposition process consists of three main stages: the loss of water adsorbed on the surface of the fibre and the zeolitic water below 200–250°C; the removal of the structure water (the hydroxyl groups) in the range 500–1100°C and recrystallization into new stable crystalline phases. The thermal stability of chrysotile, amphiboles fibres and erionite will be described in detail and will be followed by specific sections describing how the concept of thermal decomposition is used for the remediation of wastes containing asbestos to produce secondary raw materials to be recycled in various industrial application.